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sprinkles08, ASE Certified Technician
Category: Ford
Satisfied Customers: 21436
Experience:  ASE Master and Advanced level certified. Factory trained with 15 years dealership experience
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Have a 1996 ford probe with 2.5L V6. It has been throwing a

Customer Question

Have a 1996 ford probe with 2.5L V6. It has been throwing a code for an engine miss. It's not 100% obvious when driving, idle seems smooth, but power is down. Cold engine compression test showed even compression on all cylinders. have replaced plugs, plug wires, and distributor. This code came in after replacing the timing belt. Again, engine starts easy and runs ok. QUESTION - How does the computer determine the 'miss'? If my timing was off, I would assume compression would be low and the engine would not fire or barely run.
Submitted: 4 months ago.
Category: Ford
Expert:  sprinkles08 replied 4 months ago.

Hello and welcome to JustAnswer!

Misfire monitor is a comparison in crankshaft acceleration between each cylinder each time they fire. When it sees a cylinder isn't contributing as much as the others it will set a misfire code when the inefficiency reaches a threshold.

There are many possible causes for a misfire, many of them you've already covered. The problem starting after a timing belt change is significant, incorrect cam timing will cause driveability problems and it's also possible that there is valve damage.

Why was the timing belt replaced?

What P codes are currently setting?

Customer: replied 4 months ago.
The tensioner arm was worn and caused misalignment on the cam pulley. The belt ran up on the cam pulley and the belt slipped enough to cause a timing problem. This happened on an engine start and resulted in a no start condition. This is a non-interference engine. So I think valve damage is unlikely. More to come...
Expert:  sprinkles08 replied 4 months ago.

I've seen valve damage on many engines that were officially billed as freewheeling.

What P codes are currently setting?