99 SR5 V6 running rough, missing

Truck has been running fine, filled up with fuel this morning and did some running around. Got back in truck and started it up and it was running rough and check engine light was on. No choice but to drive it home (about 20mi) and about halfway back it cleared up and ran fine.
So I was thinking maybe bad fuel this morning, took it by my mechanic but he was off today and it was still running fine so I headed to run some more errands and it started running rough again. Stopped and got a bottle of seafoam and dumped that in the tank and it is still running rough. On the way home I stopped at AutoZone and had them scan the computer. 0301 popped up and the print out said cylinder 1 misfire, then list probable causes as weak/missing spark, plugged fuel injector, engine mechanical fault or large vacuum leak specific to cylinder 1
Plan on starting with plug wires but was wondering if anyone had an opinion of what the cause could be if it clears up and comes back?
I did a search on code 301 and it came back with the same broad reasons.

Have not ruled out bad fuel but feel like it would come back to more than cylinder 1 if that was all it was

Thanks for any help

 

Have you washed your engine recently?

 

I had the same sort of symptoms a few months ago. Running rough, missing and an engine light. I did a few things. The seafoam in the tank, checked vacuum lines, and replaced spark plugs and wires. Reset the computer and it ran beautifully. Shouldn't be too much of a problem.

 

Have not washed engine

If I cannot figure it out before Monday I will run it by the mechanic, think their computer is better than the little AutoZone job but maybe not

 

Honestly, I think the only difference between autozone an a mechanic, the mechanic will e able to rule out some of the issues. He will be getting the same code as autozone.

 

Make sure the diagnostic port on the left side of the intake manifold is grounded: the bolt was backing out on my '99, and the two wires were wiggling, causing an intermittent miss. Until the ground was actually lost, and the truck just stopped!

 

Diagnostic port ground is tight

Pulled number 1 plug and it looks good, does have NGK needle point plugs in it with single electrode

Assuming there is no wire to check for #1 because coil pack feeds 1 and wire comes off to go to #4 on other bank

Going to check for vacuum leak next. If can't find anything there then take to mechanic I guess. Don't think I have tools to check injector and coil pack.

Thanks for advice so far

 

AutoZone guy just checked it by turning on the key and reading code.

I got to thinking that maybe #1 was last cylinder to fire and maybe it is the fuel having water in it and the scanner only read last code.

I don't know how the scanners work

Going to put it all back together and see what happens.

 

Well I got it all back together and drove it, cranked it multiple times and can't get it to make CEL come on again

At this point I am thinking
1) It had water in fuel and after sitting overnight the Seafom had a chance to do its job and it is fine now

OR

2)There was not a good connection between the coil pack and plug and unhooking and reconnecting fixed it

OR

3) It will start doing it again and then I will have to look at vacuum and injector as possibilities

Will reply again to this thread if it starts again and I can figure out cause

 

The problem is back and I noticed it running rough before the CEL light came on this time.

Had 2 people who are not mechanics ask about fuel filter and catalytic converter. Every fuel filter I have ever dealt with just stops up and vehicle will not run and it certainly did not clear up.
Never dealt with a catalytic converter issue so no idea what symptoms of that are

Problems that come and go drive me nuts. Hard to figure out when it just shows symptoms at random times

 

I just went through that with my 2.7

Ended up being a bad coil pack.

My mechanic hopped it around cylinders to figure it out.

Same CEL code as yours...I was going to put a new MAF in but let the pros figure it out

 

I am going to church and then I am coming home and firing up the smoker.

Might change the fuel filter (probably needs it and would not hurt if it does not) and then I might move the coil pack to see if that moves any thing around.

Somebody on another site suggested a "knock" sensor. I googled that and sure hope it is not the problem because it looks like a major pain to get down to it

Worst case I will take it to the mechanic in the morning and let him diagnose. He gets a good laugh at me, he will diagnose, I will try to fix, and if it beats me down he ends up fixing it. He is impressed that I try to fix some of the stuff I do.

 

Have you tried to clean the MAF?

 

Pull the coil while the engine is running and see if it makes the engine run worse or no change. If there's no change then it's that coil but, if it runs rough then the coil is probably fine.

If I were you I would drive the truck around and try to get it to run rough again and then do the coil test.

 

I know what you are talking about I think but have not cleaned it.

Going to try this IF I can get it to act up again. Seems to do it after it has ran for a bit. Older guy at church said it sounded like coil pack.
Going to run it by the mechanic in the morning and see what his computer says. It tells you all kinds of info about the engine, not just codes.


Next question is where to get parts? Genuine Toyota parts or aftermarket?

Found coil packs from ~$50/3 to ~$70/ea

Also probably going to go ahead and change plugs and wires. It has NGK plugs with a single electrode and a needle point now and there is a sticker on the timing cover that says use only dual electrode plugs

 

I was having skipping issues with my truck. I thought it was a slip in my tranny or bad ujoints or something to do with my drivetrain since it felt like it when I drove it. I also thought I haven't cleaned my k and n filter lately. I took it into my mech.

I told them and we did a test drive also they though maybe trans. then I told them about my k and n. they check everything. I told them toss the k and n and put a stock filter in for now. they replaced the MAF and filter did plugs and wires and my truce runs perfect. no more K an N for me. and no more skips on my truck.

i also changed al my fluids i the truck at the same time.

good luck.

 

It has to be something specific to that cylinder. Fuel injector, coil pack, spark plug, etc. MAF, O2 sensor, TPS, etc shouldn't give a code specific to one cylinder.

I would pull the coil pack and plug from that one cylinder, replace the spark plug, and swap the coil pack with another one. If you have a compression tester, confirm you have good compression while you are in there, otherwise just hope and pray........ After swapping coils, reset the CEL by pulling the negative battery cable for a minute or two and reconnecting. If the coil pack is bad, the CEL will come back on with a code for a different cylinder (the one you swapped coils with).

Hopefully it's just a coil pack or even a spark plug. Rare to hear about a burned valve or similar on these engines. I have heard of a bad fuel injector that took a pro mechanic quite some time to figure out.

 

Took it to the mechanic this morning and it was not showing a code at all. Left to go back to the house and it started running crappy again but no CEL. Went to town and got a new set of plugs and wires. Got them all changed out and wires replaced.
Drivers side (2,4,6) all of the plugs were in terrible shape. Electrodes were nearly gone, thought they had been changed before I got it but guess not. Thought it was strange that only that bank was burned down so bad and surprised it ran at all.
Changed the oil while I was working on it and air filter.
Not sure why #1 was showing misfire and not 2,4 or 6 but going to drive it and see what happens.
Coil pack will be next thing I swap around if it starts up again

Thanks for all of the help and suggestions

 

I tried the cheap coils on ebay when I was trying to diagnose mine. From experience with a couple of cars the cheap coil packs work fine. That being said, if my issue was a coil pack then I would have replaced the bad one with a denso pack atleast. I got the cheap ones as something to try which didn't help at all because my truck still had the same symptoms. I put the stock coil packs back on and took the cheap ones off.

If you want to try the coil packs you can have the 3 I bought for $25. Like I said they are pretty much brand new, only on the truck for a day at most.

As for the plugs, yes I would recommend running the dual electrodes denso or NGK. Rock auto has the best prices if your willing to wait for shipping.

 

Well the plugs and wires didn't help

Cleaned the MAF and going to pick up a coil pack in a minute

If that does not fix it I am taking the catalytic converter off next, maybe it is trying to stop up. Making a noise through exhaust that sounds like CC.