8 replies to this topic

[luckymiata76]

My '99 developed an intermittent miss in 4th gear going down the straight. Here are the details:
-only 4th gear
-happened around 6800 rpm
-tach would drop down to 6500 and bounce. Hesitation would disappear after shifting to 5th
-car was going down the straight
-didn't happen every lap, but perhaps 75% of the laps
-car ran fine the previous day(Saturday)
-it did rain the previous day(Saturday) and the car was put in the trailer damp
-Changed plugs(new plugs, same brand, NGK) and air filter(paper STP) before racing in Sunday, after Saturday session.

Suggestions welcomed.

Thanks.

[pat slattery]

Jeff, do you have a wide band 02 sensor, any idea if it is going lean or rich at that point. Did the plugs look OK?
What about at 6800 when your going thru the gears, say in 3rd.

Pat

[ChrisA]

Try some new or different plug wires. If that doesn't do it, try a new coil pack.

[Keith Novak]

Similar problems have also been described with a ground issue and a bad connection at the ECU.

[Jim Drago]

Jeff
More than likely the alignment on your crank trigger is off, set the gap at .045 -.055 and see what happens. They move, there will be tech bulletin out shortly allowing a bracket to hold the sensor from moving.

If that doesnt do it, you have all the other normal stuff to look at...
plugs,plug wires
cam position sensor
coil
fuel pump
fuel filter

I would attack in that order...
Jim

[FTodaro]

What Drago said plus just some plain old fuel injector cleaner, fixed my brothers high speed miss.

[Tim Wright]

Once spent a race weekend chasing this.
Turned out to be an injector plug that would only come loose above 80mph?

Good luck.

[davew]

Everything drago said, but first scan for fault codes. may give you a direction to look.

Dave

[luckymiata76]

Crank trigger was at 0.025. Reset it to 0.050, I'll let you guys know if the problem is solved. Taking xtra plugs, wires and fuel filter just in case.

Thanks.