Right on, didn't even think about that. Could it be a O2 sensor going out?

 

Could be. When you look at your data you should be able to have an idea. (One bank may be adding or subtract a lot of fuel to compensate for a false o2 reading).

you could verify that the o2's are "sweeping" in the correct range by measuring min and max voltages on a meter. You could also response test it by introducing propane into the intake through you air box. both banks should quickly go very rich on the voltages (higher) and STFT should react by going negative (subtracting fuel to try to lean out a rich condition).

But my favorite way is to do this while oscilliscoping the o2 but i doubt you have one laying around lol. I like to see that it is switching rapidly and looking for any unusual activity is easy on the scope graph.

 

My scanner reads out what the computer is seeing. So if one or both are bad I should be able to tell. I'm just hoping it's a easy fix. It's just weird that I'm not getting any SES light from this and it's only after it's warmed up. Which could explain the O2.

 

Alright, so I got out and tested some stuff today. My scanner is limited so although it can show a lot of sensor reading, it doesn't show them all. The only thing that I could see that was an issue was the O2 sensors. They both were fluctuating from around 80-900 in both closed and open loop. And before it warmed up it was idling fine, then once it warmed up it went into open loop and started the very erratic idle.

So do you think it's the O2's? Or is there something else I need to check before I go spending money on new 02's?

 

Check the vacuum line from the opti to the intake manifold and to the air intake throttle body. Clean throttle body and clean or replace the IAC. make sure the connections are clean and tight. Check the engine vacuum and check all the vacuum lines. Check to make sure the MAP sensor seal is good. And the vacuum hose to the break booster.

 

Vacuum lines have all been checked, IAC seems fine, TB is pretty clean.

I'm pretty sure that the spark plug wire sparking against the headers shorted out the O2's. Still waiting for the guru's to pop in and confirm though.

 

Anyone have any ideas? I'm still trying to figure this out, I went through the docs you sent me craby and couldn't find anything out of wack that my scanner would read. It does it in closed mode, I might have said it wrong in the beginning. When you first start it in OPEN mode it's fine, but when it heats up and goes into CLOSED mode, that's when it starts having problems.

 

one of my issues was the tps had a bad connection. car would just die or not start. maybe take a look at the map and maf.

 

Drivability issues like this are the tuffest to figure out and normally go to the best mechanics.

A few thoughts.

I have NO faith in plug wires that where not assembled on at least a 5 ton press. I have had brand new "home cut" wires cause issues with car in the past. If you had a coil that had some internal tracking and you added a little resistance to the wire it could cause the issues you described. (a mechanic could test this with a scope)

O2 sensor report what is coming out of the motor so a motor that is not running smoothly should have erratic O2 reading. Failing sensors tend to cause performance issues and are less likely to cause erratic idle. Unless you have a spark plug wire giving off a large amount of static and it is routed very close to the O2 sensor.

Since this started with you working on the car common sense would say you did something but if you brought me a car with this complaint I would verify plugs wire where up to date. I would pull the EGR valve verify it was sealing and clean it, clean the IAC motor and port, I would also spray some cleaners around while it was running to check for vacuum leaks. After that I would grab a scope and 4 gas...

Sticking EGR valve cause this issue a lot but those cars tend to run find every where but idle. IMO cleaning the EGR valve and IAC area and checking for Vacuum leas should be part of a normal tuneup.

 

Engine runs fine when cold, in open loop (computer factory presets). But acts up when in closed loop (engine management then running off all the sensors). I fail to see how spark plugs and wires can distinguish between open and closed loop mode and change their spark delivery accordingly? Maybe I'm missing something. Wouldn't it make more sense to figure he has a bad sensor (temperature, IAC, O2, etc) causing this?