I’ve been chasing shakey idle in my 91 tbi. Changed EGR, IAC, CTS, plugs, wires, rotor and cap. No change to idle.

seems to only happen once the car is warmed up so I figured it only happening once it goes from open loop to closed.

I decided to test that theory on a short 5 minute drive by disconnecting the O2 sensor. Car ran perfect the whole drive. No shaking.

when I parked and got out, coolant was pouring out from under the car, looks like it was coming out directly at the water pump from the weep holes.

is there any way disconnecting the 02 sensor for a short drive could have caused this? Or a crazy coincidence? Temps were fine the whole time.

 

Coincidence only. Perhaps the O2 sensor itself is bad.

 

I really hope so. I’m was going to replace it today but now I have a water pump job to do first!

 

Would really get ecm data. Unless the 02 is stuck at .450mv it’s probably doing its job of reporting.

 

yeah I didn’t think of that. All I proved was that something is wrong at closed loop. Does t mean it was the 02 sensor. (Fingers crossed that it is).

if that doesn’t solve it, I’ll done some research on how to get that data from the aldl connection.

 

Geeze, tough problem. I'm looking thru the list of things that can go bad, and there's not a whole lot in there. Can understand why you were considering the O2. Perhaps checking all your ground connects and make sure all you wiring is intact, starting with engine ground.

https://www.thirdgen.org/forums/v6/4...ml#post3801073

 

thanks, this is great and something I definitely have to do.

 

Hows the fuel psi when it warms up?

 

that’s a great question, I too was wondering if the pump might be failing. I don’t know the fuel pressure. I wish these cars had a shrader valve for fuel pressure.

if I put in a fuel pressure tester, should I do it just after the fuel filter, or closer to the throttlebody in the engine bay?

also, when it warms up, the oil pressure seems like it dances around. It’s always in a good range, but the needle is jumpy. Not sure if that is normal or not.