missing, hesitation, CE, and code 176 when hot

[NoSlo]

Hey, I'm on a road trip and after many hours of driving my car started hesitating like maybe it was missing spark on one cylinder, surging and bucking a little bit. The check engine light immediately came on, and turns on and off while driving. I checked the engine codes and got a 176, cleared them and drove and immediately got another 176 (front bank lean). It's hinted at doing this before on a long trip.

I checked the spark plug wells & cleaned oil & set the spark plug gap to minimum side of spec to avoid arcing from wires, dumped in 2 bottles of stp total fuel cleaner and ran thru a tank of gas and still have the same problem. The codes were 176 and 177 (both rich & lean on front), 177 possibly from the computer adapting to a problem on one cylinder? The problem will stop for a while if I let the car cool, it only happens after lots of driving, but then continuously.

Guesses? outside temp about 60 degrees. Tach has been working fine, no CID codes etc, KOER test today gives 111 code after warming up car for 15 minutes - all OK; [I borked up the engine running test when it was really hot and having the problem since I didn't have a book, but it only had codes that would come from me screwing up the goose test.] o2 sensors with less that 10k. Spark plug wires with 120k but I don't want to replace them unless they really are the problem. I was thinking a spark problem, but that shouldn't get me a lean condition immediately and CE light I wouldn't think. A fuel system problem should affect both o2 sensors equally but all codes are coming from front bank.

Help, I need to throw parts at this problem and fix it before the dealerships close!

 

[HopefulSHO]

Perhaps if the old wires are causing some misfiring, your O2's are picking up on that with the funky fuel readings? Usually bucking is either caused by bad plugs/wires causing misfires under lower-RPM/moderate-high load situations, or the camshaft sensor. But since you didn't get a code for that, I'd guess it could be your wires. If they are that old, there's a good chance they could be causing your misses.

 

[NoSlo]

Going to buy wires

Well, I'm going to buy wires. We'll see. That's a lot easier than replacing the CID or an injector, and I guess it's time anyway

 

[projectSHO89]

Contradictory codes for an O2 sensor usually means the sensor is bad.

Be prepared to replace it once the new plug wires are installed.

Steve

 

[NoSlo]

found another thread with some info...

http://www.shoforum.com/showthread.php?t=12932&highlight=176+177 - exact same symptoms, It doesn't say how the original poster fixed the problems, but the last post is someone that had the same symptoms and it was plug wires.

I ordered AC Delco wires, the ford dealers wanted $220-$260 for a set of wires and didn't have them in stock anyway! I pity the foo that takes their SHO to the dealer for a tuneup!

 

[NoSlo]

How about fuel pump!

I'm back. The wires didn't make any difference. I've got a better idea what it might be, but it still doesn't completely compute.

The fuel pump.

I was doing the KOER test after the car was driven and having the problem again (and got 111's of course). I noticed a bit of a thumpy rubby sound every now and then, like every 5 or 10 seconds. I isolated it completely - by pulling up the back seat and putting my ear to the nice warm spot where the fuel pump is. I could hear it running and yup, sounds like it would if bearings were going out and it was 'grabbing' metal or rubbing every 5 seconds or so. Rollsy-pollsy. Maybe it has problems after it heats up the whole tank of gas?

Still wierd that I only get 176,177 front bank codes. I was thinking of switching the o2 sensors to see if the codes follow the sensor and change to 172, but if it's the pump, it might actually be the o2 sensor that ISN'T spitting out codes that's bad...

Good thing there's a wrecking yard that just got in some SHOs here! (btw: idler pulley w bearings, D4U1, 24 shims, and a fog light? $35.)

 

[NoSlo]

for posterity

Just to finish up this thread and let you know how to diagnose this on your car...

It was the oxygen sensor.

I switched the two oxygen sensors and cleared the codes, the codes changed from 176(front bank lean) to 172 (rear bank lean) immediately. I guess the nearly new o2 sensor knew it was 2 months out of warranty and decided to die. On the plus side I replaced the plug wires & fuel pump that I needed to replace anyway.