Heat soak issue

Hello all, my name is Eric from Montana, USA. I have a '93 3000GT VR4 with 148k miles. Full stock, no mods except a K&N air filter. Car runs perfectly . . . except it’s been developing the dreaded heat soak issue.

When hot, then stopped let sit for 30 min. - really hard start and sputter until it revs enough to cool, or get cooler gas through. Then runs perfectly again. This problem has progressively gotten worse over the last few summers.

I’ve searched all the forums - everything from heat wrapping the fuel lines to replacing various sensors - has anybody definitively found the source of this issue in our cars?

We know, with the engineering that went into building these - it was most certainly not an original defect. But something that must happen over time. For anyone who has figured this out, advice would be much appreciated! Thanks!

Check your fuel presure at the fuel rails. Had exactly the same problem. After being told repeateadly it was ECU,sensors Injectors etc it turned out, for me, to be the fuel regulator at the end of the fuel rail. Fuel pressure was all over the place.

Hmmm, I have similar issue on mine that it starts up horribly bad when it has gotten up to temperature, but the cold start is more or less instant… 1 crank and it starts up…
I would like to know how to check the fuel regulator??

Replacing the fuel regulator sounds like a good idea. After 29 years of use it looks ancient in there. I’ll give it a shot. Thanks for the tip!

Is it even possible to purchase new ones?? I have not been able to find any online

If not the fuel pressure regulator, check the fuel pump. I have had this problem twice and both times it was the pump getting too hot. You may find that it runs a little better with a full tank of gas.

Thanks Joe! I’ll keep that in mind after I plug that new FPR in. Fantastic videos, by the way. Keep up the great work!

There seems to be plenty of aftermarket options online. My experience has been that OEM is the best choice when possible. New OEM’s are getting harder to find. (Fuel pressure regulator for '93 VR4 is MD322989).

Will try and test that out some by keeping the tank full for a long period of time… I really hope it is not the pump as I do not want to change it… It looks like a bloody nightmare from the video you did

Quick correction guys. The correct part# for OEM Fuel Pressure Regulator for 1st gen TT (mine’s a '93 VR4) is MD164615 (1100 11FO) - not MD322989. Got this number off the original Aisin FPR I just pulled off. Looks like we can still get them at Amayama.

Amayama says that the MD164615 part can be replaced with the MD322989 part… I dont know why it says that there

Interesting. When I ordered the MD322989, they said it couldn’t be shipped. Reason: “production stopped”. They offered MD164615 as a replacement. For my car, this was the same number on the original part.

Thats just odd, but if they are shipping the original part, then there should not be any problem :slight_smile:

Any updates on this problem?

Still working on it. The car runs perfect except for this issue. Replaced the FPR. Didn’t really notice much difference. But it was probably ready to be replaced anyway. I’m waiting for Joe to get some more fuel pumps in. I’m thinking that might be the solution. With 150k on one FP, it’s ready for a new one any way.

I replaced my Coolant Temp Sensor, Fuel Pressure Control Solenoid, Idle Air Control Valve, ran two tanks of injector cleaner through my engine, cleaned my throttle body, and checked my ECU for bad CAPS.

No luck so far.

I found a crack in my EGR tube. I wonder if it may be a vacuum leak causing my problems?

A leak will cause all sorts of trouble

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I had this same issue. After changing my 3 coil packs it was recommended that the PTU be changed also. Got one from Amazon and that was when my issue started. Ran fine after startup but then after 10 minutes the car would cut off no matter how fast or slow I was driving. After awhile sometimes 10, 30, or even a hour it would run long enough to get me another mile or even back home. Changed fuel filter, fuel regulator, MFI relay, and almost changed my faith in God. Much like you I was thinking about the fuel pump but did not want or look forward to tackling that job. Changed the idle control valve and recalculated. Nothing worked. Contacted Joe and tried to purchase the flex fuel line he had manufactured to change the dreaded fuel pump, but had issues trying to ship here to the States. On one of Joes videos he mentioned some of the PTUs brought online were not up to specs as the Mitsubishi OEMs. So I put my old (268,000 mile, 29 year) back in place and have not had that issue since. So glad I was able to save doing the fuel pump for some other year. Good luck friend

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this happened on mine…replaced the ECU Water Temperature Sensor and it was fine for a while …but im told its a ecu problem…when i go stand alone programable this will sort problem…
ecu thinks engine is cold when its hot and over fuels untill you rev it .then its fine…

Replaced my fuel pressure regulator and my hot start problem is nearly gone. But now it starts a little harder than it did before when cold, and will cut out a little during the first few minutes of driving.
I’m thinking maybe all the injector cleaner I have ran through the last 3 tanks has clogged my fuel filter?