Low Compression Cylinder Misfires When Idling

Hey Guys,
I have a 2012 Ford Escape that has had the Check Engine light on for the past 8 months or so. I ran the code, said there is a misfire in cylinder 5. I changed the spark plug and coil pack but problem wasn’t fixed. Took it to a garage, they said low compression was causing the misfire I think it was around 90 psi.

The car starts and runs fine. Sometimes, maybe twice a month, the check engine light blinks while the car is idling, which indicates that the engine is misfiring. I would just let it be but I can’t pass an inspection with the check engine light on, because of the emissions test (Massachusetts).

Do you think using an additive would increase compression enough to clear the code and keep it from misfiring so I can get it through an inspection? My registration expires May 1, (its April now), so I need to get a passing inspection to renew my registration.

Any thoughts?


If the low compression is due to worn rings, I’d give this a try.



Has the mechanic identified WHY #5 has low compression?

absent more information, I’m suspecting a valve train problem

If the mechanic already had #5 plug out to perform that compression test, he could have also performed a cylinder leak down test . . .

You’ve got nothing to lose by using the Restore treatment. Short term, maybe. Long term it’s at the end.
I would also suspect with one cylinder at 90 that the others are not far behind it.

Ah, I should have posted on here before I went. So I initially had them check the one cylinder (compression test), then I went back and had them check another. They ended up doing the cylinder 5 along with another one, and said cylinder 5 went from 120 to 90, and the other cylinder was 160.

I appreciate the replies. It has some rust along the wheel wells, 175,000 miles about, and was previously in an accident. Do you think its worth bringing in get thoroughly diagnosed, or should I just get a new car? When I brought it to the mechanic initially, the receptionist told me they would have to replace the engine to fix it, and I should just get a new car. Not sure she really knew what she was talking about…

If the problem is just the valves for number 5, then it is probably economical to fix. If rings/piston for number 5 are shot, probably not a good bet that there’s an economical solution. Has the engine ever overheated or run low on oil?

what was the result of the cylinder leakdown test . . . ?

Are you sure you don’t mean “went from 90 to 120” . . . ?

Was #5 compression initially 90psi, and then they squirted a little oil in the cylinder, and it went up to 120psi . . . is that what you mean?

If so, they performed a dry compression test, followed by a wet compression test

If so, that would imply your problem is on the bottom end . . . possibly rings and/or cylinders

If so, you have nothing to lose by using that “restore” product . . . since your engine is already damaged

If you go that route and somehow get through the inspection, be aware your engine is on borrowed time

I tried the product. First few days it seemed like it was misfiring more often, in the past week it hasn’t misfired.

It was initially 120, then I went back to have cylinder 5 and adjacent cylinder checked, and the they said #5 was at 90 when they checked it again, implying that it was getting worse.

Good luck and please keep us informed.

Can you please answer the question I’ve repeatedly asked you . . . ?!

What were the results of the cylinder leakdown test . . . ?!

You really need to answer that question . . . because then we know if the problem is top end or bottom end