never-ending intermittent misfire problem

[orly_andico]

i still have this intermittent misfire problem on my '94 mazda 626, i was told it could be ignition. i've changed my high-tension wires (finally), and my plugs are fairly new, but the problem won't go away. also had the fuel pump circuit rewired (because it failed catastrophically in the middle of EDSA! dead car!)

basically, at idle, there is no misfire (this is what makes the problem hard to diagnose.. can't replicate it consistently) although very occasionally, the engine will burp. however when above 2000rpm or so, it will misfire relatively consistently (but not all the time..)

i'm now thinking maybe the fuel pump is weak (my old pet theory) although the repair guy at shell maya said the fuel pump doesn't change output depending on load, it just runs at a constant pressure. other idea, weak coil pack (expensive to fix, one-piece distributor and coil pack).

ideas? thanks...

[artpogi]

Orly, maki-ride ako sa post mo.

Just a query lang po.

Can a clogged injectors cause the misfire too?

Thanks

[ghosthunter]

too much carbon build-up in your cylinders can cause misfires.

[afrasay]

in order of cost - clogged fuel filter, cylinder head gasket, intermittent fuel pump operation, computer going bad

[orly_andico]

i forgot to add -- the misfire only happens between 2000 and 3000 rpm. if i endure the misfires and put the pedal to the metal, the misfires eventually disappear as the engine winds up.

i've already changed the fuel filter. the fuel pump used to be intermittent, but after re-wiring it seems ok now (although the impeller could be damaged.. doesn't explain why the misfire disappears above 3000rpm).

the guys on the mazda626uk list are also starting to lean toward a faulty computer box. i'll try pulling the codes to see what i can get. how much does a computer box go for? mazda's aren't that common, much less a 626. will third-party ECU's work?

[afrasay]

from what i've heard mga 25 grand ang computer box and no, a third party ECU will not work in your 626 unless you have a patient mechanic and you're willing to go the hit or miss approach.

[van_wilder]

akin naman sa mazda 323 ko... bagong spark plugs, fuel pump, lahat ng oil seal bago, hi-tension wires, walang problema makina... di ko na alam... baka magpalit ako ng battery... sabi nila baka rin daw oil distributor... ang problem naman nun akin, nagfluctuate yun RPM pag-idle... ilan beses na rin tumiriki... nun past two months, masmatagal pa siya sa casa kaysa sa labas...

[jackaroo]

orly a,
have you checked for loose ground wires? (May need a grounding kit.) Try a fuel injector cleaner too.

van wilder,
Seems common with B6 engines. Did anyone adjust your TPS? Usually, the problem goes away after cleaning the throttle body with a cleaner.