87 Turbo Supra rough engine problem
 

I have a 87 Supra Turbo that I owned for 18 yrs. It went thru a few head gaskets and finally stopped after using a HKS metal one. Recently I have a weird problem. The car runs flawlessly when started cold but if I stop the engine and restart after a few minutes it runs rough with symptoms consistent with missing a cylinder, BUT after isolating by pulling each spark plug wires indicated that isn't the case.
Each time this happens is after stop and restart. If I continue driving during the first start I would have no problem for as long as I don't turn off the engine and restart. After the engine cooled completely it goes back to normal. Temp is normal, so is everything else.
Any fellow Supra owners out there has any suggestions is greatly appreciated.
Fred
fkat668@gmail.com

Thank You Bill
 

I'll start looking into it. The funny thing is this problem never happened in my 19 yrs of ownership of this Supra until lately, and the roughness (thru the entire rpm spectrum, not just idle) won't start unless I stop the veh. I can be driving or idling for as long as I want w/o problem from the cold start.
Fred

Tried it, not heat soak
 

Hi BIll,
I tried it yesterday and it's not heat soak. I drove it a few miles, stop the engine, open the hood all the way up, waited 20 min and restart the egine, same thing. Then start again after 1.5 hrs, egine was just barely warm, still rough. It has to cool down completely hrs later before it'll go back to normal. This is very puzzling.
Thanks for the useful link though, it covers lot's of other other issues.
Fred

I have the same problem.
 

Hey, I have the exact same problem (missing cylinder) in my 1986.5 supra it has been there for a few months. I've had it in the shop for 5 weeks and they can't figure it out. Please let me know if you figure it out and I will do the same for you. Thanks!

To clarify further...
 

The problem started as the weather started to heat up (Jackson MS). It started when I would drive my supra (running great) warming it up then park it, not letting it cool all the way. When I would go to start it, it would seem to be missing in one cylinder and the miss would stay there till i parked it and let cool all the way down (hours). After a few months (and it getting hotter outside) A few times it has been running on 3 cylinders but that has not persisted or happened in over a month. Now sometimes it runs great sometimes one cylinder goes in and out while driving and sometimes it exibits the classic symptoms ie (see italics above). I brought it to a good shop(in my opinion and experience) they put new spark plugs and wires on it first, that did not fix it. even thought they said that the missing was from time to time alternating cylinders they tried putting in a new fuel injector in the cylinder that was primarily missing.

The shop said that it had fuel fire and air and that there was no reason it should be missing.

The shop said they checked the fuel and put a new distributor cap on. I'm sure they checked many other possible issues.

When I got it back from the shop I decided to look into the ignition coil I took basically the same one off a 1987 cressenda and put it on the supra when the supra was doing it's stalling thing, but it made no difference.

The only things that I could think of that It could be would be maybe the distributor it's self, the ignitor, or the power transistor in the ignitor, but my guess is that the shop ruled all those potential problems out along time ago.

the car has 50,000 miles on the engine and has great compression in all cylinders.

Help me if you can Please.

Supra rough running problem
 

My Supra's missing problem persisted for months, my mechanic finally figured it out, it was the EGC valve stuck closed, or open, one or the other (It's been awhile, I forgot which one). The reason it was so difficult to diagnose was because all symptoms points to a missing cylinder but it's not. Try replacing the EGC valve, it's a cheap item. Let me know if it works.
Suprakat

Thanks!
 

Hey thanks for the reply! I hope that that will solve the problem. I just wanted to verify that it was the Exhaust Gas Recirculation (EGR) valve not EGC valve? And do you know if he cleaned it or replaced it? Thanks!

Egr
 

Yes, I think EGR is what it was. And I believe he just clean it out. It's been several month since then, I have no more problem.