Rough Warm Start

[connor.stephens]

As stated in the title my car is running rough on warm starts after the car has been running for a while. I will go to start it (when warm) and it will turn over fine but i have to push the gas pedal to keep it going sometimes or it will die. one i get the rpms leveled out the car runs perfect. what could this be? The car has a brand new engine and starts up great every time when its cold.

I'm guessing maby fuel pump or a leak in the fuel system somewhere?

 

[SRZMK3]

coldstart injector may be fouled up its the black thing on the top middle of the intake manifold inbetween the y pipe.

 

[GrimJack]

If the cold start injector was fouled, there might be problems during cold starts, but it's rather unlikely it would affect warm starts.

There is, however, a very likely and rather simple to fix possibility. There is a vacuum switching valve under the front of the intake manifold that is responsible for sending ambient pressure, instead of manifold pressure, to the fuel pressure regulator during hot starts. This is simple to test - next time it's hot, pull the vacuum line off the fuel pressure regulator and leave it open to atmosphere, then start the car. If it starts properly, then there is something wrong with the VSV, the wiring for the VSV, or the vacuum lines from it to the FPR.

If it still doesn't start properly, the problem lies elsewhere.

 

[MPR]

I'm having the same issue on occasion. ^Thanks for that tip. Will try that out next time. Problem with mine is it is not consistent. Sometimes it starts warm and idles just fine. Other times it nearly stalls...

 

[GrimJack]

The hot start problem is from heat soak boiling the fuel in the fuel rail. If you don't suffer from enough heat soak, or if it's cooled just enough for the fuel to condense, it doesn't happen.

The system to prevent it does so by showing a higher pressure to the FPR, which increases fuel flow for a short period, flushing the hot fuel out of the rail.

 

[3p141592654]

A small vacuum leak will cause this problem. Idle quality will be bad too, but you may not notice it.

 

[jetjock]

Loss of rest pressure can also cause that symptom.

 

[connor.stephens]

I figured it out after the car died on the highway on the way to school this morning. it was one of my spark plug leads was barly plugged into the distributor. im going to check the VSV as well thanks for the tip!!!!!

 

[MPR]

I figured it out after the car died on the highway on the way to school this morning. it was one of my spark plug leads was barly plugged into the distributor. im going to check the VSV as well thanks for the tip!!!!!

That must have been the ignition coil lead that was falling off. Otherwise, it wouldn't have stalled, it would have just started running less one cylinder.