Unusual Misfire - Help!

[teamzukioffroad]

So here's the deal. Got an '00 XLS 4.0 OHV. Misfiring on #6. For about the last 2 yrs I've been eating motorcraft plugs every 6 mos. I always new when it was time b/c #4 would misfire on cold start. After replacing plugs, coil pack, and wires 2 mos. ago it ran like a new one. Now all of a sudden #6 will not fire period. Had a faint Antifreeze smell in exhaust, so I went in and replaced lower intake gaskets. Replaced uppers (again) while I was in there. Still #6 misfire. No codes yet, assumed misfire by exh manifold temps. My first thought was bad fuel injector.? but then some backfiring occurred and silver colored flakes of material started coming out of the tailpipe! Any suggestions folks? I'm kind of at a loss at this point. Anyone need a part vehicle? lol jk (for now)

 

[dogfriend]

Compression?

I would do a compression or cylinder leakdown test. The misfire and smell of antifreeze could be a head gasket problem or a cracked head.

 

[teamzukioffroad]

Thanks for the quick reply Dogfriend. I'll try a compression test and see what happens.

 

[teamzukioffroad]

Also, I should add, that I installed new plugs along with the gaskets. Ignition on 6 checks out good. After restarting with misfire, the plug from #6 had no evidence of gasoline, antifreeze, or oil on it. Just thought I'd throw that in.

 

[teamzukioffroad]

Compression checks out good, to me, topping out at 150 psi on 4th or 5th turn of motor. Any ideas? Going to check fuel pressure next. when I find or build a gauge.

 

[96eb96]

Compression checks out good, to me, topping out at 150 psi on 4th or 5th turn of motor. Any ideas? Going to check fuel pressure next. when I find or build a gauge.

do you live near a harbor freight store? You can get cheap fuel pressure gauges there.
http://www.harborfreight.com/cpi/ctaf/retail_stores.taf#NC

 

[teamzukioffroad]

Thanks 96eb. I might stop by HF in winston tomorrow. I ended up removing all fuel injectors and cleaned/soaked them in 50/50 seafoam and hi test. Hopefully I can give some more info tomorrow.

 

[bluestream1]

If you have the injectors out take them in for ultra-sonic cleaning. This is the ONLY way to clean them properly. Cost me $40 for six, and what a difference. Most diesel injecter shops will do gas injestors.

 

[Cobraguy]

do you live near a harbor freight store? You can get cheap fuel pressure gauges there.
http://www.harborfreight.com/cpi/ctaf/retail_stores.taf#NC

While it's always a good diagnosis tool, I don't think that will tell us much here where all other cylinders are fine. EDIT: I changed my mind...I think I like 96eb96's idea and want to know the fuel pressure before we go much further. Watch for pressure fluctuations.

If you have fire and compression, that leaves fuel...assuming everything is timed correctly. You might want to check and see if the injector is firing. Get a stethoscope and listen for clicking. But even that won't be definitive as the injector could be plugged. But you need to see if it's getting a signal from the pcm, then see if it's plugged. As suggested, might as well pull the injector.

 

[teamzukioffroad]

Alright, good news is that she's back up and running. I called 5 shops around here and no one could clean or knew anyone who could clean injectors! the usual. So after cleaning them myself, everything is back together and running pretty well. Believe it or not! I did check fuel pressure just for kicks. 41psi at idle, 44psi idle w/o vacuum tube, and it was still holding pressure after 5-10 mins with engine off. To me that looks good, correct? Even though it's running smoother than ever, I still don't trust the injector on #6. Probably need to replace them all. But for now I'll have to let it ride. Thanks for all your help guys!

 

[Cobraguy]

Those pressures are perfect. I'm guessing you either had a plugged injector or a bad connection. Either way, sounds like you are good to go.

The only thing I worry about when it comes to injectors is a failure could be catastrophic. Not so much on one of these, but on a boosted vehicle, it would only take a second or two at boost to burn down the piston. But you would sure get detonation on this that could do some damage.

 

[teamzukioffroad]

Thanks for the info cobraguy. My final thought is a plugged injector. I cleaned all the connections and de-ox'ed them before I put them back together. Unless the PCM was on the fritz, but I don't think so.