Random misfire/ no start yesterday

Csirny

Registered User
My car developed a sudden miss this week ( Sunday )
Accelerating at about half throttle my car will miss once then take off just fine and it's not ever time. Also yesterday after driving around through town without any issues I parked the car for a few hours and when it was time to go to work the car wouldn't start at all. Tried it again when I returned home and no problems fires right up. Today I had the same missfire issue a few times. I have no check engine light on and I've replaced the DIS and the cam sensor this year chasing down a different problem. The crank sensor is original to the best of my knowledge. When I replaced the DIS I used an aluminum heat sink with arctic silver insulating the heat sink from the accessory bracket and mounted the DIS on top of the heat sink fins and ran a ground wire to it. The car has ran great like this all summer long. Any input would be appreciated. I don't know what the symptoms of a faulty crank sensor would be. Could this cause this?
 
My car developed a sudden miss this week ( Sunday )
Accelerating at about half throttle my car will miss once then take off just fine and it's not ever time. Also yesterday after driving around through town without any issues I parked the car for a few hours and when it was time to go to work the car wouldn't start at all. Tried it again when I returned home and no problems fires right up. Today I had the same missfire issue a few times. I have no check engine light on and I've replaced the DIS and the cam sensor this year chasing down a different problem. The crank sensor is original to the best of my knowledge. When I replaced the DIS I used an aluminum heat sink with arctic silver insulating the heat sink from the accessory bracket and mounted the DIS on top of the heat sink fins and ran a ground wire to it. The car has ran great like this all summer long. Any input would be appreciated. I don't know what the symptoms of a faulty crank sensor would be. Could this cause this?



Hard to say for sure, but replacing the crank sensor probably wouldn't be a bad idea. I have read that the DIS module, cam and crank sensors should all be replaced at the same time because of the possibility of failure in any of those three can be quickly followed by failure of the other components.

Also, I know alot of members have had trouble in the past buying cheap electronic ignition components that fail prematurely. They can sometimes go thru several of the same components before they find one that lasts.

I can't recommend them from first hand purchase of these components, but Super Coupe Performance sells a package with all 3 components:

https://www.supercoupeperformance.com/38l-sc-engine-18?pagenumber=6

You didn't mention the year of your car, but the link goes to early model years......89 - 90 and 91 - 93.

It's a bit pricey, but the quality could be much better. I'd call Bill at SCP and talk to him about it.

As far as your misfiring, I have no clue. And please, please, please.....make sure to get other opinions on these matters as I am far from an expert and there are a ton of people in this club who are far more knowledgeable and experienced than I.

Good luck.
 
Hard to say for sure, but replacing the crank sensor probably wouldn't be a bad idea. I have read that the DIS module, cam and crank sensors should all be replaced at the same time because of the possibility of failure in any of those three can be quickly followed by failure of the other components.

Also, I know alot of members have had trouble in the past buying cheap electronic ignition components that fail prematurely. They can sometimes go thru several of the same components before they find one that lasts.

I can't recommend them from first hand purchase of these components, but Super Coupe Performance sells a package with all 3 components:

https://www.supercoupeperformance.com/38l-sc-engine-18?pagenumber=6

You didn't mention the year of your car, but the link goes to early model years......89 - 90 and 91 - 93.

It's a bit pricey, but the quality could be much better. I'd call Bill at SCP and talk to him about it.

As far as your misfiring, I have no clue. And please, please, please.....make sure to get other opinions on these matters as I am far from an expert and there are a ton of people in this club who are far more knowledgeable and experienced than I.

Good luck.

Thanks for the feedback. The car is a 90. The DIS is motorcraft but the cam sensor is whatever advance auto sells.
 
Car won't start this afternoon. I drove it a few miles this morning with no issues now it won't start and cranks over really hard
 
No CEL. Now it cranks easily and seems like it wants to fire. Last time it did the same thing and then fired right up when got home from work.
 
I tried starting it again and it fired up. Drove around the block with no drivability issues but now the tach doesn't work.
 
Pulled the codes lately?

Tach drop usual culprits:
- cam sensor
- DIS
- unreliable harness
- unreliable grounds
- multi-wire ignition switch connector
- failed tach
- don't ignore combos of the above

Quick way to see if the tach signal is good, and maybe the tach itself isn't, is to run the VMM test - it can act as a visual rpm indicator.

See: http://www.sccoa.com/forums/showthread.php?103268-VMM-Self-Diagnostics-Test&highlight=vmm+test+mode


Quick test on the crank sensor is if the upshift light comes on while cranking = bad.
 
I'm thinking it may be the camshaft sensor or the harness going to it. It did the hard cranking thing again so for grins I unplugged the sensor and then it would crank easily. Then I plugged it back in and it fires right up and the tach works. The DIS is a new motorcraft one so I think that should be ok. The camshaft sensor is from O'Reilly and I haven't had much luck with them and advanced auto as far as sensors go and not just with this car either.
 
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