Okay, so my truck's got a misfire at cylinder 3. I'll be double checking all the cylinders again but I know 3 is missing. 87 F150 with 300.

I found the misfire with my digital timing light though, so my question is could a problem with the distributor or TFI cause a single cylinder misfire? How likely is that?

Replaced the cap and rotor, didn't fix it. Then I pulled the spark plug, it's fouled, smells of gas.

But yea that's my question, what's the likely hood of a single cylinder misfire being caused by the actually distributor (PIP) or the TFI module?

 

Switch wires?

Hows it do w/ the SPOUT plug removed?


Could be a hanging injector. Fuel pressure test. Check bleed down time. (although you are seeing a misfire w/ timing light.

I don't think the PIP or TFI can single out the #3.

 

Chances are it is a spark plug , wire , or something wrong inside the cylinder, or since it is gas fouled a leaking injector. If you are getting spark at 5 cylinders then it is not the tfi module. Make sure your wires are in perfect condition, replace plugs and do a compression check. if you still have fouled plugs down the road i would look into an injector after you rule out the things that are cheap and easy to eliminate.

 

if you have checked it with a timing light and have no spark coming through the cyl 3 wire, the next thing you must do is switch wires on cylinder three and see if the problem follows the wire. until you have ruled out the wire you cannot continue. it would however be a smart idea to at least replace the plug on 3 since its fouled badly. my bets are on the wire for sure

 

Aight, so what I've done so far, is replace two plugs (found 5 in almost the same condition), cap (3, 5, and 6 terminals were lookin rough), rotor, and ohm'd all the wires. All pass. Ran it and put the timing light on each wire, everything was normal, but still rough.

Truck passes vacuum test, but I swear it's never idled this rough. But the idle is steady and in the correct speed range. I redid the exhaust last week.

Installed that and clamped on a tailpipe onto the end of the cat that points downward 30 degrees. No muffler, brand new smog check valve and everything. It ran fine until now.

Compression's good. Bout to try KOEO and KOER tests now. The injectors are from an Econoline van, but I drove the truck on them no problems. Doesn't take me long to swap in different ones if I need to...again.

 

If you've been missing on a couple cylinders, you've got some combustion chamber build up.How to Seafoam an Eighth Gen F150 (1987-1991) - Ford F150 Forum - Community of Ford Truck Fans

Another thought is, coils get weaker w/ age. That's why gaps are given as a spread.(.042-.046).

Error code scans are always a good idea. Also a good idea to concentrate on the KOEO results before dealing w/ the KOER's.

 

Didn't do a KOER test.

I've seafoamed the truck before, will do it again soon.

KOEO code was 11. Pass.

Continuous codes were, 14 (PIP erratic, misfiring or stalling) and 33 (EGR opening not dectected).

I cleared them cause I was running the truck without the EGR vacuum line connected before and replaced some ignition stuff today. I let the truck run and shut it off so I'll see if either of them came back tomorrow.

To be honest, the truck's running like it's cammed. The exhaust smells normal and isn't piping hot like it used to be (extra lean). My coil I bought two months ago. MSD.

 

Sounds like your getting there!

 

i would put a noid light on each of the injectors to make sure they are getting a good signal from the pcm.

 

I have a spare PCM (the one that came in my truck when bought) that I can swap back in. The one I have in now is from a junkyard truck (same year etc, but a 5speed manual not four).

I don't have noid lights, but I definitely need a set. I'll look into that.

 

So yea. Code 33 was caused by me not having the EVP sensor torqued down tight enough. The vacuum would leak back out.

Biggest mistake I made was driving it to work. Pulled in the yard and looked underneath and the cat was glowing red hot. By the time I moved my Supra (didn't wanna parallel park the truck), it was cooled off.

So this tells me I have tons of unburnt fuel. Can't really smell it though. The old cats never burned red hot.

Will do a compression test to check for burnt valves ASAP.

 

Good idea. Note bleed down time on all. How old's your O2? Gonna deal w/ the PIP code? Evp still not attached?

 

Yep I'll note bleed down times. O2 is new. Haven't driven much at all on it. PIP code didn't return when I cleared the codes. Only 33 returned, and I torqued the EVP sensor down correctly. Didn't clear the code yet, do that next time I mess with the truck.

The misfire isn't ignition related. It's fuel or compression related. I'm so afraid to destroy this brand new cat that yea, I won't even be doing a KEOR test.

 

Well, another problem that could easily cause this & at the most produce a alway's rich error code during a KOER scan is a pooched Fuel Pressure Regulator. Fuel pressure test at fuel rail would tell you.

 

Aight, so this just in.

Compression Test (psi)
1-145, 2-150, 3-145, 4-145, 5-151, 6-145

Spark Plug Wire Resistances (Kohms)
3.24, 3.35, 3.41, 3.75, 3.75, 4.14, 4.47

My brand new #3 plug is looking fouled already. #5 had light traces of fuel still as well. When I bought the truck it turned out that cylinders 2 and 3 intake valves weren't opening cause the pushrods unseated. I drove it 30 miles like that, and it wasn't as rough as it drives now.

The computer is junkyard and so are the injectors. I can swap my factory computer back in and see if that's the problem, seafoam it, and if all else fails, swap out the injectors.