GMC Sierra - Hard Start when Cold

[hanson]

I've got a number of different issues with my 1999 Sierra (5.3l V8) now but this one I have to deal with soon.

When its cold (winter) and I start the truck, sometimes I have to crank a bit to start and then when its running, it has a real rough idle. RPMs fluctuate up and down and sometimes it seams like it will stall but it never has. It runs real rough for awhile once the RPMs stabilize. Once the truck is warmed up, its fine. Truck has ran fine all summer. When it got cold a couple days ago again, she started doing it again.

Now, I also have a leaking exhaust system and I know the cats probably need replacing too but I don't know if that would have an affect on my above problem.

I'm assuming this is a fuel delivery problem. Fuel Pump? Injectors? I had the Fuel Pressure Regulator replaced again 1-1/2 years ago or so.

Now my other "fun" problem. My instrument cluster has been doing some weird things to me. Lights for the digital odometer flicker on and off. Now they just stay off for the most part. About 2 months ago, my odometer completely reset. I have 0 miles on the truck now. Some of the other warning lights come on and go off. I'll have '4WD' and 'High Beam' on at the same time. The truck doesn't even have to be on for those lights to come on, I'll get in the truck and they are on. I also have the 'Airbag' light pop on and off. This stuff is just all goofy and annoying.

Any thoughts on any of this?

[Jeremy airjer W]

When its cold (winter) and I start the truck, sometimes I have to crank a bit to start and then when its running, it has a real rough idle. RPMs fluctuate up and down and sometimes it seams like it will stall but it never has. It runs real rough for awhile once the RPMs stabilize. Once the truck is warmed up, its fine. Truck has ran fine all summer. When it got cold a couple days ago again, she started doing it again.

[ARROW 1]

Im having the same issue. I have cleaned the mass air flow sensor,throttle body, sea foamed the top half of the motor, Im in the process of looking for the idle air control valve but can't find it. That was one of the codes I got off the truck a 2003 5.3. Mine gives me a engine reduced speed message and goes into limp mode at road speed down to 20 mph i go. Very annoying. I have 183,000 on the truck All the stuff I have done above has never been done to the truck and should have been. I will check for any leaks now. Try getting the code from your truck. I didn't have a reader Napa let me use theres.

[catch22]

Had the same issue on my 1996 GMC Sierra.

Get the fuel pressure checked, tires plus did this for free for me.

The vortec is VERY fussy about the fuel pressure, should be over 60psi. Mine was 55 which not only caused hard starts in the cold, but poor acceleration. I replaced the entire fuel pump assembly in 2010 as the lines were badly corroded, $325 at napa. I did the fuel filter/regulator as well, cleaned all the crud under the plenum while I was there and the throttle body. Starts like a champ and the acceleration is back.

Not sure what a shop would charge for that, I know toyota wanted $1100 to drop the tank on my previous ride and replace just the tank bracket. It's not really hard, time consuming on the first one, that was my third tank so it went pretty well. good luck

[Jeremy airjer W]

Had the same issue on my 1996 GMC Sierra.

Get the fuel pressure checked, tires plus did this for free for me.

The vortec is VERY fussy about the fuel pressure, should be over 60psi. Mine was 55 which not only caused hard starts in the cold, but poor acceleration. I replaced the entire fuel pump assembly in 2010 as the lines were badly corroded, $325 at napa. I did the fuel filter/regulator as well, cleaned all the crud under the plenum while I was there and the throttle body. Starts like a champ and the acceleration is back.

Not sure what a shop would charge for that, I know toyota wanted $1100 to drop the tank on my previous ride and replace just the tank bracket. It's not really hard, time consuming on the first one, that was my third tank so it went pretty well. good luck

I think you had the CPI engine that had the internal fuel injectors in the intake plenum. Those are fusy on fuel pressure.

i think 97 was the cut off when they went to the external injector. A 99 5.3 will have the external injectors. They are not as fussy about fuel pressure because there is no mechanical injector resistance to overcome. Its just a straight normal injector. The intake gaskets are a known common issue on these and frequently cause the symptoms described.

[Macgyver55]

All of the 5.7s from 96 up to 03 (I believe) were internal (under the upper plenum). They went external when they went to the 5.3 (different engine) with the dry intake in 1999.

And yes, the 5.7 was more critical about fuel pressure than the 5.3.

I seem to remember there was a flash update on the early 5.3 to help a bogging problem when first started, but the intake gasket will usually throw a lean code.

The later Silverados and Sierras (03 to 05) had a dash recall for doing funny stuff, but thats not to say yours isnt the same issue.