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A tip for a common ZX chassis problem…We have 3 MXZ 600s (ours are '01 and '02) in our group and they all did it. We call it the "morning sickness". I posted this as a reply to someone who had the same problem, but some people suggested I should make this a fresh post.

Symptoms... It would do it randomly on some morning start-ups in the garage, but we could make it happen VERY consistently by parking the sled outdoors in the snow overnight (like when saddlebagging in the U.P.) and then firing it up in the morning.
- starts normally and warms up normally
- makes great horsepower if you hold wide open, but is really sluggish in the midrange
- plug(s) would foul if you let it stay in the "bad range", but would be fine if you ran 'er hard
- fuel economy would be TERRIBLE while it's in the "bad range" (like 3-4 mpg), but usually you wouldn't run like this long before noticing it, thus it would only have a small effect on that tank's overall fuel economy. If your girlfriend is riding it and no one notices it running poorly, she'll run out of fuel very quickly.
- would idle so low that the dash and the lights would all shut down
- if you noticed it happening, you would shut it down and wait 15 minutes, then it would run great afterwards. Most of the time it did not require fresh plugs.
- some of our sleds had DPM, others didn't. The problem occurred either way.

The fix... It's the connections on the MPEM module!
- pull off all connectors
- clean if needed (ours looked very clean already)
- squirt a little dielectric grease into all the female connectors. Don't worry about bridging grease across the terminals--dielectric grease is an insulator, so it won't degrade the signal at all.
- we did not change to expensive ECS plugs; the problem went away with OEM-recommended ES plugs

What's going on...

- We figure that some moisture gets into one of the connections when it sits overnight, causing the MPEM to not get all the proper signals that it needs to make a good decision about ignition timing. Once you warm the engine then let that engine heat soak thru the engine bay without having ram air blow thru, it dries things out and regains the signal.
- Filling the connectors with dielectric grease prevents moisture from building up on any connections in the first place.

If dielectric grease on the MPEM module connectors doesn't solve it, you've got to lube the connectors on the other end of those harnesses. Eventually you'll find the connector that's working intermittently.

Good luck!
 
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