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Missfire cly#1 Masda B2300

I have brought my truck in to 6 different shops 27 times in the last year for a misfire on cylinder #1, please note this is a 4 cylinder with 8 plugs) I have replaced or repaired ( plugs & wires x 4, serpentine belt, timing belt, most if not all vacuum hoses, both blocks that power the plugs, #1 Fuel injector, psi tested fuel pump, oil change, replaced the valve cover gasket because it was leaking oil on the 02 censer, replaced the 02 censer, psi tested radiator just in case it was spilling antifreeze into the #1 cylinder through the head gasket, psi tested the exhaust to make sure there was no back pressure. tested the sensors that allow injector to work properly

I know there is more, what do you suggest, other than the obvious, can?t afford a new car but I feel I have already spent enough to buy one.


I know more than I want too about my truck


Can you actually feel a misfire or is there just a misfire code generated?

Did any replaced part show a defect?

Have you tried to retrive freeze frame data when the misfire occours?


#1 Yes I can feel a misfire, and at that point it will start to hesitate
#2 wires only once no other parts that got changed
#3 I believe they have and still could not find the solution that fixed the problem
#4 1996 and 208,000 miles

With the age and mileage on your vehicle, the next cheapest thing you might try is a decarbonization of the engine. Because carbon deposits can cause misfires.

Purchase a can of SeaFoam Engine Tuneup. Get the engine up to operating temperature. Shut the engine down, and disconnect the vacuum hose from the brake booster. Adapt a hose that fits into the end of the brake booster hose and into the can of SeaFoam. Pinch off this hose with a pair of pliers. Have someone start the engine and bring the speed up to 2,000 RPM’s. Slowly open the pliers so that the SeaFoam begins to be drawn into the engine. Keep the RPM’s up and open and close the pliers to prevent the engine from stalling. Once all the SeaFoam has been drawn into the engine, shut it off. Reinstall the brake booster hose. After a half hour has past, restart the engine and bring the engine speed back up to 2,000 RPM’s until the smoke clears from out of the exhaust.


Well, I have tried everything else so far, I will give this a try. I should have an answer back by Saturday
The pros to this are that it will fix the misfire what are the cons to this? Is there something that might happen that I should be aware of?

You did not state the year and mileage of the truck but you might consider the possibility of a cylinder being down on compression.

JMHO, but with a performance problem a compression test should always be performed whenver those spark plugs come out.
If a cylinder is getting low then one can throw parts at it until the end of time with no improvement and even low mileage is no guarantee of a mechanical fault not existing.

One would have thought that somewhere during all of this a light would have come on and one of them would have considered this.

The year is a 1996 and mil is 208,000 and a compression test was done and that checked out with well

I too was going to suggest a compression check, and I’m going to further suggest a WAG that you might be having intermittent compression problems from intermittent valve problems. Is the misfire consistent? Or can it come and go? I would be tempted to hook up a vacuum gauge with a long enough hose to run it into the cab while you drive around and see what it does when it misfires. Wild fluctuations that go with the misfire would suggest the possibility of valves getting hung up.

Of course, I would also go with the can of Sea Foam. At least that is cheap and easy.

I have seen broken valve springs,not on this type engine. At this point mechanical failure is getting more possible.

Does any one have a opinion about what has been eliminated as a source of the misfire?

the misfire is intermittent, i can and have run approx 60-80 miles without issue and then the problem starts all over again.

yes, the opinion is that it is behond there knowlage now.They don’t know what to test next.

You can cross your fingers, but I think this is bad. Are you up for pulling the head and doing the valves? I obviously wouldn’t do it on a mere guess - but I’m going to put my money on something with the valves. This is a completely different motor so I doubt there is any direct relation, but late 90s/early 00 Ford Escorts - that had Mazda motors - were known for dropping valve seats. The first warning sign was often an intermittent misfire, often confined to one cylinder. The seats apparently crack/get loose, cause intermittent problems, and then one day - pow!

Define the part about “compression checking out well”.

There has been more than one post on this board in which good compression was defined as 90, 110, 130 PSI.

Low compression can also cause an intermittent misfire due to the plug being fouled after X number of miles.

I had two compression test done, two different mech. at that time ,it was stated the compression test showed no signs of a problem… I know it is documented and I will get back to you with the psi that they found