1999 Protege ES Skippnig "Misfiring?" Randomly

[theroaminglinux]

'99 Protege ES (1.8L) engine has been "skipping" {Misfiring?} lately and this is what we have done to it so far to fix it and still have the issue.

New Spark Plugs
New Spark Plug wire set.
New Ignition Coil.
New Fuel Pump.

We've tried the following products in gas tank at different times we have filled the tank with fuel.

Seafoam
Marvin's Mystery Oil
Lucas Oil


Now we are thinking maybe a bad injector(s)? Short in the Engine Control Computer?

Any suggestions? If I keep replacing parts, I will end up with a new car needing a paint job. LOL

1999 Mazda Protege ES 1.8L
195,000 miles

 

[concept]

Check for vacuum leaks:
hoses
intake manifold
cylinder head

The intake and cylinder head leaks are typically checked by spraying fuel injector cleaner onto the gasket interface. You'll see it get sucked in if there is a leak.

Another possible culprit is the EGR valve.

 

[jdoggsc]

'99 Protege ES (1.8L) engine has been "skipping" {Misfiring?} lately and this is what we have done to it so far to fix it and still have the issue.

New Spark Plugs
New Spark Plug wire set.
New Ignition Coil.
New Fuel Pump.

We've tried the following products in gas tank at different times we have filled the tank with fuel.

Seafoam
Marvin's Mystery Oil
Lucas Oil


Now we are thinking maybe a bad injector(s)? Short in the Engine Control Computer?

Any suggestions? If I keep replacing parts, I will end up with a new car needing a paint job. LOL

1999 Mazda Protege ES 1.8L
195,000 miles

flat-out replacing stuff like that is a really expensive way to troubleshoot. better to look through symptoms and find all causes first. I say that from firsthand experience! So...a misfire... If you've replaced spark plugs, wires, and coils, then you're hitting at the right usual stuff.
I second what concept said about compression. Even if you have good injection and good spark, if pressure in a cylinder doesn't build up during a compression stroke, then you have no power from that cylinder, and the spark may not even reach the gasoline. So check compression in your cylinders. There are compression testers you can buy that you just plug into the spark plug holes while you crank the engine. If you have bad compression in a cylinder, you might have bigger problems like a bad head gasket, or a valve not seating well. That's what I would check next.