Hard start when warm

[Robertwav1]

For some reason when I changed the fuel filter on my 93 the car is hard to start when it's warm. I noticed this as of last year. Cold start is immeadiate always. What changed? 70K, performance and gas mileage excellent, around 24.1 average, mostly highway. I don't smell any fuel at any time. It just tkes 3 or 4 seconds to start when I'm using the car. Input or ideas on what to check would be very much appreciated.

 

[MPoore]

I doubt the fuel filter has anything to do with it. On cold start, the ecm adds fuel to encourage the engine to fire. On warm start, extra fuel isn't necessary. Since the performance/mileage is good, then things like plugs, wires, and injectors should be fine.

I would check the temp sensor. If the temp sensor thinks the engine is cold when it is hot, extra fuel will be added unnecessarily and could cause a flood condition that needs to be cleared with extended cranking.

Mike

 

[Vettefan87]

Three or four seconds is not bad. Sometimes my car when it sits overnight will start, and stall, then run fine. Could it just be age??

 

[Robertwav1]

Well thanks for the input on this. I going to check that temp sensor like you said....it makes a lot of sense. I really don't think it's age cause like I said, this thing fires almost immeadiately, even if it sits for months at a time. Just those damn warm starts. Which sensor to check....coolant temp sensor? Intake air temp? engine temp (gauge overheat)? this last one says it's not ECM connected??? I only have a haynes manual. Thanks again.

 

[WhalePirot]

....coolant temp sensor?

That one.

 

[tigmaned]

sorry for brining back a old thread, but i was wondering what ever happened with your hard warm starts??

 

[PLRX]

Three or four seconds is not bad. Sometimes my car when it sits overnight will start, and stall, then run fine. Could it just be age??

This is accurate, it happens to my CORVETTE and it happened to my first. Maybe it needs a good engine rev on the freeway to clean itself from air filter to mufflers.

 

[Robertwav1]

Well, I had a code in the computer, 43 which is the knock sensor. Replaced it and so far, no more codes. Replaced the "Coolant Temperature Sensor" and seemed to make it less then 3 seconds when warm. So...that's where I'm at. I guess the only other thing is to replace the Opti.....but I'm not ready to do that just yet. Thanks!

 

[Vettefan87]

Maybe it needs a good engine rev on the freeway to clean itself from air filter to mufflers.

Oh, believe me, I burn out any carbon deposits that could be in my motor, every time I drive it.

 

[PLRX]

Oh, believe me, I burn out any carbon deposits that could be in my motor, every time I drive it.

Vettefan, there is no other way!!! Cheaper than fuel injector cleaner too.

 

[Vettefan87]

Vettefan, there is no other way!!! Cheaper than fuel injector cleaner too.

Yeah, the only bad thing is my mother, or anybody else at my house can hear me when I leave the gas station down on the corner about a mile from my house....Damn muffler eliminators.

 

[tigmaned]

robertwav1

so you changed the temp sesnor on the engine block right, i'll have to look for mine on my L-98?

 

[Robertwav1]

Yes, it was actually mounted on the front of the engine, up top near or on the water pump housing. I bought the sensor first, now I know what it looks like. It looks very close to another sensor mounted between the back spark plug ports on the passenger side but, the wrench size is different and it doesn't have the brass nut and thread like the one in my hand. The knock sensor is easy after removing a plate protecting it from the heat of the cat. LT1....gotta love that engine.....guess I'll get on it a little more and clean it out like suggested. Thanks all!

 

[tigmaned]

so did changeing the coolant temp sensor help??

 

[Tuna]

A few years ago when I had a 96 LT4, it was hard to start warm also. It turned out to be a faulty check valve in the fuel system that was allowing the fuel pressure to drop to zero as soon as I shut down the motor.

How's your fuel pressure after shutdown?

 

[Robertwav1]

Well, it doesn't seem as bad but, still not right. I guess as Tuna suggested I'll have to check the fuel pressure after shutdown. Why does it start up within a half a second when the car sits for a weeks? 3 seconds when it's warm. I would think a faulty check would be even more the culprit on a colder longer standing engine. :confused

 

[Vettelt193]

Try turning the key to on without starting... let the fuel pump fully run, then crank. If the car takes longer to start, you probably have a leaky injector or something along the lines of too much fuel. If it starts easier, you don't have enough. Try this a few times with different conditions to see what happens...

 

[tigmaned]

the service manual should tell us how long a certain fuel perssure should remain right.

 

[Robertwav1]

I did try the key thingy...it didn't make a difference. I do have to check the fuel pressure....It should tell me if an injector is leaking slightly causing a flooding condition. This would explain after the car sits for a week or two, it starts right up. I guess the excess fuel would evaporate in this much time. Why do ya think?

 

[tigmaned]

o.k. i tried the pedal to the floor after she was wram and it still didn't start right up like she dose after shes sat over night or in my casr a few nights. i am going to try the temp sensor since it was only $14 bucks.