Ashley P

1.8 toyota "misfire"

7 posts in this topic

1997 Corolla, 1.8l, 260k.  Over the last year it's had a "misfire" that first occurred only at heavy throttle/upper rpm.  It felt like either weak spark or low fuel pressure (smothering down) and if the throttle was lifted a little, it ran fine.  It's been a few thousand miles like that. 

Several weeks ago there was heavy dew in the morning, and the car ran terrible at anything more than about 10% throttle.  It would not run 60mph on level road.  It spit and sputtered through the intake.  It ran better that evening (dry day) and would take about 70% throttle.  The distributor cap was crusty, so I replaced it and the rotor next day.  Ran great...

...until a few days later.  It had rained and the car would not start.  It would occationally fire against the piston, sounded terrible.  The next day it sounded the same. I put a distributor/coil/cam sensor assembly in it.  No change at all.  :huh:  So, I reinstalled the original and ordered a crank sensor.

Tonight...car started fine.  Put a crank sensor in it, still started fine.  Looked at the timing belt, even though it's only 40k old, it's cracked bad.  So, I'm gonna do TB and WP.  But.....I've never seen a TB cause intermittent/moisture related misfires!    :huh:

Anybody gotta :idea:?

Edited by Ashley P

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Plugs from Toyota 10 years / 40k miles.  Originals lasted about 12 / 220k.  Wires are still original, routed well, don't see any way they can crossfire  BUT.....maybe I should hit 'em with a squirt of water at night.

Edited by Ashley P

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I agree that the load/rpm sounds like blowout, but the dang thing is firing so far advanced at times that it won't crank anywhere near normal speed.   It's rained today and now the humidity is close to 125%....prime time to test. 

 

 

And....it runs FINE tonight.  :rolleyes:

Edited by Ashley P

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On 10/10/2017 at 9:02 PM, Ashley P said:

  Looked at the timing belt, even though it's only 40k old, it's cracked bad.  So, I'm gonna do TB and WP.  But.....I've never seen a TB cause intermittent/moisture related misfires!    :huh:

I got a TB and WP and started digging...found the tensioner pulley was about to lose it's bearings causing the heat damage to the belt.  The belt was very loose.  I have no idea how that could cause such intermittent symptoms, but hopefully a repair of those will fix it.

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New belt and tensioner.  Old CKP.  Still missed when warm.  I quickly installed the new CKP and the test drive was perfect.  Time will tell.

JohnC likes this

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