Warm start problems...

[mvbighead]

If it reliably restarts after you let the fuel pump re-pressurize the system... well... I think that clearly points towards a fuel system related problem. The fuel check valve, fuel pressure regulator, any fuel-related vacuum lines, and fuel pump are good options to investigate. That's where I would start.

Well, that's the thing though... I have never had this problem on a cold start. One would assume the problem would be worse the longer the car has been sitting if it was losing pressure and the fuel was bleeding back to the tank. But instead, I only have the problem when it is warm.

Perhaps my logic is wrong there, but it sounds right in my head.

In all attempts to start the car, I generally just stick the key in and turn to start. I have yet to turn it to the on position, wait any given time, and then turn.

And further, at this point, I have gone through another 3 warm starts (and a cold start) without experiencing the issue at all. That being the case, I suspect that if it was a sticking valve related to fuel, perhaps the seafoam cleared the gunk, and it less likely to stick in the future? That may also explain why it is sporadic. But it doesn't really explain why the problem only seems to occur when it is warm.

All that said, I suppose it is possible that I could experience this problem when the engine is cold, and it just hasn't happened yet. But the two times I have experienced it, the engine had recently been running about a half hour prior to the next attempt to start it.

As I drive it more, hopefully I can provide more detail.

 

[JCH13]

Well, that's the thing though... I have never had this problem on a cold start. One would assume the problem would be worse the longer the car has been sitting if it was losing pressure and the fuel was bleeding back to the tank. But instead, I only have the problem when it is warm.

Perhaps my logic is wrong there, but it sounds right in my head.

In all attempts to start the car, I generally just stick the key in and turn to start. I have yet to turn it to the on position, wait any given time, and then turn.

And further, at this point, I have gone through another 3 warm starts (and a cold start) without experiencing the issue at all. That being the case, I suspect that if it was a sticking valve related to fuel, perhaps the seafoam cleared the gunk, and it less likely to stick in the future? That may also explain why it is sporadic. But it doesn't really explain why the problem only seems to occur when it is warm.

All that said, I suppose it is possible that I could experience this problem when the engine is cold, and it just hasn't happened yet. But the two times I have experienced it, the engine had recently been running about a half hour prior to the next attempt to start it.

As I drive it more, hopefully I can provide more detail.

The thing about hot-starts is that they use considerably less fuel (10-20% enrichment) than a cold start (200%-300% enrichment) thus the concern that maybe it's going too lean on a hot start.

Try priming it with the key (I thought you had, oops) and do a visual check of all the vacuum lines you can possibly find.

 

[phucheneh]

I think cleaning the throttle is a good (and easy) start. Another random tip that comes to mind: Be careful tightening the bolts...both intake and throttle are going to be relatively soft aluminum, and the bolts are not supposed to be terribly tight. Using a new gasket (cheap insurance against a leak) helps this, as they usually have raised areas meant to crush while torquing the bolts. You'll want do it corner to corner, like a wheel, and tighten in small increments.

Agreed that you should try letting the fuel pump prime. Even cycle the key more than once. Might not be conclusive with an intermittent problem, but with enough starts you should get enough of a 'data sample' to guess if it does anything to help or not. I'm still betting on 'no,' but it is not outside the realm of possibility (...cars do some weird shit). For comparison, you need to try sticking the key straight in and starting the engine with no delay...don't let it sit in the 'run' (forward) position, go straight to crank. A good fuel system really shouldn't need the prime at all- it should hold most if not all of its pressure for a pretty long time. The 'priming' function is (supposed to be) more for if the car has been sitting overnight. Or longer. And even then, it's not meant to compensate for a complete loss of pressure in the line (as happens with bad regulator and check valves).

And again, if you don't mind...how many wires are on the EGR valve connector?

 

[LTC8K6]

The most common solution seems to be to step on the gas pedal lightly to get it to start when the engine is warm/hot.

The cases I have read about on the net, they never found the cause or the cure, they just adapted to the condition.

 

[phucheneh]

The most common solution seems to be to step on the gas pedal lightly to get it to start when the engine is warm/hot.

The cases I have read about on the net, they never found the cause or the cure, they just adapted to the condition.

That, especially coupled with the OP's complaints, sounds like problems with the throttle system, imo. Some combination of pedal, throttle, and programming is off. You're basically manually commanding it to idle up as soon as it starts hitting.

Just don't floor it. That (should) command 'clear flood' mode, which cuts fuel.

 

[BUTCH1]

I have an '05 Malibu V6 3.5 that does the exact same thing, usually only happens when the car is not quite up to operating temp, a few times after reaching operating temp. I had the dealer reflash the BCM which was supposed to include a fix for this condition but it didn't work, what I do is when it happens I stop trying to start the car for 20-30 seconds and it cranks right up, kind of a minor annoyance so I just live with it.