Engine misfire?

Ok I'll check on you.

No luck. Drove it around today and it once the truck warmed up, it started misfiring each time I idled for at a stop light. The CEL flashes and the truck misfires for about 20 seconds or until I start driving before the power kicks back in and the CEL goes away.

I took it in to a local shop today. They did another compression test and this one came up bad. I'm going to give in and let them take care of it. They want to do a valve job.

The only thing I'm concerned about is that the issue is intermittent. The way it comes and goes when idling (and the fact that another reputable garage misdiagnosed it) makes me worried that the problem isn't what it appears to be.

test should be done on warm engine, all plugs removed, engine cranked three times with fuel relay removed. test dry then test with a few drops of oil in cylender.

I think that's probably why the first garage missed it. Once it's back from the shop I'll post an update.

Spoke with the shop today. Exhaust valve in the 5th cylinder was sticking. I sent them the TSB on the Ford heads that were manufactured wrong to make sure they replace them if that's what caused the exhaust valve to go bad.

Makes sense that at idle the valve would stick and then free up once the truck once the truck was in motion.

I get it back on Tuesday. I'll follow up on whether it's fixed or not.

ok

Mangeris 1, hello, did the work on the head resolve the issue? I'm having the exact same issues your had or have. I've worked back words from injectors to O2 sensors. It's the same misfire #4 and my patience is running thin now. Lol.

O2 sensors won't cause a misfire. How is the compression on #4? Here is a guide to help:

https://www.2carpros.com/articles/how-to-test-engine-compression

Please run down this guide and report back.

When I take off from a stop or jump on the interstate and reach about 3,000 rpm's, it feels like the whole engine is shaking. Had spark plugs replaced, still does it. A friend told me that older vehicles are not designed to run on ethanol, that is why it skips like that. Could this (professor of useless knowledge) actually be right? Thanks, Glenn

Hi and thanks for using 2CarPros.com.

To be honest, your vehicle is not old enough to have such issues. Also, if the fuel was the problem, it would most likely happen all the time.

Has the check engine light come on? If the fuel is causing a misfire, the check engine light should have come on. When you feel the shaking, do you lose power? If you get a chance, read through this link. It discusses different things which can cause engine vibrations.

https://www.2carpros.com/articles/vibration-noise

After you get a chance to read through the above link, let me know your thoughts and hopefully, we can work through this together and figure out the issue. Also, is this a 3.0L or 4.0L V6 engine?

I will watch for your reply.

Take care,
Joe

Joe, my truck is a 4.0L six cylinder. Engine Light does not come on. Does not lose power. Thanks, Glenn

Welcome back, Glenn.

Honestly, that is a great engine and if there is no power loss or check engine light coming on, I would suspect that there is a problem with a motor or transmission mount. Make sure the rubber mounts are not crushed. When you get a chance, do that and let me know what you find,

I will watch for your reply.

Joe

I have replaced tons of coils and plug wires for this concern. The quickest and easiest way to check coil output is to carefully pull each plug wire boot from the plug and look at the spark intensity. The coils that are bad will not even spark past the boot when you pull it. There could also be trouble codes stored in the PCM even though the light is not on.