Andre.servin

I just purchased a 2001 Suburban 1500 4WD with the 5.3 Vortech, 160,000 miles on it.

The Suburban was pretty solid for what it was, no red flags, ran and drove smooth, everything on it works great. There was no check engine light during the test drive and the drive home.
Then the next morning I go to drive it and I noticed the check engine light was on, I didn't think too much of it since the SUV was driving fine, I thought okay well, I'm already running errands so I figured I'll check it out when I get home.

When I got home I plugged in my code reader and I got P0300, random misfire.

So I checked the plug wires first, I figured maybe the previous owner never changed the plugs and wires and now they're worn out. Then I notice the plug wires were actually OEM aftermarket and so where the plugs, which I'm guessing where probably replaced at about 120,000 miles, maybe sooner. regardless I still visually inspected the plug wires and checked them with my multimeter, I then removed a couple plugs and they looked decent, nothing out of the ordinary at all. I then checked for spark on a few of the cylinders, it was working fine, I figured since the plug wires where changed and the plugs, chances are the rest are probably okay. I then blew smoke through a vacuum line to check for vacuum leaks and got nothing, its sealed nice and tight.

The SUV still runs well, and no the check engine light is gone but my code reader still said it was there, which I take it the light will probably come off and on until its fixed.

The previous owner did mention he changed an 02 sensor, not sure if that has anything to do with it.

Heres some more info from my reader

Fuel Syst 1 = OL
Fuel Syst 2 = OL
Calc Load = 2.0%
ECT = 75 Degree
STFT B1 = 26,6%
LTFT B1 = 13.3%
STFT B2 = 28.1%
LTFT B2 = 15.6%
MAP = 10inHg
Engine RPM = 715
Veh Speed = 0mph
MAF = 0.74 lb/min
TPS - 0.01

Could it need a new 02 sensor?

any ideas?

Thanks

cj1

Can you post the same data at full operating temp/closed loop?

Andre.servin

kevinkpk

O2 sensors are for emissions, and won't effect engine control. Did you replace the plugs, and wires?

cj1

OP- Maybe return code reader to Harbor Freight and purchase their scanner that will read real time data.
Probably can get it for under $100.00.
The data you posted shows very high positive fuel trims but need to be able to see whats going on in real time.

Andre.servin

I have not changed the plugs and wires yet. Im going to change the plugs tomorrow to the ACDelco ones and test the wires with my Multimeter. the current wires dont look too bad, and theyre not the stock ones, so they must have been replaced at some point in time. I dont know... anyone have any idea how I can check to see if theyre arcing? it runs too smooth to be mega arcing though... It runs perfectly fine, it just has a slight random rumble at Idle.

I'll look into taking the code reader back but, I totally kinda ruined the packaging.

73shark

You van check for arcing with the hood open at night.

Frank3

Is your check engine light on all the time or is it randomly happening at only certain times like high-speed driving on the interstate? My 2002 Tahoe would only light the check engine light ONLY with high speed driving. Chased that one for a while but finally nailed it.

https://chevroletforum.com/forum/tah...1/p0300-78970/

Andre.servin

Well, I'm hoping I fixed it. I removed all the plugs to install my ACDelco iridium plugs, while removing the wires I noticed the 8th plug wire had some heat dents into it, like it was getting burnt on somewhere, probably on the exhaust shield. It was entirely burnt through, but it was close enough that I bet once it got nice and warm the wire would maybe arc on the shield affecting the rest of the plugs.

Anyways, the cheap autolite plugs were gapped from 65-70.

New plugs and wires seems to have fixed it, I also put seafoam in the gas tank for good measure.

It now doesn't reek of gasoline or dump gas out the exhuast during warm up, My gas mileage seems to have been restored (it was really poor). My check engine light hasn't come back on after running errands for 2 days. I hope its gone, I still will feel a random very small shake at idle, but Im beginning to think its probably a bad motor mount, it is 17 years old, probably has original mounts. other than that its driving perfectly fine.

Andre.servin

**It [wasn't] entirely burnt through**