mytrplseven

I did a wiper adjustment of both the original and replaced AFM's to make sure the AFM wasn't the issue. Still didn't affect any changes in my case.

mytrplseven

What wiring issues would this rule out?

Sysgen

Could you give more specific information about the stumbling, what happens exactl and is it random? Ive just been through this, just need to know if you have the same symptoms.

mytrplseven

It isn't random. It's slightly worse when the car is cold but is a constant irritation when using normal acceleration. Wide Open Throttle (WOT) it seems to be fine, as the car goes full tilt to redline without an issue. Car idles fine and it's not particular to a certain RPM range. As you'll see in the opening post, I've done a lot of swapping of known good parts or bought replacement parts outright to try to get a handle on this problem. It's been ongoing for a long time.

You can be certain that I'll tell everyone, especially those who have taken the time to join the "brain trust" to help me resolve this thing.

Sysgen

I second the idea of running without the o2 sensor, the dme will revert to the fuel maps only.

fejjj

Does it just stumble once accelerating to redline or several different times?

konakat

O2 sensor wire

konakat

One thing I see missing from your list is the TPS wiring. I have seen several threads where people ended up having a short in the wires rather than the TPS itself.

raleighBahn

I think the WOT is your clue. At WOT the dme is ignoring inputs from certain things (like afm I believe). You may have replaced or checked off these items, but check again. And if you just decide to give up and set car on fire, consider your wiring - maybe it is rusty/brittle under the sheath and causing strange behavior.

mytrplseven

I decided to follow the quick and easy recommendations of SYSGEN and KONAKAT and disconnect the O2 sensor. It is a brand new Bosch 3 wire unit and don't know what it's disconnect might be masking, but IT WORKED!! The car runs like it should in all RPM ranges, regardless of the throttle application.

The only concern I have now is that the idle cycles +- 200 rpm. I'm 100% sure that there are no more vacuum leaks so whatever it is, I can live with it, just to get the car running like it should. Now on to recovering the front seats.

Thanks to all of you whom offered your inputs. I appreciate your involvement and insights. I'm sure that any one of the ideas could have caused the symptoms I was experiencing.

Sysgen

Glad it worked One of 3 possiblities I can see, the o2 sensor was DOA, the heating element in the sensor was defective sending wrong signals to the DME, or a bad connection, broken wire, etc from and to the sensor. You can test the sensor with an ohmeter, it should read around 8ohms, Clarks-Garage also has a test with the engine running, that's how I found my o2 was dead.

mytrplseven

Actually, I read on a website that the O2 sensor can mask a vacuum issue. The vacuum leak causes the engine to run lean (which it was) and by disconnecting it, the engine runs rich, which is why mine ran so good. I plan to change the vacuum leak check per the website, using propane for a search tool. On the later cars, the computer check port has the b and c pins to be jumpered (which takes the ISV out of the mix and with the O2 sensor disconnected, applying propane to the different possibilities for leaks, a leak will show up as an inrease in rpm. Since my sensor is a new Bosch unit, I'll try this to see if I missed something using pressurised air for a leak check.

adrial

Don't underestimate the propensity for old wiring to drive you crazy ...

mytrplseven

I hear ya. I have good ignition wires (tested before installed) with Beru connectors and new Bosch cap, rotor copper plus plugs and coil. The wires are all installed cleanly using the looms (brackets) so they lie nicely along the top of the engine. Another poster also suggested that ignition wires sometime cross-pulse and interrupt each other's firing. I would imagine that the problem would still show up though even after removal of the O2 sensor makes the engine run fine.

After I re-check for vacuum leaks again I'll reconsider re-routing of the ignition wires. Thanks

adrial

I was more so thinking about the wiring to the O2 sensor.

I think I have a narrowband a/f gauge that you can have for the price of shipping if you want it to check out what the o2 sensor is indicating.

I wouldn't worry about the routing of the ignition wires too much if you used OEM parts. Remember it runs fine at WOT...so you are chasing something that is only an issue when the ecu is reading the AFM and o2 sensor and you are asking for power.

On an N/A there shouldn't be too many places for vacuum leaks.. Is the idle screw still in the top of the throttle body? The o-ring can get old/brittle/leaky. Easy to check by putting your finger over the top of it.

Good luck