engine miss

[l1driver]

I have a 2000 Silverado Z71 4x4, 4.8, 4l60e tranny. The truck has 190,000 miles on it and just recently started having the following issue, Cranks up no problem, after driving a little bit the engine develops a stumble. Not throwing any codes. It seems to be worse on the drive home after the outside temp has heated up ( central Florida) Any help would be appreciated. Every now and then I hear a pop like a backfire through the throttle body.

[kenny-1907]

I used to have a 2000 Silverado and it had some very similar symptoms as you are describing with the rough idling, stumbling now and then, yet running fine at other times. My issue turned out to be the mass air flow sensor but it also went in the middle of winter. Not sure if this helps any.

[l1driver]

Thanks, I will definitley look into the MAF.

[j cAT]

Originally Posted by l1driver

I have a 2000 Silverado Z71 4x4, 4.8, 4l60e tranny. The truck has 190,000 miles on it and just recently started having the following issue, Cranks up no problem, after driving a little bit the engine develops a stumble. Not throwing any codes. It seems to be worse on the drive home after the outside temp has heated up ( central Florida) Any help would be appreciated. Every now and then I hear a pop like a backfire through the throttle body.

with this best get the check engine DTC pulled again do not shut engine down when this occurs . post back exactly what they are. the codes will direct you to the problem area. this vehicle throws codes very easy..anything in the fuel management that is slightly off will throw codes..

lets say you find no codes . then check the fuel pressure. with the engine on you need 53psi minimum....on engine shut down pressure should not drop quickly...

replace the fuel filter every 30,ooomiles...if over this amount it may be the problem ..filter is easy pump is not and very expensive..

pumps fail when running with restricted filters and low fuel levels under 1/4 tank..pump heats up !

[l1driver]

On Saturday it threw a code for Mass Air Flow Low Input. I pulled the MAF and cleaned it with CRC MAF sensor cleaner. Reinstalled and the service engine light went out. Also replaced fuel filter but problem still persists. Right now I have no Check light coming on. I will check fuel pressure as soon as iI can get hold of a Gauge. Thanks for the info. I will post the results after I check it.

[j cAT]

Originally Posted by l1driver

On Saturday it threw a code for Mass Air Flow Low Input. I pulled the MAF and cleaned it with CRC MAF sensor cleaner. Reinstalled and the service engine light went out. Also replaced fuel filter but problem still persists. Right now I have no Check light coming on. I will check fuel pressure as soon as iI can get hold of a Gauge. Thanks for the info. I will post the results after I check it.

best give the dtc code number so we can look it up and figure out the cause.. the air ducting or intake leak can give these type of problems/code types..

check the fuel pressure next..check when engine cold / then when it acts up !

[l1driver]

Checked fuel pressure and it was good, 54 PSI. Had it rescanned and no codes were present. A friend suggested new plugs. Going to do that today. Although I am a little confused. Haynes Manual says to gap plugs at .60 but the guys at Napa say that GM put out a TSB and now say on the 4.8 they recommend the gap be .40 and to use the Iridium plugs. Is there any truth to this?

[j cAT]

Originally Posted by l1driver

Checked fuel pressure and it was good, 54 PSI. Had it rescanned and no codes were present. A friend suggested new plugs. Going to do that today. Although I am a little confused. Haynes Manual says to gap plugs at .60 but the guys at Napa say that GM put out a TSB and now say on the 4.8 they recommend the gap be .40 and to use the Iridium plugs. Is there any truth to this?

you should use these ac delco irridium plugs..also you do not mess with the gap..do not adjust the gap..If the gap looks off return for another plug..these plugs will break if you mess with the gap..the gap has changed from date of manufacture..that is why ...

still however your problem may be a intermittent fuel pressure problem...I would expect P0300 CODE IF PLUGS CAUSED YOU ISSUES.

engine on what was the fuel pressure ? engine off what was the fuel pressure ? how long did it stay at that pressure ?

engine cold running pressure ? engine hot fuel pressure ?

[l1driver]

O.K I changed the plugs and used the AC Delco Irridium at .40 Gap. Took the truck out twice and no miss or stumble what so ever. Got on it hard a couple of times and it ran just as smooth as ever. I'll give it a couple of days and see how it goes. j cat, with engine at Idle I had 54 PSI on the fuel rail. After I shut the truck off it dropped to about 45.

[j cAT]

Originally Posted by l1driver

O.K I changed the plugs and used the AC Delco Irridium at .40 Gap. Took the truck out twice and no miss or stumble what so ever. Got on it hard a couple of times and it ran just as smooth as ever. I'll give it a couple of days and see how it goes. j cat, with engine at Idle I had 54 PSI on the fuel rail. After I shut the truck off it dropped to about 45.

sounds good. I think your fuel pump is on the low end of the spec. ..keep the fuel above 1/4 tank at all times...perhaps you'll luck out and not have the expense of replacing the fuel pump..