1988RedT2
1988RedT2 UltimaDork
9/4/19 9:42 a.m.

So I've had this car forever.  Wife and I used to take it to the dragstrip back in the years BC (before children).  Now, my son is 16 and taking an interest in the car.  Mostly it sits, maybe once a month I'll start it and go for a drive around the local 2-lane road.  It has literally seen 3,000 miles in 17 years of ownership.  Currently showing 103,000 miles.  Engine is almost 99% certainly the one it rolled out of the factory with in 1988.

Lately, I've noticed that it seems to be running very rough on cold start, as if it's running on just one rotor (pretty sure it is).  It smooths out after a few seconds and runs like it always has.  Idle is smooth, especially for a rotary ( I attribute that to my excellent tune on the laughHaltech).  Hot restarts have always been a bit sketchy, even before the Haltech install.  For the record, nothing has been done to this car in over 10 years, so it's not something I did.

Compression has always been a little over 100 psi on the front, 90 on the rear.  I just checked it this morning.  Interestingly, both rotors read about the same, but at 80 psi, which is wicked low.  Pulses are even.

So, I know a rebuild is needed, but I'm not in a place where that's going to happen anytime soon.  I've heard these engines can get sticky seals that can result in low compression.  Some say to soak in ATF to "restore lost compression." 

So, rotary gurus, hit me with suggestions.  Do I take it out and flog it 'til it breaks?  Do I soak it in ATF?  Amaze me with your brilliance!

 

 

WonkoTheSane
WonkoTheSane SuperDork
9/4/19 9:59 a.m.
1988RedT2 said:

Rotary Question... words words words...

Do I take it out and flog it 'til it breaks? 


Sounds like you already know the answer :)  That car needs some sweet redline loving, stat.

The rough start can be caused by a leaking fuel injector eating away some of the oil film on one rotors' worth of apex seals.  It might be worth sending those out for a good cleaning.

1988RedT2
1988RedT2 UltimaDork
9/4/19 10:05 a.m.

In reply to WonkoTheSane :

I hear ya!  The stock primaries were sent to RC Engineering for cleaning just 16 years ago.  Secondaries are 750cc, new from RC Engineering, also about 16 years ago.  LOL.  I think I have a freshened set of factory primaries here on the shelf.

WonkoTheSane
WonkoTheSane SuperDork
9/4/19 10:12 a.m.

Only 16 years ago?  That's still practically new! 

Mazdax605
Mazdax605 UberDork
9/4/19 10:41 a.m.

I'd atf it, and then flog it. You might get some carbon to come loose, and the compression comes back a little. Rotaries don't like sitting. 

Brett_Murphy
Brett_Murphy UltimaDork
9/4/19 11:00 a.m.

Sounds like the seals are a bit sticky. An ATF or other detergent bath with a 24 hour soak followed by high RPMs repeated a few times is stage one, rebuild is stage two. Selling me the car, as it sits, for $500 is the easy button.

EvanB
EvanB MegaDork
9/4/19 12:18 p.m.

In reply to Brett_Murphy :

I'll offer $600 as it sits. 

1988RedT2
1988RedT2 UltimaDork
9/4/19 2:08 p.m.

Haha.  Not really looking to sell at this point.  I even have a spare engine and transmission from a parts car I had years ago.  Sold the roller to a guy looking to do a V8 swap.  I might have to pull down the spare engine and see what kind of shape the rotor housings are in.  I know it popped an apex seal, though, so it's likely to be ugly.

Heck, I got at least $1000. for the roller, and that was like a dozen years ago.  These things are getting pretty scarce, and this one is nice.  Don't see many with the leather interior.  Original paint.  Just a few small dents and scratches. 

Knurled.
Knurled. MegaDork
9/4/19 2:27 p.m.

I hate to mention it, but... are you using coolant?

 

Symptoms are a lot like a coolant land that broke out and is allowing coolant to leak in to one rotor overnight.

 

Or you might just have a leaky injector, which was also an incredibly common problem when these roamed the earth in greater numbers.

Knurled.
Knurled. MegaDork
9/4/19 2:28 p.m.
Brett_Murphy said:

Sounds like the seals are a bit sticky. An ATF or other detergent bath with a 24 hour soak followed by high RPMs repeated a few times is stage one, rebuild is stage two. Selling me the car, as it sits, for $500 is the easy button.

Ack!  No!  The ATF thing is to pickle an engine for several months after you pulled it out of a junkyard.  Anything else does little more than reduce the local mosquito population.

Mazdax605
Mazdax605 UberDork
9/4/19 2:46 p.m.
EvanB said:

In reply to Brett_Murphy :

I'll offer $600 as it sits. 

$601

Brett_Murphy
Brett_Murphy UltimaDork
9/4/19 4:20 p.m.

It sounds like it is set up a lot like my '87 was. 

Knurled's way more current on rotary things than I am, but I did have luck getting slightly stick engines behaving better using a briefer ATF soak and high RPMs. It could've just been the high RPMs and fresh gasoline that did most of the work, though.

1988RedT2
1988RedT2 UltimaDork
9/4/19 6:27 p.m.
Knurled. said:

I hate to mention it, but... are you using coolant?

 

Symptoms are a lot like a coolant land that broke out and is allowing coolant to leak in to one rotor overnight.

 

Or you might just have a leaky injector, which was also an incredibly common problem when these roamed the earth in greater numbers.

That's a darn good question.  I haven't messed with coolant since I replaced a hose near the oil filter a couple years back.  I know it has a buzzer that goes off if the level is low, and it's not buzzing.  Probably due for an oil change and a coolant change and every other darn fluid change at this point.

clutchsmoke
clutchsmoke SuperDork
9/5/19 2:53 p.m.

In reply to 1988RedT2 :

And while you're in there might as well throw some fresh spark plugs in. Rotaries love fresh plugs.

1988RedT2
1988RedT2 UltimaDork
9/5/19 2:58 p.m.

In reply to clutchsmoke :

Yeah, I checked the leading plugs when I did the compression check.  They look fine.  Dry.  Just a hint of light brown deposits.  They probably don't have 1000 miles on 'em.

 

fidelity101
fidelity101 UltraDork
9/5/19 3:00 p.m.

sounds like the housings are worn out if your compression dipped to the 80s. I usually run my cars until the 70s comp wise, Pete is in the realm of 35psi is fine if i hold the rpm at 3000rpm stoplight okay shennanigism but it sounds like regular old wear is contributing. 

 

If you want to get wild, remove the turbo/exhaust entirely. spin the engine over by hand until the apex seal passes the exhaust port and spray seafoam at the apex seals and work them in and out with a rubber mallet or piece of wood, that should let you know if they are free or not, maybe any visible rotor damage too but with what you described I find that hard to believe.

 

also to piggyback pete, wonder if you got a pinhole coolant leak? I dont think its far fetched but not much you can do about it unless you wanna rebuild it and have it last another 16-20 years :)  

1988RedT2
1988RedT2 UltimaDork
9/7/19 9:15 a.m.

Prolly should start a new thread but I'm hoping I can get a couple rotary enthusiasts to pop back in here.

What oil do you run in your rotary? 

I've always used 20W50 as that was what a bunch of rotary forum individuals were touting in the early 'oughts.  Now I'm wondering if that's not a good thing.

OMP presumed working.  I checked it back a while ago and it was working.  I've added some TCW-3 2-stroke oil if I knew I was going to be beating on it, but I haven't been consistent with it lately.  Honestly, it only gets filled up a few times a year.

So what engine oil for hard use?

Much benefit to changing the gearbox lube to synthetic?

TheRX7Project
TheRX7Project HalfDork
9/7/19 10:05 a.m.

I know everyone says to run 20W50 but I have been running 10W40 for over a decade, with a beehive(!) and even with plenty of abuse (even a few times getting it "hot hot") it hasn't done anything wrong.

As for your original post, check the compression. Watch your coolant level (mine eats a little coolant over time like was mentioned). Go beat the snot out of it for a day (it will appreciate it). The fact that you're having some hot start issues points to either compression or leaky injector.

1988RedT2
1988RedT2 UltimaDork
9/7/19 10:56 a.m.

In reply to TheRX7Project :

Thanks for the reply!

I remember when I first got the car, hot restarts were terrible.  I added the little fuel line pressure bleed-off dealie and that helped a little.  It got much better after the Haltech install when I cleaned the factory primary injectors and added the new bigger secondaries.

Yes, the compression is marginal.  I may take it out right now and give it some exercise.  It's probably just feeling neglected.

Knurled.
Knurled. MegaDork
9/7/19 11:01 a.m.
fidelity101 said:

sounds like the housings are worn out if your compression dipped to the 80s. I usually run my cars until the 70s comp wise, Pete is in the realm of 35psi is fine if i hold the rpm at 3000rpm stoplight okay shennanigism but it sounds like regular old wear is contributing.

 

My general opinion is if it starts, it's good.  I have had 12As that read 25psi that started and ran just fine.

 

I have also had 13Bs that read 60psi that did absolutely nothing below 4000rpm because of how worn they were, and a 13B bridge that had difficulty starting when ONE rotor face was under 60psi, so... it depends?

 

Also piston compression testers suck.  Beg or borrow a genuine Mazda or Mazda style tester.  Or buy a Pico compression adaptor and a Pico scope and scope the compression that way, if you want to spend a thousand+ instead of a couple hundred bucks.

 

Knurled.
Knurled. MegaDork
9/7/19 11:07 a.m.
1988RedT2 said:

Prolly should start a new thread but I'm hoping I can get a couple rotary enthusiasts to pop back in here.

What oil do you run in your rotary? 

I've always used 20W50 as that was what a bunch of rotary forum individuals were touting in the early 'oughts.  Now I'm wondering if that's not a good thing.

OMP presumed working.  I checked it back a while ago and it was working.  I've added some TCW-3 2-stroke oil if I knew I was going to be beating on it, but I haven't been consistent with it lately.  Honestly, it only gets filled up a few times a year.

So what engine oil for hard use?

Much benefit to changing the gearbox lube to synthetic?

Oil viscosity is hard to determine if you don't have a mechanical pressure gauge so you can monitor your hot oil pressure.

 

I usually run 15W40 because that is what you can get in gallon jugs for $9.99.  But that is mostly because I change my oil every 800-1000mi or so due to fuel dilution.  Not as much a problem if you still have a stock port and a functioning crankcase ventilation system.  I have been trying to run (the cheapest) 20W50 that I can, but I also have heavily ported oil passages into and out of the oil pump, which mitigates the pump cavitation issues that can happen at high RPM with thick oil.

 

When I played with carbed 12As, I usually ran 5W20 because it got better fuel economy.  On the other hand, I also didn't have an oil pressure gauge, and stockport 12As don't make enough power to hurt themselves.

 

Basically the main things for using high viscosity oil are if you are expecting very high oil temps, or if you need to deal with heavy fuel dilution.

1988RedT2
1988RedT2 UltimaDork
9/7/19 1:20 p.m.

Well I just took her out for a romp, and she still pulls like crazy.  On cold start, there was just a short period of rough running until she smoothed out.  I took my new neighbor for a short ride.  He's a twenty-something engineer with a crazy sport bike modified for racing.  He really enjoyed the car.  Remarked at how smooth it was ripping up to redline.

I know my fuel map is pig rich under load, so I do suspect a considerable amount of fuel dilution.  In reviewing Mazda's recommendations, it seems 20W50 is the right oil.  I don't drive the car unless it's like 60 degrees.

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