Low compression on 3 cylinders!!!HELP!!!

Wasup guys... I want to start off this thread by saying that I am a long time member of this forum, but I had to create an alternate screen name to hide my identity. I guarantee you guys know me very well over here, & I'm not trying to hide my info from the members of stangnet, but I need to get some major warranty work performed on my car soon, & these 3rd party warranty's go so far to search internet forums nowadays to deny us of our warranty claims...


Anyhow, I have had horrible vibration occurring on my 03 Mach 1 for a few months now, @ idle & while cruising at any speed. After getting exhausted checking out everything from plugs, mounts, balancer, vaccuum, u joints, etc, I ended up doing a compression test & found out that my compression was @ 180 psi on cylinders #1,2,3,4, & 7, but on cylinder six it was @ 150 psi, & cylinders 5 & 8 were @ a measly 120 psi!!!! What would cause this on a 55k mile car that is well taken care of, & the only mods were full exhaust, C&L 85mm, intake spacer, & a tune??? I religously change the oil, & I rarely beat on the car. What do you guys think the cause of this issue is, bad rings, bad valves??? My car has had the valve tick issue for about 3 years, even before I had any bolt ons, or a tune, & after I removed my cats & got LT's, you could hear a very pronounced "put, put, put" out of the driver side tailpipe, sort of like a misfire sound. It has also thrown the misfire code on more than 1 occasion on the #8 cylinder...


I am gonna take the car in for warranty work after I remove all the engine mods. The only mods that will remain will be suspension mods, what do you think my chances of getting the 3rd party warranty to honor my warranty. I have yet to try to use the warranty, so I don't know how good they are, but I do know that they send out inspectors, & they have people that do internet research in certain cases to try to find info on the customer. Anybody have experience with these type of warranty's?


Thanks in advance for any type of info you guys can offer....


****BTW, how do you like my screen name? I tried to come up with the corniest name I could think of LOL...

bhuff30 said:

Does it burn oil?

How was the compression checked? What kind of gauge? Was it checked at least 2 or 3 times and came up the same on each cylinder? How long was it cranked each time? It is very easy to get poor compression numbers from inconsistent and poorly done tests.

It looks like 3 of the low cylinders are on the same side. That makes me think it is a timing issue. Improper cam timing affect cylinder filling and thus the cranking compression.

Another possibiity would be the rings, but if the car doesn't smoke, I wouldn't think so. Lastly, the valves could be burnt, but I seriously doubt that would happen with a tune that the engine runs smoothly on. It just isn't common on modern engines.

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The compression was checked by removing the sparkplugs & cranking the engine 6 times. To be honest, it was some off brand tester, but I'm sure it was accurate enough to show that I have a F'd up engine. 60 psi of difference from 1 cylinder to the next is a HUGE difference IMO...


The car smokes a little from time to time, but only if you let it idle for a long time. But on top of that, most 32V's are known to burn a little oil & smoke a little...

So what do you mean by it being a timing issue? You mean the tuner added too much timing?

The tester was a screw in, & I'm pretty sure it was nice & tight. I could go ahead & do the test again with a different tester, but we did recheck all the cylinders twice that day. I need to get this taken care of Asap though....

Kilgore Trout said:

I know who you are...

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You probably do, but don't spill the beans

Midnight2V said:

If you had just one cylinder or if it was on both sides I would say rings. But all in the same side? Its either a warped head, cracked block, or blown head gasket.

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Maybe a warped head, or blown head gasket, but I haven't had it drink any coolant or overheat at all...

Midnight2V said:

Has iT ever been oVer revved. I mean EVER?

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Midnight2V said:

I don't mean shifting late. I mean like shifting at top of third into second.

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Nope, not that I ever remember, but I remember hitting the limiter a few times LOL...

Midnight2V said:

Hmm, I was thinking if someone had "taken the tach to the black" that some valves may have floated and gotten slightly bent. That would explain why it's only 5, 6, and 8. Since you have over 50# in each cylinder you are getting fire. I am thinking since 7 is ok that there may have been some bad gas at some point and detonation occured, in which case I would guess damaged rings. But there is really no way to be sure even with a leak down check...sounds like you are going to have to do one of three things.

1. Let it be. It may end up being fine for years.
2. Drive it like you stole it and run it into the ground.

or 3. Don't waste time, just tear it down now before you get stranded on the road somewhere.

Sorry I don't have any more ideas, I know none of these solutions will sit well for you. I wish I had a better solution but I am tapped.

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I personally have never over-revved it like that, but I did buy the car with 30k miles on the clock, so I cant speak for the previous owner. I have also never used any gas other than Chevron, Shell, or 76.
I know that I have taken excellent care of this car, I only ran Mobil-1 synthetic in the factory recommended viscosity, & most of the times, I have changed the oil way under 3k miles because the car doesn't get driven other than weekends. I have never ran it low on oil either, & have only tracked the car a total of maybe 10 passes...


As far as my option's go, I think I am better off letting the warranty company take care of this issue, I mean that is why I paid for a warranty...


Thanks for your info BTW....

So I returned the motor to complete stock trim. I removed my C&L Maf, LT's, o/r H, intake spacer, & tune. The only aftermarket part is the catback, & the suspension. Man the car is quiet as hell, & with the cats back on, you can barely hear the head tick. Hopefully the car will be dropped off at the shop tomorrow night.

I will keep you guys posted on the outcome...

flstang65 said:

Yes, keep us posted. I have heard and seen all kinds of horror stories from 3rd party warranty companies. I hope it works out for you.

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Thanks... I hope it works out too, & they don't try to shaft me. I decided to take my car to a local private shop rather than taking it to a dealer. I know the owner, & they will be more on my side than the stealership will be.

I'm hoping this goes smoothly, because I don't have the cash to cover the cost of a teardown if the warranty company screws me & tries to say its not covered.

BTW, what type of horror stories have you heard?