So to start things off, i purchased a pretty cherry 2001 neon on the weekend for my girlfriend . So when i bought it , it had a check engine light on, the code was p0171. She said the engine light had been on for over a year! lol. silly girls.. anyways, i plugged in the scan tool and monitored the 02 sensors and sure enough the upstream o2 wasnt switching and staying at 0.01 volts. The car was acting very sluggish and barely would accelerate it also burnt fuel like crazy ,like half a tank in 125 kms! . So i hit up the local parts store and purchased new spark plugs,(champions) s, the upstream o2, and they had a nice msd coil pack on the shelf for a measly 49 bucks, so i bought it and i picked up some new msd wires aswell. So i get home, changed the plugs and wires and coil. changed the o2 sensor , changed the oil, did a trans flush and new filter, cleared the codes, disconected the battery for about an hour, then took it for a test drive , it felt a little better.

From a stop it accelerates a little bit better than it did, shifts through the gears nice, however at highway speeds aprox 90kms an hour when i step on the gas it doesnt accelerate any faster i can let off the gas a little and then it decides to acclerate a little. I did the sea foam treatment after work today, burnt a ****load of white smoke , and it seemed to idle better, but still bogs, and you can barely drive it with the a/c on.

So my coworker thought i should hook up a fuel pressure guage and see what the pressure was at.., screwed the hose on , looked at the guage, it read 58 psi when i turned the key to on, i started it, and it stayed at 58 psi. when i blip the trottle it drops to 55 psi, but goes right back to 58 psi. so i am thinking the fuel pressure is good.

At this point i am completely stumped. My only other thought is the cat might be plugged up from driving around with a non functioning o2 sensor for an entire year!..

Wondering what you guys think, and wondering if anyone had any ideas of other stuff to check..

Please help before i burn this thing to the ground LOL.

 

PO171 means that the system is running LEAN. You should be looking at your fuel trims to help you diagnose the problem.

It either means 1 of 2 things.
-too much air.
-not enough fuel.

Check for vacuum leaks, especially under the accordion tube going to the TB. Due an Injector balance test (if you have the equipment.). Verify the MAP sensor is operating properly.

 

I did swap out the o2 after i scanned it with snap on solus at work and found the upstream o2 was not switching , it was stuck on rich, and it read 0.01 volts all the time no matter what. After i replaced the o2 i cleared the code, and disconnected the battery for about 30 mins so the computer could reset. I fired it up, my st and lt fuel trims looked good. my long term is no longer stuck at 24.2 . I tested the map sensor this eveing, i removed it from the intake, back probed the signal wire, i got 4.5 volts and every 5 inchs of vacum apllied it dropped almost a volt. at 15 inch pounds of vacum it read 1.9 volts.. it held 15 inch pounds with no droppage over a 2 minute span.. does this sound like an accpetable reading for map?

 

Could this lack of power possibly be a bad cat? she said she drove around with the check engine light on for over a year. I am assuming it ran really rich for that whole time and plugged up the cat.. I am wondering what kind of tests i can do to see if its plugged without having to unbolt the thing from the car and actually look down it...

 

If the cat is plugged, it should be glowing bright red after driving it.

 

Went down to the muffler shop this morning and they performed a back pressure test and they said the cat is working fine, and no restriction. Still dont have a CEL, picked up a new map sensor, new tps, new crank sensor, and new cam sensor. Un hooked the bat, replaced all the sensors. took the car for a drive , same issue, same hesitation ...

My next thought is with the timing belt.. i am unsure if its been ever changed so i talked with the previous owner and she had got it 4 years ago at 75,000kms and never did get the timing belt changed. it has 210,000kms on it now.

I had a friend come over and looked at the data streams with Torque for android, and went for a drive. Brought up the ignition timing , and it showed at wot it was 40.5 degrees advanced. does this sound right or a possible error? that seams a little high to me. i am thinking that possibly this belt is off a tooth. I was reading somewhere else on this forum that 1 tooth on the cam gear equates to 20.25 degrees of timing. So 40.5-20.25= 20.25 one tooth... coincidence?

 

Hard to say exact values. The PCM adjusts the timing based on several conditions/factors. However, based on other info I've seen, I'd say that could be a bit too high.

 

so if i wanted to check to see if the belt was off a tooth without taking everything apart, would find tdc compression stroke, and remove that little plug off the side of the timing belt housing and look inside there for something?

 

here is a shot of timing advance and rpm i took earlier with the torque app

 

Usually if your belt jumps a tooth you will get a cam/crank correlation code (hopefully) and they will usually crank funny.


I'm not convinced that your ignition timing is that far off. For example on a small block Chevy total timing is around 36 degrees.


You said your fuel trims are looking fine now?