Thread: P0302 Misfire Code - 2004 Pontiac Grand Prix N/A 3800

Is the correct ACDelco part number 213-1592 for the MAF Sensor? I went to the boneyard today and couldn't find anything newer than a 2002 GM anything.

That IDK but the Delphi one is a direct OEM part

Ordered the new Delphi MAF Sensor, probe only ($47.79). It comes with the "key" to be able to change out the probe. I watched a video on how to do it and it seems rather simple to do.

I really hope this is the solution to this problem. While the #2 misfire isn't setting a steady CEL anymore, it is still aggravating to see the CEL flashing while at a stop sign/light for any length of time.

I just decided to leave the code in pending to see if it will clear itself or actually develop to trigger the CEL. If it clears, it's all good. If it doesn't clear, or if it triggers the CEL in the next couple of days, then I will have that new probe to put in the MAF housing and that should be the end of this issue - I hope. Next couple of days will tell I guess.

New MAF Sensor probe in hand now. My daughter says that the car ran great while on the way to work this morning and the CEL did not come on at all. I will recheck the pending codes tonight for an update on whether the P0302 code cleared itself or not. I'm thinking that 40 minutes back and forth to work should be an ample amount of time for the system to have relearned that it can breathe correctly now. It will have a lot of chances to work through various RPM ranges and a lot of stop lights. If the pending code did not clear itself, should I just go ahead and change the MAF Sensor probe, or go ahead and clear the pending code and wait a few days to see what happens? I've heard that the system relearns can sometimes take a few days depending upon what it is trying to relearn. I would think that it would almost immediately recover from having COPD to being able to run cross country again. LOL

Originally Posted by Pooterosa

This is probably the going to be the oddest damned thing you've heard in a long time. I kept running this MAF sensor thing through my head over and over and tonight, for some reason, I was thinking about nothing but "air flow". I decided to pull the air filter housing completely out of the engine compartment. The air filter was fine because I had recently changed it, but I found 2 of those plastic shopping bags sucked up in the front of the air filter housing which probably blocked off 40-50% of the airway to the air filter, MAF sensor, and of course, the intake. I put everything back together, minus the 2 plastic bags of course, and I went for a test drive again. The CEL was not flashing at me while at idle, or while at a stop sign/light. The scantool does show the P0302 under pending codes so I am hoping it is a residual code from prior to the shopping bag removal. A couple of trips back and forth to work with it should tell the rest of the story and give it enough running time for the system to relearn. I will have the other MAF sensor probe tomorrow, or the next day, so if the P0302 code doesn't clear out from the pending codes on it's own by then, I'll swap it and see if that finailzes this deal. The next time you go flying straight over those plastic bags in the middle of the road and you don't see them flying away in your rearview mirror - go dig them out of the front of your air filter housing. LOL

Damn! Yea let it run a few dats before you throw that MAF in

If the pending P0302 code is still there this evening, I'll clear it and then wait until this weekend to give it time to decide how it wants to run. The new MAF Sensor probe came in a plastic formed enclosure that has a paper seal on the edge. They won't accept it back if that seal is broken.

I find it very strange that through all of the forums I've reviewed about this particular topic, other than referencing the MAF sensor itself, I didn't see anyone reference an air flow restriction as being a possible contributing factor to the cause of a rough idle, or misfire, on these newer engines. I'm guessing that is mainly in part because everything on them is controlled by sensors and there are only a very limited amount of vacuum lines that could cause any issues. I'm more old school where it would have been obvious if there was a plastic bag stuck in the airflow because it would have been staring me in the face once the hood was opened. LOL. The rough idle made me keep thinking that it was an air flow problem. Especially since I was able to verify everything else was good. I think that is why I decided to pull the entire air filter housing out and check it. There was no whining, rustling, or any other type of noise from the housing area or anywhere else that would have made me even think something could have gotten into it. Those plastic bags were sucked up in there and wrapped up so tight that I had to go in there with needle nose pliers and yank them out of there.

We all know that an engine needs spark, fuel, and air to be able to run properly and those are generally the first things that are verified when there is a misfire or an idle problem. Maybe we need to put a sticky for the troubleshooting process somehow so that it would go something like this now: 1.) Check wires and plugs for spark 2.) Check for fuel. 3.) Check entire air filter housing for plastic shopping bags. 4.) Check air filter. LMAO!

This has been one weird experience I can promise you that. I'll follow back up on, or by, this weekend and post an update for this issue. I am hoping I will be able to tell everyone that it has been fully resolved. If I have to install the new MAF Sensor probe, I'll let you know that as well. Until then, take care and be safe!

I also wanted to just point this out that the last copyright date on the Haynes manual, that covers the 1988-2007 Grand Prix, was 2008. I purchased it in 2012 and it had not been updated to reflect the 41-101 Iridium spark plugs, even though we all know that it needs the Iridium's and that is what is called for now. Just wanted to show that I wasn't making this up. The 41-921 spark plugs were double platinum and the correct number now is 41-101.

This has been one weird experience I can promise you that. I'll follow back up on, or by, this weekend and post an update for this issue. I am hoping I will be able to tell everyone that it has been fully resolved. If I have to install the new MAF Sensor probe, I'll let you know that as well. Until then, take care and be safe![/QUOTE]

Follow up to this issue:

I did clear the pending P0302 code last Tuesday evening and each evening after, even through the weekend. The code would only come up under pending and wouldn't set the CEL. Sunday I replaced the MAF Sensor Probe with the new one that I had purchased. Upon start up, the P0302 code showed up under pending again - unless I fat fingered the keys on the scan tool and didn't clear it the one last time before changing the probe - so I cleared it and it has not come back since.

I do believe that the problem is now corrected. Thanks everyone for all of the help with this matter as it was a weird one. MAF Sensors do not like plastic shopping bags. LOL.

Take care and be safe!

Hey there, I seem to have a similar issue chasing a misfire. 2003 Buick Lesabre N/A. I probably skipped some steps because I dove straight into the LIM because I have a P0300 and what seems like a lifter tapping noise. A few mechanics even seem to think so as well.

So where I am at is, clean cam lobes, lifters are not pitted, push rods ok, rocker arms ok, springs intact. Dead misfire on 6 and tap noise consistent with RPMs, seems to be upper engine area not lower end. Valvetrain appears in perfect condition.

I will be working on the car again today and putting the LIM back together, and start over and head where I think I need to, which is towards an injector issue.

Intake port on the head looks dry and not oily on #6, but #2 and #4 are oily as well as 1,3,5. P0300 is the trouble code and Tech 2 data shows it as #6 misfire in engine data, also unplugging the SP wire, rpms don't change. Spark plug is very wet. Other plugs are blackish, also had a P0128, but I don't see anything that explains the tapping noise.

However, one mechanic noted that the cylinder could be flooded with fuel and causing a pinging/tapping noise and also misfiring because it is fuel soaked.

I guess my next step is to get LIM together, swap plugs around, maybe a wire and lastly an injector, probably do a Tech 2 injector balance test? I will also be definitely checking the upper plenum for a hole or something from the EGR port and for restrictions in the air intake housing.

Anyone have any input or experience to add here? Thanks for any and all help

-MAC