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Engine Hesitation

Yahoo Message Number: 86209
My Cat engine has worked perfectly for the past 12 years, 112,000 miles. On a recent return from the West, the speedometer and tack would instantly dropped to zero -- they both flat-lined, the engine hesitated and then the engine instantly regained its' normal rpm/speed. This happened very infrequently over a one-month (5,000 mile) period of time. It started when I would slow down for a sharp turn and then it would happen while at cruise speed . A couple of times the engine just stopped. It would immediately restart.
I thought that it was poor battery connections or simply old batteries, since they were over six years. I replaced the batteries and cleaned all of the connections. The problem seemed to go away for the next 1,200 miles. Then I had two very brief occurrences again during the last part of the 1,800 mile trip.
I think that it is electrical since both gauges on the dash simultaneously went to zero and then back to normal. Could it be something else......fuel pump, injector pump???
Any recommendations as to what should be investigated would be appreciated.
Denny Zarnt 2001 42' Bed and Breakfast Affinity #5972 Cat. C12 - 455HP

Re: Engine Hesitation

Reply #1 –
Yahoo Message Number: 86224
I had nearly the identical problem with a CAT C-9. Turned out to be the electrical connector between the transmission and the ECM. Although still apparently connected, the connector was partly disengaged and under the right circumstances(strong side winds was one) would part just enough for the speedometer/tach would go to zero and the engine warning would come on. Then the engine would start to derate. Suggest you take a look at this connection. I don't know where it is on your rig, but it was easily accessable from under the engine/tranny. A CAT tech. in Yakima, Wa. found the problem for me.

Jim Hodges 2007 Inspire 360
51969

"Dennis Zarnt" wrote:

Re: Engine Hesitation

Reply #2 –
Yahoo Message Number: 86233
I had the sme thing happen to me after 115,000 miles. finally discovered it was a lose wire connection. It makes it lose power to trans. Just have to do a lot of searching for the lose wire.
Fred Walters 03 Lexa

Re: Engine Hesitation

Reply #3 –
Yahoo Message Number: 86270
Denny,

My situation may or may not be related to yours, but I'll repeat the essentials in case. Just after we purchased our 2000 42' Affinity #5801 about 5 years ago, I first noticed the cruise control kept disconnecting. Then the transmission started to down-shift and back quickly and erratically. Finally, we lost power and had no throttle/accelerator. (Perhaps no tach, but can't remember.) I shifted to "N" so I could coast easier to a safe spot, then noticed the tack was now showing idle RPM and now I could blip the RPM with the accelerator pedal that had been dead. At this point I was able to shift back into gear and keep going with about 5 more repeats over a couple hundred miles. The Allison shop hooked into the diagnostic port, said they couldn't see the engine or transmission - only the ABS brakes - so they decided to do nothing not knowing the coach! I agreed when they said they may run up a $4000 bill without fixing it!
One of the techs at Country Coach (before bankruptcy) gave me two letters on the diagnostic port to test for ohms to see if I had a bad terminal resistor on either end of the J-1939 (I think) Data Link. This is the "data" circuit over which the engine and transmission computers, transmission shifter, etc. communicate - including speed of the engine so the transmission knows how to respond, etc. When a terminal resistor fails, the circuit no longer meets appropriate transmission parameters and you get errors or nothing. Sorry I can't give you more specifics since my manuals and notes are in the coach in the shop without access until probably sometime next week. (The data link number is from memory so I could be off slightly on the number and there is also another circuit, maybe 15xx or so. One is primary, the other secondary. I was able to find the twisted wire pair - mine was blue - with a bare wire strands, like ground, twisted around the covered pair. I think the wire labels were listed in my manual as speed +/- and ran the length of the coach. The ohm reading confirmed my front terminal resistor was bad. I simply unplugged it, plugged the replacement CC sent me for under $10 in its place and I was in business. To get rid of the bad shifting history influence, I had Allison re-flash the transmission computer so I started fresh from that point. Problem solved! (I think this was via the smaller of the two ports but it has been a long time...) My biggest problem was finding the front terminal resistor from the back side of a monster wire bundle in the bay under the driver's seat. At least the one in the engine compartment along the frame rail, passenger side, was easy to spot so I know what to look for up front.

Good luck,

Kent McCoin

2000 B&B Affinity 5801
 

Re: Engine Hesitation

Reply #4 –
Yahoo Message Number: 86282
Thanks to all who have responded......When I get back next month I've got some things to talk about with the repair shop. Hopefully one of these will insure that it doesn't happen again.

Denny 2001 Affinity, 42' B&B #5972