BMW Headache

Hey Guys!

Recently picked up a nice SIMPLE project car E30. It was a track vehicle at one point in time and the last owner decided to swap in an M50 non vanos from an E34. I picked the car up a few months ago in pretty rough condition inside and out.

The ride home was interesting as it kept stalling at stops, but on the highway it ran great! 125 miles later I had it home with the help of a buddy. I was able to buff the exterior and make it look half decent. The interior was refinished slightly and I put back some of the interior bits to make it look somewhat presentable. I added a thermostatic fan switch and did some minor shifter work as well. The idea was a fun weekend and autocross vehicle.

Specs are as follows:

1985 325E

1994 E34 M50

Autopower cage and Sparco Evo2 Seats

E36 suspension bits

LSD rear

Nice brakes

Etc.

Anyways after doing a lot of work I am left with one issue that is driving me insane and is keeping me from registering and tagging it. I have searched tirelessly for solutions on several forums and I am not coming up with much. Perhaps the knowledge here would lend a hand.

Basically the vehicle is started revs to 1800, drops to around 500 and settles at about 900. The idle is dead smooth at 900. If you rev the engine over 1400 it will then drop to around 500 up to 1000 down to 800 and eventually settle at 900. It seems to make a whooshing noise when it drops in the IACV area; however I find no leaks here. It never stalls, but it is very annoying.

I will try to post a video of this ASAP.

The car also seems to smoke more than normal, kind of a white colored smoke but it smells fuelish. I do not lose oil or coolant but it is very strange. Possibly water in the gas? I am thinking this car sat for at least a year while the swap was being done but I did fill it up on the way home.

What I have done:

Swapped TPS, MAF, CTS, IACV. Checked all sensor harnesses for damage, checked for vacuum leaks and replaced several hoses, connectors and boots. Cleaned spark plugs. Compression tested good on all cylinders. I have also stared at the engine while running in an attempt to will it into working right.

I should note that a few things have happened since I have been working on it. First some fool (me) left the fuel pump on overnight killing the battery. After charging it back up, car started fine. Also the car has a small water leak issue, the ECU got wet at one point and the car would not start at all. I dried both the connector and the DME, and waited a few hours and it eventually started up.

Thanks in advance for any assistance the folks here at GRM can provide, I would really like to put this car on the road before I end up deciding to sell it. I have already been surfing craigslist recently and that is never a good sign. Sorry for the long writeup.

Have a great weekend everyone!

Does it have a lightened flywheel? If so, the chip may have a tune to raise the idle speed.

m

In reply to 7pilot:

I contacted the PO and he stated that it had a stock flywheel and wasn't sure about any chip in the DME. I cracked open the ecu (413 red label) and checked it out. Looks to be a stock chip (1-267-357-623) with no aftermarket marking that I can see. The injectors are also the stock green tops.

I wonder if it is possible to reflash the stock chips? Perhaps this is what I am dealing with?

I was able to capture the action in a video as you can see. Check it out and let me know what you think!

http://www.youtube.com/watch?v=ZD0GWvBFx9Q&feature=youtu.be

Gar... I want to be helpful, as I've owned a very similar car, but it never did exactly this.

I can't help but wonder whether there's something wonky at or around the IACV or its plumbing.

Between the fact that it makes a noise near there, that poor response could see the IACV cycling as it lags behind what's going on... It just seems like the right area.

I'm trying to remember how those are plumbed. Air comes in, is filtered, goes through the MAF sensor,then there's a bypass that goes around the throttle which is controlled by the IACV, right? So IACV air is still measured by the MAF, it's just controlled by the IACV and not the throttle...

You said you replaced several hoses, connectors, and boots and checked for vacuum leaks. My assertion above totally falls under the "your PC is plugged into the wall, right?" level of troubleshooting, but those sorts of things are frequently worth asking...

It resulted in a much more obvious issue than what you've got, but I did have some issues, IIRC, with the IACV connector to the intake manifold jumping out a couple of times (on coughing back during startup? It's been a while...)

ransom wrote: Gar... I *want* to be helpful, as I've owned a very similar car, but it never did exactly this. I can't help but wonder whether there's something wonky at or around the IACV or its plumbing. Between the fact that it makes a noise near there, that poor response could see the IACV cycling as it lags behind what's going on... It just seems like the right area. I'm trying to remember how those are plumbed. Air comes in, is filtered, goes through the MAF sensor,then there's a bypass that goes around the throttle which is controlled by the IACV, right? So IACV air is still measured by the MAF, it's just controlled by the IACV and not the throttle... You said you replaced several hoses, connectors, and boots and checked for vacuum leaks. My assertion above totally falls under the "your PC is plugged into the wall, right?" level of troubleshooting, but those sorts of things are frequently worth asking... It resulted in a much more obvious issue than what you've got, but I did have some issues, IIRC, with the IACV connector to the intake manifold jumping out a couple of times (on coughing back during startup? It's been a while...)

Thanks for the help!

The IAC is as follows: air from intake through IAC to throttle boot which is after the MAF. I have replaced the intake manifold connector, the hoses to the IAC, the IAC itself, and the throttle boot.

So from what I see this is not measured by the MAF. The IACV I replaced mine with was a JY unit that I cleaned up. But both seem to be snapping on and off well and perform exactly the same.

On a side note I am getting 20-21 inches of vac at idle. It is strange because I see other swapped cars idling much lower (around 600) while other seem to be 900ish like mine.

Thanks

Well now I'm doubting myself as to whether IACV air should be measured by the MAF, but it sure seems like it ought to...

Dang, I can't find a good diagram online.

Do all the parts seem factory and like the routing must be correct, is everything just hooked up however the PO had it?

Hopefully someone with an E36 can chime in here...

Just seems like the computer should know about all the air that's being let into the engine. If something drags engine speed down then yes, the IACV should let more air in. But if the computer doesn't know about it then it's just a big vacuum leak and it'll go lean, right?

This is a long shot but what about the cam or crank sensors? My E36 had a similar problem where the revs would drop down below 500 to the point of stalling, back up over 1200 and finally hone in on 800. Drove me nuts until I replaced the cam sensor and now it holds a perfect idle.

The idle dither. It sounds like the ECU thinks that there is a small unmetered air leak, and is trying to correct the problem. The condition seems to improve somewhat as the coolant warms up. Speculation points at a leak around a material that has a self sealing tendency like a rubber hose. I would have a smoke test done , in order to rule it out or locate the source.

The bounce. This is a common complaint from E36 owners. I have seen it myself but it has been sporadic/episodic and has not bothered me enough to inspire a fix.

Your ECU is retuned by changing the chip, OBD1.

m

Ransom: The routing is similar to what the PO just modified slightly because I deleted the ASC throttle body. But from what I can see online (and I have been researching this for over a month) I am 99% sure the lines are going to the correct locations.

Stargazer: These are a possibility I suppose, unfortunately I cannot check for codes at this time. I do have a parts car in a local JY that has a cam sensor I will snag this weekend and try out. Crank may be more challenging to pull at the yard but I will try that as well.

7pilot: Thanks for the tip, I don't have access to a smoke machine but I have been researching DIY plans. I will go through the hoses again tonight and see what i can find.

Thanks again to you guys and the folks at GRM for the assistance!

Have a great day guys.

7pilot wrote: Your ECU is retuned by changing the chip, OBD1. m

This, chances are Turner or Conforti(I think they do turner's) have a tune for it, just buy the one that matches your DME number, vehicle, and model year.

Thanks guys!

Update from tonight. No Vac leaks detected, flipped IACV to see if direction changed anything and had no luck. I was able to notice that when a vac line is pulled the car idles smoother and the dip is less noticeable, maybe 100-150 rpm compared to 200-250. I also noticed when pulling the maf sensor connector nothing seems to change with the way it is running.

So I am guessing by bringing a vacuum leak into play it slightly leans out the engine, making it run smoother?

Current plan: Pull cam sensor from JY and swap. If fails then try to find a DME and swap it (2 other JY in the area). If no luck then pull intake manifold and go over it. If this does not work I will have to dive into the wiring. Maybe do an MS install.

you can pull the connector on the MAF at idle and it will not change the idle at all. My Ti needed a new MAF and that was how I discovered it. My car was doing the same thing yours is.. rough rough idle with lots of drops then rises to over 1000rpms.. and then eventually a stall.

I know you replaced the MAF and other things.. did you replace it with the correct ones? Your car is a bit of a frankenbmw.. so it might be a mishmash of parts under that hood

mad_machine wrote: you can pull the connector on the MAF at idle and it will not change the idle at all. My Ti needed a new MAF and that was how I discovered it. My car was doing the same thing yours is.. rough rough idle with lots of drops then rises to over 1000rpms.. and then eventually a stall. I know you replaced the MAF and other things.. did you replace it with the correct ones? Your car is a bit of a frankenbmw.. so it might be a mishmash of parts under that hood

Actually now that you mention this, the MAF i pulled made the car run even worse than the one in it. Both are identical, and I tried cleaning them as well.

What are the chances of having two bad MAF sensors? Mad machine did you notice the car running rough when your MAF was bad?

mine would run pretty good when off idle.. but would occasionally bog for a second or two without warning or reason. I have noticed since replacing it (last week) that I have more power and better economy..

With the bad idle.. you could see the car blowing carbon smoke from the exhaust each time it stumbled.. so mine was running very rich at idle

Thanks mad machine. I have been doing some research and the MAF could definitely be causing this. I would like to try and get another known good unit and try it out. Hopefully I can make it to a salvage yard this weekend before they close, otherwise I will try to get one off ebay.

Thanks again.

Update:

The nightmare continues. Tinkered for around 2.5 hours tonight. Came up with the following.

Unplugging MAF results in no change Unplugging cam sensor results in no change unplugging 02 sensor results in no change

Unhooking one small vac line, removing oil cap, and removing dipstick equals a perfect idle and return to idle.

Pulled the plugs, all are black due to richness. I have ruled out the smoke possibly being oil, as the level has not changed in over a month with a lot of idle time and a lot of smoke.

I thought maybe FPR was not functioning, but the fuel return line is flowing from what I can feel and hear.

Another thing noticed was after the ecu is reset the idle seems to function properly and catch itself. After it begins to warm up the issues begin.

So anyways anyone interested in an E30 with a solid chassis, nice suspension/brakes, stripped interior with roll bar and sparcos?

If you were in my situation what would you do next? Rip out the intake mani and inspect everything? Re do the wiring? Get another ecu or MAf to try?

Thanks

What you are experiencing is probably going to be more common as the bloom falls off the 24v swap Lily and these cars get passed along. There usually won't be a written build log for the particular car and there are so many dodges and quirks specific to any one swap car. This leaves the new owner in the dark when problems crop up.

Before giving up I suppose I would ID the engine harness and then re index to verify that the C101 plug now on the harness is correctly configured for the age, engine, and model of the chassis it now inhabits. I'd make sure that the connections behind the instrument panel are sound as the DME won't tolerate intermittent road speed and other info from the dash. Make sure that the engine is grounded at least twice. Make sure that the DME has a solid 13v power supply or it may have some brain fade issue.

When I did my swap, I used all new sensors in order to avert the nightmare of a future electrical problem. m

Does that engine have a pcv system in it? if unplugging a vaccuum hose or opening the oil fill cap allow it to idle properly, sounds like you have something blocking the flow or building pressure in the crank case.....food for thought I suppose

Thanks guys! I will check out all of your suggestions. I will be spending all saturday night through sunday evening on trying to resolve this.

I've been through this... Seems to me that there is a leak in the intake system somewhere, after the MAF. Is the throttle plate clearance correct? The IACV is trying to compensate for unmetered air from someplace it sounds like. Once it warms up, the ECU sees the MAF is closed, but the O2 sensor see's its in a lean condition, the ECU increases the fuel flow to the injectors, the rpm's rise, then it catches that is now rich, rpm's fall. Its nothing worth ditching the car over. When I pulled my throttle body, I found the PO had used silicone in place of the proper throttle body gasket.

Take a bottle of water or windex (or starter fluid if you want to be ballsy) and spray around the intake until the idle changes... zoom in until you find the leak.

It is there somewhere after the MAF. It could be the intake gaskets themselves.

Giant Purple Snorklewacker wrote: It could be the intake gaskets themselves.

That's a good one, most people don't spend the money on a new gasket set when they do a swap.

Like mentioned earlier, I did all new seals/sensors when I did my swap.

Did you replace the IAC with a new unit or a used one?

Wow thanks a lot for the responses guys! I will find this intake leak this weekend!! It may be a good idea to pull the intake and replace all seals? They don't appear to be too expensive.

The IACV was used, cleaned and performs the same as the original that I also cleaned. I just picked it up because it was available and cheap.

I appreciate the kind words everyone, I wont give up on this one yet.

Pulled the intake tonight, looked as if someone had done it before and cleaned up the surface on the head real nice. Valves looked fantastic as well.

Found no leaks, gaskets looked to be in good shape. Stumped....and a bit frustrated.

I sprayed water and ether everywhere before and after intake removal (and I mean everywhere). Not a change in idle at all.

On a positive note, pulling the intake was fairly simple, and I could do it again fairly quickly.