I had an engine fire about 6 months ago. I had to replace all the vacuum lines and the wiring harness. Ever since then I am having a random stumble at idle. It runs great at all rpm speeds but randomly stumbles when I am coming to a stop or stopped at a red light or if I let it sit in park. It does not do this all the time just sometimes. When it happens I tap the throttle and it idles smooth few about a minute then stumbles again.

I have replaced the iac,tps,map sensors. I also replaced the pre cat o2 sensor after the fire.

The wiring harness came from a junkyard truck. I had to cut the o2 sensor wires off of the "new" harness because the frame of the truck was on the ground and I couldn't get to the plug. I spliced the o2 connector from my old harness to the new one. When I spliced it all but 1 wire matched up color for color so I figured by process of elimination the last wires went together. I get codes saying P0132 (1/1 O2S Shorted To Voltage) and P0135 (1/1 O2S Heater Failure). The CEL comes and goes on it's own.


I was thinking about it this morning and began to wonder if the truck the harness came from had the square shaped o2 plug. Could that be my problem? The truck I pulled it from was either a 2000 or a 2001 I don't remember which.

If it's not the o2 what else could be causing this problem?

 

Anyone?

 

Can anyone help me with this?

I forgot to mention that when I first start the truck cold it dies almost instantly. When I restart it stays running but the rpm's seem lower than they should be for a cold start. It almost feels like a choke issue. Isn't that controlled by the ECU?

 

I think the problem is that O2 sensor...something is wrong there....you've already replaced everything else that it possibly could be. Can you easily disconnect that upstream O2? I would go out and disconnect it and see if that helps the truck idle...it'll make it run rich, but it should idle better and that way you can know where the problem is (or isn't if it makes no difference)....what kind of shape is your catalytic converter in?

 

Another vote on 02 sensor or wiring of it. IAC could be a suspect too, since it's happening at idle is when throttle plates are closed. Is the iac from dealer?

 

I am still having this problem. I never got it figured out and now I NEED this fixed. My wife is going to have a lung transplant and I need to be able to jump in the truck and drive 300 miles.

I checked the wiring to the o2 and it's fine and I replaced the o2 sensor, plugs, and ignition coil.

When I come to a stop it either stumbles instantly or it idles fine then the idle gets progressively worse like it's building up then starts to stumble. If I accelerate after it's been stumbling it continues to cut out and I have very little power. I have to press the throttle harder to get it to go. It will move but like it's running on a couple cylinders. Then the stumbling will suddenly stop and the truck will surge forward.

Edit to add: I have just let it stumble before (was looking for arcing from plug wires)and it does not die. The idle drops way low like it's going to die then surges back up to normal (or maybe a little higher)and does this over and over but it never dies.

What else could this be? Crankshaft position sensor? Distributor pickup coil? Low fuel pressure?

 

Pull out the idle air control solenoid and clean it very well with brake cleaner see if that solves your issue. The IAC will cause all of the symptoms you are describing but not throw any codes.

 

I replaced the IAC and it didn't make a difference.

 

What brand? And, it wouldn't be the first time new sensors were defective.

Okay, just re-read...

I am leaning towards the O2 issue also, maybe. We need to check the color codes for the wiring on the donor truck send yours. You don't remember the year it was, do you?

 

Don't remember the year (would have been 2000 or 2001) but I checked the wire colors and they matched up. Well 3 out of 4 did but the one that didn't is for the heater.

Iac was from advance so probably bwd or whatever that brand is