1999 Chevy Silverado Hard Time Starting

I have a 1999 Chevy Silverado with 5.3 It is hard starting and has a miss at low RPM around 1500 and then it clears up when you accelerate. Any ideas what may be the cause.

ProTech
Does the problem go away when the truck warms up?

No it doesn’t it still does it when warm.

Ok, usually the intake gaskets leaking will cause a problem like that, but only at first startup or when cold. Since your truck does it all the time, it is probably fuel related. I would check to see if your fuel pressure regulator is leaking, as that can cause the same issue.

I have replaced the fuel regulator and it did not help at all.

How about spark plugs and wires? Have they been checked/replaced? Fuel injectors could be clogged/faulty as well. You might also want to check fuel pressure, as low pressure will create a hard start condition, but be fine once started.

I have replaced plugs but it’s been awhile it did the same before plug change. Do you think the hard start problem and the miss are related?

Yes more than likely they are related. I would really do a fuel pressure check just to find out where you’re at pressure wise and if more diagnosis needs to be done.

OK! can i get a fuel pressure gauge at local part store.

Probably can, just make sure it has the correct fitting and can read at least up to 65psi.

One more quick thing…have you replaced the fuel filter? Also is the check engine light on?

One other thing I left out of my original question is that if I press the accelerator down just a little and hold it seems to start better. Yes I have changed fuel filter. Yes the service engine soon light is on.

Well you’re giving it more air by doing that which tells me that maybe you’re getting a bit too much fuel at start up, which again would lead to believe either a fuel pressure regulator leaking, or injector stuck open. You’re compensating for the extra fuel by opening the throttle blade. If the check engine light is on, I would definitely get it scanned to see what code or codes are set, that will help in diagnosis as well.

OK! I will try to get a fuel pressure gauge. Like i said i replaced the regulator and just checked it the other day and seems to be fine. What can i do to correct of check the injectors

You’d need a little more advanced tools to check/diagnose injectors. An injector balance test and injector leak down test would be in order, but you really need dealership tools to do that stuff.

Yeah that’s what i was thinking. So there is really know way to see if that is possibly the problem?

I’d still get the truck scanned as soon as you could. You could have something as simple as an oxygen sensor code that is causing the truck to run rich and have the problems you are experiencing. Don’t jump the gun until you know what codes you have.

OK both upstream o2 sensors have been replaced

Start simple….fuel pressure check, scan for codes…go from there. Have you replaced all these parts with GM parts or aftermarket junk?

From Napa so probably aftermarket. But have had the same problem before i changed the parts. So I don’t think I have changed the problem part

I understand, but always have to recommend GM parts. They are worth the money, trust me. And always remember, just because you replaced a part, doesn’t mean it’s not bad again. And even though you replaced and checked the fuel pressure regulator…it’s quite easy to pull of the vacuum line to see if there’s a leak. I’d do that too.

Yes I totally agree with just because it has been replaced that it’s not bad again. But the things I have replaced have made no difference. So just don’t think they were the problem. Yes that’s what i did just checked it yesterday and no fuel in the vacuum line.

And like I said earlier, start simple…get that truck scanned, check the fuel pressure…both really easy things to do and go from there.

True.. Do the down stream o2 sensors cause problems also or just the upstream? Fuel pressure should be 50lbs. from what i have read??

Usually the upstream mainly, but any oxygen sensor can really cause driveability issues if it’s shorted or non-functional.

So the downstream could cause a problem like I have?

The actual spec from GM is 55-62psi for fuel pressure. If you check it and it’s anywhere around 50 or below, you have a problem…or if it drops off after sitting for a few minutes, you have a problem. Yes they can cause a problem like that.

So to do the fuel pressure put the gauge on start the truck get reading then turn it off and see if it bleeds down?

Put the gauge on the test port and just turn the key on. Watch the gauge, it should jump quickly to almost the max reading and stay there indefinitely. Then start the truck and make sure it stays in the 55psi range.

2001 Chevy Silverado

Hard to start after it sits up for 12 hours are longer. Had the fuel pump replaced 3 months ago.

You might want to check the fuel pressure regulator for leaks. If the diaphragm is ruptured inside the regulator, fuel will leak into the intake manifold and cause a hard starting condition. This usually happens after the vehicle sits a while so it fits your symptoms. Other than that, possibilities could be leaking intake gaskets, a fuel restriction, ignition problems…or the fuel pump you installed is going bad already.

Intake Gaskets

I replaced intake gasket truck started right up afterwards. took it for a drive to get it up to running temp, everything seemed fine. shut it off in driveway, tried to restart, it turned over hard like it was out of time but started. put in garage to check the timing set the timing, now it won’t start. it will turn over a few times then hesitate like it is out of time and will not start. got a code reader to see if I could find answers there but it doesn’t work. checked fuses for this problem still doesn’t work. I replaced the coil checked to see if I had enough power there and I do I am stumped as to what it might be.