Rough idle at cold start, P0303 troubleshooting, engine death

First gen 2004 3.4 V6, automatic, 220xxx miles
(TLDR: Leaking head gasket and poor compression, so I'm having the engine replaced for $3500)

*I'm posting this for advice and tips on solving the issue and for the benefit of others in the future. I have searched the forums and have learned a lot, but more input is welcome*

-Recently my truck has had a rough idle when first started in the morning. Definitely sounds and feels like a cylinder is missing, but the cylinder starts to fire and the idle smooths out after 10-15 seconds.

-After the rough start the engine runs just fine for the rest of the day, with multiple stop/starts, and under heavy load.

-Only once in the last week has the CEL come on at startup, showing a code P0303: Cylinder #3 Misfire. Revving the engine doesn't seem to help it clear up noticeably faster.

-A bit of white smoke/steam is present during this, but the mornings here have been cool and I don't generally inspect the exhaust so I don't know if that much condensation is normal or not; it's not excessive just noticeable when watched. The exhaust doesn't smell particularly sweet like coolant, but it sure burned my nose/sinuses more than an oily exhaust would.

-I've marked the coolant tank and I don't appear to be losing a noticeable amount of coolant (EDIT: I've lost almost 1/2" from the reservoir in the last week or so of mostly letting the truck sit. That coolant is leaking into Cyl3)

-The first morning this happened I was just about to do regular maintenance anyways so the oil/oil filter/fuel filter/air filter are all new, and the MAF is clean. The trouble has continued after this. Oil looked fine, transmission fluid on dipstick looks fine, coolant is nice and clear-pink.

-I burned about half a quart of oil in the last 4500miles between oil changes but I have also been driving heavily with a loaded trailer. These last 10k miles I have been driving the piss out of this truck towing a 4000lb travel trailer at 9mpg, so the engine has been working very hard including some long steep grades. No overheating though. (Yes I have a transmission cooler too)

-The day after the oil change I replaced my spark plugs after at least 50k miles. The wires are 30k miles old(original ones chewed by rats) and in good condition externally. See pictures below, spark plug from Cyl3 was hotter than the others.

-When changing plugs I let the engine sit overnight then dipped Cyl3 with a "straw" of tightly rolled paper, but no fluid absorbed into the paper. The engine started rough anyways.

-Ran injector cleaner with a full tank of gas, no change.

-After all of the above, the engine still starts with a misfiring cylinder (presumed Cyl3) even though the CEL has only indicated once.

This problem could be a dirty injector, a leaking head gasket (cyl3 is usually the first one to go, I've learned), oil dripping down the valve, weak coil?? I'm about 250 miles from finishing this trip, so when I get home I'll do more troubleshooting and update here. Any suggestions or advice would be greatly appreciated.

Spark plugs


Same plugs, rolled over to other side. Cyl 3 is more heavily sooted than the others (The dielectric grease on the threads happened AFTER the plug was removed. The rest of the gunk on the threads is old anti-sieze)


(Error code keywords to help future peeps find this post P0300, P0301, P0302, P0304, P0305, P0306)

 

So I had this problem a while back! but mine was due to cheap coil pack arcing to the motor I finally caught the little spark jumping, I replaced plugs and check comp all that stuff i was swamped but check your coil packs at night see if the insulation on one is bad. Since then I only run oem packs! Ive still been running the NGKs but only the single. hope this helps!

 

Awesome lead, thanks!
But it was only arcing at cold startup? That's weird

 

its almost like it warmed up it would transfer the spark properly, no clue why but it always seemed to smoothen itself out!

 

Very interesting. I'll check for arcing when I get home in a few days when I can let it sit all day until nightfall so it's cold cold

 

keep me posted!

 

It warmed up, the material expanded sealing up the conduction path. Coil packs would definitely be suspect #1; swap them around for a bit and see if the misfire code follows that coil pack.

 

Agreed!

 

My first guess would be leaky injector.

EDIT: But, I agree with the other poster -- I would move the coil packs around to see if it follows to rule that out first.

 

That could definitely explain the misfire, but that plug does appear to have been running hotter than the rest, can't really equate that with leaking injector.

 

It also looks a little wet in the second pic. But, the paper test the OP did probably should have shown something if there was enough fuel leaked to cause it to run rough. I've just seen a lot of 1st gen threads on here, about the same age and mileage, where there was a leaky/faulty injector causing similar symptoms.

Again, moving the coil pack around is an easy test to rule out ignition. An air issue would likely be spread around more. So fuel would be next, and maybe a compression test.

 

Injectors definitely start dying around that age.

 

Well it's a blown head gasket for sure. After letting the truck sit for a few days I dipped cylinder #3 again with a paper tube and was able to wick up a bit of coolant. So off to the shop she goes! At least this solves the mystery and I hope it helps the next person.

 

Bummer... at least you know.

 

Just chatted with a very reputable shop here outside of Cleveland about doing the headgasket. He ballparked ~$1800 to do the job but warned that on an engine with this many miles (225,000), doing the head gasket might just be passing the buck onto the next weaker component. I'm going to do a compression test this weekend to get an idea of how my piston rings are holding up.

Still, compared to a full engine swap, $1800 is small beans.

 

Those beans get a LOT bigger if the next major component fails three months down the road. With that mileage, I'd be hard-pressed to spend the lion's share of $2K. It's not a terribly difficult job; you could do it yourself for a LOT less than $1800, even if you have to buy a bunch of tools.

 

Had a similar situation with my 98/3.4L. Turned out to be a cracked head, dumping coolant into #3 cylinder. Started out with just a tiny bit of steamy exhaust at start-up, but after a couple weeks, it looked like a Stanley Steamer going down the road. This occurred at approx. 250,000 miles. Replaced with a rebuilt head. Ran great for about 15 minutes, then threw the #4 connecting rod through the side on the block. I've been told the 3.4L has problems with cracked heads, and connecting rod bolts occasionally coming loose. I've experienced both. Replaced the wrecked engine (block, crank, and 3 pistons destroyed) with a JDM 3.4L that came out of a 4Runner.

 

For the price of 2k you can get a lower mileage engine.

 

I paid less than 1k (ebay, yeah I know) for my replacement engine. It allegedly had less than 80,000 miles on it. It's been a good, strong motor.

 

Here are my compression test numbers.

Cly#.____PSI-Dry(Day 1)______PSI-Dry/Oiled(Day 2)
1__________175______________145/160
3__________155______________120/160
5__________175______________145/180
2__________182______________155/180
4__________165______________130/160
6__________155______________155/190

So those numbers aren't good, especially on Day 2(today) when the oil added to the cylinders boosted the pressure so much, indicating poorly sealing piston rings.
I'm not sure why there is such a great discrepancy between Day 1 and Day 2 dry pressures. I only drove the truck six miles between the two days just to get it warmed up for the test. Day 1 was about 30 degrees warmer ambient temp than Day 2 and the engine might have been warmer from being driven more prior to testing on Day 1?

Either way, not good. I'll be exploring my engine swap or rebuild options. Does anybody know of a good rebuilder in/near Ohio? Any reason not to have the engine rebuilt? Would labor hours end up costing more than a donor engine swap?