Any ideas for enging miss/cutting out

hssnpny · Aug 7, 2008

I've been having an intermittant miss/stumble for over a year now. At first it would only happen once a month, or even longer . . . just long enough to make ya think it just went away. Now it's more likely to happen daily.

The duration of the miss varies, it may just be a fraction of a second, or as long as a couple seconds. With the longer ones, it feels like you just turned the ignition off . . . it throws your body forward. What seems like a key point to me, is that with the longer lasting stumbles, the tach dies and drops to zero. I would think this would eliminate possible issues like o2 sensors, TB, MAF and such. Once the stumble stops, it's back to running great.

It can happen any time, regardless of load. So it usually happens when I'm cruising at a steady speed. It has happened when I'm standing on it, and I thought I broke something . . . not a pleasant feeling. Has also happened at idle, so the car stalls, but starts right back up (so far).

Took it to a Mustang specialty shop once, but they didn't find anything.

Car is a 94 Cobra. Mods are Novi 2000, Edelbrock Performer heads, E303, BBK shorties, BBK TB. Stock block with 80K miles.

So I guess it's time to start throwing parts at it. Any educated guesses for parts or ideas for diagnosis are sure welcome.

Thanks.

toyman · Aug 8, 2008

Im thinking ignition coil. They often die a slow death and fail when hot. Tan/yellow lead off coil is the tach feed. Might explain loss of tach reading.

cbarr300 · Aug 8, 2008

Intermit. problems can be a bear to diagnose....sometimes all you can do is throw parts at it.

before you do that though, try and pull the codes. Even if there's no check engine light the computer may have stored a code.

My bet would be on the PIP sensor inside the distributor.

after that I'd guess coil. If you can find someone that's willing to let you borrow a known good coil then that'd be great. You could just swap them out and see if it fixes it.

Also, I'd throw some money at diagnostic equipment. Go buy a set of noid lights and a fuel pressure gauge...and if you wanna be really fancy grab a spark tester. If it gets to the point to where it won't start these would be some good things to have to help diagnose the issue. All three of those can be had for like 40 bux easy

Chythar · Aug 8, 2008

I agree on the distributor being the likely source. When was the last time you changed the cap & rotor? I had a similar problem and turned out I had corrosion under the cap.

HISSIN50 · Aug 8, 2008

Did you pull codes? A bad PIP sometimes will generate a code.

Look inside the dizzy bowl for ferrous material. That indicates dizzy mainshaft runout and/or a PIP failure.

Good luck.

hssnpny · Aug 26, 2008

Thanks for all the suggestions.

Since it was only $20, I tried a new coil. No joy. Cap and rotor look fine.

Since the car is pre-OBD 2, what is a decent (and cheap) code reader? Is the OBD connector under the dash like the OBD 2 cars?

If it comes to the distributor, is there a good source of reliable rebuilts? I haven't had very good luck with rebuilt anything. A new MSD was around $300, I'd rather not drop that much if I don't need to yet.

toyman · Aug 26, 2008

The reader port is on the passenger side strut tower towards the firewall. I have a reader and manual that I no longer need with my setup. PM me if you are interested.

BlackVert · Aug 26, 2008

cbarr300 said:
My bet would be on the PIP sensor inside the distributor.

i'm with this dude. good luck

Dino Dino Bambino · Aug 26, 2008

Could be the fuel pump dying slowly. The only way to find out for sure is to monitor the fuel pressure while the engine's running and see if it drops when the engine stumbles. Intermittent faults are definitely the biggest PITA to diagnose but rather than throw parts at the problem (it gets expensive very quickly), it's better to narrow down the list of possible faults first.
The hard stumble throwing your body forwards suggests to me that it's a fuel delivery problem.

hssnpny · Aug 26, 2008

I'll make it a point to watch the fuel gauge . . . I haven't noticed a pressure drop, but then I'm usually just swearing and saying "Oh crap, don't die on me here". A new 255 lph in-tank pump went in with the blower, but it's been 5 years, so it's certainly possible.

desertcox05 · Aug 27, 2008

dizzy. you should be able to get a rebuild one from advance, az, oreilly, etc for about 100+core. it's a common prob. with 94-95's. a haynes manual will tell you how to pull codes by using a paper clip and tell you what most of the codes mean too

hssnpny · Aug 27, 2008

Anyone know if the Cobra distributor is a diff part than the GT? All the online stores I've checked, if they offer a reman distributor, say "EXC Cobra", which I assume means except or excluding, or something equally bad. An example is the cardone part 30-2888.

So, if anyone knows where I can get a Cobra rebult part, lemme know. Thanks.

Methodical · Aug 28, 2008

hssnpny said:
Anyone know if the Cobra distributor is a diff part than the GT? All the online stores I've checked, if they offer a reman distributor, say "EXC Cobra", which I assume means except or excluding, or something equally bad. An example is the cardone part 30-2888.

So, if anyone knows where I can get a Cobra rebult part, lemme know. Thanks.

They are the same distributors.

Here you go: http://forums.corral.net/forums/showthread.php?t=988107

svtdrop · Aug 28, 2008

i had the same issue on my 94..... i threw alot of parts to fix it, but the only part i installed and made a difference was the ECT sensor..... after that, my car has been perfect, im running e cam with 30lb injectors on a stock tune.... my car runs like a champ now.........
change the ect sensor, cost only $45........ make sure you disconnect the battery and reset the comp......

pirotec354 · Aug 28, 2008

Try this

Hey man i had this same problem on my 94 cobra. I also have a novi 2000 on mine and i thought it was the throttle positioning sensor at first but it wasnt. It was my maf sensor. Well the ****ty tubing they give you for in between the intake of the charger and the air filter housing had come loose and fell off,( the mass air flow sensor is located on the air filter housing) and because my air filter is hidden in my wheel well i could not figure it out for a while. But mine was doing it a lot worse i couldnt even drive the car. So check that out maybe you have a minor leak right there. Hope it helps man, let me know?

red95gtconvert · Aug 28, 2008

My stumble that I had on my car that took me forever to figure ended up being a sparkplug that the ceramic section was cracked, I know how many hours of my time and how much money I spent throwing parts at it. It was only a 2 dollar plug

Any ideas for enging miss/cutting out

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