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Discussion Starter · #1 ·
A few weeks ago I was almost home after an hour drive when the vehicle began to stumble and miss before settling into Limp Mode, with reduce power/RPM/speed. Luckily I was 2 minutes from home so I indeed limped home. Checked codes and got Random Misfire P0300 along with a few other cylinder misfires. More importantly I checked the oil and it was about 1.5 quarts low (0.5 qt. below the crosshatches). I discovered later about the faulty PCV system and sure enough the rubber air intake snorkel was full of oil and the throttle body was coated in black deposits. After reading about this issue I enlarged the holes on the rear PCV "valve" and cleaned the throttle body/air intake. Also spray cleaned the MAF sensor just in case. Also made mental note to check oil weekly . . .

Also discovered the #1 coil was partially melted and had a crack on top. Not sure if this was caused by the low oil or if was faulty to begin with. Replaced this coil and all spark plugs, and still had codes P0300, 0301, 0303, and 0305. Later I learned about camshaft solenoids possibly becoming restricted with sludgy oil so I pulled all 4 and cleaned.

After this latest fix I now have pending codes 0303 and 0102 (MAF sensor). I have swapped coils and the misfires have only been limited to the rear bank of cylinders (1-3-5). My biggest fear was the low oil level causing timing chain issues. However I don't have any of the other codes that I've read will accompany a timing chain issue. I also pulled the rear valve cover and rotated the crankshaft to get a peek at that timing chain and it appeared fine. Can't see lower chain or front bank. With the intake manifold removed I did see plenty of black deposits on the valves. Need help and ideas to try to pinpoint this problem. Obviously the vehicle is preventing me from normal driving use and causing further damage. I'm trying to decide between Timing Chain, excessive deposits on rear valves, or maybe the recent MAF code 0102? Thanks
 

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Aftermarket coil? If so they can be bad out of the box. Try cleaning the MAF with its dedicated cleaner before replacing it. It's probably oil fouled.
|What are the Possible Causes of the P0102 CHEVROLET Code?
  • Dirty Air Filter
  • Dirty Mass Air Flow (MAF) Sensor
  • Intake air leaks
  • Faulty Mass Air Flow Sensor
  • Mass Air Flow Sensor harness is open or shorted
  • Mass Air Flow Sensor circuit poor electrical connection
 

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Discussion Starter · #3 ·
I did clean the MAF in the early stages of this problem. Wondering if there's an air leak somewhere. I have re-used the intake manifold gasket after removal several times. Maybe a new one would help. Still wondering about the Limp Mode, seems like a severe reaction for something like a bad MAF sensor . . .
 

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1st thing that comes to mind is excessive carbon buildup. It can also build up on the lip of the valves. Sticky valves I think they call it.
But this also causes misfires and.....and when folks do a compression test, the mechanics say time for new engine as the 1 or more cylinders are showing low compression.
There was a member couple years ago who was having issues, misfires and everything and his mechanic said that he needed a new engine or a junkyard engine and he'd gladly pop it in for $4,000 or some crazy amount. bunch of us told him nothing to lose.... to first try running CRC intake valve cleaner and or Techron, which he did . Fixed his issue. he came back more than a year later and updated the post saying that he ran the cleaners and the vehicle had been running great over a year...
 

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Discussion Starter · #7 ·
Yes I did use the specific MAF cleaner. Also forgot to mention I did a compression test back at the beginning and all cylinders were 180-185, which seemed a little high. I'll definitely try the Techron and CRC cleaner first.
 

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Some people say no to crc.
Or any cleaner that cleans by that method. They say carbon breaks off and may scratch cylinder walls as it tumbles in there. Leading to oil burning.
But oil burning in 1st gen DI engines is bound to happen as miles add up.
Then again, if car is running like crap... or mechanic says replace engine....what do you have to lose?

I did run crc yrs ago.
I do burn oil. About 0.3 qts per 1000 miles
Or about 1.5 qts on a 5000 miles oil change interval.
My traverse will hit 182,000 tomm.
 

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Discussion Starter · #9 ·
Yeah I'm not too worried about burning oil after I saw all the oil in my air intake from the PCV "valve", which hopefully I have remedied.

My one concern about the CRC is with the engine misfiring badly I can smell strong odor of unburnt fuel. Wouldn't it be harmful to the catalytic converters to run a misfiring engine long enough to use a whole can of CRC?
 

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One possible way to clean the valves is, with the engine off, intake manifold off, make sure the valve is closed and spray the cleaner in the closed valve cylinder. Let the solvent sit and do its thing. Then remove all the residue and cleaner. I have seen one video on this method but have not tried it myself, this is what I would attempt on my vehicle.
I guess the hard part is having a vacuum which would not melt nor ignite while extracting the carbon and solvent.
Making sure that your valve is sealed is another issue, if they are sticking or a piece of carbon is lodged on the surface, then there is no way to guarantee they would be sealed.
GM had a procedure using the spray into the intake method with engine running up on Tech-link for a couple of months, but then they quickly did away with it, I assume it created more problems than it solved. They also recommended running a bottle of cleaner, Techron, and then changing the oil afterward.
Pennzoil was touting a synthetic oil a couple of years ago, which supposedly cleaned the valve deposits but I haven't seen any more on that.
Using Top Tier Gas, using full synthetic oil and changing it at no more than 5,000 miles is probably the best way to prevent these deposits.
 

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Discussion Starter · #11 ·
Just updating this thread . . .

Took vehicle to mechanic friend who was unable to diagnose the exact issue. Before I completely give up and take it to a dealer I have to ask again about the #1 coil that was melted originally. This was the first thing I noticed when I got the vehicle home. I wonder if the coil was defective and melted during the trip, which caused the Limp Mode and initial breakdown, and if there are residual effects after that. For example, when changing out the coil I noticed a really obnoxious smell from the coil and in that cylinder. Would a melted coil cause damage to the engine itself?

The other side of that question is- was there something wrong with the engine already (i.e., low oil) which caused the coil to melt? I heard somewhere that exhaust heat could do that.

Those are the only two things I noticed after the original breakdown (melted coil 1, and low oil). Never had any performance issues or check engine lights for almost a year before that. Any help or advice is greatly appreciated.
 

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Melted coil will stink.
Misfire will not hurt the engine short term but unburnt fuel will overheat and kill cats. That's why the CEL blinks when it detects a continuous misfire as to make it a more urgent alert.
Low oil will not hurt a coil. Too low of an oil level will only affect internal moving parts of the engine. Exhaust temp will not get any higher with low oil levels.
 

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Discussion Starter · #14 ·
UPDATE: So I solved this mystery by accident and found the fuse which controls cylinders 1-3-5 was blown. Apparently when the coil melted it blew the fuse. So that part is solved.

My new issue is a stubborn misfire in cylinder 2. I believe it's PCM related because I have replaced or checked everything related to that cylinder. Definitely getting fuel, I swapped coil and plug and the misfire remains at #2. Cylinder compression is good (180 ish) on all six cylinders. I even have voltage at the #2 coil when the key is turned on. But for some reason the misfire won't go away. Anyone else have this issue and could it be PCM?
 
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