cjoenck

A question to everyone much smarter than me... The car starts fine when the engine is cold and it starts fine when the engine is hot. If I let her sit for about 45 minutes, the only way to start is with the gas pedal half way down. The "Check Engine" light stays on for a minute and then everything goes to normal.

It feels like the air / fuel ratio is way off when warm but fine when cold or hot.

Any suggestions?

- ICV is fine
- MAF is fine - I think

Since it only happens when warm, I am thinking fuel pressure regulator. What are the symptoms when they go bad?

Rocket Rob

Since the check engine light is on, I would want to check the error codes. Do you have access to a Scantool or Hammer?

cjoenck

Just pulled the codes using the Durametric software - no fault codes. Somehow I think it is not DME related since the car starts fine in cold and hot condition. The "Check Engine" light goes off after a couple of seconds and the car runs fine.

crg53

"Check Engine" light will come on if you step on the gas pedal prior to or when you start the engine, it then goes out a short while after.

cjoenck

Exactly. The problem is not the "Check Engine" light. The problem is that I have to depress the pedal halfway to get the engine started. The engine will not start if I leave the pedal untouched when the engine is warm.

993PET

Get a leakdown check. You may have broken piston rings causing oil in the cylinders.

parsecnc4

Perhaps leaky injectors, which richen/flood one or more of the cylinders. It happened to another car of mine from a while back and it was tough to track down.

Basically, there is always residual pressure in the fuel system even after it has been turned off. When the engine is hot, the extra fuel leaked after shut down would evaporate quickly and not be an issue on restarts. The same is true when the engine has enough time to cool and for the fuel to evaporate over a longer period of time.

Worth a shot.... Good luck with your search.

cjoenck

Had a leakdown test done a few months ago and the numbers seemed fine. The numbers came back as:

4%, 5%, 6%, 5%, 6%, 6%

for an engine with about 82K miles. The injector suggestion is intriguing, I'll look at that next, I think.

If I have injector issues, shouldn't i see evidence on the spark plugs, i.e. run rich all the time?

Makmov

you can test the injectors themselves with 9 volts. look for spray pattern.

I thought about injectors but usually an injector problem will show up when it the car is hot and you try to restart it right away.

cjoenck

Not sure it is relevant here but I am getting about 12 mpg in the city and 22 on the freeway.

boxsey911

FWIW I get the same problem as you now and again and have to give the throttle a prod for it to fire up. I've always put it down to the engine being betwixt and between full cold and full warm and the DME not being intelligent enough to give it the right mixture in that state. Mine doesn't have a check engine light (I don't think early 964s in Europe had them), hence I've never worried about it.

Navaros911

Cjoenk,

Did you ever get this looked at or resolved?
My car has the same symptoms and I'm having a new fuel pump fixed as the current one is on it's way out
The symptoms really sound identical, but ofcourse that doesn't mean anything with these machines - but it would give me a good lead to go on.

vagluv

just came across this: http://www.pelicanparts.com/911/911QA/911Q_misc4.htm#5

Navaros911

Thanks for the link Vagluv.

Hmmm.... well I'm having a new fuel pump fitted anyway so lets see.

My Mech pointed in the same direction.

The paragraph referred to is for an SC though and I'm not sure if the CIS is the same as the injection in our cars.

Navaros911

Fuel pump and filter replaced... no change... well only a marginal change.

Advice welcome... thinking of fuel accumulator and fuel pressure regulator... could be an injector too, but they were "cleaned" and supposedly tested about a year ago. Which helped the same problem I had back then.

Interestingly enough I had one of the knock sensors that had gone off... it was cancelled out and will check again tonight.