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Yukon XL 2004 Stalls on Acceleration

I have a Yukon XL 2004 that very occasionally stalls on acceleration. It does not do it unless I drive about over 3 hours time, and happens with these other conditions:



-When it is a warmer day - over 30 degrees.

-Only happens during acceleration and at about 40-45 mph. One time it stalled when I was passing someone however.

-The last time it stalled, the engine pulsated on acceleration (footpedal held steady but engine RPM going up and down), but did not stall. However at the next stop light, on acceleration, it stalled.

-I can usually start the vehicle right up with no issues, but on a couple of occasions, it seemed to stutter or act like it was missing sparkplugs or something when I tried to start it. Stuttering is the best way to describe it. But you sit long enough, it will start.

-It seems like it happens on damp days as well.



The vehicle never stalls going down the road when acceleration is not needed or when I am sitting at a stop light. Acceleration is always key in this issue.



So, I am thinking this is fuel related, but wondering it it could be spark plug or ignition related as well. Any direction here would be really great.

Anyone have any ideas on this?

Taking in mind the symptoms you describe, I would look at the Throttle Position Sensor. It acts like an acceleration pump on a carburator. It tells the computer that the throttle openning is changing; that the fuel metering needs to go open loop; and a slightly richer mixture is needed to prevent stumble, hesitation, and stall.

Hope that is the problem.

OK. I had the mechanic do a number of things a couple of weeks ago. Tested fuel pump (just a slight erratic bump - nothing big), replaced plugs and fuel filter. So, today it was warm so I drove the thing about 3 hours and tried to reproduce the problem and whamo, it started acting up again. I got it to stall 3 times on acceleration and then drove it to the mechanic shop and he hopped in with the computer on it. While driving, heading out of town, I really cranked on the accelerator and it just could not get speed quickly - engine missing, yet the RPMs were going high. Almost like trouble shifting, but really not getting any fuel or air??? It would almost stall and he said a “couple are missing” I am assuming cylanders. He also noted that that O2 readings were really low - which I think is probably key here. So, we are thinking something along the lines of a bad catalytic converter or something with the air intake. I am taking it in tomorrow. There is also the chance it is fuel related, but I just am not sure right now. So, with this said and what I listed in the first posting, any warning flags that come up in anyone’s mind? Any clarifying questions let me know.

Oh yeah, when I brought it in, they said the Throttle Position Sensor is good. Do we need to go back to that? Would that be creating these numbers on O2?