01 Tahoe fluctuating oil pressure and sluggish engine (only some times)

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01 Tahoe fluctuating oil pressure and sluggish engine (FIXED)

UPDATED TODAY JULY 29, 2013

I just bought a 01 Tahoe 5.3l with 160000 miles. When I bought it, it had the P0446 CEL on so I know what to do to fix that when I get a chance, but yesterday I was towing my trailer (24ft 6000lbs) at about 50MPH and the CEL started to flash for a couple seconds, so I took my foot off the gas and slowed down a little and the CEL stopped flashing this was the only reason I knew something was wrong with the truck as there was no hesitation, etc. I get the trailer home and look at the wires and plugs and notice that they are original so I change them out with NGK wires and new plugs. I did notice that cyl 6 and 8 had white tipped plugs while the others were all that nice golden color.

This morning when I start the truck and start driving I find the truck is slow to respond and somewhat sluggish. I WOT it and the hesitation goes away. I look at the oil pressure gauge and it's now about 8psi higher at idle then it was before I did the plugs and wires. I start driving and the pressure continues to climb in conjunction with amount of gas I give it (this is normal I know), but when I go WOT the gauge is almost ******* at 80PSI and under normal accell the gauge goes up to 70psi. This never happened before I did the plugs and wires it was always about 10psi less.

What is happening??!?! I'm at a loss. No oil leaks, new plugs and wires, oil was changed about 300 miles ago and is full and golden brown.

Any suggestions for me as I need to tow my camper to the lake this weekend.

Thanks in advance!

 

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Update

Pretty significant update...

Went under the truck last night and did the fix for the 0446, and reset the codes. Took the truck for a ride on the highway and truck seemed to be running fine at 60 with the OD enabled and running around 1650RPM. Enabled the tow mode and the rpm went up to about 2100 and after about 3-5 mins the flashing CEL came on again. Pulled the codes and i'm getting the P0300 as pending. I rechecked my new plugs and wires and they were all seated fine. Checked all the coil connections and they were seated fine.

What the heck could this be?? And where should I start looking to fix this?

Thanks in advance.

 

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Update again... Still looking for suggestions. Brought the Hoe into GM and they ran 1.5 hours of diagnostics. Found all ignition components were good, but my MAF readings were all out. I replaced the MAF and hooked up the camper and headed out. Ran great on the way out with no issues. Heading home last night about 40 miles into the trip I get the flashing CEL again. I slow down and about 15 seconds later it stops flashing and we continue on our way for the last 30 miles with no other issues. Get home pull the code hoping for something new, only to find out it's the P0300 again.

Any more suggestions to what could be causing this?

 

[Screwd up 6]

Well I cant say that this is the problem for sure, but I have read many times that GM motors are picky, and that non acdelco spark plugs and wires can still cause a misfire, even when they are only 1 week old.

Have you by chance looked at the distributor cap? I know when I had the intake gasket issues, I had P0300 code, but it was with other codes and mine only misfired at cold start up, not on highway.

I know that when a catalytic convertor is going out, it can cause problems when at freeway speeds and when it gets too hot if its clogged or border line failing. Have you checked the cats?

 

[kschumake83]

Did you check fuel pressure? It sounds like 2 cylinders are running lean. If you meant NGK plugs, they are the same as the factory delcos so that shouldn't be the issue. Do you have a scanner that can read sensor data? If so what's your long term fuel trim when this is happening.

Sent from my Nexus 7 using Tapatalk 2

 

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I had brought the hoe into GM and they had run the scanner on it and said that the fuel trim was all over the place due to the faulty MAF. This morning when I fired it up and went to head to work, I had very limited power for about the first 5 minutes, after the truck warmed up it had it's full power again. I was told it could be an O2 sensor causing all of this. They suggested changing the passenger side front O2 and see if that helps. Does anyone think this will help?

 

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UPDATE JULY 29. Please help, i'm going nuts with this! HELP!

Ok, So I'm still working on this problem and i'm going insane.

Problem - 2100 RPM for more than 2 minutes causes the flashing CEL with P0300 error doesn't matter if it's gentle accel or WOT; if I WOT on the highway I get detonation as well and the RPM surges as if the tranny is slipping (but the transmission has been checked and there are no issues whatsoever with it) and when I start truck up in the morning and drive, it is sluggish and bucks and takes about 2-5 minutes to run properly. After the 2-5 minutes it runs great. I never get a CEL under normal city street driving only a flashing CEL at 2100 rpm with P0300 code when i'm on the highway in Tow mode or 3rd gear. I took the Hoe to GM, and they said that the MAF readings were out so that's why I changed the MAF. When I unplug the MAF and force the truck to go into (closed loop I think it's called) everything is perfect and I don't get the CEL or the sluggishness.


What I have done so far...

Changed plugs and wires
Changed air filter
Ran seafoam through pcv line
ran fuel injector cleaner
changed intake gaskets
changed all 8 coil packs
changed pass side 02 sensor
changed MAF
cleaned TB

I'm going insane with this problem as I have tried every possible solution listed on this site. Can anyone give me some suggestions before I just leave this thing on the side of the road and let it rot.

Any help or suggestions would be very much appreciated!

 

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So after working on this issue for quite some time, I was able to finally figure it out. I would not wish this issue on anyone.

The issue was the EGR. I swapped it out and the truck runs perfectly.