When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Oh, we are talking about a used car lot (GM or not)? The Chevy used car lot rarely uses the chevy service department, usually a lot boy does that stuff.
Whoever is playing with the car does not have a clue about cars built since 1996. I hope they are paying for all of this part swapping.
No other codes, just the misfires. I believe it is bone stock. Map sensor is stock Delphi and there is not a "Premium fuel required" sticker on the gas door. I believe it says "premium fuel recommended".
Donbrew has asked the most telling question: why go to a chevy dealer at all?
The crankshaft sensor sense a misfire, sends P0300
The camshaft sensor senses which cylinder, sends P030X
If it keeps up in a drive cycle the CEL will start flashing to warn of possible damage to the catalytic converter.
If you are assuming false faults that is where to look.
If it is actually misfiring your choices are fuel supply, air supply, spark supply.
A cylinder compression check would alert you to air supply issues.
You have already addressed spark supply.
Since it is all 4 cylinders it is unlikely to be air or spark related.
Unlikey that all 4 injectors would randomly fail, especially at 56K miles.
That pretty much leaves fuel delivery, could be a glopped up tank screen to glop in the fuel rail, to bad wiring to the High Pressure Fuel Pump.
One interesting note is that excessive vibration can cause a misfire code, motor mount is not out of the question.
Just curious, how did they clean the injectors? To clean injectors, or the tips you have to remove them. If they are removed you have to replace the injector seal. From the freeze frame data you were driving it pretty easy, FP was ~ 695 PS, so I don't think fuel pressure was an issue give the load.
Given all the things changed and you still have the issue. It could be the back side of intake valves are coked up and not seating completely and/or one or more of your injector seals are leaking.
Took everyone's advice and bought some testing gear to be able to have as much information as possible before proceeding back to a chevy dealer.
Tested Compression: #1 - 167 psi #2 = 165 psi #3 = 164 psi #4 = 163 psi
Fuel Supply Pressure: 64 psi
While I had the hood up also pulled the Upstream O2 sensor (pita to remove). Found it had approx. 1/4 carbon buildup around sensor body. May or may not be unusual, I don't know but I decided to change it.
After replacing the O2 sensor the cel cleared a couple of days later and remained off for a total of 525 miles of driving about 20 different trips over 14 days.
The cel did come back on a couple of days ago, (P0300, P0301, P0302, P0303 and P0304) after several more trips the cel cleared and is off as of today. Perhaps the O2 sensor was just coincidental and had nothing to do with the cel staying off that long. Any comment would be appreciated.
I am convinced that the "misfires" are not real, because I would think that on a 4 cylinder a real misfire on all 4 cylinders would be somewhat obvious.
Any advice on how to proceed would be appreciated.
The misfires caused the carbon build up and could be damaging the catalytic converter.
Has anyone thought about looking at the plugs for wear and correctness? Somebody may have thought they were smarter than the engineers and put the wrong plugs in. AC/Delco 41-108. Any other plug is a suspect.
10-27-2017, 09:59 AM
Random Misfires