99 SR5 V6 running rough, missing

Got the new coil pack on and it ran fine.

Not declaring it fixed yet though. Acted fine a few other times for a bit and then started missing and acting up.

 

Well

Truck ran great going to work this morning and on the trip back home.

Blaming the coil pack for the problems. I cleaned the MAF at the same time I replaced coil pack but it did not look dirty at all.

Thanks for all of the help

 

Coil packs wear out internally unless they show cracks.

 

Well it is back

Ran fine on the way to work then started running rough on the way home. No CEL constant but it flashed a couple of times.

Back to square one I guess

Not sure what kind of problem comes and goes. Might see if Oreilley's has a rental scanner that I could hook up and run and see if I can catch a code. With no constant code none of the auto parts stores can scan it and not off again when mechanic is open until Monday

 

Changed the fuel filter and still problem came back. Sprayed carb cleaner all over top end and no change in idle

Took it back to autozone and now getting P0300 code (random multiple misfires)

Going to crank it and tap on the MAF to see if anything changes
Then I am going to clean the intake
Might put seafoam through the vacuum line
If none of that works I guess I will take it to the mechanic Monday and see what they can figure out

It has been running rough with no codes, CEL may flash a few times then quit.

Might borrow a compression tester and check but this random misfire/run fine mess is starting to get aggravating

 

So I pulled the hose from the air filter to the intake and fliped the butterfly open and looked in with a flashlight and it looked real clean

Truck has 195,000 miles

I think I am done, supposed to rain tomorrow so I will just take it to the mechanic Monday

All I did find was a crack in the muffler on the bottom edge but I don't think that would cause a problem. Just have to get it welded or replaced once I figure this other issue out

O2 sensors look like they have been on it since it left the factory but I would think it would be throwing some code if the O2 was bad?

Battery charger did not show a problem with the battery but I might run it by and get them to check the battery just to eliminate that

I do think I am going to buy an Ultragauge or scangauge for future issues though

 

I think taking it to a mechanic with all the proper diagnostic tools is the best thing. I have been in similar situations before and throwing money at a vehicle without actually knowing the issue is the worst. After all that you have done/ tried, I say take it to a mechanic and pay the $70 to get it diagnosed or whatever they charge. Hopefully whatever it is you can do it yourself.

 

Did you check your chassis grounds?

Between Fuel/Air/Spark, sounds like you are on the right track with spark, but there are many different things it could be. You have eliminated the easy and cheap ones so far, it sounds like. Other things, from cheapest to most expensive:

Crankshaft position sensor
Camshaft position sensor
Ignition Control Module

A mechanic should have the ability to check the operation of those things. Beyond that, you need to start looking at fuel/air and everything that controls it. Fuel pump and filter, injectors, MAF, O2 sensors, EGR, etc. It's a process of elimination, and it is always the last thing you try.

 

Yeah I am hoping the mechanic can eliminate a few things off of the list and save me some money.
I have just started replacing things before and that gets costly if you don't choose correctly
I have about decided that if one of the injectors are bad I am going to see what it would cost to have all of them rebuilt (if possible) and flow tested while they are accessible.
Read on another thread in my research that some come from the factory not up to spec

It is pouring rain here at the moment. Going to head to the mechanic when it slows down

 

Took it to the mechanic this morning and naturally it was running fine and only showing the random misfire code. So we took it for a drive and did everything we could think of to try and make it misfire.
So I left and drove it about 30min and went back to the house and grabbed some lunch. Got back in it and it was running like crap but no code. So back to the mechanic and when I pulled up he said he could hear a dead miss.
He hooked the computer back up and it was showing cylinder 1 misfire. So we pulled the coil pack and put a plug in and it was firing. Next we unplugged the injector and no change in miss. So he plugged some little LED into the harness and it was blinking so he said the injector was getting the signal.
We looked at what it was going to take to get the injector out and he asked if I wanted to do it or him. I asked how much for labor and he said $100 so I left it with him. It has been raining all morning and no place for me to get inside.

So apparently the coil pack was not the cause of the misfire.

It needed plugs though and it didn't hurt to change out wires and fuel filter.

So I only spent about $70 that I did not need to before the problem was identified. That is better than some of the past mechanic work I have done.

Thanks for all of the help and suggestions.

I am sure I will be back on the forum some more for future issues

 

Have you driven it yet? Hopefully that's all it was

 

Just picked it up this afternoon, so far so good b

If it is going to continue missing it should start back up in a day or two. Only thing I know to do is drive it and see

 

Been a little over a week and no problems

Seems the #1 injector was the culprit