New MX-6..Engine Problem or easy fix?

[jmitch62]

Hey everyone,

If you read my thread from yesterday you would know that I just got a new MX-6 and I just had a chance to take it for a long drive on the highway (about 2 hours), and noticed something that may or may not be a major problem.

When I was going around 100-120 km/h, I felt the engine jump a bit and it sounded like pressurized air being let out for not even half a second and then the car would be back to normal, and it would do this almost exactly every 60 seconds. The sound is kind of like letting the air out of a balloon (not the squeek noise, just normal air leaving noise) really quick and the car would jolt a bit and go back to normal.

If anyone could help me out I'd really appreciate it.

Thanks.

[dmark101]

that almost sounds like a misfire or you're blowing out compression of some sort.

[94MX6pilot audio master]

Couls be the VRIS solenoids...if it's the v6

[jmitch62]

Sorry I should have had this in the first post..

Its the 1994 4Cyl RS...god I'm hoping its not a misfire or blowing out compression, that sounds really bad and expensive.

Hope it being a 4cyl changes some ideas.

THanks again

[cloakmurderer]

not being familiar with the 2.0L i can't be 100% sure of anything i am about to tell you, but from a general knowledge of engine operation and a personal mechanics standpoint i would say that it is blowing out compression, most likely through a valve as it is not a constant loss. Most likely cause would be some thing causing a valve to stick temporarily, it may be returning to the closed position from a tap from the top of the piston, if this engine is in fact interference design, or the lifter or valve spring finally causes it to retract. The most likely causes of a sticking valve on an overhead cam engine would be a problem with a hydraulic lifter assembly or the lifter bore in which it slides. Another couple possibilities involve the valve spring, valve stem, or if it happens to be like my 4horse B&S pressure washer motor, the valve seat breaking loose from where it should be, very unlikely in an automotive engine as quality control should be far tighter. Sadly all these possible problems would require the head to be removed from the engine, whether or not this is possible within-car i do not know, but either way it is a big enough job to undertake.

P.S. most of the issues stated would likely be due to top-end oil starvation, with the valve cover removed, removal of one camshaft bearing cap and inspection of the surfaces will be a tell tale sign of this. History of severely low oil usually means only one thing... Even more problems.

Hope i could help..

Cheers

[jmitch62]

Hey cloak, thats a bunch of scary scenarios in your post but I appreciate the reply..

I just went out for a drive on the highway to see if I could get a better idea of the problem and this is what I found:

It ONLY happens when the AC is on..never happens without it on.

So I am hoping this is not an engine problem at all or at least not a major one.

Thanks guys and hope this update brings me more optomistic solutions.

[94MX6pilot audio master]

check the a/c compressor belt...with a/c on and rev the engine and see what happens..

[vandejm]

ah yes...when i still had my a/c i could feel it engage every minute or so when driving at a steady speed....

the noise might be the a/c clutch engaging and making a bit of a whine because its on its way out.

[cloakmurderer]

Ok, i guess i was referring to what would be the worst case scenario, but if it's only with ac on, then it's quite possible it's only an issue with the ac, and because ac takes a good portion of power from the engine, especially a smaller engine in your case, you would notice a bounce in power, my 93 ls has ac, but the compressor clutch doesn't even appear to engage so i can only venture a guess that these mazda a/c's kind of suck, or maybe they just don't work very well after higher mileage is acquired, i didn't want to scare you but unless more details are supplied i assume an internal engine issue, maybe i'm just that way, you may just have to recharge the a'c system or replace the compressor and recharge, but i would say in an older car it isn't really worth it, unless you can't live without ac. my saturn HAD a/c working till i ruptured a line when i did the engine swap in it but i just compensate with m sunroof and what some may call 2/70 air conditioning (2 windows down, 70 miles an hour - old technology is the most reliable). anyways, good luck with everything.

Cheers,