Running Rough and a P0306 code

SGaynor · Apr 12, 2007

I've got a 03 D2 HSE, 38,700 miles. About a week ago I changed the plugs and cleaned the throttle body (not throttle position sensor, just the butterfly valve and area).

Yesterday, the truck started running rough and CEL came on.:ack: Bought a code reader and got P0308. Last night checked the wire/plug on cyl#6 and all seems OK. Reset codes and this morning had same problem - rough idle and P0306 - but also got a pending code - P0301 (cyl 1 misfire).

I did a search on P0308 on dweb. and the suggestions were to clean the TPS and replace the wires. Before I buy wires, I'm going to clean the TPS.

Question: Can I use throttle body cleaner on the TPS or do I need a different cleaner so as not to mess up the sensor (ie, MAF cleaner)? (Did I fry the TPS when I cleaned the throttle body?)

Any other suggestions? Thanks,

PS - Bought an Actron 9175 at Autozone ($130). Very nice tool and very helpful.:bigok:

Chris-St Louis · Apr 12, 2007

Whose spark plugs did you use?

SGaynor · Apr 12, 2007

Champion 318s - gapped at 0.040"

skippy3k · Apr 12, 2007

Did you disconnect the TPS when you cleaned the throttle body? If the connector isn't tight, then that could be your problem.

SGaynor · Apr 12, 2007

No, I didn't disconnect the TPS when I was cleaning the throttle body.

An additional observation: My CEL occassionally blinks for a few minutes, then goes solid, then blinks. (But only the P0306 code). Also, can smell gas coming out of the exhaust.

SGaynor · Apr 12, 2007

UPDATE: Ran out to lunch. Now it's throwing the following codes: P0300, P0301, P0306 and P1300. All are misfire codes.

Mudquest · Apr 12, 2007

It's possible that when you changed the plugs, damage may have been caused to the wires at the plug ends. I'd make sure the contact's inside were'nt damaged and are still making a good connection with the plug.

You could also invetigate spark issues in the dark with the hood open and truck running. The better the light show, the worse your plugs are working...

Just an idea.

lordkenyon · Apr 12, 2007

Also, did you put in a bunch of diletric grease or silicone or anything in the boots that might have messed things up. Doesn't sound like this would be the only thing going on, but it's possible that could interfere.

How did the old plugs look coming out? Have you tried pulling them to clean them up and reinstalling? They're going to be carbon fouled when you pull that bank.

As Mudquest suggested, this evening or when darker, try running and see if you are getting arcing around the wires. Misting some soapy water can facilitate in seeing this too (just be careful you don't shock yourself if the wires are cracked or are arcing).

SGaynor · Apr 12, 2007

The old plugs were pretty dirty, but I don't know how long they were in there. Just got the rig 4 months ago. The #6 plug, when I pulled it last night, looked perfect - it was only in there a week.

Yes, I did use dielectric grease, but not that much. And when I put it back together last night, I didn't use any. Could hardly tell there was any on there, and no big clump in the boot.

The more I think about it, the wires were rather difficult to get off, so maybe I stretched the boot/wire connections when removing? I'll try the spray trick tonight and try to clean up the TPS. If that doesn't work, or the wires are arcing, I'll replace the wires.

lordkenyon · Apr 12, 2007

Hopefully, they didn't stretch out. If you can get your hand back there to the coil pack though you might want to make sure nothing got pulled out on that end as well. I kinda doubted grease being an issue, but you never know. Some people use half a bottle and wonder why there isn't a solid connection.

Are those still the only codes you're pulling? If you do need new wires, I can vouch for the Magnacores (let's try to not turn this thread into another wire debate) as being a good replacement. Easy to install, but a little shorter than stock and as such I didn't use all the stock retaining clips for them.

SGaynor · Apr 12, 2007

Well, cleaned the MAF, the TPS was clean. Cleared the codes, started it back up. More of the same codes: P1300, P0300, P0301 and P0306.

Next up: New wires. I'll probably be ordering the 8mm Kingsborne, per Rovercanus' suggestion.

Anything else I should try before ripping my plenum off to replace the wires?

SGaynor · Apr 12, 2007

Follow up question: I was reading the Rave CD about the ignition coils. Since cylinders 1 and 6 are paired for the wasted spark principle, if one is misfiring due to a bad wire, is that why I'm seeing a code for the other?

How would I know if it was wires vs. coil pack?

lordkenyon · Apr 12, 2007

I have the 8mm Kingsborn's on my DI, look to be a good product also and cheap too.

You do NOT have to take off the plenum to replace the wires. Might have a bruised knuckle or two, but I got the new ones on the DII without taking off the plenum without much trouble. It helped to lay an old comforter across the engine and basically lay on top of it while switching them. Also, print out the routing order from the RAVE and have that handy. Remove all the wires from the coil pack and then replace from the centre ones out.

Well, if all the misfire codes are associated with cylinders that are all on one pack, that could be an issue. I don't have the code list or rave in front of me, but basically look to see if the cylinders that you're pulling the codes for all go to one pack or the other. If it does, that could tend to indicate a bad pack.

But wires, (esp. Kingsborn) are a much cheaper way to test first and are a definite upgrade over stock if you're still running those.

EDIT: I pulled a code list and I see what you mean now about cylinders 1 & 6 both misfiring. Interesting. If those are one the same pack (I don't remember or have rave handy) then that could be at issue.

Mudquest · Apr 12, 2007

X2 on leaving the plenum on. The blanket on the engine worked great. Take your time, be patient, have a cold Guiness near by, and enjoy. Pulling codes for both 1 and 6 could mean a coil pack issue. I'd try new plugs first since you know you need those anyway.

I recently replaced my plugs a few weeks back - not a tank later my wires starting acting up somthing serious. Replaced the wires - life is good... truck never ran better.

Remove all the plugs for the coils noting each cylinder position and write them down. The help of a small wrench or pry device is needed. Replace from bottom up. Did I mention patience already?

Oh ya, and wear gloves this time. I'm curious to hear the outcome.

SGaynor · Apr 13, 2007

Don't think I'll be able to leave the plenum on. My '03 has secondary air injection and there are two metal tubes behind the plenum and above the coil pack...I can barely see the coil pack, let alone get my hands in there.

I may try just to remove the metal tubes, but may have to remove the plenum to get to the bolts holding it in place.:banghead:

Thanks for the advice. It's nice to have someone to talk to about this and work through it. My wife and friends just look at me like I've lost my mind.

Mudquest · Apr 13, 2007

Ahh....secodary air. Well then. Sounds like a true PITA. Sorry. One more tip I found helpful was to number the wire ends with the appropriate cylinder. That way when your hands are down in there, it makes it easy to know which plug your holding.

Still didn't stop me from switching 4 a 6 though. Geez - talk about rough idle and flashing ses light! The OBII reader basically told me the two cyliders I switched up and it was a quick fix. Best of luck. Still curious to find out if wires will fix your misfire codes.

Cheers.

Durda · Apr 13, 2007

No Freeeekin Way!

Scott, thanks for the thread, I was going to post the exact same thing! I've got an '03 with 55k miles running rough with all the same codes. P1300, P0300, P0301 and P0306

The only difference is I haven't changed my plugs recently and never threw P0308

Engine began to run rough at idle, intermittently at first but quickly worsened and now runs like crap. :ack:

Wires look good and I read the misfires in cyl 1 and 6 so I assumed it had to be a coil pack. I'm replacing it this weekend and was going to post here 1)To confirm my diagnosis as bad coil pack. and 2)Get advice on removing the plenum, (and everything else needed to get to the plenum)

Man this is weird!

SGaynor · Apr 13, 2007

Durda,

See this thread: http://www.discoweb.org/forums/showthread.php?t=25408&referrerid=8035

There's a good description on removing the plenum. That should help. I'm hoping that it's just my wires; that I damaged them during removal. Cylinders 1 and 6 are paired in the spark; simply put, when one fires, the other is used as a discharge spark (See Rave CD), so that may be why I'm getting a misfire on 1/6, but not the others. That leads me to belive (hope?) that it's just a wire issue. Otherwise, it'll be the coil pack.

According to all the threads on wires/coils, you should probably change the wires while you're in there. I just order Kingsborne's 8mm wire - $60 shipped ($40 + $20 for 2nd day air).

I won't be working on mine till next week, but I'll post the results when I get the wires in.

Good luck!

MonLand · Apr 13, 2007

Durda said:
Wires look good and I read the misfires in cyl 1 and 6 so I assumed it had to be a coil pack.

Wires never "look" good. There is high voltage that goes through them. They age and should be replaced regularly. Typically they will start cracking when you touch them (like when you replace your spark plugs).
You'll get a lot of misfire code with wires that are dead (and rough engine).
Change you wires (and spark plugs) before even considering a coil pack (or start by replacing your coil pack and send me your old one, I'll pay for shipping! ;-) ).

Durda · Apr 13, 2007

MonLand said:
Wires never "look" good. There is high voltage that goes through them. They age and should be replaced regularly. Typically they will start cracking when you touch them (like when you replace your spark plugs).
You'll get a lot of misfire code with wires that are dead (and rough engine).
Change you wires (and spark plugs) before even considering a coil pack (or start by replacing your coil pack and send me your old one, I'll pay for shipping! ;-) ).

Err, right. I didn't mean that they looked good literally. I meant that I checked for cross sparking and found none and there is no heat cracking on the boots. The plugs and wires have never been touched, as far as I know, so I don't think there is any internal damage. But there certainly could be.

I ordered new wires along with the coil pack. Trust me I'll replace the wires and plugs (Bosch Plats right

) before I commit to changing out the coil. If new wires fix the problem, the coil goes back to AB, sorry MonLand.

I order all the parts I think I might need and I'll return what I don't, rather then try something, and have to order more parts later and wait for shipping.

I've had plugs and wires go bad on me before, but it was always gradual decline in performance. This seems too sudden and too profound to be wires, but I certainly hope it is. The Disco feels like I've totally lost cyl 1 and 6, rather then an intermittent missed spark. Granted, all my vast

experience is with older chevy v8's, and I'm relatively new to LRs.

Running Rough and a P0306 code

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