Logo

'06 Excalibur 330, 5.7L will not go faster than idle speed

NorthshoreDawg

New member
I have a 2006 MB Sport 190+ with a 5.7L PCM engine. Bought used about six years ago with very low hours. Engine runs strong and is well maintained. The problem: At first intermittently, but now most of the time, I cannot get the engine to accelerate past idle. It starts like a champ and shifts into both forward and reverse just fine, but hit the gas to pull a skier out and absolutely no Schlitz.... It's idle forward or idle reverse only. The throttle linkage is confirmed hooked up at both the handle and TCP (Throttle Control Potentiometer?) sensor arm ends, and actuates normally. Also, cannot get the engine past idle with the neutral knob on the throttle quadrant pulled out.... HELP! My guesses are either: (1) The TCP Sensor (Part #R119004); and/or, (2) The Throttle Actuator Control (TAC) Module Assembly. Before I start throwing parts at this though, hoping to get some second opinions. Would appreciate any inputs. Thanks!
 
Awesome! Thanks makomark. I'll dive into the pdf you sent and see if I can figure anything out. Really appreciate the link. Hey, do you happen to know if a new TCP (part #119004) fixed the problem for "Compassion" back in July 2015 when you responded to him? Compassion's description of his engine problem exactly describes what's happening with mine now...
 
Nope, never heard "the rest of that story" for that thread.....sadly, some people never close the loop....

Seen similar issues on newer ford trucks - one pot opens up and the 'computer' doesnt see the expected voltage changes as the throttle moves (one output goes up in voltage, the other goes down) and the similar 'no throttle response' occurred. could be the TCP itself or a crusty connector....
 
I now suspect the TAC (Throttle Actuator Control) Module, but........ Here is what I've found so far with a Fluke Multimeter....

> All six leads in the harness between the TCP and TAC test good.
> Pins A, B, and C on the TCP test good (engine running)
> Pins D, E, and F on the TCP do not test good (engine running)
> Pin D - Orange - open ground....
> Pin E - Red - 0.8V at 0% throttle, 1.6V at 100% throttle (specs are >4.0V at 0% and <2.9V at 100%)
> Pin F - Black - 0.004V... Effectively zero volts (spec is 5V)

Then did a partial test of the TAC.
 
Cont'd... Then did a partial test of the TAC:
> Pin B, Orange, open ground.....
> Pin D, Black, grounded... supposed to be the TCP Sensor 2 5V reference.

That's as far as I've gotten so far. Limped the boat to the boat launch today and trailered it home so it's easier to troubleshoot/work on.

Will try to further test the TAC and perhaps the Throttle Body itself tomorrow... My bet right now, though, is a bad TAC (Part #R116020)

Thoughts from anyone else?

Cheers!
 
Voltage at E can't be higher than at F!

you can check either TAC supply (sources) with the voltmeter function - and they should be there with the cable removed....

you can check the TCP circuits, unplugged, with the resistance function. connect one side to the signal and then the other to either the 5Vref or gnd - but be consistent when going from #1 to #2.....the resistances should change about the same but one will be offset (higher or lower) than the other - that how the voltage swings have opposite 'slopes'.
 
Hey Makomark, Thanks again for the quick response... Worked loooooong day yesterday, so didn't get to do any more testing till this morning... Here's what else we've found:

> Concur: TCP Voltage E can't be higher than F.... IF everything is working correctly...
> Checked the TAC supply (5V Reference) voltages with the 10-pin TAC TCP harness removed as you suggested and got the following:
> Pin D, Black, TCP Sensor 2 supply/5V ref: Almost zero Volts.... 0.005V (effectively just stray voltage?)
> Pin G, Blue, TCP Sensor 1 supply/5V ref: 5.000 Volts.... Perfect.
The above results out of the TAC may help explain the goofy earlier test results for TCP Pins D, E, F
Conclusion: TAC to TCP supply/reference voltage is missing..... >>>> Faulty TAC

I then did the resistance check for the TCP circuits as you suggested. Results: TCP tests 4.0.
> TCP 1 Signal to Ground resistance test, Pins B-C, Brown-White: Throttle position 0%/100%, Resistance 1.22 k-Ohms/4.42 k-Ohms. Delta: ~3.20 k-Ohms
> TCP 2 Signal to Ground resistance test, Pins D-E, Orange-Red: Throttle position 0%/100%, Resistance 4.35 k-Ohms/1.23 k-Ohms. Delta: ~3.15 k-Ohms
Conclusion: The TCP is working as designed.

With all your help I'm now fairly confident the problem is a bad TAC. I'll order one, install, test, and let you know the results. While waiting for the new TAC, I'm very open to any other suggestions. Again, thanks so much for your help. Couldn't have gotten anywhere without it.
Cheers!
 
sounds like you have reach a reasonable conclusion and have the data to justify it - dont get no better than that.

wouldn't hurt to verify the integrity of the TAC-TCP cable wires - continuity between the appropriate pin pairs and no shorts between conductors (not likely but being thorough). when the new TAC shows up, you know it won't have any reason not to work...

Finally, there are many 'module repair houses' that deal with the various auto modules - may want to check with one of them to see if the bad box can be repaired to have a spare just in case....
 
Makomark, hello again. Great idea to check the continuity of the TCP to TAC harness. Actually already did that and it checked out 4.0/good test, so I think we can eliminate the harness as a culprit.

Had no idea there may be repair houses for the TAC modules. I likely would have just tossed it in the recycling bin. Thanks much for that info. Will pull the string to see if I can find an outfit to do that and, if reasonably priced, get the current TAC repaired and keep as a spare as you suggest.

Again, can't thank you enough for all your help! It's going to take a week or longer for the new TAC to get here, but will follow up and let you know if it does the trick. Till then, Cheers!
 
Dawg - you are quite welcome!!

It may take a few attempts before you connect with somebody that has a clue what you are talking about.....

Good on the harness....don't forget to post back with "the rest of the story" once the issue is resolved....that's what makes these forums so useful!!
 
Makomark.... No joy.... :-( Fedex just dropped off the new TAC an hour ago. Installed the new TAC, hooked up the hose, fired up the engine, and..... still, nothing above idle. What a bummer!!! So, either I received a bad TAC (unlikely), or, the problem is further upstream. It's too late to dive into it tonight. Working over the weekend, so may not get back to it for a few days. My gut is now telling me TP2 (Throttle Positioner #2... at least that's what I think it's called), in other words, the throttle body, or (hopefully not) the ECM ($$$). I'm very open to suggestions. I think one thing I will try is to contact PCM to get a list of things/faults that will cause an engine go into idle/limp-home mode... I thought I read somewhere that if one of the throttle body positioners is inop, the engine will not go above idle... All for now. Will keep you posted. Thanks again for all your help.
 
Mongo Bummer!!!

The TPS's work like the TCP's (generate complimentary voltages based on actual throttle position) but are used as a check that the throttle is opened to the amount commanded.....unfortunately, from what I've read, the TPS's are integrated into the motor housing on the side of the throttle body....and may not be a 'serviceable subassembly.

I'd guess you have the MEFI-4 ECU due to the separate TAC module; ETC appears integrated in the MEFI-5 ECU's - do you know which one you have?
 
Hey Makomark, didn't want to think I'd forgotten about you... My schedule has gone to $#!+ and I likely won't be able to jump back into troubleshooting the PCM for several weeks, if not months. I currently plan to do more wire chasing with a multi-meter when I do get the time. If that doesn't point to the problem, will then likely bite the bullet and drag the boat to a shop that has diagnostics equipment. I'll make certain to close the loop with you when we finally figure out what the problem is. Thanks again for all your sage help. Cheers! Dave Oh, and regarding MEFI-4 or -5 ECU, not sure. The parts manual for the 2006 5.7L says the part number for the ECM is R116021 cksum-(7663)(1DEF) Don't know if this answers the question or not... By "ETC", I'm guessing you mean "Electronic Throttle Control"....
 
Understand....in life, stuff happens.

yes, you got the ETC message correct.

regarding the ECU ID; there should be a GM part number on the 'bottom' which will help ID the specific version....many www resources available - many times, just entering that part number in a search engine will tell....
 
Back
Top