starts hard when warm?

[cry4me_sky]

Hey guys you've helped many many times before maybe you can again.

So my 90 7mgte starts up great from a cold start. But, when i start it up while the engine is already warm, like after going to a restaurant and coming back to my car, it acts strange.

The idle will sort of sputter, and go up and down, if i rev the engine for a bit it evens out and runs fine. If i dont it dies, sometimes it sorts itself out.

Usually it bouces around between 500 and 800 rpms when it is doing this.

I was just wondering if this is a symptom of somehtin serious i should be worrying about, or if there is an easy fix for it.

thanks a lot.

 

[omfgitsdonovan]

correct me if im wrong people but dont some of the supras get heat soaked it called i beleive?

 

[cry4me_sky]

nothing at all?

 

[kikdurazz]

Sounds like Heat soak. No real fix and no real harm.

Heat soak, from what I remember is when the fuel inside the injection rail vaporizes or otherwise becomes too hot to burn or run consistantly through the injectors. It will cause some stumbling if the engine is hot on start up. Hot intake temps plus fuel that has been heated up in the rail=bad idle until you get a cooler charge of air through the intake and a more consistent spray of fuel through the injectors. That's why the idle usually clears in about 30secs to a minute if left to idle before trying to take off.

This is why best to let the car idle for a few minutes after parking so the temps will drop. this doesn't mean that it can't happen. things get hot under the hood of turbo cars so it can be hit or miss.

 

[cry4me_sky]

Great. Thanks a lot man!

 

[GrimJack]

Might check the FP VSV under the front of the intake manifold, too. If it's fried, it will make this kind of problem worse.

 

[92nsx]

is you vsv for your fuel pressure regulator working correct and hooked up? The VSV is what toyota installed to prevent heat soak.

EDIT: I see that GrimJack can type faster then me. lol

 

[jdub]

I don't suppose you have any ECU codes do you?

It's highly unlikely it's heat soak.

 

[cry4me_sky]

I don't suppose you have any ECU codes do you?

It's highly unlikely it's heat soak.

no i haven't thrown any codes. So idk, any tricks for testing the vsv, or directions to where it is lol. Sorry I know it's sad, but i still don't know my car inside and out yet...

 

[GrimJack]

I forget whether it's open or closed when starting hot, to be honest. It's in the TSRM, of course, or you can just jimmy it - try pinching the vacuum line to the FPR when starting hot, see if it starts normally.

 

[Rennat]

yeah i never have this problem. its a problem, so find the cause and fix it.

 

[jdub]

I forget whether it's open or closed when starting hot, to be honest. It's in the TSRM, of course, or you can just jimmy it - try pinching the vacuum line to the FPR when starting hot, see if it starts normally.

When coolant temp is greater than ~100 deg C, the ECU signals the VSV to open to the atmosphere. This increases fuel pressure...the same as if you removed the vac line from the FPR.

The surging idle is the real problem here

 

[cry4me_sky]

sorry for resurrecting my old thread but i may have found the issue.

A while back i installed a turbo xs bov i bought used from somone here on sm. This type of bov, unlike the Greddy bov, doesn't need to be put into piping and installed. It just replaces the stock one. The stock bov circulats back the the (accordian?) pipe inbetween the maf sensor and the turbo. The new bov is atmospheric.

So i had to plug the hole in the pipe with a distributor cap as recommended by someone on sm. It worke fine for a while, but upon checking the other day i noticed that the rubber was cracking around the hole with the cap and was NOT airtight. I Didn't have the 60 bones for a new one from toyota so i sealed it up myself and now it is working just fine. It appears to be spooling a little faster too, but that might be my wishful imagination.


So does that soud like what the issue must have been?
After christmas when i have money again i'll probably go buy that pipe from toyota depending on how well my seal is holding up.


thx again guys.