Engine surges and stalls at cold idle

[PetroleumJunkie412]

Ok. Update. To answer some questions... I did test the map sensor early on in this problem. Mine was testing bad, so I got a new Motocraft one. No change. I checked my wires, and double checked them. Today I checked the O2 sensor wiring and a new sensor is installed. No change.

However, I did remember a detail from when I did the work. I disconnected the catalytic converter to pull the engine up, and in the process snapped two of the three bolts holding it on. I got a nice exhaust leak right there where my sensor is. Is it at all possible that this is letting air in and giving it a false lean reading?

Wait. I have headers, and my O2 sensor may be in a different place than yours. How close is your sensor to your leak?

 

[Paulos]

I've heard people on this forum say that an exhaust leak at the front of the cat would cause problems with the O2 sensor readings, but I never understood how. With the engine running there should always be positive pressure on the exhaust, which should prevent air from the exhaust leak getting in (that would require negative pressure). I wouldn't think it could create a venturi effect either, because of the positive pressure. But what do I know? I can't get cheap Mevotech ball joints to work right.

 

[Nez'sRanger]

Wait. I have headers, and my O2 sensor may be in a different place than yours. How close is your sensor to your leak?

It's less than 2" before the leak, immediately before the cat's seam.

I've heard people on this forum say that an exhaust leak at the front of the cat would cause problems with the O2 sensor readings, but I never understood how. With the engine running there should always be positive pressure on the exhaust, which should prevent air from the exhaust leak getting in (that would require negative pressure). I wouldn't think it could create a venturi effect either, because of the positive pressure. But what do I know? I can't get cheap Mevotech ball joints to work right.

Yes, that's what I thought too, but I'm at my wit's end, so I'm starting to open to crazy sounding ideas! Haha!

 

[Alaska Diesel]

I have a similar issue. Except I'm pretty sure my vacuum is good. And I changed my ECT temperature and swapped my IAT out. Still is hard almost impossible to keep run when cold. Have to really play with the throttle to get it to rev up. Has a smell of gas in the intake. I've also put a different map sensor on, tried a different computer. If I unplug the ECT or IAT sensors it will run good. I'm stumped on this little guy.
O2 sensor is new a couple years ago. I've only put 55 miles on it since then because the fuel pumps went out and after the fuel pumps went out I've had this issue.

 

[Nez'sRanger]

I plugged my exhaust leak... No change... Except it's quieter.
I can't imagine what it could be.

 

[PetroleumJunkie412]

Just out of curiosity, what's the part number and make of the O2 you have in it?

 

[Nez'sRanger]

I got a Bosch 13953.

 

[Shran]

I am under the impression that since our trucks have heated O2 sensors, it does not matter much where it's located as long as it's in the exhaust stream. I can't imagine why even a large leak would affect it at all - there's still exhaust flowing over it. It would be a different situation if they were not heated and relied on catalytic converter heat to read correctly.

 

[BSwift]

I watched a number of U-tube videos on O2 sensors and your exhaust leak could cause the issue, plus an exhaust leak is not good and could possibly lead to carbon monoxide poisoning.

 

[Nez'sRanger]

I watched a number of U-tube videos on O2 sensors and your exhaust leak could cause the issue, plus an exhaust leak is not good and could possibly lead to carbon monoxide poisoning.

Yes, I was thinking that too... However, I fixed the exhaust leak, and it didn't fix the problem. I've yet to figure out the problem.

 

[PetroleumJunkie412]

I may be wrong, but I think you have the wrong O2. Bosch I had was a 13942.

 

[Nez'sRanger]

I may be wrong, but I think you have the wrong O2. Bosch I had was a 13942.

Yes, from what I read, the only difference between that one and the one I got is the length of the wire. I got the 19 inch wire on mine, and that one is an 11 inch.

 

[PetroleumJunkie412]

Yes, from what I read, the only difference between that one and the one I got is the length of the wire. I got the 19 inch wire on mine, and that one is an 11 inch.

Read that as well. I have a used 13942 if you want to give it a shot

 

[alwaysFlOoReD]

Exhaust leaks don't only let exhaust out, they also suck in outside air in between pulses. This can screw with the o2.

 

[Nez'sRanger]

Read that as well. I have a used 13942 if you want to give it a shot

The first one I bought was a motorcraft with an 11 inch. I didn't know the difference existed yet, but soon found out my harness was too short to reach, so I ended up splicing longer wires in. At this point, I think I'm gonna step back and reevaluate some electrical stuff.