Thanks in advance to all those willing to lend some advise on this misfire issue that I just can't figure out. I'm searched every webpage on the dang net and still having a difficult time getting a proper diagnosis.

I have 2001 D2 with 147k with a slight coolant leak (about a soda can every couple weeks) but no overheating. Cruising down the highway one day and my check engine light comes on, soon after starts blinking. Took it back to the house and these are the codes I get...

P0303 misfire on cylinder 3
P0300 random misfire.

I changed my plugs and wires approx 5k ago and the truck ran smooth as silk (random brand 8mm wires, bosch plats), so I assume those should still be in proper working order. So I decided to changed the coils, no change but this time with different codes...

P0301 cylinder 1 misfire
P0306 cylinder 6 misfire

Took it to a local shop (OC Rovers) and ran it through the computer to confirm the misfires, check the plugs and wires which were good, but also found my O2 sensor was out of range (passenger upstream) but no code was set off (I guess that would be a p0150). He found that it was covered in dirt, oil and other fun stuff. He sent me home to clean it out myself before spending money at his shop. After cleaning I got NO misfire codes but another one, P0150. I went ahead I changed both upstream sensors with Bosch ones. And now....back to square one...p0303 and p0300!

So my question, where do I start next? Injectors, maf, common leaks, issues with the fuel pump or filter, etc? Also I know a blinking check engine light means "stop driving moron", which has been switching back and forth from solid to blinking, does a blinking light, oppose to a solid, point to different problem even if they have the same codes?

Help! Any advice is appreciated! Thanks

 

Clean the MAF and clear codes and see if it comes back. But if you are losing coolant and it's not leaking externally it has to be going somewhere. Like mine it could be a cracked block leaking coolant into cylinder 3. These are the same symptoms I had. Check your oil for evidence of coolant mixing with it.

 

Good idea, I'll go ahead and clean the MAF. Actually I did have connection problems between the MAF and airbox as those two clips broke off, but they're secure for the meantime with a web of twisty ties. The coolant leak is external, i see a few drops every morning. I check my oil frequently and have not seen any evidence of mixing, looks pretty clean and not milky at all.

How about inspecting the 3rd cylinder itself, the spark and wire appears to be fine. If I pull the plug what should I be looking for to help diagnose the problem? (Soot, oil, excessively dirty, abnormally clean, etc.)

Thanks again

 

Go get a spark plug tester. Plugs between the wire and plug to check for spark.

 

I have a similar problem. Although, mine is P0300 and P0306. Going to follow this thread and go through the same steps to see what I find. Checked the wires for arcing last night, and found none. Going to pull the plug to see how it looks. Apparently, I do have a small coolant leak at the timing cover, but not sure if that factors into the misfire.

 

So cleaned out the maf last night, no change. Still getting the 303 and 300 code, but now also the dreaded p1300 (catalytic damaging misfire!). Looks likes I'll be spending more than I thought. Would it be safe to say it's not an injector problem since the unburnt fuel is damaging the catalytic? I guess that's one way to rule out a problem. Would this rule out fuel delivery issues as well (pump, filter)

Although I checked and believe the plugs and wires to be good, I'll go ahead and check them again for arching and abnormal wear as you did.

I'll be taking the truck to the garage the next couples days, I'll keep you updated on what they say. Hopefully save you some cash.

What else is there to check? Ahhh!

 

Go back to the shop and make sure the O2's you put in are functioning properly, it's not unheard of to have them be duds off the shelf. I had, what sounds like, an identical problem and they were the last thing I checked because I had just put them in. The O2 code only popped up once as a pending code but everything else was misfires and cat codes. Changed out the sensors again and it instantly cleared up.

 

I don't have much help to offer but I'll add a data point. I have a 2001 (124k miles) with recent plugs and wires. I get random misfire codes on the first cold start of the day perhaps once or twice a week. Today's included the P1300 code in addition to the common P0300, P0304, P0302 codes.

Once the engine is at operating temperature the codes stop and I won't see them the rest of the day, even if many hours between starts occurs.

Today I noticed the open loop indicator remained on during the misfires - this usually goes to closed loop quickly. I've got a set of cats and some raw piping ready to do the exhaust replacement project. At that time I'll install new non-Bosch O2 sensors. It might be a project I have to do soon...

 

Hi all thanks for the suggestions. I had my truck diagnosed and shows low compression in cylinders 1 and 3, high 20 psi blah! Likely going to cost a pretty penny. I'm wondering what are the possible causes of low compression given the truck does not overheat and shows no signs of internal gasket issues (no oil/coolant mixing)? Also, I'm pretty familiar now with the top end take down, is it possible to do the valve work myself (aside from the machine work that may be needed)?

 

Hey all, just wanted to give you some closure on the issue...

Turns out the gasket blew between cylinder 1 and 3 causing all the misfires. Ended up doing the head gasket job myself that took a few hours here and there over the course of a month or two. Anyways, everything seems to be working fine (please last forever!).

Thanks y'all for the advise!