Vechical inspected was running rough, hard to start, no compression clylinder 4 AT ^60 psi, removed Cly head found very little, head straight of to machine shop , possible blown gasket between ports, but head only required small amount of skim, refitted , Note mechine shop said liftes hard to bleed down, after fitting head ran for 3 hrs car cutting out pining bad, checked for codes, nil codes, checked fuel pressure at 250 psi and moves to 350 psi under load, replaced ecu with exchange , still the same , replaced crank sensor , map sensor, coil pack, then thought may be pumped up liftes deslugged engine 4 times, note checked compression when hot and the problem is there but compression good all clylinders over 174 psi, removed cam, checked oil feed checked coolant sensor, ecu at 89 degs, note checked timing belt markes 4 times ?????? can any one help iam at over 45 hrs on this bad bad car (KMS are at 117 000)
Hi, This Might have nothing to do with your problem, but you have nothing to loose by the sounds of it, the breather pipe from the bottom of the sump (behind the starter motor) to the top of the rocker box, mine was clogged up with slug like greese causing sencer problems and giving false information to the computer. (running rought) you got nothink to loose, try it.
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Sorry to say I would tend to agree with the mechanic at this point. Too bad all of that didn't get sorted out before spending big bucks on the head gasket repair. The cylinder with 90 psi is probably the reason for the rough running-makes me wonder if the mechanic used due diligence. Was the head checked for straightness of the head to block mating surface? It doesn't take heat very long to warp an aluminum head, and subsequent head gasket failure. Or it could be an exhaust valve not seating well, or a worn cam exhaust lobe on that cylinder. The bottom end has not "now failed", probably pretty worn piston rings; it is just questionable that the low cylinder is from the bottom end or the top end. A leakdown test of that cylinder would pinpoint the problem-I think I would suggest you get that test done-it is more precise than a compression test. It may help you decide-the leakdown test definitely will find the reason for the low compression in that cylinder. Even so, if you got that one cylinder back to snuff, you would still have an engine with 130 psi as top compression-that is a bit on the low end, probably below the minimum compression that Mazda would recommend. It would still run good, but you might notice a loss of power, compared to an engine with 150 psi or more.
If it runs that well at higher revs, you could just drive it as is-what harm could it do? If the engine craps out, it was just meant to be! It's your call to have this engine rebuilt (again), swap in a better engine, or just run it into the ground till the engine finally gives up. But I would do the leak down test just to know what is up in that cylinder. Good luck, Vern. Post back with what happens. Put a vacuum gauge on a manifold vacuum tap and check the vacuum reading; from the hard brakes, it probably has low vacuum, but whether from a loose vacuum line or the engine can't make good vacuum with that low cylinder, I don't know.
I think with the lower pressure reading that the knocking will be coming from a broken compression ring or cracked piston. There is only 10% difference allowable between pistons in a compression test.. However check that the valve train is not causing you problems with a failed rocker or cam shaft bush gone.
Absolutely!. The dealer shafted you, if he told you nothing was wrong. 80 psi leakage out of exhaust (valve,;;;where else?) is a dead give-away: You need a good old fashioned VALVE JOB. Your exhaust valve, see, is not seating properly, not sealing as it should. It leaks, bigtime in your case, so compression is low, unburned gas escapes out the exhaust (You smelled it!), no power from that cylinder so it idles like ****, and will try to die, and of course, mileage suffers. Sound familiar, Robin? Now of course the dealer knew what it was. Apparently he didn't want this time-consuming job. All he wanted was his in the door and out money. From the shop mechanics point of view, a cylinder head job is a relatively low paying and time consuming job. But there's no excuse for somebody not telling you that you need a valve job. Take it somewhere else. It's gonna be expensive, no getting around it, cause the head has to come off, but at least it's a whole lot less than an engine overhaul. And just give those figures to your new mechanic-the diagnostics are all done. Good luck.
I am going to take a stab at this....as I think you may have a head gasket that has blown out. The head gasket will cause a lil white smoke, and make idling extremely rough. Sometimes water will fill up in the top of the cylinder in the compression chamber when this leak, even minor occurs. That would explain some of the compression issues. Obviously with no compression it will not run properly or even fire if there is water vapor pentrating into chamber mixing with fuel giving you that white smoke/steam.
These are somewhat time consuming to change, but not difficult. The backfiring is caused by the computer trying to compensate for the firing issue. The computer when you change the head gasket is easy to fix. After repairng gasket, try to start the car a few times but not allowing it to run as it will just continue backfiring. Turn key off, let the vehicle set about 30 minutes or so, then go back and the vehicle should run properly again.
is there smoke coming out of the exhaust? if so what color? if it has white smoke is usually a blown head gasket. if it is a bluish gray it is oil. check your radiator when it is cool. if it appears to have oil in it it could be a blown head gasket. if you leave the radiator cap off start the motor, if you rev the engine and coolant shoots out of the radiator (compression from the cylinder forcing water out) it is a blown head gasket. this can cause the motor to run weak and idle rough and oil to disappear. if you happen to have a compression gauge take out all of the spark plugs look at the spark plugs if they all look the same or is there ones that look black and sooty(running rich) or looks green(burning antifreeze/water) white Burning hot) http://www.dansmc.com/spark_plugs/spark_plugs_catalog.html check the compression of each cylinder it is easier if you have an assistant for this. place the gauge over the spark plug hole crank the motor once or twice. the gauge should be around 120 psi (pounds per square inch). if all of the cylinders are under 120 psi more than likely you have worn or broken rings which will cause low compression causing it to run weak and consume oil.
sounds like a head gasket or warped head. go buy a compression teseter. pull the spark plug wires off. remove spark plugs insert teset. turn engine over 3 times for each cylinder. should be within 10-15 of each other. check dipstick look to see if oil is milky.
Not the difference shoulD NOT be more than 10psi and some may say 20 psi. I SAY 10psi between each cylinder if this is 50 psi difference then you have at least a head gasket problem. But when you remove head have it check by a machine shop for cracks and warpage in head. Good luck and thanks for using FIX YA.