Pontiac Repair/2002 Bonneville hard starting issue
QUESTION: I have a 2002 Bonneville with 80,000 miles and a 3800 V6 that has an issue with starting no matter if it's cold or up to temp. It will however start right up if you depress the accelerator pedal slightly. Parts that I have replaced:Plugs,IAC,Fuel Filter,Fuel Pressure Reg. None of these helped it at all. Fuel Pressure with KOEO is 49psi. This seems low but not sure why throttle position affects how it starts. I also cleaned the port where the IAC goes.
Your help would be great, not sure what my next step is.
ANSWER: Hi randy:
Well a few things to check and do here. make sure the throttle plate and throttle body are clean. I assume this has no service engine soon light on and it runs fine other then the hard start? It doesn't have a higher or lower then avarage idle when it's hot or when it's cold and it's started and running? As for as the fuel pressure that is right on approx 50 PSi key on and about 45 running is normal on that engine. This is another thing you need to do with the engine running put a fuel pressure gauge on. shut the engine off. wait 1 minute then just key on to prime the fuel system and note the pressure. afetr about 15 minutes check it again. It should slooowly bleed off but after 15 minutes or so it should still have "Good" pressure if the pressure bleeds off to fast they fuel in the rail will vapor lock when hot and cause a hard start. if the pressure does bleed off fast pull the vasuum line of the regulator and see if you smell gas in the line or there is raw fuel in the line if so replace the regulator. if that is ok then pull the fule rail off the engine leave all the fuel lines hooked up put paper towel under the injestors lay the rail on top of the paper towels. key on again and let it sit. ans see if you have an injector(S) leaking if so replace the leaking ones. If you don't have any leaking and the pressure still bleeds of quickly it's either going past the regulator or past the check valve in the pump module. pull the return line off put a rag over the rail key on and let the pressure prime and bleed off some. after that just keep an eye on the line going to the return if it's leaking you will see it there. good luck :-)
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The fuel pressure reg is new but I did check to see how fast the pressure bled off and it only dropped a few pounds after 15 min. I don't seem to have a leak any where because the pressure looks good. I also cleaned the throttle body and that didn't help. I still need to press on the throttle pedel slightly to get it to start. If I press the pedel a little and hold it then hit the ignition switch the engine starts right up.
On a cold start and you have to press on the pedal to get it to start does it have a fast idle like it should cold? or does it idle real slow? If so I might suspect a bad Idel control motor. other then that your sort of out of luck because there isn't much else you can check with out the aid of a scan tool to look at the engine data in the engine computer. it could have an input that is skewed and it's not bad enough to set a code but bad enough to cause a hard start. The only last thing you could try is to clean the MAF sensor it's in the throttle body. there is a special cleaner you need to use on it it's called madd air flow sensor cleaner you can't use carb cleaner that leaves residue. other tyen that I don'rt have anything else you can try.