02 GT 3.8 warm start issue

2002 GT 3.8 with 108k. The car runs great and only has an issue starting when it’s warm. After the car has run it usually take a couple extra cranks to fire up. Sometimes after firing up it will Rev up a little and stall out. Next crank seems to start the car. Once started no issues remain or are noted while driving. Never has it not started.
I replaced the MAF sensor 1 year ago with the cheap autozone brand when unpluged it starts just the same and runs ok. I also replace the IAC this weekend and didn’t notice any real change. I unplugged the vacume line from the fuel injection pressure regulator and tried to start it. No fuel was noted leaking from it. My next guess is the fuel pressure regulator but I thought it would leak if unplugged and the diafram was broken (read it in another post but not sure I understood it). I also could look into checking the fuel pressure from the schraider value looking for 40 to 50 psi to confirm the fuel pump while the car is running or starting? Basically I am looking for confirmation other suggestions that I am heading in the right directions. Thanks

clean out your throttle body well, the carbon build up on the butterfly plate can cause that issue. good place to start, easy, cheap and it will need it anyways.

replaced the fuel filter and cleaned out the throttle body i believe... by removing the air filter assembly, silver screen, and scrubing the butterfly assembly with choke cleaner to get as much carbon build up as I could. No change in the starting of the vechilce.

2002 GT 3.8 with 108k. The car runs great and only has an issue starting when it’s warm.
When you say when it's warm, does this mean that you can shut the engine off and immediately when you try to start it it's difficult to start, or you have to wait 20 minutes before it's hard to start? You could have leaky injectors if it's hard to start after 20-30 minutes.

When you say when it's warm, does this mean that you can shut the engine off and immediately when you try to start it it's difficult to start, or you have to wait 20 minutes before it's hard to start? You could have leaky injectors if it's hard to start after 20-30 minutes.

It is immediately after i shut it off. It cranks over like it going to start just doesnt always fire right up and sometimes it will fire up and rev up and die. It never seems to happen after the car has sat overnight it starts just as you would exspect.

Have you tried holding the gas pedal down a little and see if it helps?

ravis,sounds like your on right track,check fuel pressure

Ok I decided to double check everything again. Started with the Fuel Pressure Regulator. Shut off the car after my drive home and pulled of the vacuum tube and found fuel. Thought great i found the problem... Ran to autozone and purchases a new one and while i was there did the u-loan on a fuel pressure kit. Got home and decide to swap out the fuel pressure regulator. I bleed the schrader value to relieve fuel pressure. I didn't look at the new one so i unscrewed the screw out of the one on the car then noted the ring so i pulled that and pop the regulator shot out! I guess i didn't get all the pressure out. I then put the new one in and primed the car putting it to start a couple of times. I attempted to start and it just rolled over and over so I gave it some gas and it fired up but dies as soon as the gas is let up. I did this over and over finally giving up. I then decide that it had to be the new regulator. I tried to put the old one back on screwing on the screw on top that i loosened in error. Same thing car will not run with out giving it gas. Getting frustrated i called NAPA getting the OE equipment and replaced the part again. This giving me the exact same issue. The car will start and run with gas but as soon as you let off the car dies.... When my wife got home i put the fuel pressure regulator on and started the car giving it some gas. The reading on it is 49 to 50 PSI when the car is running or off.

So at this time did i find another issue when i swapped the pressure regulator? I tried unplugging the MAF sensor each time to make sure that nothing changed and it didn't. Any suggestions?

Yeah, I'm wondering if it is your Crank Position Sensor. It might be that when it gets hot, it does not work very well. Does it still start in the morning? There are some experts that should chime in here shortly.

Yeah, I'm wondering if it is your Crank Position Sensor. It might be that when it gets hot, it does not work very well. Does it still start in the morning? There are some experts that should chime in here shortly.

Until i swapped out the fuel pressure regulator it would start and run on its on first try in the am. After swapping the fuel pressure regulator it will not start or idel without giving it a little gas warm or cold. It will stall within seconds of letting off the gas. From memory i dont believe the fuel pressure diped when the stall happens.

fuel filter
cleaned butterfly plate
replaced iac
replaced fuel pressure regulator x 2
map sensor (under a year old)
tested fuel pressure (49 to 50 psi)

found another thread suggesting pcv and tps. I will swap them out tonight and see if that makes any difference.

Is there a guide or a picture that explains how to check the vac lines. I read something about spraying carb cleaner on them while the engine run's and it will stall if they are leaking? Just not sure I know were all of them are and if thats correct.

Thanks for the help

Your fuel pressure readings seem OK, to perform a vacuum leak test I would suggest to use a propane torch (not lighted) instead of the carb cleaner (this one corrodes paint and rubber).

Move the propane all across the engine specially near the Intake manifold, when the RPM's go higher you have found a leak, start inspecting the hoses by hand. Every hose that comes out form the throttle body is vacuum, one goes to the FPR, the other goes to the EVAP Purge valve and I think a couple more at the back of the upper manifold, the smaller one provides vacuum to the cockpit for controlling the dash controls.

Have you checked your coils for spark?, I remember someone said that electrical problems show up more often with a warm engine but I've never had an experience with it...

Oscar.

Have you checked your coils for spark?,

Oscar.

I haven't and will do a quick search on how to or is there a simple trick to check them also?

if the old p/regulator was leaking make sure you dont have gas in oil
when regulator was leaking the extra fuel went some where.if you have to
hold gas pedal down,most likely its flooded.do you smell gas??

if the old p/regulator was leaking make sure you dont have gas in oil
when regulator was leaking the extra fuel went some where.if you have to
hold gas pedal down,most likely its flooded.do you smell gas??

I don't smell gas and the oil smells like oil without gas in it from the dip tube... Not sure if that is the best way to tell.

When i got home i changed out the throttle position sensor and the pvc value. I did note oil in the value area but the value rattled when i shook it. I started the car to find it running at 1k rpm then slowly creeping up to 1400 or so. I shut it down and tried again and got the same result. It seems like it starts where it should 800 to 1k then slowly rev up on its on. I disconnected idle and MAF sensor with no change. If i press on the far side were the throttle cable is in it drops to normal idle and slowly creep up again. It feels like the TPS springs are stronger than the throttle springs on the opposite side making it idle higher than required. After they heat up a few time will they start to give a little?

So at this time it seems the car is running again but still has the difficult start so i have made no progress on that... I still need to look into the vac and spark plug issue suggestions above though. Its hard to say but I think there is a whoosh like noise when I shut it off.

Thanks

To test your ignition system disable the fuel pump by removing the fuel pump relay in the fuse box under the hood.

You can buy a spark tester at most autoparts stores or you can disconnect each wire, insert a screwdriver (with a plastic handle in a good state) into the rubber boot of the wire and put it close to a grounded part in the engine compartment (again, grab the screwdriver only by the handle), ask an assistant to crank the engine and you should see the spark jumping between both.

To test your ignition module remove each ignition coil and using a cable tester connect it across both terminals, crank the engine and the cable tester should light up (it may look like it's pulsing, that's ok).

I think I read in the manual that the TPS has to be adjusted when you replace it, I'll take a look at it and will post if there's such adjustment procedure.

Oscar.

Just to let you know there is no adjustment procedure on the TPS, at least none that my manual points to...

Regards,

Oscar.

Started it up this morning and it went strait to 3k rpm. Popped the hood and tried to force it down to a normal idle and it wouldn't. I shut it down maybe 1 minute later and started it again and it started as the day before at 1k and slowly moving up but finally through a check engine code. Drove to work parked it and started again after work to 3k again. Shut it off and started again to 3k... killed it and started again and normal 1k and revved up.

So I through in the towel and stopped at my local shop for help. They called me in the back asking about what I had done. I explained the parts I changed and the order. He looked at the tps and throttle cable and said the he would suggest checking it as it should shut flush and wasn't saying it pointed to a tps or the assembly but he couldn't tell without letting it cool and taking it apart. It being close to closing he said to check it and stop in tomorrow if It wasn't the TPS or assembly. He checked the code for free and said it was a low voltage on the tps? I stopped again and purchased the same part again and went home to swap it out. I pulled the tps out and looked at it this time. If you put it on at 85 degree's you have to force it back to 90 to screw the part on. If you put it on at 90+ degree's you can easily slide it on and tighten. I tried 90+ degrees and tightened it down and started. The car fired up and idled as it should. I really believe the mechanic was trying to tell me i had installed it incorrectly :banghead: in the nicest way possible. Really cool of him to suggest checking it.

So to recap I have done a full 360 and i believe or think I fixed two issues.

First one being the fuel pressure regulator with the fuel leaking after I shut off the car.
Second the throttle position sensor after changing fuel pressure regulator and not running after without giving it a little gas.

I still find the same issue of the strange warm start that began this little trip. Now I am a little ahead. I have swapped out a few thing and I am leaning on taking it to the shop. It always starts just seams to run the starter a couple cycles more that it should. Again any suggestions I will gladly try them. Thanks

It's good to know your TPS problem seems to be gone; I would advise you disconnect the battery for 15 minutes in order for the PCM to reset and relearn the ideal values. I always do it when I replace an electrical component in the engine.

When I replaced the MAF in mine I forgot to do it and it was still idling bad, better than before but still bad; I disconnected the battery and after that everything was fine.

About you starting problem I used to have a similar symptom but mine was when cold. The problem ended up being a bad fuel pump, even when the readings where almost normal after I turned the engine the fuel pressure dropped to 0 within about 30 seconds and that was when I decided to install a new one, so far so good!

Both problems happen under different conditions, but they are similar after all... You should check that too, see how long it takes for the fuel pressure to drop down to 0 after you have turned off the engine.

Oscar.

A bad Intake Air Temperature or Engine Coolant Temperature sensor can cause idling problems either when hot or cold. You should test both by measuring resistance across each one.

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