So here we go again. First a little info on my car: 99C A4,95k, Vararam,airbridge, long tubes w/high flo cats, x pipe and tri flos.

Drove through some heavy rain yesterday and car started to misfire and got codes:
P0300 Engine misfire detected
P0131 (O2S circuit low voltage bank 1 sensor 1)
P0171 (fuel trim sensor lean bank 1).

Thought it might be due to the drivers front Oxygen Sensor being bad or having a short. Got underneath it today and visually inspected the wires I could get to and cleaned the terminals in the harness. Also cleaned the MAF and IAT sensors. Cleared the codes but the engine runs rough and they come back after a short time.

Could it just be a bad oxygen sensor? Is there anything else I should be looking at?
I have also been having another issue that I have already posted about and I'm not sure if it is related. was. Thought this was an issue with the TAC module.
These are the codes from the other issue:

P1120 TP Sensor 1 Circuit
P1220 TP Sensor 2 circuit
P1221 TP Sensors 1, 2 Performance
P1516 Command vs actual throttle position performance (TAC module)

Also, I am showing some U codes. have heard that these are inconsequential but I am including them just in case:

U1016 Loss of Communication with PCM
U1064 Loss of Communication with BCM
U1096 Loss of Communication with IPC

I am feeling pretty lost here and I really don't want to have to take it in somewhere to just have them start replacing parts that might not be needed. Don't have a lot of extra money to spend right now either. If anyone can help me out it would be appreciated.

Thanks
Scott

 

I would start by clearing the codes and then drive it until you get a check engine light and see what code(s) come back.

 

Did that. Same three codes come back; P0131, P0171, P0300. Don't have a scanner so I'm not sure where the misfire is. Should I start checking plugs and wires or could these be a direct result of a bad Oxygen sensor? The other codes are an intermittent problem that seems to come about at random.

 

I would check and replace, due to mileage, your plugs and wires. I had a plug wire break on the dyno with 86k. if the plugs not firing it basically turns your left bank into a air pump, remember o2s only are capable of reading o2. I would say a leaking exhaust manifold gasket, but that wouldnt cause a misfire only a lean code on the bank thats bad. As far as the tps sensor above the gas pedal the tbw connector comes loose and doesnt seat properly, on occasion. That can also cause reduced engine power light. Check your oil to see if theres gas or smells like gas to see if theres gas getting by the rings due to the plugs not firing. Also may have a bad exhaust gasket. I think the threshold for a po171 is ~+25ltft. I wouldnt worry about the u codes i believe there a CAN code where it has a disrupted signsl bw ecu's, if i remember correctly. A po300 is a random multiple misfire, its not on a specific cylinder. ex. if there was a consecutive misfire on cyl 1 it would be a po301, cyl 2 po302, etc

 

Another thing ive heard of tps codes come from 1"-6" from the sensor itself on the t.b theres a frayed of broke wire.

 

Replaced the plugs and wires about two years ago with knology wires and new plugs. I will check them tomorrow.

 

I would almost say you have an exhaust leak for the ltfts to be >25 on one side, might want to check the AIR gasket off the ex manifold because there bad about detiorating once theyve been taken off.. If its idling funny maybe a lower intake gasket leaking on bank 1. Do you have a cam? PO300 is common with a cam swap and can just have the ses light to not come on. Im running LS2 wires and tr55 plugs and havent had any problems.

 

No cam.

 

What plugs? I know nology wires have built in capacitors, which is funny cause thats kind of the purpose of the individual coils, but i would try some stock wires and see if it clears it up. The po300 could be in conjunctoin with the lean condition or could be a seperate issue. Hard to diag without having the car. Just adding my $0.02 for what its worth

 

I appreciate the help! Just need to know if the oxygen sensor could be causing the misfire or if the misfire is causing the code on the sensor. This is my daily driver and I need it to go to work on wednesday. Guess I will have to bring it in somewhere tomorrow.

 

Hard to tell without having it in front of me but i would suspect an exhaust leak. The 02 could be causing the misfire, but for some reason my gut is telling me its either the plugs, wires or exhaust leak. Also, on the rear drivers fuel rail the wiring harness could be rubbing causing the tps codes. Good luck! Let me know what you find.

 

You could shotgun it and buy 2 new o2s, plugs, wires and AIR gaskets lol

 

Lol. That's what I'm trying to avoid.

 

So, I was stressed out about getting to work tomorrow so I decided to go ahead and take it in somewhere to get it fixed. I recieved a card in the mail last week from a place called Insty Tune on N. Dale Mabry Hwy in carrolwood saying that they specialize in Corvettes. I decided to give them a shot.

I took it in and explained what was going on and that I thought it was the drivers side front Oxygen Sensor. The guy at the shop hooked it to a scanner and it was showing misfires on 1,3,5, and 7. He asked if I had maybe gotten water in the intake and I told him it was possible. He said he needed to check the spark plugs and wires so he pulled all the plugs cleaned and re-installed them. Still misfiring.

He replaced the drivers side 02 sensor with a bosch unit from advanced auto parts. Problem solved.

Then I get the bill. $305.00. WHAT!?? Charged me $85 for labor to remove and clean spark plugs on drivers side. $199.00 for the Oxygen sensor. Plus tax.

I called Advance Auto to see what the O2 sensor runs and they quoted me $75. Called Insty Tune to ask about the $125 difference in the price of the part and the guy says he charged me $120 for the part and $80 for the labor to replace the part. WHAT?!! I could have replaced that part in about 15 minutes.

I'm pissed that I just spent $305.00 to replace a part that I could have just changed myself for $75.00. GRRRR. This is why i hate taking my car to a mechanic. Thank God for this forum. I should have just trusted my instinct and went ahead and replace the Oxygen sensor myself and saved the $230 for something else. This sucks.

 

Price sounds about right to me, plus you have no worries about getting to work tomorrow.

 

Figuring in you doing the labor, you could have bought 8 tr55s for $15, ls2 wires for $85 and that o2 for $75 ALL for $175. LOL, thats why i work on my vette

 

YomasterScott, it's called CORVETTE TAX. Why do you think their advertisment says "Specialising in Corvettes," instead of "Specialising in Old Chevy Trucks." Chalk it up as experence, the lesson is worth about $300.

 

I have a similar code appearing on my car. I have had the O2 sensors replaced twice. Is the Bosch unit you replaced your malfunctioing one with an aftermarket one or an OEM?

Thanks.