Lack of power first minute after startup.

[dcountiss]

There is a service port on the fuel rail to connect your fuel pressure gage. Like I said before, mine was running around 20 psi, I think the spec is 60-65.

[bwforum]

Originally Posted by dcountiss

There is a service port on the fuel rail to connect your fuel pressure gage. Like I said before, mine was running around 20 psi, I think the spec is 60-65.

Thanks dcountiss, I'll see if I have something that will connect and check it.

[99SilveradoGuy]

i'd pull off the cap and rotor from the distributor and see if theres any burn markings or anything like that (its a little hard to get to) it could be a number of things like , 1-2 cyclinders not getting the a good spark causing a sensor in who knows where to read wrong etc. I'd try the basic though, check fuel pressure, check condition of cap and rotor and spark plug wires (easy to replace if needed), check the pvc valve (helps control idle like $3 for a new one at napa).

My 99 4.3L would kinda do the same thing , it would run fine for awhile , then sometimes it would hesitate starting up , or not start at all. Brought it to a garage who replaced fuel pump and a few other things and still didnt fix it. I eventually found out that there was a very tiny nick on a spark plug wire causing it to die down when it hit the engine block, but also the pvc valve had some dirt in it causing it to run rough at start ups

[99redsilverado]

its a little hard to get to the distributor because it doesnt have one...

i think you have a fuel pump going out or a vacuum leak..... good luck i hope you find out whats up with it...

[bwforum]

Originally Posted by dcountiss

Have you checked your fuel pressure at start-up? My fuel pump went out on my 2000 Tahoe a while back, it was putting out around 20 psi instead of the 65 or so that it was supposed to put out. When I would start it, it would stall and sputter until it got past around 2500 rpm's for the first time, then it would run just fine. It turns out that it was taking the fuel pump that long to catch up with engine demand. After the new pump went in, it felt like I had a new engine.

Well, I checked my fuel pressure, and as soon as I hit the key, it jumped to 55 psi. and didn't change much at all after running for a bit. Instead of bringing it into a shop, I picked up a fuel pressure guage from Autozone for $36.00. I can't imagine that is as accurate as the ones in the shop, but I figure it is close enough to see a problem that will cause the chugging problem that I have. Anyone have any idea if +/- 5 psi. would cause this problem? Thanks.

[99redsilverado]

no it shouldnt.....was it running rough when you got the 55psi reading???

[bwforum]

Originally Posted by 99redsilverado

no it shouldnt.....was it running rough when you got the 55psi reading???

It was running fine, but it doesn't typically misfire when it is idling anyway. I'll have to try it again, and have the wife powerbrake it this time when I am checking it...I hope she doesn't run me over!

[99redsilverado]

jack up the rear end

[bwforum]

Originally Posted by 99redsilverado

no it shouldnt.....was it running rough when you got the 55psi reading???

I checked my pressure again, actually a few times. It is usually right in the 48-52psi range. While checking it, I pulled the vacuum line off of the fuel pressure regulator and it jumped to 58psi. I would be interested in trying to drive it around a bit with this hose unhooked and plugged. Will I cause any damage running it like this?

[Marmots]

Even though you already replaced the fuel pressure regulator, are you sure the replacement regulator is not bad?

Marmot

[bwforum]

Well, I have been fighting this for awhile with no luck. I had it to the shop and they put the scan tool on it. There are no trouble codes, and there is nothing that they could see that would be causing the problem. I had a fuel pressure gauge hooked up, and drove it while watching the gauge. The pressure stayed the same, whether it was stumbling shortly after startup, or I had driven it for awhile. Another person in this forum has the same problem, but I didn't see any resolution. I am baffled. Any help?

The other forum can be found here:
http://www.automotiveforums.com/vbul....php?p=2442274

[99silverado32]

i have the same problem and i have no idea what it is

[bwforum]

Originally Posted by 99silverado32

i have the same problem and i have no idea what it is

I had my truck to the GM dealer tonight, and I think I stumped them. I told him what the fuel pressures were, and he said they were in range. I told him everthing that I checked and tried so far. He hooked the scan tool to it, and while it was running, the MAF senson seemed to be out of range a bit. He said that I could try and clean it with brake cleaner, but no guarantees. He applied a computer update (Bulletin # 010604006), but it didn't help at all. I'll try and clean the MAF sensor tomorrow and see what happens, and I will let you know the results.

[bwforum]

Well, I cleaned my MAF sensor, and it didn't make one bit of difference. I have a question though. If it was my MAF sensor causing the problem, and I unhooked it (which I already did) and it didn't seem to have the hesistation anymore during the first 30 or so seconds, would that be a good indication that it is causing the problem. Any other way to diagnose the MAF? Thanks.

[bwforum]

After dealing with this for quite some time, I finally solved the problem. It was the Mass Airflow Sensor. I finally unhooked the connection, and the hesistation problem after startup seemed to go away, so I decided I would drop the $200 on a new one. It solved my problem, and my truck once again runs great.