It was time. I changed the plugs, hand threaded them and half a turn to tighten them down. Had two COP's loose their boots during the change. Battery died when I did this, listening to the radio. Unplugged the ECU and moved the air intake, unpulgged a few sensors to make room to make the change easier, I'm a big guy.

Took about two hours to finish. Put it all back together again and now the truck runs rough. WHAT! Yes, rough. BTW, it wasn't running rough before just drinking gas water in the desert. I'm not a newbie here, but I haven't changed plugs in 10 years frankly. I got the bright idea to save myself some cash and now I got a rough running truck.

So I need help. I really don't want to bring this in to get repaired. I put in double platium plugs, did not replace the COPs. So I start the truck, no code on the ECU, but major loss of power and rough idle. So it's miss firing. I'm not a jedi, so I can't tell what cylinder is the issue.

I was assuming that the ECU went into safe mode or something at first, (why do I assume that, well I started the engine with alot of sensors unplugged by mistake) so I reset the ECU by unplugging the battery and thought that would put the ECU in learn mode, but then I heard that this model ECU stores all the data on flash, and a reset of the ECU doesn't do anything but cycle the power.

So I played with the throttle and got the ECU to code by finding a rpm that had the engine struggling to fire in order, I got a 0306. Which I thought was a error on the #3 cylinder on the driver side, that being the third back in the engine on that side. I checked the plug and reseated it with the engine cold (I heard these engines throw plugs because of cross threading and removing a plug when it's hot will take the threads with it from time to time) anyway that all seemed okay, and replaced the COP with a upgrade COP and started it up.

Same thing, rough idle, loss of power under like 2500 rpm, over that it seems to run okay, but probably because the motor is running at a speed where the misfire is harder to feel.

Now, I have no code on the ECU, I could force one I think, but should I be looking for another bad COP? Does the ECU have to re-adjust to the new plugs or did I loose data when I unplugged it?

Help would be apprecaited. I am alittle upset and short on cash, so please help if you have any ideas. I can't afford to buy 7 new COPS at $55 a pop, and I think driving the car in this state will damage the engine.

Please help...

Erik

 

What plugs did you use? Did you replace all the boots or just the ones you broke during the change? Year of truck and mileage would be helpful too.

 

The truck is a 2005. The plugs are autolite ht1. The boots that came off, seemed to slip back on without a problem (is that a problem?) ... mileage is around 105,000 ish

 

If your opposed to replacing all the COP's, I suggest it might be time (speaking from 2v 5.4 experience), you could purchase another new one and start swapping them out to test for an improvement. Maybe someone else has a better way?

 

The 2 things that come to my mind first is either a cracked/bad boot or a bad connection. Think of the COP boot as the insulation on a traditional spark plug wire. The seal between the COP and the spark plug is critical. I am assuming you went over the parts you removed for the plug change to assure everything is plugged back in and installed properly. Forgetting to plug something like the MAF sensor back in can cause a major issue.

The spark plugs on the 3V modulars made prior to 08' are not known for having plugs eject from the heads. They are known for possible issues with removing the old plugs and plug breakage during removal.

 

Okay, I'll check all the boots, I'll start with the two that seperated. Honestly the COPs seem to just sit on the plugs, it's hardly a tight connection, which doesn't seem logical to me. Thanks for the help so far.

Any insight to the ECU thoughts? Is what I was told correct?

 

NCon - I thought of doing that... seems to be logical. Issue would be two or more bad COPs. I heard that a failing COP could make others start to fail in time? True?

 

From and electrical point of view they are all independent...I think its just age, or number of cycles, that they are closer to the end of their service life. I tried doing a couple, then my dealer said he would give them to me for $38 a piece since I was buying so many

I see the aftermarket COPs are even lower price, so if you start changing brand COP, I would say change them all for sure. Its an expensive tune up, the price we pay for longer maintenance intervals I guess.

The ECU limp mode is apparent through the entire range, and just make sure you clear any codes in-between tests (free scanner tool at most autoparts stores). I have tried unplugging the primary connectors (one at a time) to attempt to see which COP is bad, but unless it's totally dead...its hard to find ones failing under a load. After a few hours of testing it turns out cheaper to replace them all I expect.

 

The pcm setup on the 3V trucks is more complex than my 2V 04' but I doubt you hurt anything by unplugging the pcm. Someone will let me know if I'm wrong. I had to pull the pcm on my truck and my dads truck to get the pcm code for the tuners.

I find it hard to believe a COP just went bad right after the plug change. Honestly if it were me I would have replaced all of the COP boots during the plug change because they are not that expensive and do not get better with age.

 

Success! This morning I went out and pulled all the COPs and checked the boots. I pulled all the new plugs again, cleaned them and I found.... two loose COPs and one of the new plugs had a crack in the insulator. I am not sure how that happened, perhaps a mfg defect in the plug, or I damaged it putting it in or the malfunctioning COP did that? Not sure, but I reseated everything, replaced another COP and the bad plug and boom. All good. The truck passed inspection and is running MUCH better. Thank you guys so much for the help, you seriously saved me some cash and I learned alot.

God bless!

Erik