Is there an engine thermal cut-out?

[Off Road SHO]

Okay guys, here's my question. I have been having the engine cut-out and quit at high rpms whenever the temp is above 200 degrees.

If I manually turn the fans on and use the thermostat to keep the temp right at 190, it doesn't do it. But if I forget to turn on the fans and wait for the PCM to turn them on, which it does at 210, then it craps out at high rpms.

I'm starting to wonder if there is a line of code to disable the ignition when high rpms are encountered during periods of high temperature.

It happened twice while giving rides to YAMAHASHO and AutoSHO last week and once down at the dunes. HMMMM.......

Any ideas?

Tom

 

[billyshoe]

Vapor lock. What temp does the fuel get up to. Maybe cooling the fuel will help. Maybe the reroute lines. Maybe a cool air vent under the intake runners will cool the rails enough solve the problem.

 

[Off Road SHO]

billyshoe:
Vapor lock. What temp does the fuel get up to. Maybe cooling the fuel will help. Maybe the reroute lines. Maybe a cool air vent under the intake runners will cool the rails enough solve the problem.

My fuel tank is in front of the radiator on The Other Woman so it does not get hot air on it. The intake is at about outside air temperature so I don't think I'm vapor locking it.

This is a complete shut off of the ignition system, the buggy just dies, no amount of gas pedal movement changes anything. It did it one time this past weekend at the Sand Drags (with my AWA in the car, wouldn't you know). There we were, stopped dead in the middle of the strip with quads, buggies and trucks blasting by. Hit the ignition switch and she started right up, and we sheepishly moved on down the track.

I'm running a PCM out of an ATX car, maybe there is something in the PCM programming for ATX's to protect it from lead foots'.

Tom

 

[AutoSHO]

Tom -

I know you're going to get a mountain of codes, but I think the answer is held within them. I think the computer is looking for a transmission temperature sensor or something once the fans kick on and it isn't finding it. Its very possible I am wrong on this, however. I do think it is something in the programming of the computer.

Did you put a tach on yet so you can see what RPMs are doing it?

 

[Off Road SHO]

Chris,

No tach yet, will be doing that this week or next.

Now that you mention it, PDHarley, who is also running a 3.2 turbo'd has a bunch of codes from his lack of input from the tranny sensors. His is starting to crap out at high rpms also but it keeps running, mine just flat out dies.


My code reader is not able to read The Other Woman's codes for some reason. I am going to go back through the wiring diagrams to make sure I have everything right.

This only happens when I take it to redline, (is there any other place to take it?)


Tom

 

[AutoSHO]

I really think you should try swapping the 5-speed computer. They have a more aggressive timing advance program, so she'll be a little more powerful. And, with any luck, won't cut out!

 

[Off Road SHO]

Chris,

Want to sell yours'? And would the injector pulse widths be the same?

Tom

 

[gmorrell]

Tom,

there is no thermal shutdown in the engine control code, but a few things come to mind.

1. The ATX computers will rev limit at ~4K if EEC sees that the transmission is in park or neutral.

2. I see the DIS module is off the intake. Make sure the module has a good solid ground directly back to battery negative. The DIS dumps a lot of pulse current into ground, and if its seeing a resistive or inductive ground, the noise can upset the PCM. Amazingly enough, the heat spreader on the back of the DIS module is a poor ground. One of the four mounting screws actually grounds the DIS internals to the chassis, I can't recall which of the 4 screws is the right one, but you need to have all four screws into chassis to be sure. Additionally, make sure the DIS has a good heatsink, I've seen them shut down if they get too hot.

3. You mentioned it shuts down after hitting the rev limiter? You may be hitting the PIP filter, which will sort of shut down the ignition system until you do a key-on reset. (PIP filter should be set well above the rev limit, some LPM programmers forget to do this...) The SHO rev limiter looks at rate-of-change to determine how aggressive the limit action will be, and if the engine revs very quickly, say due to wheel slip, its easy to over-run the PIP filter.

Jesus Tom, that engine is just beautiful! Is there any part on it that I couldn't use as a shaving mirror?

<small>[ January 22, 2004, 06:03 PM: Message edited by: Gary M. ]</small>

 

[AutoSHO]

Tom, I'll PM you about the computer so that I'm not advertising on the forum.

As for the computer, the injector pulsewidths are going to be very very close to the same. The difference between the 3.0 and 3.2 injectors is very minute, and the programming changes are as such. There are quite a few people who are running a 3.0 computer in their 3.2/MTX swaps with 3.2 injectors and no problems.

 

[luigisho]

I also sent a PM regarding possible sources for PCM's.