hard to start when warm

[mjtr21]

i have a 99 GT and i am having problems starting the car when the engine is warm. there is no problem starting when its cold. but if i go to start it when its already warm, it will start then shut off. sometimes if i get lucky it will stay started but idle will jump up and down, like its going to stall. idk what to check. i already replaced the IAC valve so that cant be it. im stuck.

[Airjer_]

Does it seem to take longer to start when its warm? cranks longer then starts then stalls?

Check the pressure regulator and make sure it is not leaking.

Unplug the MAF and see if it starts easier.

[mjtr21]

okay well its starting to get worse. when i go to start the car it turns over for a couple of seconds then finally starts. and sometimes it even shuts off after it starts. but if i push the gas pedal or put it in gear, it will stay running. does this sound like a bad fuel pump? what are other symptoms i should look for for a bad pump?

[3100]

if your idle is jumping up and down and then shuts off, check your Oxygen sensor.

[3100]

sorry for some reason it did not allow me to edit my previous post, but just wanted to tell you that in this case you will not have any codes. I am 100% sure that if you replace O2 you will be

[mjtr21]

yeah im not getting a check engine light or anything. so your saying that if i replace an O2 sensor it will fix this? yeah but which one?

[xeroinfinity]

I wouldnt go wasting you money on an O2 sensor just yet!

How old is your air filter and fuel filter ??

I'd also check your engine grounds, and the ignition system connections. How old are you plugs and wires ?

When was the last time you cleaned your TB and IAC ?

[3100]

Check what Xero said but if you never replaced your O2 before and you have more than 60K replace it anyway. So you need the AF 02 sensor. Right behind your cylinder #3 on the exhaust pipe. You will need the special socket. Sensor is $58 at Auto zone (Bosh).

[3100]

Xero I think that if it was the grounds he would have the problems all the time not just when the engine is warm. IAC was replaced from what I understood. I still say AF 02 replace it and get it over with .

[3100]

Originally Posted by mjtr21

yeah im not getting a check engine light or anything. so your saying that if i replace an O2 sensor it will fix this? yeah but which one?

Just to double check disconnect your AF 02 when you try to start it next time with warm engine, if you don't have the same problem then you know it is AF O2 repeat this 2-3 times just to be sure. I wanted to edit my previous reply but it is not working.

[xeroinfinity]

How about testing the O2 sensor to see if its bad before wasting money on it.

My 99 SE had 198000 miles on both and worked fine up untill that point.

[mjtr21]

well my air and fuel filters are only a couple months old. and yes i already stated in one of my first posts that i replaced the IAC and cleaned the airways.

[3100]

it is called an OXYGEN SENSOR,!!! obviously you don't have much skills or experience to do it yourself, so just take it to a shop and pay 5 times more

[mjtr21]

hey asshole. dont tell me that i dont have much experience. i was answering XERO's questions because he asked if I changed the air and fuel filters. i am not getting any hesitation or anything relating to a bad oxygen sensor. no service engine light either. so i dont see why i should go and replace them.

[3100]

You probably used a lot of injector cleaners, upper intake cleaners etc, if you connect your car to good scanner you will notice that your cross count is higher than necessary about 13 and it should be about 4-5 for GA 3.1 that is where the problem is, I told you how to check disconnect it and drive your car for one day with disconnected sensor and come back here and tell me what happened Ok....

go on junk yard they remove 3-4 sensors they will usually give them to you for free, try one or two and see the difference, if you do not see difference come back here and say that I was wrong