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Nuke'em til they glow!
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Discussion Starter · #1 ·
Guys,

As some of you may remember from a few other posts, my Prelude has been having these odd RPM issues.

Basically, I've been having these symptoms:

- Tachometer needle bouncing up and down, especially at higher RPM's.

- Severe engine knock (so bad I thought it was a wrist pin).

- Engine cuts out (but quickly resumes).

At any rate, the problem was the distributor ignitor.

It appears that the vehicle speed is determined by the VSS or vehcile speed sensor.

The RPM's are determined by the distributor.

So, any odd symptoms on with the RPM's are either going to be distributor related or ECU related.

Other folks have reported that the distributor ignitor generally fails completely. When this happens that car will do nothing.

It's important to note that the ECU generates no MIL's or DTC's when the ignitor is going bad.

If this were a MAP sensor, it would be more likely to generate a code.

-Gerhard
 

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571 Posts
Just be certain its the ignitor first, as it isnt a cheap part. Its $156 at hondaautomotiveparts.com, list is over $200. I bought one thinking that's why my engine was missing last year, but it turned out that there were loose harnesses either in the engine bay or at the ECU. (Even though they looked ok, the miss went away after I unplugged the harnesses and plugged them back up) I ended up selling it to a friend whose ignitor died completely, which we diagnosed by swapping distributors. So if you suspect a failed ignitor, switch distributors with a friend and see if that solves the problem. If it goes away, you know what needs to be fixed.
 

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Zoom-Zoomin
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3,497 Posts
Gerhard said:

The RPM's are determined by the distributor.
That's not completly true. The ECU gets crank (engine) speed from the crank position sensor (CKP). It passes this signal to the ignitor (called the Ignition Control Module or ICM in the helms) which uses that and the signal from the CYP sensor (No 1 cylinder postion) to modulate the primary ignition coil voltage. It also sends a signal back to the tach and to the ATTS contol unit or auto trans contol unit if equiped.
 
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