Idle Stall

[2001Yukon]

My 2001 Yukon 5.3 is stalling and then hard to start. I have narrowed down what I believe is to be an electrical issue. If I avoid using power (radio, cruise control, Auto 4wd, power windows) then the Yukon does not have the issue.

Basically what happens is the RPM gauge will start bouncing at idle. This is usually 20-40 minutes into a trip. So the motor bay is warmed up. Basically when I stay on the gas she will run okay until I can to a stop sign.

I thought after some basic maintenance to the mechanical system it would go away. Cleaned the throttle body and put a can of Sea Foam in a full tank of gas. Changed out air and oil filters and filled her with Q TorquePower 4x4 Full Synthetic 5W30 Motor Oil.

She ran perfect for a week with no stalling issues. I ran her in Auto 4wd on a cold rainy morning to put the fix to the test. Also had on the radio, heater and heated seats. After turning off the Auto 4wd the RPM gauge started bouncing and I knew she was gonna die. Got her onto surface streets and sure enough she died.

Hard start and then another block and she died again. Had a real tough time getting her started. Parked her for the day and fired right up and drove back later that afternoon with no problems.

So I changed out the fuel filter to stay on the path of basic maintenance to the mechanical system. No codes are showing up on a basic computer hookup and the battery and alternator are testing fine.

A few electrical issues that have me concerned. One day the compass / thermo on the rearview mirror was acting up and not displaying properly. All LED's were lit up. Also the dash dimmer switch functions properly most of the time. Something is causing it to light up to full brightness even with the switch dimmer down.

What is the next thing to check? Should I stay on the basic mechanical maintenance and hope that I find something, or should I start more electrical testing?

 

[amaz]

Fuel pump? Mine acted just like yours when I had a faulty pump...

 

[2001Yukon]

I've been told it could not be the fuel pump. The theory is that it would not be able to get up to highway speeds with a bad fuel pump. Also, why would the fuel pump work for some trips but not other trips?

 

[amaz]

I've been told it could not be the fuel pump. The theory is that it would not be able to get up to highway speeds with a bad fuel pump. Also, why would the fuel pump work for some trips but not other trips?

Have you noticed difference wheter you have full tank or less than 1/4 ?

Mine started to stall when I had less than 1/4 tank, with more than 1/2 tank it worked well. And it never died in the highway driving, only when rpm's dropped to idle.

 

[2001Yukon]

It has never died on the highway. Only dies when I come to a stop. I have seen no correlation with the amount of fuel in the tank. I had close to a full tank the other morning when it died. Down to a 1/4 tank now and about to go on a trip. So it will be interesting to see what happens.

 

[fire730]

Check all of your ground wires. Especially the ones that ground the engine block.

 

[Thumper8302]

clean ur throttle body man.. i was having the same issues.. i thought it was my alternator cause at night when i got to a stop light or sign my idle and amperage would drop way down like to 300 rpms... i took a rag to mine a month or so ago and i tell u what it was nasty as hell..... i no longer have this issue after i did it.....

 

[hassoun]

it sure does sound like a ground issue. fuel pump does that too if its about to die. check your fuel pressure before you waste any money. put a gauge on the fuel rail and test the pressure. with the truck on and the vacuum line disconnected form the fuel pressure regulator, you should have 58 PSI of fuel pressure. if it bounces up and down then you know you have a faulty fuel pump. i highly doubt its the pump. You sea-foamed teh truck wrong. you put half a can in less than a quarter tank and the other half through the vacuum line. that way you get all the build up out of your engine. you putting a whole can in a full tank just dilutes it. sea-foam it again using half a tank if quarter tank of gas then the other half to your pcv valve vacuum line. let me know if you need more info on what i said. good luck

 

[2001Yukon]

Found out that the battery was not the right size, so I bought a new Super Start 34/78 EXT tonight.

* Cold Cranking Amps: 800
* Cranking Amps: 940
* Reserve Capacity: 115

Took it out around the block after installing the new battery and it stalled. After it stalled it sounded like it was flooded and was tough to get started again. I was pretty sure I had narrowed it down to an electrical issue, especially after the load test on the old battery.

It still could be an electrical issue... Basically what happens is the trucks acts like it is flooded. It starts to surge and the RPM gauge starts bouncing around. Here is what I have already done.

* Cleaned the throttle body
* Can of Sea Foam in a full tank of gas
* Changed out air and oil filters
* Filled her with Q TorquePower 4x4 Full Synthetic 5W30 Motor Oil
* New fuel filter
* New battery

No codes are showing up when hooked up to a computer at the auto parts store. The alternator was also checked and everything tested good. Why is this thing stalling out on me? Will taking it to a dealership shop help me troubleshoot the problem?

What is the next thing to check?

---------- Post added at 09:02 AM ---------- Previous post was at 08:54 AM ----------

Check all of your ground wires. Especially the ones that ground the engine block.

I will get under the hood again today and check these wires. You are speaking of the battery ground wires right?

The positive should go into the electrical box. I noted that last night when I replaced the battery?

The negative battery ground routes down the front and goes down to where I could not see.

Not really sure What else I would be looking for in ground wires.

Am I looking for other exposed wires under the dash? If I find them should I tape them up? Previous owner had an electronic tow brake system. Should I disconnect that too?

Should I be checking on some fuses?

 

[Thumper8302]

u could have a bad iac motor man... that would be my best guess.. i really dont think u have an electrical issue other than that.. take it to a mechanic and have him check the voltage...