Hello Everyone. I am trying to fix a friends 88 Turbo Coupe. It all of a sudden began having a bad miss and backfire and had to be towed. This was right after getting gas so I figured it was bad gas. It passed all of the fuel system tests except for driving because it can't be driven at all. I dropped the tank and got rid of all the old gas, put a new strainer on even though the one on it looked ok, replaced the in tank hose that is known to split, and changed the fuel filter. I put everything back together and put 10 gallons of good gas back in. Started it up and it was still missing and backfiring with any throttle. I turned it off and restarted it a couple of times, still missing then all of a sudden it smoothed out and idles and revs normal. I drove it up and down my driveway twice then bam right back to missing and backfiring from running perfect. Any ideas? I haven't ran codes yet just hoping that maybe it's something obvious that you all would know right off. Thanks for any help.
Have you run the COMPLETE PCM self test (KOEO, CM, KOER)? That is where to start.
Have you checked fuel pressure at the rail? Should be 39 psi with the vac hose off the regulator.
Firing order correct? Use only the correct Motorcraft or equivalent NGK plugs. These engines run like crap with modern Platinum / Irridium plugs or with any Bosch plugs. Has the dist cap and rotor been checked for carbon tracking? Cracked insulators on plugs?
Failing TFI or failing PIP can cause missfires, sometimes with CM code 14 for the PIP or CM code 16 for the TFI, but often these failing components will not result in codes.
Has the cam timing been checked?
Hey Jeff. I haven't ran the pcm test yet because I have to replace the check engine bulb. It is 40 psi with the vacuum hooked up and 43 without it. I'm planning to check the plugs, cap, and rotor tomorrow, didn't have a chance today. The cam timing should be good seeing as it was running great until this happened but I'll check that as well. I'm working on this car for free except for getting paid for parts that I have stashed over the years so I'm trying to use as little of my stuff as possible because everything is hard to find. I'm not new to Turbo Coupes seeing as I've had mine since 2011 but I haven't had an issue like this. I also haven't had to work on one in a few years either so I'm kinda rusty.
(03-19-2019, 01:41 AM)KP88TC Wrote: [ -> ]Hey Jeff. I haven't ran the pcm test yet because I have to replace the check engine bulb. It is 40 psi with the vacuum hooked up and 43 without it. I'm planning to check the plugs, cap, and rotor tomorrow, didn't have a chance today. The cam timing should be good seeing as it was running great until this happened but I'll check that as well. I'm working on this car for free except for getting paid for parts that I have stashed over the years so I'm trying to use as little of my stuff as possible because everything is hard to find. I'm not new to Turbo Coupes seeing as I've had mine since 2011 but I haven't had an issue like this. I also haven't had to work on one in a few years either so I'm kinda rusty.
You will throw parts at it until/unless you pull the codes.
Many wrench-turners are thrown off by a good set of results in the middle of bad ones. Bottom line: does it run well now? No? Then those results mean little.
I have spent hours going ahead with bad theories based on one good set of results. My advice is, diagnose what you have now and keep the good ones in the back of your mind. So many things on any car can lead to a properly running engine—temporarily. Use the SCIENTIFIC METHOD—go through ALL of your tests as indicated by the codes/common sense, and don’t stop just because you got one positive result, which so many tend to do. There might be more information in the remaining ones that could alter or improve what you already know.
Thanks for the replies and help everyone!! It turned out to be a bad wire on cylinder 2 which had stopped firing. Looks like they were the original plug wires, I could barely make out the motorcraft on them. It also had Autolite 104 plugs in it which I don't know about those because I've always used NGK plugs. I installed new plugs plus a new set of motorcraft wires and no issues. My friend should have had this done when he bought the car three months ago but he didn't want to spend the money since it was running fine. I guess that I haven't had that issue with any turbo coupe that I've owned because I always do a tune up first and check everything out instead of assuming everything is good just because it is running well.
Glad to hear it was an easy fix!
(03-21-2019, 02:54 PM)KP88TC Wrote: [ -> ]Thanks for the replies and help everyone!! It turned out to be a bad wire on cylinder 2 which had stopped firing. Looks like they were the original plug wires, I could barely make out the motorcraft on them. It also had Autolite 104 plugs in it which I don't know about those because I've always used NGK plugs. I installed new plugs plus a new set of motorcraft wires and no issues. My friend should have had this done when he bought the car three months ago but he didn't want to spend the money since it was running fine. I guess that I haven't had that issue with any turbo coupe that I've owned because I always do a tune up first and check everything out instead of assuming everything is good just because it is running well.
I've been running autolite 104s in all of my turbo coupes since the first one I had in 2006. I believe the autolite is the same as the motorcraft sp-447. perhaps
or
can confirm.
https://www.sparkplug-crossreference.com...TOLITE/104
I have been running NGK 2238 (TR5) in my TC for years with great results. The only brands of plugs I put in all my Fords are either the stock Motorcraft plugs or their NGK equivalent.
Stay away for Platinum plugs in a TC, and of course NEVER put Bosch plugs in a Ford. They just dont work well for some reason.