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volvoclearinghouse Dork
9/12/14 4:16 p.m.

My younger brother is blessed with a keen ability to get berkeleyed over by mechanics, it seems. His DD is a 1986-ish Mercedes 190, with the 4 pot gasser engine and a 5 speed. He loves the car, loves driving it, and gets pretty decent gas mileage with it. Recently it had an overheating problem and he didn't have the time to deal with it himself, so he took it to a mechanic...

Let me back up. When I say "recently" I mean, well, a few months back. The mechanic dicked around with him, kept pushing it off, and I kept telling him to rescue the car and either sell it or find a better mechanic. Meanwhile he's driving this hand-me-down Chevy pickup with 300,000 miles and the 4.3 V6. Well, that engine pops, so now he's driving his g/f's old Accord. Which she is overly joyed about, of course. Meanwhile the MB 190 still sits...

Finally, he managed to light enough of a fire under the mechanic's ass to get the car fixed. He took off and machined the head, replaced the valve guides, ground the valves, installed a new head gasket and head bolts, new exhaust studs and bolts...

New radiator, hoses, t-stat, coolant...

Flushed the coolant system and oil, changed the oil...

Then it wasn't running right, so they began replacing E36 M3.

A whole new exhaust...

A brand new distributor...

New fuel pump, fuel filter, fuel distributor, air meter flap.

And the car still doesn't run right. Basically, it hesitates off the line, stumbles, etc. Once it's going, it runs OK, but it's that initial tip in that's a problem. The "mechanic" (I will henceforth use that term in quotes) said to run a few tanks of gas through it and see if it clears up. He made excuses that its impossible to troubleshoot older cars without OBD where the computer doesn't tell you what's wrong.

Bro's into the fix now for $,$$$ money and it seems like it's almost there, but not quite. I feel like there should be something simple that will fix this stumbling issue. Anyone out there have any ideas to help my poor brother, before the mechanic extorts more $,$$$ out of him?

Appleseed MegaDork
9/12/14 4:26 p.m.

I'm not defending the mechanic, but it sounds like he didn't want or know how to work on the car, and tried to tell your brother that. That said, he might have to bite the bullet and find a shop that is known for working on older Benzs. I believe he'll spend more dicking around going to the cheaper guys in the long run.

chandlerGTi SuperDork
9/12/14 4:41 p.m.

Is it fouling the plugs at idle then ok once wot? My brothers did that and it ended up being the fuel distributor was off. Same basic prognosis. I may have a good one here I would have to look.

Ojala HalfDork
9/12/14 4:42 p.m.

Time for a mechanic familiar with CIS-E...

Or learn how to work on the car its not that hard. A test kit can be bought for $100 and that would let you diagnose the car.

Seriously, the dude has apparently said, in several ways, that he doesnt know how to work on the car and yet your brother keeps going back to him?

volvoclearinghouse Dork
9/12/14 4:46 p.m.

The mechanic wasn't picked blindfolded out of a phone book. Apparently he had some rep as an MB guy. And if he really wasn't comfortable working on the car he should have simply flat turned him away, not strung him along and led him on with the "Oh, I'll get to it"-s.

For me, the big red warning light was the whole sitting on the car for 3 months thing. But that's in the past now. I agree, he needs another mechanic, but I'm curious if anyone else has had a stumbling off idle issue with these engines/ cars. Fuel distribution was replaced already.

chandlerGTi SuperDork
9/12/14 5:12 p.m.

I sent this to my brother, he had all these symptoms and was able to beat it; mine, once rewired runs like a top.

Ojala HalfDork
9/12/14 5:12 p.m.

Yup, sounds like the dude is a parts cannon. Its sad that someone that calls himself a mechanic seems unable to use the diagnostic computer between his ears...

Im not an expert but a sticking air flow meter or clogged injectors could do what you are describing. But you really need a test kit and some education to figure that out. I am assuming that all of the vacuum lines are good. Hopefully some of the MB or VW experts here can chime in.

9/12/14 7:46 p.m.

ChandlerGTi's brother here... A couple preliminary questions...#1. Can you snap the throttle and have instant throttle response? #2. Did you clean the tank screen? #3. Does it foul plugs or a plug and if so is it always the same one? CIS cars are notorious for drivability issues if they sit for any length of time. Unfortunately, the fuel we have now magnifies the problem.

volvoclearinghouse Dork
9/12/14 9:22 p.m.

In reply to standard125r:

Thanks for the tips, I'll pass them on. I had a suspicion it might have something to do with the car having sat for a few months.

Opti Reader
9/12/14 11:23 p.m.

Normally something like this you look at what the mechanic had touched. Too bad he has touched everything.

Things I've seen do this...mechanical timing, spark timing, broken plug. Burnt wire.

Mind you I have no 190 experience so I don't know about any of the weird systems it has that can cause this

MailmAn New Reader
9/14/14 12:37 p.m.

Hello, all! My big bro passed along the link to this post, so I figured I'd become a member and join in on the discussion so you can get all the info first hand. (I haven't posted there in a while since I've been really busy with work, but I am also a member over at BenzWorld.org, so if you check over there I have a bit more history on the car as well... My username over there is 85BabyBenz.)

So anywho, formalities out of the way... the car is a 1985 190E with the 2.3L 8-valve 4 cylinder and a 5 speed manual. I specifically bought the car because of the manual transmission. I've owned the car for about a year and 3 months now. The engine ran great when I first bought it, but it leaked oil a lot and I kept having to add about a quart in-between oil changes. During that time, I had brought the car to a few different shops for various things (tires, alignment, etc...), including the local Mercedes Benz dealer (Keeler Motor Car). They all said the car was leaking oil bad and it looked like it was coming out of the back of the head and they suspected a bad head gasket. Well, as time went on, the oil leak kept getting worse and worse... Then I was adding in about a quart every week or two, depending on how much I drove it.

Over this past winter, the upper radiator hose blew out on me while I was driving and I had to get that fixed ASAP. It seemed totally random and the rest of the hose seemed in good shape and I thought it very odd that it just ripped open a like 1-2 inch gash in the middle of the hose. I kept driving it after I replaced the radiator hose and topped off the coolant.

Around April or so, I was checking the coolant level in the overflow tank and noticed the coolant looked creamy, like there was oil in it. I figured the head gasket got bad enough that it started pushing oil into the coolant passages in the block. At this point, I knew it needed a head gasket and I didn't have the time, tools, or knowledge to try to tackle it myself. I started researching shops in the area that specialize in foreign (European) cars and I stopped by about 4 different shops that all said they specialize in BMW's, Mercedes', Porsche's, Volkswagens, and other German cars. I first took the car to see "The Bavarian Rocket Scientists" (I sh1t you not! That is the name of their shop in downtown Albany...) However, they primarily seem to work on high-end Porsche's and BMW's (as well as some Mercedes'), but they didn't seem very interested in working on my 190E and they quoted me an astronomical number of close to $5,000 just to do a head gasket job on the car, so I figured they didn't want to bother with my rinky-dink little Benz...

Long story short(ened a bit?), I ended up taking it to Capital Mechanics in Speigletown (just north of Troy, NY). I had stopped into his shop 3 times over a month or so and talked at length with the owner about my car before I decided to bring it to him. He seemed to know his stuff and he bullsh1tted me enough to make me think that this was the guy who would do justice to my car and get it fixed the right way. (Not necessarily the cheap way - but I wanted it done right.) He does work on a lot of older Mercedes', BMW's, VW's, and Saab's. Oddly enough, he said he originally started his shop as a Saab specialist and he had so many people asking him to work on Mercedes' and other German cars that he just became an all-around European specialist shop. Granted, the owner looks too old to be actually working on cars anymore (he is an old Russian guy, looks to be in his mid-60's at least?), so all the work on my car was done by one of his guys in his shop that is a Mercedes mechanic (supposedly).

So, he did all of the work on the car that my brother already outlined above (that is second-hand from me telling him over text messaging yesterday). I just picked up the car Wednesday of this week and he handed me a bill for $$$$$$$$$$$$$$$$$$$$$$$$ to fix the car. My jaw about dropped to the floor. Granted, after he did the head job on it and got the engine put all back together, it would hardly run at all for some reason. He kept checking different things and he outlined some of the potential issues that could be causing it. First, he thought the exhaust could be plugged up and causing the engine to not run right. However, this was the same exhaust that was on the car since I bought it and the engine never seemed to lack power before. Still, he cut off the old exhaust and put in brand-new piping from the end of the manifold back along with a new muffler. He showed me the cat in the car was a cheap universal one that was replaced at some point and it was much smaller than the OEM cat. It was partially plugged, but you could still see light through it. Then he showed me the resonator, which looked like it was coated with a mixture of used gear oil and carbon deposits and was almost totally plugged up. It looked nasty inside. Still, just the exhaust alone tacked on an extra $650-$700 to my repair bill which I wasn't expecting.

Then it STILL wasn't running right after that, so he put a timing light on it and noticed that the timing wasn't advancing at all when you reved the engine. The vacuum advance was shot on the old distributor, so he put in a reman ignition distributor, which was another $200 or so for that. Once that issue was resolved, he told me to stop in and test drive it to see if the car drove like this before or if it still had an issue. The car idled fine, but when I went to drive it down the road, I was almost rear-ended pulling out of his parking lot because the car just fell on its face when you gave it any throttle and it would not accelerate to save its life. I said no way was it ever this bad before when I was driving it!

So, he thought it was having a problem delivering fuel. He pulled the injectors out and cleaned them and made sure they were spraying okay. He said the injectors seemed fine and were not an issue. Then he diagnosed that there was an issue with the fuel distributor and he thought a diaphragm in there went bad or got a pin hole in it and it is causing a drop in fuel pressure so the injectors aren't delivering enough fuel when there is a high demand. So, he had me get a used fuel distributor for it since that part is hard to find and a new one will run over $1,200-$1,400 easily from Bosch.

I had a guy out in the New Milford, CT area that I had bought parts for my car from before, so I called him up and asked if he had a spare fuel distributor I could get from him. He said he parted out a manual shift 190E a few months ago to a guy who wanted to convert his auto to a stick and he had the engine for the car still. He said he drove the car before he pulled the engine and transmission out of it and it drove fine through all the gears and through the rev range, so he said he knew the fuel distributor was good. I paid $120 for the entire assembly - the air meter flap housing, fuel distributor, fuel pressure regulator, etc... he even gave me all the fuel injector lines with it, which if you look on eBay, most other @$$holes just cut the lines off at the connectors to the fuel distributor... >:-(

So, I brought this to the "mechanic" (to keep with my brother's theme here...) Monday morning of this past week when he opened up and his guy swapped them out and the car ran much better than it did before. Then on Wednesday he called me up and said my car was done, I headed up there, he handed me a HUUUUUGE bill (Damn you, Billy Fuccillo!!!) and I drove the car home. I called him back on Thursday to tell him it STILL wasn't running right as it seems to hesitate when you give it gas and especially when trying to take off in 1st gear, which is very annoying. He told me that it is probably the throttle position sensor that got some oxidation on it from sitting and it just needs to be driven a few 100 miles or so and hopefully it will sort itself out. If it doesn't, then maybe that part will need to be replaced as well. He also said to put some fresh gas in it as the tank was almost empty and run some fresh gas through it to see if it will improve. He also thought it could be an issue with the 5th "enrichening injector" in the intake manifold, which gives it extra gas to help with cold starting as well as extra fuel when you floor it.

So, I stopped by my local Sunoco station and filled the tank with 93 octane fuel (which is all I run in the car). I also added a little StarTron fuel additive for the Ethanol and even put in half a bottle of SeaFoam in the tank as well for best results. I've since put about 70-80 miles on it the last few days (I do drive a lot for work...) and it is STILL acting up, so I don't think it is a problem that will "fix itself" with time...

Could it be that those fuel distributors are uniquely tuned to each car and you can't just swap them around without having to tune them to the engine? Maybe there is more tuning and tinkering that needs to be done to make the engine run right? It is STILL not running as well as it did when I first bought the car over a year ago and I figure with all of the work done to the car and all the money I've thrown at it, it should run like a brand-new car and it doesn't. I'm not very happy with it right now and I'm frankly very, VERY disappointed with the mechanic, especially after all my interviewing shops and I had figured that this was the guy who was going to do the best work on my car... Boy, was I mistaken...

. .

(P.S. - Sorry I wrote a novel about my car, but I figure more information is better so you can get the whole picture... There is nothing I hate more on forums then when noobs post, "My car is broken, what's wrong?" and they don't tell you what it is doing, lol...)

MailmAn New Reader
9/24/14 7:30 a.m.

Okay, well I haven't seen any replies to this thread in a while (since I posted), so I thought I'd try to kick it back up here in the hopes that I'd spark some more discussion.

Since the last time I posted, I have brought the Mercedes back to the mechanic twice now (against my brother's better judgement, I know...) to have him "fiddle with it" some more to see if he can iron out the wrinkles in it. THANKFULLY, so far he hasn't charged me any more $$$ for doing so, but I am worried that it might eventually lead to even more expensive repairs down the road if he can't figure it out.

The first time I brought it back to him, he checked the fuel pressure regulator and the pot on the air flow meter/fuel distributor assembly that electronically regulates the firing of the 5th injector (as well as sending data back to the "computer"). (I believe this part is called the "Volume Air Flow Sensor Position Indicator" in the Mercedes service manual, but I could be wrong...) When he gave it back to me saying it was "all fixed", it still wasn't running right though. The idle still fluctuated between 500 and 1,000 RPMs and it wanted to stall when decelerating to a stop. It also had a hard time starting when you shut it off hot and tried to start it again after less than 5 minutes.

So, I brought the car back to him again last week and he supposedly fiddled with the lambda fuel enrichment a bit (or at least checked it under varying conditions - cold, hot, under load while driving, etc.) to be sure it was set okay. He also adjusted the Idle Air Control Valve to fine tune the electronically controlled idle speed of the engine. When I got it back this time, the idle problem had been fixed and it now idles nicely at around 750-800 RPMs steadily. It also doesn't act like it's going to stall when you decelerate to a stop.

However, the underlying issue of the hesitation and stumbling at lower RPMs is still very much present. Oddly enough, it seems to present itself more when the engine is up to operating temperature and it runs a lot better when it is cold. Where I feel it most though is when I'm trying to start out in 1st gear and it just falls flat on its face when trying to get it to accelerate up to speed. I've found I can make it work by revving the engine up to about 3,000 RPMs and slowly letting out the clutch so I end up taking off at around 2,000 RPMs and the car will take off fine, but that will quickly wear out my clutch doing that every day! If I try to take off like a normal human being who knows how to drive a stick-shift, the car will stumble and hesitate and run like crap all the way up to about 3,000-3,500 RPMs where it will finally start to pick up speed and then it will pull fine up to about 6,000 RPMs (redline). It also runs best at about 3/4 throttle and it will start to bog down if I try to floor it at any point.

I called the shop back up yesterday and I told him it is still not running right after all he has done to it so far. I told him I still think that there could potentially be a problem with the timing of the engine and the timing chain may be off at least a tooth on the cam gear. I think it at least warrants checking it, but he keeps telling me that it was set "dead on" when they installed the head and he doesn't want to waste time going over things that he "knows are right" with the engine. If you're not even willing to go back and double-check your work to make sure it is right though, then what good are you as a mechanic? That is my thought at least. Plus, I didn't see him put the engine back together, so if nothing else I'm not totally convinced that the timing is right, even if he is. He should at least show me it is right to satisfy my curiosity I should think - or am I asking too much here?

Now he says he is running out of ideas as to why the engine is still not working right. He is now suggesting that it may be the engine control "computer" that went bad and it is not able to make the engine work properly under all conditions. He said he had a 1987 Mercedes 300 I-6 gas engine that was running like complete garbage too and he kept adjusting it and adjusting it and replaced a bunch of parts on it and it still wouldn't run right. In the end the only thing that fixed it was replacing the ECU and then it ran beautifully after that. He thinks I may have the same problem. He says these old ECU's aren't like modern OBDII computers and they can't "learn" and adjust engine parameters accordingly to compensate for a variety of different conditions. They just take raw input in and adjust engine controls as needed based on the data - so if either the data it receives is out of factory spec or there is a breakdown inside the computer preventing it from outputting the appropriate signals, the engine is not going to work right. However, I also don't need to throw more $$$ into it to replace the computer if it doesn't need it and that is not the problem either.

Thoughts? Has anyone else had a problem like this with a CFI Mercedes engine? What fixed it and what do you think the most likely culprit is? Thanks!

Dusterbd13 Dork
9/24/14 7:42 a.m.

It sure sounds like a vacuum leak somewhere. And probably legal action action against the shop. Did you agree to all this money before the work was completed?

volvoclearinghouse Dork
9/24/14 7:45 a.m.

How hard would it be to check the timing belt yourself? Cam timing could shift the power band way up the RPM range as you're describing.

I don't blame the mechanic for not wanting to check it. He's got nothing to gain and everything to lose. At this point you may have to do something like offer to pay him for his time to check it, if it turns out the timing is fine. And make sure you are there to witness it.

Mezzanine Reader
9/24/14 10:18 a.m.

I have a lot of experience with CIS, including my daily driver. What you're describing really sounds like a vacuum leak. Major service like you've described touches a lot of things in the engine bay, and it is easy to miss a hose here or there. This happens to me every so often, and is usually the result of one little hose sliding off of the vacuum nipple. Results in the same conditions you describe.

Time for some troubleshooting. Start by pinching or otherwise restricting each vacuum line to see if the idle changes. For some ancillaries, you could remove the line all together and hold your finger over the engine-side vacuum nipple to see what changes.

Be sure to try disconnecting the vacuum line to the brake booster and plug it too.

Good luck!

volvoclearinghouse Dork
9/24/14 11:03 a.m.

In reply to Mezzanine:

Good tips about the vacuum...especially since MB seems to use vacuum for everything.

chrispy Reader
9/24/14 11:30 a.m.

I have a little CIS troubleshooting experience. Taking the "mechanic" at his word that he set everything correctly, I also suggest checking for vacuum leaks (CIS cars don't like them at all) as well as check the timing. My Golf had a similar stumble and a slight distributor adjustment took care of it. One thing I didn't see listed was a check of the Warm Up Regulator, Control Pressure Regulator (it's a metal box, rectangular, with wires and fuel lines going to it mounted on the block). There is a small screen in there that can get clogged and I recall a potential issue with the metal strip from my BMW E21 days.

Forgive the plug, but the E21 section on Bimmerforums has one of the best CIS troubleshooting sections I've found. The parts may look slightly different, or have different names, but the mechanics are all the same. There is also a good DIY base tune that I have used with great success on both BMWs and VWs.

GameboyRMH MegaDork
9/24/14 12:23 p.m.

Sounds a lot like a problem I had with my 4age, the main problem turned out to be that the magnetic trigger wheel in the distributor had become demagnetized and wasn't putting out a good signal. Also the FPR wasn't putting out quite enough fuel pressure but that was a minor problem in comparison.

The_Jed UltraDork
9/24/14 1:28 p.m.

My Scoob has the same low rpm stumble. I haven't had a chance to look into it.

I second the question of whether the work was approved before the parts changer dove into the car.

mfennell Reader
9/24/14 1:30 p.m.

Another thing that jumps to mind when I read "runs better when cold" is O2 sensor. My wife's '92 VW Cab (also CIS IIRC) would run OK cold then fall flat on its face as it warmed up. The tell (for me) was when I noticed it would run OK for a few seconds even when hot before going to sh*t. My wife just about fell out of the car when I opened the hood in a parking lot and "fixed" the car (disconnecting the sensor) in about 5 seconds.

Kendall_Jones HalfDork
9/24/14 2:50 p.m.

With all that top end work done, I'd do a compression & leak down before throwing any more parts on it.

Does the MB crankcase have the same vacuum on it like the old BMWs? Pull the dipstick & idle drops and runs erratic...

Frigidaire New Reader
9/24/14 3:07 p.m.

Personally I would not be going back to this same shop anymore. You have given them more than enough chances to show whether or not they know what they are doing. I had a CIS SAAB 900T that was real low on power. turns out it was running static timing, the distributor had broken and someone had done a temporary patch on it which resulted in static timing. So check the timing yourself or via someone you trust, but also watch to see that the timing adjusts as revs change. And agreed on the repeated vacuum leak suggestions. Intake boot or something beyond just a vacuum hose could be hiding a leak. Check torque on intake as well.

volvoclearinghouse Dork
9/25/14 7:11 a.m.


Lots of good suggestions here. Definitely run down the list from easiest to hardest and report back here so all the CIS expurts can help you along!

MailmAn New Reader
9/25/14 2:27 p.m.

Thanks for all the great replies everyone! I'll update you when I know more. I haven't taken the car back to the same shop yet. I did have an appointment this morning with another Mercedes shop in Schenectady and he took it for a drive and said he thought it was just running a bit too lean when he test drove it. He pulled out this long T-handle allen wrench and inserted it into a hole in the middle of the air cleaner and adjusted the base mixture on the air meter/fuel distributor to enrichen it up a bit. Then we went out again in the car and it improved the low-end response a bit, but it is still acting up a bit. It seems better than it was, but still not 100% yet.

He said he didn't really want to get too much into the engine though as he didn't do the work on it and doesn't know what the other mechanic did and doesn't want to get into his rat's nest of sh1t that he could have potentially focked up. He did say that he was expecting the car to run a LOT worse than it does because of how I was describing it to him over the phone before I stopped by with the car. He says it does have some small driveability issues, but overall isn't bad at all and the car seems to run fine and pulls well above like 1,500 RPMs.

He mentioned it could be a lot of different things causing the problem though (many of the same things that were listed above, actually...) I did ask if he thought the engine (cam) timing could be off and he said that at this point with the way the car is behaving, he doesn't think so. He said it would run "like a bag of @$$ all the time" if the timing chain was off a tooth and it doesn't. That said, anything is possible... It is possible to compensate for the timing being off a bit so the car will run and it could be hiding the fact that the timing is off, but he didn't think that was the case. However, I had another mechanic go for a test ride in the car and he definitely thinks the timing is off, so there seems to be some debate over whether this could be timing related or not. Until it is double-checked though, we can't know for sure.

More suggestions this other mechanic gave me this morning included a vacuum leak somewhere, bad coil/weak spark (the plugs, wires, distributor, cap, and rotor are all new though, so the coil is the only weak link there I think...), bad O2 sensor, or fuel delivery problem (running lean, plugged fuel filter or screen in gas tank, bad injector, etc...) However, I would think if it is just a fuel delivery issue that it wouldn't be able to run at higher RPMs as that is where you need more fuel, not at lower RPMs. He did mention though that these CIS Mercedes' rely heavily on vacuum and if there is a tiny leak anywhere, it will throw off the performance of the whole engine. The fuel distributor itself needs proper vacuum to work right.

It is just such a colossal pain in the ass to check every vacuum hose for leaks and that it makes a good connection where it plugs in at both ends. But, since the head was off of the car, you know that pretty much every vacuum hose was unplugged and disturbed!

TRoglodyte SuperDork
9/25/14 2:35 p.m.

If you want to check for vacuum leaks the quick and dirty way is with a non flammable aerosol.(CRC Lectra Motive). Spray around hoses with car idling and listen for engine to bog (leak is pulling aerosol into engine).Also intake manifold if that was off.

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