Periodically my 2006 H3 has been throwing a multiple misfires on cylinder 3 (P0303) code & a multiple misfires (P0300) code. It threw it a few times last year and it went away after I fixed an issue I was having with the thermostat (the thermostat was sticking making the truck run cold, so I replaced it). Well it started throwing the P0303 code again. I clear it and it goes away for a few weeks then comes back. I did a compression test and a leak down test to see if it was in fact the heads going bad. My results for the compression test are below but I couldnt get the leakdown test to work (not sure if my compressor or gauge was broke or I just didnt know what i was doing). Although when I attempted the leakdown test, it did sound like air was coming out of the oil fill and dipstick holes. Also, there was a lot of oil residue in the throttle body. There was also a small amount of oil in the part of the airbox that sits on top of the engine. What should my compression numbers look like? Does this sound like bad heads? Thanks!

Compression test

1D - 190
1W - 195

2D - 190
2W - 197

3D - 157 (slow falling)
3W - 165

4D - 179
4W - 195

5D - 195
5W - 205

2nd test on cyl 3

3D - 164
3W - 170

 

Oil residue in the intake and TB is blow by from the two PCV feeds into the intake vacuum... ie heavy footed throttle. I wouldn't use the word normal, but I can definitely tell you it is not unusual.

You did not provide mileage, so your Compression Test could be reasonable, or not so much?

You can get a better idea about your 06 H3 head if you check to see if your Vin # is early enough to have the bad valve seals. Search it, tons of threads on all that.

 

Thanks DocOlds! I saw a post you made on a thread stating "The S/Ns affected is any 2006 H3 lower than 287591 .... the first one started with 100,001". Is that the last 6 digits of the VIN (the production sequence number) that I should be looking at? The last 6 numbers of my VIN are 102354 so I guess they would fall within that VIN sequence. My milage is currently 116,500.

 

I was having a missing problem also on cyl. 3. I would start with checking the spark plug, and then after that check the coil pack. Mine also started doing this about the same mileage. Mine ended up being the coil pack. these are a lot cheaper to get and change than a head.

 

Yes that would mean your truck is within the affected range for the 06 valve seal issue. That does not mean you have a bad head in and of itself.

Skeeter made a good point, I would also suspect a bad plug or coil on plug pack. You can move the #3 pack and swap it with... say #1 and see if the miss follows the pack to where you moved it. That will verify if the pack is the culprit.

 

Update:

Switched the coil pack on cyl 3 & 4. P0303 went away but now I get a P0171 (Lean Mixture) code. Still lost on this one.

 

Start by cleaning the MAF sensor... ONLY use MAF cleaner and let dry completely before reinstall. Make sure the air filter is clean too. Clear codes and drive. GL