How can I be sure if I have a sticking/warped/bent valve? I have a misfire that I cannot find ( changed plugs, wires, coilpacks, injectors, put a noid light on the injector harness, nothing works!!!). The major problem cylinders are 1 & 3. If I put brand new plugs in, it goes away for a week or two, then it's right back. I've tried about every brand of plug that there is. Compression on all cylinders in that bank is within 5lbs of each other. I've put oil in the cylinders to check the rings. No change in compression. I've cleaned the EGR and TB. It only misses under load. I've ran Sea-foam through the oil and vacuum. I know engines pretty well, but this problem has me beat...badly...:o

Any advice out there?

 

have you tried having an oscilliscope hooked up to do a cylinder balance test or breakdown test? that is what i would do.

 

No, haven't done that...Can't even say I've really heard of it. Can you give me some more info on what it does?

 

Put a vacuum gauge on it when it's acting up. You should have around 18-22in/hg at idle with the gauge holding steady. Anything else, and you've got problems.

What do the plugs themselves look like? Are you losing any coolant? Depending on how many miles you've got, leaking intake gaskets are a possibility...seeping coolant into the plug wells, causing random/intermittent misfires.

 

I'll snap a pic of the plugs tomorrow, but they look decent to me. The coolent level has always been fine, never noticed loosing any. It's got 220,000 on the odometer, bought it at 205,000, and at about 215,000 it started acting up. I've got a rebuilt 5.4 in the garage waiting to go in, but I'm getting out of the military, looking for a job, and have a house on the market. Needless to say, I haven't had time to even think about that project...:o
I'd like to get it fixed at least until I can settle down in my new location, then the swap will ensue... But it run's pretty bad right now, and burns way more gas like this than normal.

 

Like I said they look pretty normal to me, but I might be missing something...

 

Throw those in the trash and put some Motorcrafts in it.

 

X2 to the plug swap. motorcraft only unless you can afford iridium denso's.

 

The scope attaches to your plug wires and measures voltage on each cylinder and indicates the energy needed to jump the spark plug gap. If it is running lean it should show a high kilovolt reading and rich running will be notice by low kilovolts.

 

If you're chasing random misfires, the very first thing you need to do is lose those lame *** Bosch plugs and get Motorcrafts or Autolites in it.

 

I agree with Quinton. Lose the Bosch plugs. Also a compression test is not that great of a test. I leak down test is way more accurate and will help you pinpoint if you have sealing issues.

 

Well, I put the old plug wires back on, with which it was missing before, and the miss went awat...

Until it starts acting up again, I can't really do much...

 

Bosch!

Of course you're having misfires!!!!!!!!! With those plugs, who doesn't!? God knows I did! Burned up a bunch of COP's with them too.

Bosch is the suck!