Red_Vette_93

I have a 93 with 94K miles. Car runs fine until the it gets hot, like moving slow in traffic. It will stall out, start right back up and do the same thing until it gets cooler. I have plenty of power when its cool. I have read some threads where it might be the temp sensor, anyone else have similar problem?
I don't think its a sending unit or opti as the car runs fine at lower temps.
Thanks

JimLentz

Any codes?

Red_Vette_93

no codes. I'm thinking since I got headers and the fuel filter is up front that when the engine gets hot the gas is too. going to change filter and get some heat wrap to put around it.

aklim

That is kinda old school where they were worried about vapor lock, carb not set right, etc. I have headers too and I don't think that is really an issue. Have you checked ignition and fuel pressure? Are you SURE that the wires are not leaking? Are the plugs good? Is the fuel pressure right at KOEO? Is it right at WOT? Before I start worrying about heated fuel, I'd check those things first.

If you think it is a temp sensor, scan it and see what the ECM thinks the temp is when it is cold and as it gets hotter till it reaches steady operating temp. Check what the sensor is doing by hitting it with an IR thermometer. So if the sensor is within a few degrees of what the ECM says, that part is good. Still, your pressure and ignition has to be good. Not sure if your injectors are Multec but I am suspicious of them getting problems when hot.

Red_Vette_93

plugs and wires were replaced couple years ago all GM, I don't think its fuel pressure or ignition because car runs fine until it gets real hot. Drove it today and temp didn't go above 185 no problems. I guess I could get a pressure gauge and check fuel pressure. Don't have a scanner or access to one so I am kind of limited to what I can do. unless there's someone in SE michigan that wants to give me hand with one.

aklim

Doesn't mean it is good today. Always test when you are having issues to rule out things and not guess.

Check the fuel pressure when you turn the key on without cranking. See if it holds pressure for a while. See what happens at WOT and especially if it will deliver when hot.

I think you are going to buy one sooner or later if you want to do diagnostics so why not now?

Do you have multec fuel injectors? They could be causing problems when getting hot?



If they are Multecs, the ethanol will kill them sooner or later so might as well dump it today for ethanol resistant ones so you can fuel up anywhere you want and not be limited to a few places that are "do or die".

auggy

On the subject of vapor lock, check your gas cap. You should feel a rush of fumes come out as you open it. If not then the system is no longer under pressure and this makes it easier for a vapor lock to occur. Letting out pressure too quickly in hot conditions will allow the fuel to boil and form a temporary vapor lock. This has happened to me on my 94. You just might need a new fuel cap. BTW don't be smoking when you do this.

aklim

IDK about the 94 but I have run cars without the cap on. Most I got was a code. On the 91,i did not see anything on the scanner indicating a lean or rich condition

Red_Vette_93

First of all I definitely get the fuel Vapors coming out when I turn the cap. Second just got done doing fuel pressure check 36 pounds at idle, pressure goes up or down a couple of pounds depending on how much throttle it is given. Let the car warm up once it got over 210 degrees started to have a bogging issue with the accelerator. Didn't drive it because I still had everything taken apart. Could be the fuel injectors like it was suggested

aklim

So do I but I don't think it changes anything.

Again normal. What I am trying to see is if the pressure holds or not and whether it maintains pressure after the shutdown and at WOT.

Which ones do you have?

Red_Vette_93

Pressure barely moved when I gave it gas. And when it was turned off I let it sit for about 5 minutes in the pressure didn't change. I have multic injectors

aklim

Don't care. What happens when you turn the key on WITHOUT cranking is it pressurizes for 2 seconds. After that the pump stops. That is the pressure that we need to see so we know it can get up to a minimum of say 43 psi which is what the regulator is rated for. After that, if you shut it down, you are trying to see if the regulator will hold pressure for a while. It should have some bleed off after say a couple of hours but not much. That confirms that the regulator is holding the pressure as it should. Next step is to run the car and when it does this, check pressure so you know that at idle and with the hose off, it DOES have 43 psi. Put hose back, do a WOT and see if the pump, WHEN THINGS ARE HOT, can deliver or not.

Multec injectors should be thrown away even if they are good since they limit you to pure gas only fills. Sooner or later, if it hasn't already, it will die off since they are not built for ethanol. FIC should have replacement injectors.