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bdaball · 01-01-2007, 02:42 PM

On our last trip of the season this fall we experienced an unusual situation. While driving our 2002MACA W22 I noticed the tachometer was moving up and down from 2100-2300 RPM's. Very similar to downshifting. Someone suggested it was water in the gas. I put in six bottle of ISP and it seemd to go away after we got back on the road. But what I later found out was if you would pull over, shut the key off and start back up the surging would go away. Later the same day, we stopped for lunch at a rest stop, shut the engine off for about a 1/2 hour. Then started down the road and it started suging again. We pulled over, shut the engine off and restarted. Surging went away. Since that last trip I have only driven it to the gargage to have the oil changed and an inspection sticker. It is covered and stored for the Maine winter right now. Has anyone experienced this. Not sure to focus towards the engine or the Allison transmission. Seems electronic to me. Any thoughts?

bdaball · 01-01-2007, 02:42 PM

On our last trip of the season this fall we experienced an unusual situation. While driving our 2002MACA W22 I noticed the tachometer was moving up and down from 2100-2300 RPM's. Very similar to downshifting. Someone suggested it was water in the gas. I put in six bottle of ISP and it seemd to go away after we got back on the road. But what I later found out was if you would pull over, shut the key off and start back up the surging would go away. Later the same day, we stopped for lunch at a rest stop, shut the engine off for about a 1/2 hour. Then started down the road and it started suging again. We pulled over, shut the engine off and restarted. Surging went away. Since that last trip I have only driven it to the gargage to have the oil changed and an inspection sticker. It is covered and stored for the Maine winter right now. Has anyone experienced this. Not sure to focus towards the engine or the Allison transmission. Seems electronic to me. Any thoughts?

DriVer · 01-01-2007, 03:00 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by bdaball:
On our last trip of the season this fall we experienced an unusual situation. While driving our 2002MACA W22 I noticed the tachometer was moving up and down from 2100-2300 RPMs. </div></BLOCKQUOTE>
Did you actually hear of feel the engine rev up and down during this event aside from observing the tach?

It sounds possibly like a TAC or a TPS. Throttle Activation Control or Throttle Position Sensor. The TPS is a computer type device mounted under the dash and the TPS is a rheostat mounted on the gas pedal.

A TAC problem will usually post a code that will be evident by diagnosing your coach with a TECH-II instrument at a WCC service center. It may display reduced engine power or some other type of numeric code or text. If there is a problem with the TPS that will also display a code as well.

It is unlikely that there is a problem with the Allison transmission unless a problem is located via a TECH-II.

In the spring take your rig to have it scanned for codes at a service center.

bdaball · 01-01-2007, 03:04 PM

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Did you actually hear of feel the engine rev up and down during this event aside from observing the tach? </div></BLOCKQUOTE>
Yes, I could actually feel and hear the engine changing RPM's.

Edited quotes