1999 Tahoe 5.7L random misfire

[Oleg]

1999 Tahoe 5.7L random misfire cylinder 2 and 8

Hey guys
My gf has a 1999 OBS Tahoe with a 5.7L. One morning it started running rough sputtering and misfiring so I told her to park it until I have a chance to look at it. I checked fuel pressure and it is good. No vacuum leaks. Last tune up was around 40K miles ago when I did plugs, wires, cap and rotor. The plugs still look fine.

In open loop before it warms up it runs a little better but when it goes into closed loop it starts to sputter and misfire. I scanned it with my hptuners but the only code I get is P0300 for random misfire. o2 sensors seem to be switching like normal.

Any suggestions on what else I can check? I don't want to throw random parts at it and she doesn't have the money to take it in anywhere. I was expecting something to jump out at me when I scanned it with hptuners but everything seems normal.

 

[DR CHOP]

My 98 just had the same symptoms, bad injectors. I put GM mpfi injector upgrade in it. Best money ever spent. Runs good as new with more power.

 

[Oleg]

Is there any way to verify injectors before buying them? I know they are expensive and I'd hate to spend so much if it is not my problem.

 

[grampadirt]

You might try removing and cleaning the EGR valve & the cavity it goes in,might be a lot of carbon buildup.Also check the Ignition Control Module,they go bad occasionally.

I also did the injector upgrade on wifey's burb,big improvement.

 

[slippy3002]

Is there any way to verify injectors before buying them? I know they are expensive and I'd hate to spend so much if it is not my problem.

It would be running lean.

Check to make sure your plug wires aren't grounding out.

Sent from Robl@and!

 

[Oleg]

You might try removing and cleaning the EGR valve & the cavity it goes in,might be a lot of carbon buildup.Also check the Ignition Control Module,they go bad occasionally.

I also did the injector upgrade on wifey's burb,big improvement.

From what I read if the ignition control module goes bad it would not start?

Keep the ideas coming guys I appreciate all of the help. Weird thing is that it started all of a sudden. When she drove it the day before it ran fine.

 

[1997chevydriver]

From what I read if the ignition control module goes bad it would not start?

Keep the ideas coming guys I appreciate all of the help. Weird thing is that it started all of a sudden. When she drove it the day before it ran fine.

It depends on how they fail. They can be bad but still run

 

[1997chevydriver]

Check your dizzy cap and rotor too

 

[GMstrong]

You need to look at the misfire counts while in gear with your foot on the brake and oon the throttle alittle.

 

[Oleg]

These are the misfire counts on each cylinder
#1: 12
#2: 492
#3: 0
#4: 2
#5: 1
#6: 1
#7: 0
#8: 130

Bank 2 short term fuel trims go up +15% under load so it is going lean.