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My roommate has a 2004 impala and it had died on him so he got it towed to a repair shop, he already had a check engine light on for a long time and knew what it was, 02 sensor. so when he took it to the shop that is what they found and replaced it. drove it home and it died several times on him. He showed me and it would hiccup and the rpm’s would bounce around and then it died. My wife has a chevy and awhile back it was doing the same thing and it had a really bad spark plug so it was miss firing,so I checked his spark plugs and they looked pretty bad, 2 even had what looked like a spider web in between the gap.So I replaced them and I let it sit for 20 mins and it was fine. when i went to test drive it, it hiccuped while accelerating once, maybe twice. Let it sit and it did nothing, even while in park and bringing up the rpms. drove it around the corner again and it hiccuped again and then when I stopped the rpm’s bounced around like crazy and almost died. gave it some gas and then it seemed fine.
so that’s where I’m at, any help would be very much appreciated. and the only other thing he could tell me is that some technician said that his battery was not working very well when they did a test on it i guess.
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well i replaced the fuel pressure regulator seems it was only 50 bucks. the psi made a huge improvement, but it was still acting up, this time it took longer to act up and it didn’t die once. possibly the fuel pump and regulator were going bad at the same time? only other thing is that maybe what is applying vacuum to the regulator is acting up? although as revving the engine i had a gauge on the vacuum line and it was jumping from 20 to 15. which makes me think its fine, unless its just deciding to act up randomly after the car warms up. but still mostly doing it while accelerating and while at idle.
something else to add, the book states that when in the on position the pump should run for about 2 seconds and then hold pressure steady. which as of right now it is in the correct rang for the first 2 seconds then dropping to about 44, which is the range it should be at while the car is running, but the car is not yet running.
Does it still run and not die? Maybe a bad batch of gas? You did change the fuel filter already correct?
The gas should be fine. We put gas in it in the middle of this as it was on e. did it before and after. I’m still thinking fuel pump. Only be because the book says it should be holding the same pressure after the 2 seconds that it runs. But I’m just letting my head clear for a couple days and then redo the psi test. Before I never got to see that the psi was normal for the first 2 seconds because I was the one turning the key then looking. This last time I had him turn the key and I saw that. So I assumed the regulator fixed it. But I’m sure it was always like this I just wasn’t able to see it.
At least it stays running now. You could almost use this as a grace period to save up money for the pump, because chances are that is the cause.
Just another status update. This one is kinda funny. So I was goig to go get the new pump today but I had this idea to run the car and listen to the fuel pump seems I have easy access to it from the trunk. Well it did bog down as the car was acting up. But just to make things more interesting it got a check engine light this time. Ill get it checked on Sunday and hopefully this will help.
Could be the Crankshaft Position Sensor as well. I’ve changed a few of them over the years, for similar driveablility issues (including one on my own Impala) Not a hard job to do. Might be worth doing it before changing the fuel pump. Also make sure you don’t have any knock sensor codes, those sensors like to crack, and on a supercharged car, those sensors are VITAL to maintaining safe air/fuel ratios and spark timing. Arcing plug wires or coils or ignition modules could be suspect as well.
Cheers!
so the code was p0171 which is for fuel too lean. if it were one of those other sensors you stated above i should have gotten a code for that right? so anyway the fuel pump has been replaced becuase it could have been causing a lean condition but it is still doing it even though i did notice a slight increase in psi. so anyway i looked up what to check when that code comes on and it is as follows.
1- The MAF (Mass Air Flow) Sensor is dirty or faulty
Note: The use of “oiled” air filters may cause the MAF to become dirty if the filter is over-oiled. There is also an issue with some vehicles where the MAF sensors leak the silicone potting material used to protect the circuitry.
2- There could be a vacuum leak downstream of the MAF sensor
3- Possible cracked vacuum or PCV line/connection
4- Faulty or stuck open PCV valve
5- Failed or faulty oxygen sensor (bank 1, sensor 1)
6- Sticking/plugged or failed fuel injector
7- Low fuel pressure (possible plugged/dirty fuel filter!)
8- Exhaust leak between engine and first oxygen sensorso i here is what i did for each of those above.
1- cleaned maf for a second time. couldn’t find anything in the book for checking resistance on it.
2- checked 2 times over the last 2 weeks for a vacuum leak using carburetor cleaner. did it again today using the propane method, still could not get the idle to change even while dumping propane down into every area
3- checked all the lines and they look fine and like i said above did the propane test and nothing.
4- checked pcv by taking out and shaking and i could hear it move ( apparently if you can’t here it move it is gunked up and bad)
5- this specific o2 sensor was the first thing replaced when he had it towed to a shop before i started all of this.
6- listened to the fuel injecters with a long screwdriver, they all seemed to have the same consistent click. no idea if they are clogged though. he has always put mid grade gas in it from either shell or chevron.
7- everything related to fuel pressure has been replaced………………..
8- i looked up info about exhaust leaks in this area and i should be able to smell it or maybe see that exhaust is coming up, but everything seems just fine.when we were at the parts store he even said the spark could cause this such as coil packs, wires, plugs, well everything but the coil packs has been replaced. so today i checked the resistance on them and they were all consistently the same although the primary resistance on all of them was under what the book says but this book doesn’t cover the supercharged model so that could be different. and seems they were all consistent I would think they are fine.
so as of right now I think im pretty much done with it and want to push it off a cliff lol.
and as I have said before, very odd that it only does it once the car warms up
So I had pretty much given up on it and told him to take it into a shop. But with one last idea I went to a junk yard and found a mass airflow sensor that was partially broken. Soldered it back together, stuck it on and that seemed to fix it lol. It ran for 35 mins with no issues and drove it not very far around the block without any hesitation. I’m assuming with my luck though it will start doing it again tomorrow lol…
So turns out the junk yard mass air flow sensor just didn’t work at all and the car basically runs amazing with the sensor unplugged. But we bought a new one and the car runs worst than it ever has(un drivable). I reset the computer and I did hear it can take awhile for them to adjust to the computer but I have a feeling that’s not happening. No idea what the hell is wrong with this car lol.
So he took it into the dealership and after doing some diagnostics they said it was the maf sensor and apparently the one I bought from a local store was bad. But then it still acted up and they found a crack in the intake manifold. I kept thinking I could hear a vacuum leak but with the 3 different test I did I was never able to find it. They want 1000 to replace it and already charged almost 500 for the diagnostics and sensor. Sucks I wish I could have found that before I replaced the pump and that sensor. Everything else definitely needed done anyway.
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