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Discussion Starter · #1 ·
I'll try to keep this short and to the point. I have a 2004 MXZ Renegade X 600HO SDI. The sled has 4,500 miles. Cudney pistons and rings, Cudney clutch kit, and J&T silencer were installed in the fall. All components have 1,250 miles on them. Original rings had some flaking, but not horrible. All updates were performed when sled was in its first season and has run flawlessly until now. A few days ago after 75 miles of a 115 mile trip, the sled began to bog at WOT pulls. Almost like fouling a plug, or loosing fuel. I was able to finish the ride under my own power. Spark plugs look good - nice light carmel color. Top electrodes were pretty dusty (sooty), so I replaced them and cleaned the boots. Engine light was flashing when I parked the sled. Next day sled starts and runs fine. WOT pulls are awesome. No flashing lights. After 15 miles or so, things begin to happen again. WOT bogging, but sled will run under part throttle no problem. Shut it down and the engine overtemp light is flashing, also a constant beep for 30 or so seconds (check engine light is flashing also). Coolant reservoir is full and heat exchangers are melting snow - snow conditions are excellent (plenty of snow). Restart engine and everything returns to normal. Problem comes and goes a couple more times. I unplugged the muffler temp sensor and sled seems to run pretty good. Check engine light continues to flash, but overheat light stays off and beep does not come back. Engine bogs a couple of times on way back under WOT conditions. Stopped at dealer on the way home and was told "we can hook it up to the computer". Sled was not with me at the time, and I will probably do it next weekend, but wanted to pick everyones brains before that. Thanks for reading and thanks in advance for any suggestions. Mike
 

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Some people have written about bad EGT sensors giving a false high temp reading and fooling the computer into giving an overly rich mixture. That would make sense in your case, including the intermittant condition.

Does anybody know what the computer does with the EGT (or maybe, more accurately, muffler temp) reading? Does it affect mixture throughout the range, or does it just trigger richening/limp mode when it reaches some particular high temp?

And the overheat warning is a puzzle to me. Does a high EGT reading trigger that too? Maybe someone knows how all that works.
 

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Hey Mike-
I am certainly no expert with SDI stuff, but it sounds like you may have a bad temp sensor or you may have bad fuel in the sled which is causing the sensor to actually do its job and retard your timing to save the engine.

If you don't want to take it in....or if you want to do some stuff before you take it in, I would suggest draining the fuel (pull the line between the pump and tank). Fill it with fresh and some isopropyl and retest.

The big cold snap we have had recently may have contributed to condensation in your fuel. Worth a try.

Tom
 

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Discussion Starter · #4 ·
Was also thinking about fuel. I mainly use fuel that I run through a cartridge filter on my fuel setup. I began having issues about 15-20 miles after topping off at the only show in town (in Alba). That fill up was 4 gallons, and topped it off with 5 or 6 gallons once I got back. I have never changed any fuel filters since new. I know, I know, I can hear everyone now!!!!!!!!!! I would think if it was an issue like that, that it would not be intermittant. Was also thinking about a broken silencer and plan to put the old suitcase back on for diagnostics. All these ideas came to me, however the sled brains (electronics,ecm, pcm, whatever) seem to be telling me an electronic problem.
 

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Discussion Starter · #5 ·
Update on my problem. I took the sled to the dealer and it was the muffler temp sensor. Should have it back on Saturday - just in time to fog it for the summer.
 

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big mike said:
Update on my problem. I took the sled to the dealer and it was the muffler temp sensor. Should have it back on Saturday - just in time to fog it for the summer.
[snapback]752872[/snapback]​
Thinking of loading up tonight and heading to Paradise for one last ride. John Dee's page shows 23" still on the ground. 50/50 chance of rain and that is no fun to ride in. I just might have to suffer and go for it.
 

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tenacity said:
big mike said:
Update on my problem. I took the sled to the dealer and it was the muffler temp sensor. Should have it back on Saturday - just in time to fog it for the summer.
[snapback]752872[/snapback]​
Thinking of loading up tonight and heading to Paradise for one last ride. John Dee's page shows 23" still on the ground. 50/50 chance of rain and that is no fun to ride in. I just might have to suffer and go for it.

[snapback]752984[/snapback]​
 
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