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Engine Car randomly shuts off or miss fires, what to look for?

  • Thread starter Thread starter GSXR1216
  • Start date Start date May 1, 2023

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 1, 2023
#1
  • May 1, 2023
  • #1
So my '92 has something going on with it, started last fall was cruising 70mph for 15 miles or so and i felt it do something odd, not sure if it misfired, temporarily died or what but it felt like it lost power for 1-2 seconds then it was fine and back to normal?

a few weeks later it did it again. Now this spring i get it back out of storage and have only driven maybe 100 miles so far and the issue seems to be occurring again, had driven 20 miles or so and was exiting the expressway i toss it in neutral to coast up the the red light and after coasting for1/8th mile or so i see the tach drop to zero? hmm thats odd, put it in 4th gear and drop the clutch and it fires back up, stop at the light it idles fine, light turns green drive away like normal. going about 30mph down this next road a few miles and it stumbles like its going to die, does it 2 different times then runs fine the whole rest of the time going home ( another 15 miles).

Not sure where to look, not sure if the fuel pump is acting up since i only have a pressure gauge under the hood, not sure if its loosing spark, or if maybe something is going in the ECU or some sensor? Car runs perfect and normal at all throttle positions besides these isolated few second long random events.

It does have a MSD distributor in it, also has an old school crane interceptor in it (early version Anderson PMS) all of these parts have been in the car 25+ years and never had an issue before with any of these items, also has a 190 LPH fuel pump in it. Car only has 15,000 original miles, always stored inside, never seen rain or snow so all of the wiring is in good shape and not typical of a 30 year old car.
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,920
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Claremore, OK
May 1, 2023
#2
  • May 1, 2023
  • #2
With it being an intermittent issue its hard to troubleshoot. First thing is to check for codes and then go from there.

Basics would be to check the cap, rotor, plug wires and plugs. If they all check out then bypass the Crane ignition and see if that makes a difference. Typically a coil will just die but it could be possible that there is a problem there. If it still happens then swap the TFI module out if you have a spare. Still happening swap out complete distributors with a known working unit.
 

LILCBRA

I wish I didn't have all of these balls in the air
Mod Dude
Dec 6, 2005
6,402
5,385
194
Corn County USA
May 1, 2023
#3
  • May 1, 2023
  • #3
Had a very similar sounding problem with my 87 when I bought it. Ended up replacing the distributor since the price difference wasn't that big at the time, but it's likely that it was just the TFI.
 

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 4, 2023
#4
  • May 4, 2023
  • #4
Ill have to pop the cap and look at the rotor also and see how they look. i dont remember if it has to OEM TFI in it, or if the MSD distributor came with a new one? Regardless it would be 25+ years old. Plug Wires still look like new, they are FMS, but also 25 years old.
 

JD1964

there is enough sticking out to grab on to
15 Year Member
Jun 28, 2013
3,443
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Maryland
May 5, 2023
#5
  • May 5, 2023
  • #5
Due to the age of these cars, an important thing to check is the capacitors in the ECU. They leak and corrode the board. It causes intermittent problems at first usually, then it will eventually quit altogether and be a no start. It’s easy to check them.
 

Essn95

5 Year Member
Jun 21, 2017
817
622
113
May 5, 2023
#6
  • May 5, 2023
  • #6
I had the same issue, it gets worse and eventually the car won’t start at all, still haven’t figured mine out. My bet for you is PIP in distributor or TFI
 

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 8, 2023
#7
  • May 8, 2023
  • #7
Well it did it again this weekend, TFI didnt come in yet but should be here today, but i really do not think its anything in the distributor now. When it did it today i was able to look at the crane interceptor screen and it showed rich on both banks and it stayed stuck on rich for probably 20 seconds before they went back to the normal way of alternating between rich and lean in under a second usually. The car only stumbled for maybe 1-2 seconds, i remember last year when it did it once i also noticed it stayed showing rich for a long time also so I'm thinking it its either something going in one of the computers that it pouring a ton of fuel at it for some reason, or a sensor is going bad that makes the computer thinks it needs a ton of fuel?

I have a WB sensor from one of my race bikes that i had in this car years ago, so i guess i will put that back in so i can get a real feel for how rich it really goes when this happens. Ill have to see if there is any codes still also, have to find my notes from years ago on how to retrieve codes from this thing!
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
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May 8, 2023
#8
  • May 8, 2023
  • #8
I have to apologize as I just read this again and did not realize you are running a piggyback module on your EEC-IV. I see Crane and immediately think ignition as there just are not many running the Interceptor or Interceptor II being they sold and then it sold again to Anderson Motorsports and became the PMS. With all that I do know the history on it but have never used one so my knowledge is zilch.

You may just want to test your narrow band O2's and see if they are good to go as I believe that is what your Interceptor is reading?

Testing the o2 sensor

Im trying to troubleshoot a code 41 &91. I pierced the corresponding wires at the computer and am getting a fluctuation of 12.4 to 17.5 that is at the 200m setting on the dmm. If I set it to 20m it goes from 0.1 to 0.2. I am getting 12v at the connector for the heater and have also made sure...
stangnet.com
 

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 8, 2023
#9
  • May 8, 2023
  • #9
Yes the interceptor is reading the O2's, i doubt there is an issue with them since both banks go full rich when it acts goofy and they both go rich then lean quickly when it runs right and thats how they always acted for 25 years, i doubt they would both go at the same time?
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,920
4,041
183
Claremore, OK
May 8, 2023
#10
  • May 8, 2023
  • #10
Yeah, highly unlikely. Will the car run without the Interceptor? Was just thinking if it would start and idle without it then that would be a good check.
 

FastDriver

I was uncomfortably high & wearing a helmet
SN Certified Technician
Sep 5, 2001
6,104
2,713
224
Vass, NC
May 9, 2023
#11
  • May 9, 2023
  • #11
I have a specific recommendation for you, but I'm going to go on a little spiel, first:

So, one of the toughest things about Dailying these cars is that there are a number of fairly unreliable parts that can cause it to have ignition/fueling problems. My strategy is to have a spare, and most importantly *known-good*, TFI module in the car with the tools to replace it, an entire spare distributor in the garage, a spare coil, & a spare computer. I don't screw around anymore, I just start replacing parts until I get it narrowed down.

But, that can still leave the things I still need to diagnose, which include: unplugging the MAF to force the car into open-loop, checking the fuel pressure (fuel pump , filter, & relay). It's nice to have a gauge, though my current daily doesn't. The TPS needs to go from right under 1V at idle to something close to 5v (?) at WOT. The 10 pin connectors can kill the injector harness if there's corrosion.

Now, I just went through exactly what you're experiencing for the first time, and it turned out to be my MSD 6AL. It would go 20 min down the parkway running normally, then stumble. Then, maybe get worse and alarm me to the point if pulling off into a parking lot to diagnose, or... maybe it would just run fine for the rest of the day. It was basically impossible for me to figure out, because at home, it would run completely fine. I'd swap the TFI and thing I'd solved it... till it happened again 2 days later. Finally, it failed completely, leaving me calling for a buddy to come haul me off of the roadside. Then, I finally could diagnose it when it wouldn't start anymore. I tried everything else first, because I had it wire-tucked, but finally got around to pulling the fender. Bypassed the MSD box, and bang! No more problems.

So, that's my guess, and I hope it solves your troubles, too, but I definitely recommend that you stock a few extra parts to help diagnose your fox. It won't be your last issue.
 
Reactions: AeroCoupe and General karthief

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 9, 2023
#12
  • May 9, 2023
  • #12
Yeah it has a 6AL box on it also, certainly if the car would just die it would make it way easier to find the issue! A couple of seconds of trouble per hour of run time really make things a bit more complicated to figure out! Next time i take it out it will have the new TFI in it and the wideband O2 guage so that should pinpoint a bit more to whether its a ignition cut out issue or something else telling it to pour fuel to it for some reason.
 

GSXR1216

Founding Member
Jun 12, 2001
735
16
38
ROCHESTER, NY
May 9, 2023
#13
  • May 9, 2023
  • #13
OK i got the code reader in the mail today, in continuous memory with the car off it shows a code 64 and 96. 64 has something to do with a ACT sensor fault, 96 has something to do with a fuel pump secondary circuit fault?

Any idea what these may be actually telling me? i could replace the ACT, its not much $$$, but i dont know if something else may lead to that code 64? would this sensor being bad cause the random issues I'm seeing?

the 96 code. not sure what to look for there, fuel pump obviously runs, car runs fine 99% of the time? So far it seems the car is going full rich when it acts up so i woud not think its related to a fuel pump circuit error as i would assume the fuel pump stops running when that error occurs?
 

AeroCoupe

lube between the nut and the face. I know my lubes
Founding Member
Oct 28, 2001
5,920
4,041
183
Claremore, OK
May 9, 2023
#14
  • May 9, 2023
  • #14

Code 96 - Secondary fuel pump circuit fail - no pwr pin 19

That is what ford says. This just tests the harness between relay and 60 pin . If lite stays on your good.All of the j pin test are 4 fuel pump circuit. Why i asked if code 87 was present.here is what sc96 says.A continuous memory code 96 without 87,indicates that during vehicle operation one...
stangnet.com

Anyone know how to fix a code 96? (Has to do with fuel pump)

My buddy did a burnout last night at the top of my street in his stock 91 vert auto and then about a mile down the road his car died, LOL, but yea we need to fix it now. I pulled the codes with KOEO and got a code 96 which was fuel pump secondary circuit failure/high speed fuel pump relay open...
stangnet.com
 
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