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Discussion Starter #1 (Edited)
1989 MX-6 LX, 5 speed
I bought this car about a year ago and its been great. It was a one owner car. The car must have sat for 10 years. The sticker on the windshield when I bought it said the oil change was due at 82,000 miles, but 10 years ago. I bought it with 80,000 miles. Body is in great shape so I think it was garaged ( looks new ).

I have done the maintenance and made this car my daily driver. I changed, the spark plugs and NGK spark plug wires ( purchased from Rock auto ). I also had to replace the alternator with a Denso unit also from rock auto. All this was done when I bought the car.

Recently at very low rpm. I usually feel it in 2nd gear at about 1200 to 2000 rpm. At that low rpm it is under slight throttle, but sure it would happen if I gave it more.
It feels like there is no spark for a split second. Its not consistent. I tested it in 3rd gear and it will happen, just never that low in the rpm at higher gears. I have not felt it when the engine is cold. Usually feel it once a day.

No codes, no lights on dash indicating stall. I am thinking it could be fuel pump but not likely. I am leaning more to Pick up coil and icm. Maybe coil. Or maybe the NGK wires are bad.
12866
 

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1989 MX-6 LX, 5 speed
I bought this car about a year ago and its been great. It was a one owner car. The car must have sat for 10 years. The sticker on the windshield when I bought it said the oil change was due at 82,000 miles, but 10 years ago. I bought it with 80,000 miles. Body is in great shape so I think it was garaged ( looks new ).

I have done the maintenance and made this car my daily driver. I changed, the spark plugs and NGK spark plug wires ( purchased from Rock auto ). I also had to replace the alternator with a Denso unit also from rock auto. All this was done when I bought the car.

Recently at very low rpm. I usually feel it in 2nd gear at about 1200 to 2000 rpm. At that low rpm it is under slight throttle, but sure it would happen if I gave it more.
It feels like there is no spark for a split second. Its not consistent. I tested it in 3rd gear and it will happen, just never that low in the rpm at higher gears. I have not felt it when the engine is cold. Usually feel it once a day.

No codes, no lights on dash indicating stall. I am thinking it could be fuel pump but not likely. I am leaning more to Pick up coil and icm. Maybe coil. Or maybe the NGK wires are bad.

Any thoughts on what to start on first. Wish I kept the old wires. View attachment 12866

From your description and symptoms it is hard to say what could be causing this.

Honestly I can't ever remember shifting gears and seeing rpm's below 3000.
Because of where your power loss is in the RPM range and possibly the way you drive the car or from your description it is hard to say if it's a cylinder misfiring. A misfiring cylinder can be felt by a momentary loss of power under acceleration to which you can feel the other three cylinders fire and pull then nothing then more acceleration, this is easiest to diagnose when on the throttle.

99% of the time arcs and spark problems occur under heavier acceleration. The causes can be plug wires, cap and rotor, spark plugs and engine grounds.
For engine grounds and plug wires the symptoms definitely get worse or become noticeable at higher rpm, in higher gears when the demand and spark is stronger. So an arching wire or weak ground can show no symptoms until 4th and 5th gear above 5000rpm but the engine can run great to redline in 1st, 2nd and 3rd gear.
As RPMs gets higher the spark from the distributor gets stronger which can make it difficult to find arching wires when revving the engine in neutral .

If this is a spark related problem than I would assume that below 1200 rpm even with a spark issue spark is still strong enough to fire all the cylinder, from 1200 to 2000 rpm when spark is still weak but spark demand is greater something is causing enough resistance between the coil and electrode to reduce spark enough to cause a firing issue. I haven't phrased this properly, that resistance would be present trough the whole rpm band but wouldn't be enough to affect low rpm low spark requirements and isn't enough to resist the higher current delivered at higher rpm when the spark is stronger.
I would start by inspecting the distributor cap center point inside and out, look for corrosion or discoloration, than check the coil wire fitting and 4 other cap points. Than check the plugs, check the porcelain for cracks (I have gotten shit batches of NGK Vgroove plugs over the last 15years, some from Rockauto, some from elsewhere, these plugs sometimes shater while installing them because the metal nut shaped base distorts enough under tortion to crack the porcelain before achieving factory torque specs), check the elctrodes and color on the plugs, also check the plug gap, it should be .039" to 0.43", you can try gapping them to 0.035" reducing the chance of spark arching.

This could be fuel related, after ten years gasoline can turn into a thick beige resin. This could make one of the injectors stick or partially clog, yes it could take a year to free up and soften a glob of resin and suck it through both filters.
Check all the engine grounds, wire harness grounds (4 of them), check your engine connections, vacuum lines and intake hoses for cracks , check the pvc system, pull the oil cap and check for engine blow by (exhaust out the oil cap hole when revving). Is there any oil in the coolant or coolant loss?
Is this happening right after you shift gears? The clutch slave cylinder could be sticking when the pedal is released.

Has the timing belt been changed? Is this car still running the original head gasket?

This seems like one of those issues that requires more throttle to diagnose. This car is 31years old, millage isn't always the symbol for healthy, I would take an F2 with 186 000 miles (A) of highway driving, regular oil changes and occasionally flooring of the pedal over 40 000 miles (B) of short local drives with regular oil changes and never flooring the throttle.
Engine A would have a bit more cylinder wall wear (ring wear) but would have evenly worn cylinders.
Engine B would have a ridge at the top of the cylinder walls and due to the possibly long oil change/sitting intervals could have seized rings, most common on "lady" driven automatic engines ( I use "Lady" because people can relate, what I mean is people who ride in cars while sitting in the drivers seat, never floor the throttle, shouldn't be on the road or wasting oxigen, follow all the rules and therefore are partially responsible for the existence of the rules. Imagine beeing bor a car you where born to run but some jerk buys you and feels running is dangerous and you will exist longer if you never run, but it's better to live a fun life that is short than to exist a long time and never live.)

The good news for you is if the timing belt breaks there is no engine damage and unlike the GT (turbo) a failing head gasket won't warp the head and scorch the pistons .
 

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Discussion Starter #3 (Edited)
Thanks for the reply, it gives me a lot to go on. Just fyi, I did have a 90 626 that I drove for over 20 years and up to 400,000 miles when I gave it to a friend that was sharing one car with his wife. As far as driving the 626 and MX-6. The mx-6 is a little faster due to being lighter, and handles a bit better. But the way the engine feels, its exactly the same. The mx-6 does not get as good of gas mileage as the 626 got for some reason. Maybe I am just driving it harder. I am getting in the low 20's, where the 626 would get in the upper 20's city driving.

I did do more to the car when I bought it. I just didn't list it because I did not think it applied. But here is the list
Alternator, spark plugs, wires, all coolant hoses ( if I remember right there were seven replaced ). Thermostat, water pump, timing belt ( used the kit with the pulleys ). Cam and crank seals, valve cover gasket, clutch master cylinder (slight leak), slave cylinder.
Changed all fluids, transmission, power steering, brake and clutch fluid, coolant, and engine oil, air filter. pcv valve and grommet.
Saw a ford probe v6 at the pick a part, waited till half off day and got the parts and did a rear brake conversion, (drum converted to disk ), and new brake pads all around.

I did all these things because I did not know the history of what has been done, and I am really thinking not much has ever been done to it. It needed some things, but I just wanted all things done so it will be reliable for years to come.


Edit
Well now I feel like and idiot. When I changed out the champion spark plugs to NGK, one of the crush gaskets stayed attached to the head. Came off with the NGK spark plugs when I was checking them. Thanks for that tip. I have never had that happen before. Hopefully that is what caused the problem. Will update again in a week to make sure it doesn't happen again.
Also checked for blow by and did no see any smoke.

12868



Update.
after driving it for a few days its running flawlessly.
 
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