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09-20-2009, 01:53 PM #1
Stalling at startup, had codes checked
Hello everyone. I've read through the forum posts, but haven't found one with my same symptoms. I've got a 1999 Tahoe. After it has sat for awhile (30min or more) It stalls when I get on the gas until it's run for a couple of minutes. After a couple of minutes, it runs fine, but you better not try to pull out into traffic before it's ready to go! Also, even after that, if you floor it, it will also stall. You can quickly accelerate, but not put the pedal to the floor.
The check engine light is on, and I took it in and got the codes read. It came back with the P0300 (Random/Multiple Cylinder Misfire Detected) The guys at the shop told me I needed to replace my plugs and wires, which I did. The problem did not go away, I got the codes read again, and now it comes up with the following:
P0101 (MAF or VAF CKT Range/Perf)
P0300 (Random/Multiple Cylinder Misfire Detected)
P0171 (System Too Lean Bank 1)
P0174 (System Too lean Bank 2)
I don't know how closely the stalling problem and the check engine light coming on are related. The check engine light comes on when driving up a hill on the interstate, and then seems to clear itself after driving around in town for a couple of days, but the stalling problem never goes away, even when the check engine light isn't on. The guys at the shop are now telling me I need to replace the MAF sensor. I'm hesitant to do this because I've read all of the possible reasons for these errors, and they told me to replace my plugs and wires, but they were wrong about that. I don't want to spend money on repairs that don't need to be done or aren't going to fix my problem. Any suggestions would be greatly appreciated.
09-20-2009, 02:09 PM #2
I would be looking at a fuel delivery problem. Pump/filter/regulator. Poor fuel supply could cause misfiring, which would result in a lean condition.
Don't piss any more money away on parts till you are sure you have the problem isolated. Go to AZ or wherever and get a fuel pressure gauge. Super easy to use. Let us know what the readings are engine off, key on, engine running, reving up engine, etc. See if it changes if you pinch off the return line flex hose.
Also, have you put any fuel system cleaner through? SeaFoam is great stuff, as well as Techron. Add a can to 1/2 tank or so of gas and run the tank down low.When you hear hoofbeats, look for horses not zebras.
09-26-2009, 10:22 PM #3
Ok, ran through some sea foam, and replaced the fuel filter. Cleaned out the MAF, and the check engine light is off, but still stalling some when you first start it up and try to get on the gas. It's better, but still far from 100%. Considering it got better when the MAF was cleaned, do you think I should replace it altogether? Fuel pressure guage is still on backorder at the parts store.1999 Chevrolet Tahoe LT
09-27-2009, 04:56 AM #4
I wouldn't purchase the MAF before checking the fuel pressure. You might want to try another parts store for the tester. You might also want to clear your codes. Pull the underhood ECM fuses for a half hour or so. If your fuel pressure is good, and the MAF code comes back, then I would probably replace it. Do you have a buddy with a similar truck you could borrow the MAF?
Also, read through this thread. More low buck maintenance you can do.
09-30-2009, 07:55 PM #5
Well, it turned out to be the MAF afterall. My father in law had picked one up at the scrap yard, and it did the trick. Cleared the codes, and so far, nothing has come back. No more stalling, and I've noticed an overall improvement in performance in stop and go's as well as rapid acceleration.
Thanks for the suggestions.
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