Hard Start When Cold - 2001 Tahoe

[OldDirtySpartan]

Hi all,

 

Long time lurker who finally created an account. Y'all have been a wealth of info and I really appreciate it.

 

I have a 2001 Tahoe LT Autoride with the 5.3. My father-in-law bought it new and I bought it from him when he upgraded to a 2019 Tahoe Premier. I've been going through the Tahoe since buying it from him. It was always maintained at the dealer and serviced at every interval.

The issue I am having now is a hard start when cold. It takes at least 2 cranks to get it started in the morning or after a long period of not driving.

I have searched the forums and found some help but no threads with results. Here is what I have done so far to remedy the issue.

-New plugs

-New fuel filter

-New fuel pump

-Techron in tank (one bottle so far)

I have a new fuel pressure regulator coming and will swap that next but the telltale signs of failure aren't there (gas leaking through vacuum line).

 

The truck had one other issue that has since been fixed. It would overheat (on the gauge) on hot days mainly at low speeds and belch coolant when turned off. I ended up replacing the fan clutch, coolant temp sensor, expansion tank, thermostat, and expansion tank cap.

 

Any advice would be hugely appreciated!

 

Thanks all!

[riverbanks]

If you cycle the key a few times and it starts better, your on the right track with the regulator

[OldDirtySpartan]

Thanks riverbanks.

 

I cycled the ignition 5 times.

 

It did start on the first crank but it stumbled pretty badly until getting to a good idle.

 

UPDATE: I removed the pressure regulator vacuum line and gave it a sniff. There is a very strong gasoline smell. Does this mean it failed?

Edited September 8, 2020 by OldDirtySpartan
Correction

[CamGTP]

Yes, it's possible.

 

Also clean the MAF sensor and throttle body too.

[OldDirtySpartan]

Hi Cam, thanks. Do you have a MAF cleaner you recommend?

I am running an AEM Brute Force Intake.

[sefiroxx]

- CRC MAF cleaner
- if you smell fuel at the vacuum connector, then the diaphragm in the regulator is leaking. Recommend a new one. Also, have your fuel pressure tested. You can rent a pressure tester at the local parts store. (On or 3rd fuel pump since purchasing our 01 new.
- clean your throttle body and butterfly.
- your ISC motor may be going. It controls the opening of the butterfly to allow for higher idle under cold start.

[OldDirtySpartan]

FPR went in and the cold hard crank time is almost completely fixed!!!

 

It does still stumble for a few seconds before smoothing out. I plan to get MAF cleaner, and carb cleaner sometime this week to clean. I'll update after!

 

Thanks all

[OldDirtySpartan]

UPDATE: Cleaned MAF and throttle body. It definitely helped. There is still a stumble and a slightly long crank but it's slowly getting better.

 

I'm bummed to not have a quick fix but at the same time if I am replacing the OE parts after nearly 20 years, I'm happy to get another 20 out of the work done. Plus my other car is an electric BMW and there's nothing on it to tinker with

 

On another note. I replaced the rear diff gasket and noticed the drain plug o-ring/seal is cracked, anyone know the PN?

[OldDirtySpartan]

So it's been a few days and the Tahoe is still hard starting when cold. I have the idle air control valve on order.

 

Any other items that may be causing this?

 

I did replace plugs before this all started and they were dry.

[sefiroxx]

You can verify the isc problem on startup by giving a teeny bit of pressure on the pedal. That will manually open the throttle like the isc is supposed to do.

[OldDirtySpartan]

OK. I just tried that. While starting I pressed the pedal down slightly. It would crank and then die, I tried multiple times with the pedal pressed and cranking and it would die. Then I tried just cranking again and it stumbled, started and then ran fine.

 

Does this mean there is another issue?

Edited September 21, 2020 by OldDirtySpartan

[sefiroxx]

When it started, did you keep holding the pedal down?

BTW, the ISC only controls the air gap. If the fuel pressure problem is still there, then the isc test will create a more lean condition.

[OldDirtySpartan]

To get it to start I had to release the pedal. It would not start with any pedal input.

 

There has never been an issue with the car dying while driving, hard starting when warm/hot, or rough idle once warm.

 

UPDATE  : New AC Delco idle air control valve installed just now. Tahoe fired right up on first crank. Idle jumped up to close to 2k then leveled out back at it's old value. I will give it another crank when it cools back down but this made the most noticeable change from all the other things I have done.

Edited September 22, 2020 by OldDirtySpartan

[sefiroxx]

Tada. . .

It'll need a relearn. Let it idle for a minute. Shift through the gears. Turn on the ac. Turn off. Restart and take it for a drive.

[OldDirtySpartan]

Seemed to be fine today. Final check will be tomorrow morning.

UPDATE: Checked this morning. It stumbled a little but only needed one crank to start. Maybe I just didn't have the key turned long enough.

 

On another note I was looking at picking up a 2017 Yukon XL Denali with 90k miles and wondered if anyone had pointers on what to look for. I’ve been reading up on transmission issues with the 8spd but I don’t know if the 6.2L has that trans. Thanks!!

Edited September 24, 2020 by OldDirtySpartan