Alright, my Cobra is worthy of its name yet again... it had to be a bad, new plug. I was running Motorcraft 32c's and i will bet it was the #4 cylinder. I have never had any issues with these plugs, and because they were new I refused to believe it was a plug... It just goes to show that you can do this stuff for years and still learn something new. I knew it was a plug just as soon as I started it this afternoon with new plugs. Before there was somewhat of a rough idle... now she is running very smooth. Oh well, i have done one heck of a thorough tune up and i love working on these cars.... thanks to all of you for the awesome advice, i really appreciate it!
1993 Cobra Misfire
- Thread starter 93_SVT_Cobra
- Start date
You may have cracked the insulator when installing it, not to uncommon. Or it was cracked when you got it.
+1 ...I've gotten bad 'new' plugs myself before
Alright, so i have something new happening.... i have already found/fixed the misfire and the car is running smooth at idle. I took it out last week after fixing the misfire and it ran fine. I also drove the car pretty hard to see if it acted up. I drove it all last week to work every day. Again, it seemed that it was fixed. Well today i drive it to work and at idle it seems like it is running fine. Also at a moderate acceleration it seems to run well. I havent experienced the misfire that i had before at all. However, if i go from part throttle (1500-2000 rpm) in a lower gear to WOT, the engine bogs really sharply and backfires, spits/ sputters and there is no throttle response. The engine wont die but it will only handle partial throttle. Again there is no misfire as before only when you gun it does it start to spit and sputter.... does anybody have any advice? TPS or TFI module?
Didn't you test or replace the TFI already? Anyway, TFI's are known for being fine one day, bad the next. That's not to say that's what is wrong with your car.
The TPS is an easy test with the key on, engine off. Just check the voltage with it shut, and then again with it WOT. I doubt you have a TPS issue, but it is possible it's part of the problem.
The TPS is an easy test with the key on, engine off. Just check the voltage with it shut, and then again with it WOT. I doubt you have a TPS issue, but it is possible it's part of the problem.
No i didnt replace the TFI because it was running fine once i found the misfire. I believe i should replace it now.
Okay so i havent replaced the TFI as of yet but i ran the EEC test (KOEO and KOER). The codes that purged are 13,19,21,33,44,67,94. Code 13 is for the ISC, which i am not sure what the ISC is...? Not sure about code 19 either. 21 is for engine coolant temp sensor out of range.... should i just clean this? 33 is an EGR not responding, opening, closing...etc... should i replace the EGR? Would this cause a backfire and bogging situation at half throttle to WOT? 44 is air injection system inoperative ( removed). 67 is park or neutral circuit fault??? Finally 94 is also air injection related which has been removed. Any advice? I thank you all in advance!
I know this is going to sound weird, but I had a similar issue once. Ending up being a valve spring.
That's seems to be a lot of codes for vastly different systems....my first thought is, check your ground strap. It should be bolted behind the driver's side head and screws into the firewall (it's somewhere slightly inboard of the clutch cable if I remember correctly).
So for the valve spring issue, did you run a compression test to isolate it, or did you bend a lifter or push rod?
That does seem to be several codes, if you have one problem it may be causing several codes to pop up too. If the valve spring is broke, a compression test could show the problem so it wouldn't hurt to run one if you have the equipment.
Did a compression test, what was weird was I would be driving, all would be fine and then all of a sudden it would start missing, then drive a couple of blocks and it would run fine etc. I did what he is doing and changed and checked everything under the sun, got tired of it and took it to the ford house to see if they could isolate it. #4 ended up not having compression. Mine threw a bunch of bs codes also.
Ignore the EGR and the 67 error.......not that uncommon to throw them when the car isn't running right.
ISC is Idle Speed Control or the Throttle Bypass. Just make sure it's cleaned out and working. It's worth checking into though, as I know over on the Corral had a super lean issue, all do to this little guy.
The one I'm looking is the engine coolant temp sensor. If that one is all over board, it can cause all sorts of problems. I'd check the wire, and possible replace that.
Thank you all for the advice. Replaced the tfi, tps, and ran a compression test. It has great compression on all cylinders. I ran the compression test twice, once cold and then again after driving the car for twenty.... also pulled the valve covers.... springs are fine. It is still bogging under acceleration. It didnt backfire at all during my driving... it just acts like it is either starving for fuel or not getting spark under a WOT condition. Im looking at replacing the coil now... however it is an MSD. Anybody had problems with these?
Did you check your TPS voltage at idle?
Have you cleared the codes and run them again? Did you check that coolant sensor? If it's giving false info, the EEC may still think it's in a cold start mode, running it way to rich. It's a long shot, but you never know.
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Checked the TPS voltage and it is 0.95 at idle. Alright so i took it out on the road a few minutes ago after clearing the eec-iv. I am still getting the EGR code as well as the coolant temp sensor code. Just to ad to what the car is doing under load, it will rev to about 3800 but that is where it stops. It is like a rev limiter is kicking in. In 2nd i just floored it and watched the tach. It runs to about 3800 and holds. I dont get and backfiring or smoke, just feel like it is starving but it stays running. From zero to 3800 it seems to run like it should. Feels like i will run as hard as it is supposed to but then it stops at 3800.... well im starting to repeat myself now.... this is driving me out of my mind. Has anyone experienced one doing something similar with only revving to around 3800 under load?
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