So Ive been having this intermittent problem. Once in every 3 starts or so the car would stumble and stall everytime I push the gas pedal. The car will idle ok but if I push the gas it just wants to die.

Sometimes I could turn the car off and on and it would go away. sometimes I could just let it warm up and it would go away.

Yesterday leaving work it would NOT go away.
Now the car is sitting in my work parking lot 5 miles away from home.

No mater what I do I cant give it any gas or it will stumble at 500 rpm or so and sound as if its only running on 2 cylinders. If I release the gas it will go back to idling normal.

No codes.

what could this be?

 

Does the SES lamp work at all? It should come on for about ½ second when the ignition is first tuned on, go off for about ¼ second, then come back on and remain on until the engine is running. Does it do this "bounce?"

 

Check the resistance on your injectors with a multimeter, mine has acted similar when I had bad injectors.

 

Wow well before I answer your questions -- I got it started, working and drove it home. It was acting like it wanted to have the same problem the whole time I was driving it (very slight miss on throttle tip in) but It made it.

Got the ses light while driving and pulled code 33.

I am currently getting the tune down on this car so that indicated I was a little too lean. But that definately was not the same problem I am having with the stumbling.

To answer questions -- yes I get the typical SES behavior you described vader.

All the injectors tested fine about 2 years ago when I sent them to rich at cruzinperformance.com. I do have the fuel pressure set high (50PSI) could that cause a problem with the injectors locking under too much pressure.

I really think this is an ignition problem though -- not a fuel prob.

 

Could be ing related, but don't rule out the injectors i have burnt them in under a year (multicraps though) don't know what brand your runnin. And the injector test is very simple takes about 5 minutes.

 

If you're getting a DTC 33, you might want to go back and scrutinized the TPS voltage at idle. You may want to raise it a bit.

 

The code 33 gets set during part throttle driving. TPS voltage reads .55-.57 at idle in the logs.

At this point I am going to swap out the coil to see what that does. Then I will change the module. Other than those two components I can imagine the pickup coil being bad but that is a more detailed process to change than the former two.

 

Update-- replaced coil cap rotor module and pickup coil and the problem still exists.

I am thinking that its a computer related problem. I started it today and it idles great. Just when I push the gas and get to about 2000 rpm it starts to stumble and if I push the gas down more it will stumble so much that it will barely run. rpms go down to about 500 and it fires maybe on 2 cylinders per rev.

So I got the idea that maybe the fuel pressure was so high that the injectors were locking when I opened the throttle enough to reduce vacuum on the regulator and raise fuel pressure. No dice though I put the FP gauge on and even removed the vacuum reference and the FP is steady at 52 psi no matter what I do. the problem even went away while I was testing and there was no change in fuel pressure the whole time.

I had a vacuum guage on and the car idles at 18 psi and will shoot up to 22 if I give it a little gas. with a small amount of gas like this the engine will rev like I said to about 2k rpm without stumbling but if I give it any more revs drop and so does vacuum.

I am stumped. I guess I will hook up the timing light and see if the spark drops out when the problem exists. I could also back probe the EST wire while the problem exists to see if the computer is doing something weird with the spark advance command voltage...

Any other Ideas are greatly appriciated.

 

Check the pins in the MAF connector. Look for one of the pins being pushed back into the connector.

What does your scanner s/w show the MAF flow at during acceleration?

 

I checked the MAF pins and none are bent back.

During accel the maf tops out at 15-16 g/sec and wont go any higher. This is a good catch as I had not seen this before. I went back to old logs of the problem once you mentioned this and found that the old logs display this problem as well.

It seems that the MAF wont go any higher than about 18 grams per second in an older log. Today it wouldent break 16.

What does this mean?

 

I replaced the MAF with an old one and the problem went away....


HALLELUJAH!!!!!!


Thanks to all that helped.

The bad MAF was a fairly new Wells 145 by the way so HMMMM...

 

I had a similiar problem a while back. One of the pins in the MAF connector would slip back into the connector, when I plugged it into the MAF, and it would only make intermittent contact.

When I would unplug the connector it would fall back into place so everything looked fine when I gave it a visual insp. Spent abt 3 weeks scratching my head over that one!!

Anyway, good to hear you got it fixed.