I have a 2001 GMC Jimmy SLS. It's cutting off after I decelerate and stop, sometimes. Enough to be a major pain and putting a lot of wear on my starter at the least.

No fault codes are shown, and this is a new behavior. I've made two modifications to it (other than putting in a yellowtop battery and a new fuel filter) which was to install a Spectre air filter, which I don't recommend, and a new stereo(head unit & amp, which I installed -- which I also don't recommend :-) -- and the stereo currently isn't making sound, for a reason I also can't identify. It was working great and then stopped as well.)

When I pull up to a red light or stop sign, the RPMs drop and it just cuts off. Not always, though, just about ~50% of the time. Sometimes they'll bounce back up to ~ 1000RPM, but then maybe bounce around and even down to 300 even. Then kaput. And then when I restart at the light, it'll keep cutting off as I wait for it to change, so I have to sit there in neutral and just start it when the light changes. That's getting old for everyone.

If it's in park, it idles fine. It's just after decelerating.

I'm wondering if the "new" air filter/intake has something to do with it? It's been in there for over a year and there wasn't this issue.
I'm wondering if the new stereo is drawing a bunch of current which is deriving the vehicle of juice it needs to stay running? Maybe I messed up some grounding somewhere? (I'm trying to think of anything, here.) I'm going ot detach the stereo at the battery and see if that makes any difference with it running.

To run it needs sparks air and fuel. The fuel filter is new. The battery is new. The spark plugs are all new. New spark plug cables, also. (When I say "new" I mean a little over a year ago. I'm not putting much mileage on it, just around town a few days a week.)

 

You need to travel with the ability to test voltage, spark and fuel pressure so you can catch it in the act. When it happens first measure the voltage into the ECM1 and ECMB fuses. That will check power to the ignition, fuel pump and fuel injectors. Then test spark and then fuel pressure.

And yes I would reverse the radio install.


George

 

I appreciate the response. "When it happens" is so quick -it just cuts off - I'm not sure how I'm going to catch that information on my reader and drive around at the same time. I'm going to give it my best shot and diagnose more deeply. Thanks again!

 

I may have misunderstood. So it stalls when slowing down at a light and then starts right back up but runs poorly or does it then crank but not start? How does it run at cruising speed? How does it idle at first start up?

Have you done the fuel pressure and leakdown test in the sticky?

Can you read live data with a capable scanner?


George

 

Another thing to check/test is the Idle Air Control valve. The IACs is on the side of the throttle body, and is how the ECU controls engine idle by allowing more or less air into the engine when the throttle is closed (idle). The IACs and throttle body can get dirty over time, which can cause it to stick closed, which will cause poor idle. Removing the IACs and the throttle body and giving them a good cleaning might help diagnose/solve your problem without costing you anything but a bit of time and degreasing fluid.

 

That probably needs to be done, regardless. I was suspecting the airflow at some point because it gulps air with this new Spectre intake I regrettably installed.
What it ended up being was a consequence of having a power line connected to the (yellowtop) battery for a new amp I installed. It just doesn't fit on there well at all and getting it secure to the post any other way seems impossible. I'm sure a pro could have done it, though. Lesson learned.

 

Nice looking truck

George