Engine Run-on Issue

[gottadiesel]

I have an issue with my 88 7m-gte. The engine runs-on after shut down (key is turned off) It does not sound like dieseling... issue with build up on pistons... I have had cars with that issue and it sounds rougher than what this is doing and from my experience, sounds like it wants to or does backfire when done dieseling, this does not sound that way, although a couple of other things point to it, one is that if I start up when cold and shutoff after a few seconds, it does not have this issue, but after normal op temp it does have this issue of run-on. But in case it is build up I ran through the cleaning process with seafoam 3 times back to back and no change.

I bought this car just a couple of months ago and only put 70 miles on it prior to pulling into garage to re-do interior, replaced turbo, ex man gasket, numerous seals, gaskets and vacuum lines on the top end, along with cold air intake and pipe from intercooler to throttle body etc...

I do not recall this issue when I bought it, so it begs the question, did something during this process. I assume the supra has a pressure control valve for fuel, I assume it could cause this issue, if there is still a lot of pressure behind the injectors that should not be there…
Anyway I am still digging, but thought if anyone has had the same issue, I would appreciate any feedback.

 

[JDMMA70]

im a little confused with what you wrote

~JDMMA70

 

[theKnifeArtist]

gottadiesel has an 'Engine Run-on' thread!



haha

 

[gottadiesel]

Yea I just saw the irony in that one LOL... I've got a Jetta TDI diesel and a Dodge Cummins... hence gottadiesel which started as my username for forums on those sites...

For the one confused... basically I shut key off and engine runs for anywhere between 2 seconds and 7 seconds before giving up, but seems to run smoothly but at low rpm like starving for fuel...

 

[jimi87-t]

Isn't this usually caused from improper timing of the cams?
The first thing I would check would be to see it the cams are timed with the crank @ TDC.
And then recheck ignition timing.

EDIT: BTW, when checking TDC, make sure the crank pulley is accurate. Ours has a tendency to slip, so check that the #1 piston is actually at TDC.

 

[gottadiesel]

I know that can certainly be an issue, but I guess I was still on the fact that i did not remember it going that when I bought and drove home, but as you mention, in the process I did find some corroded wiring from the cam position sensor, could this cause an issue if it is not reporting accurately.

Then again I am back to that it does not do it when cold, wouldn't timing issue show up regardless of Engine Temp?

 

[dumbo]

Don't you need fuel to have a run on problem.(BTW That is a pretty priceless name now)

Could your CSI be leaking, or any of the other injectors? Plus your engine needs to have hotspots, or running be running too hot doesn't it?

Couldn't hurt to check your codes either.

 

[HitmansEVO]

I do know the TSRM mentions this problem in the troubleshooting section.. I believe it said it was related to fuel injection. I'd post the link to the page, but i'm short on time right now.

 

[djazem1]

yo hes lucky man he has a built in turbo timer....just figure out how to adjust it for about a minute or so lol

 

[gottadiesel]

Yea I have the TRSM all printed off, I did not see that in TS area, but I will check again... But I am thinking it has to be in fuel injection somewhere...

As it is running very well otherwise, idles smooth, acceleration is smooth, might be lacking power a little, but is does have 124k on the motor, although do not know its history...

Still in the middle of moving, which this car was in the garage, so had to hurry to get it back on the road, but that also means most of my tools are still buried... but I was planning to pull plugs not that I have about 300 miles since running again and see how they are looking and also do a compression check... not that it would have to do with this issue, but anyway rambling...

I start to check for bad injectors, bad spray patterns, see if I can get a micro snake light to see top of pistons

also not familiar with acronym CSI, please spell out so I know what type of control system you are referring to...

Thanks again.... and yes I know will never live down the name now... oh well such is life...lol

 

[dumbo]

"Cold Start Injector"

I would follow the TSRM, and start with the CSI and then check the other 6 primary injectors to see if they are leaking.

You may have high compression if you have lots of build up in the cylinders, that may help burn any "dripping" fuel from a leaky injector.

But I would start with the injectors, and a thought might be to check your FPR if fails and FP goes to high may cause leakage, but thats just an educated guess, someone should be able to confirm.

 

[HitmansEVO]

Yea I have the TRSM all printed off, I did not see that in TS area, but I will check again... But I am thinking it has to be in fuel injection somewhere...

I'll save you some time:

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=EM&P=5

It was in the engine mechanical section. It's not very specific, though.. all it says is to check the EFI system. That's a bunch of checking.

 

[gottadiesel]

Thank you to all! - Very helpful in speeding up the process... As soon as I get my stuff unpacked... tools anyway (just moved) I will check into this issue further.

Thanks Again :icon_smil

 

[Mikek3]

its deiseling, and the fact that you say it sounds too smooth to be deiseling suggest that it is all the injectors are leaking(usually the dieseling is only a few cylinders causing the roughness) which would lead me to believe that it is a CSI or FP issue cause i doubt that all your injectors are leaking

hope this helps