Rough start and idle

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M

mister bean

Joined
Sep 20, 2005
Threads
26
Messages
241
Location
Boulder, CO
This has been going on for at least a week, maybe two. The truck has trouble starting, idles a bit rough, and feels down on power. There was no CEL or pending codes though.

Not having any other ideas, I cleaned the throttle body. It was dirty, but there was no change after cleaning.

Finally yesterday I got a CEL - P0307. So I swapped coil packs to verify that is the problem. The behavior is exactly the same as before - rough idle, feels like it's missing, and again there is no CEL or pending codes.

Normally I would just buy a coil pack and keep it as a spare if it didn't fix the problem. But this month we're refinancing the house, so it's much better not to spend the money unnecessarily.

Any thoughts on next steps aside from replacing the coil or just driving it the way it is and hoping a code pops up eventually?
 
Trunk Monkey said:
Well, if it threw 0307 that's a coil pack. When you say you swapped coil packs do you mean you moved #7 to a different cylinder or swapped in a new one?
Click to expand...

I thought P030x was a cylinder misfire, which can be caused by a variety of things, but is most commonly caused by the coil pack on these trucks. For example on a series of ears of Sentra engines, it was frequently caused by blown head gaskets.

I moved it from cylinder 7 to cylinder 5. Though considering it now, I should have swapped 7 and 1 to make it easier to replace.
 
So, you probably moved the bad coil pack from 7 to 5, hence the same symptoms, and it hasn't thrown 0305 yet. The CEL aren't just instantaneous, the ECM requires a certain set of faults to occur and usually a couple of start cycles before it will throw the code.
 
Yes, hence the desire to verify this is the problem and fix it without driving another week or two waiting for the CEL to come back so it can be read. Maybe that's not possible though.
 
Check to make sure a spark plug hasn't backed out. I had a very similar issue to you and found one plug almost all the way out and another very loose. Tightened them down (and checked the others), problem solved.
 
I went out and bought a coil. On the way home it finally threw a CEL. It's P0307 again. Seems that if it was the coil pack it should have been P0305, no?

So, next on my list:
- Go through service records and see when spark plugs were last replaced.
- If I can't find anything, buy new ones and change.
- If it is recent, make sure they're plugs are tight.
- Verify all the connections are nice and tight.

Sound logical?
 
Might be more than one coil pack, there are threads on here where people blow a series of them at once. That small amount of money spent will not affect your refi, they want to know you are not buying a boat or a house full of furniture on credit throwing your ratios off.
 
Gottagetone said:
Might be more than one coil pack, there are threads on here where people blow a series of them at once. That small amount of money spent will not affect your refi, they want to know you are not buying a boat or a house full of furniture on credit throwing your ratios off.
Click to expand...

I'm probably just being overly caution with the refi.

If it was a series of them, shouldn't there be multiple codes?
 
mister bean said:
I went out and bought a coil. On the way home it finally threw a CEL. It's P0307 again. Seems that if it was the coil pack it should have been P0305, no?

So, next on my list:
- Go through service records and see when spark plugs were last replaced.
- If I can't find anything, buy new ones and change.
- If it is recent, make sure they're plugs are tight.
- Verify all the connections are nice and tight.

Sound logical?
Click to expand...

Mister Bean: I would remove and inspect the number 7 spark plug. If that plug is fouled, then I would replace all 8 spark plugs with OEM iridium plugs and put the coil packs back in their original positions.
Ensure that all connections are tight.
Carry the new coil pack as a spare.
 
I haven't had much time to do anything until this evening, and was still limited on time. Here's what I did.

First:
- Replaced the #7 plug.
- Put same coil pack back on.
- Road test. Felt even worse than before.
- The base of the plug had some build up on it, almost like stuff was blowing through the threads and being deposited on the base. I've never seen this before. I'll post a picture of it shortly.

Next:
- Removed and reinstalled the #7 plug.
- Replaced #1 plug.
- Swapped #7 and #1 coil packs (#1 has shown no problems at all, and is OEM vs what doesn't appear to be OEM that was on #7).
- Road test. Felt better than the first test, but was definitely still missing when I did some 2nd gear starts. No CEL and no pending codes.

So, next steps:
- Plugs looked old, so I'll go back and replace the rest of them.
- Wait for the CEL to come back so I can determine which cylinder is missing now.

Here's a photo of the #7 sparkplug and its deposits.
Sparkplug-1.jpg
 
Last edited:
You should check ALL the plugs. Yes, it's going to be a bit of a PITA, but it will help you eliminate plugs as an issue and/or possible resolve the issue.
 
Yes, all the plugs will be replaced eventually. But since it's just the one cylinder that's been causing problems and I've had little time I haven't done the rest yet.

Anyhow, it threw another CEL this morning. The Code is still P0307 with a secondary P0307P (I haven't been able to find any documentation of what the second one means). So, same cylinder again. Based on what I've read in other threads, the injector for that cylinder seems like the next thing to check out. What's the best way to test that? The factory manual says to measure resistance with a multimeter. I don't have one, but they're not that expensive. Replacement looks like it might take a little while to do, but doesn't look very difficult.
 
I didn't have a multi-meter, so I had to order one. It arrived today so I did the in-vehicle test from the factory manual. I tested the injectors on cylinders 5 and 7 so that I would have a control. The manual said that they should be in the 13.4 to 14.2 ohm range. Both injectors measured at 14.1 ohms.

My brother suggested testing spark. So I did that and it was present for cylinder 7.

Any other ideas?
 
Nothing? I'm hoping not to take it in to the mechanic, but I'm going to have to if I don't figure something out soon.
 
I've had coil packs die a slow death before throwing a code. Might try getting one more, and systematically swap it through the cylinders to see if it goes away.
 
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