MAP sensor "locks" up!!!

[23tbucket]

I've got my 900cc DOHC engine starting and running very nicely...however..every once in awhile the Map sensor info going to the Microsquirt just freezes up. The gauge on tuner studio shows this and with the laptop dissconnected I can tell when the sensor isn't feed the correct information by the engine going lean or rich...depending where the MAP freezes. I shut the engine off and re-start and all is good for awhile again...sometimes for an hour or so...then bingo..it freezes up again.

I have tried three new GM 1 bar MAP sensors and one new pigtail

I have put in a different throttle position sensor (they share some of the same wiring)

I have gone through all my wiring three times

I've checked the resistance on the wires from the harness to the sensors twice

I have double checked all my ground wires..did find a loose connection..but problem still exists

I have tried three different systems (diodes and resisters) to getting the tach signal from the coil, but I see no tach spikes at all...the signals are nice and steady at all speeds

I went through all of my ignition wiring and checked all the adjustments. If there was the occausional spike coming from the tach signal wouldn't the MAP clear itself and start working again?..or would it freeze up and stay in one spot as what is happening now?

I am stumped with this problem...I may have to change the MAP table to TPS instead, but I sure would like to stay with speed density.

I'm open to all suggestions...thanks; Clifford

[Matt Cramer]

Could you post a data log of the problem and a copy of your MSQ?

[23tbucket]

Matt: Of course..sorry 'bout that! Give me a bit to sort out the latest datalog. Here is the MSQ (I hope?)
:

CurrentTune.msq

(30.11 KiB) Downloaded 88 times

[23tbucket]

Matt: It says my megalogviewer file is too big. I'll try to do a shorter run tomorrow.

Thanks; Clifford

Note: I reviewed my log a few times today...I did notice at one time the engine just kind of slowed right down and eventually stalled.....at the same time the battery voltage slowly dropped from 14.7 down to 12.9. Re-started and everything seemed normal again. Maybe I have a charging or connection issue?

[Matt Cramer]

Or you could put the log in a ZIP file.

[23tbucket]

2013-01-08_11.07.25.msl 2013.zip

idling up to 645s
645s; engine started slowing down? Plugs fouling I think?
650s: engine going into cranking
658s; engine stalled
676s; re-started engine
709s; started to slow down again
716s; cranking again
728s; stalled again
767s; re-start..no MAP****
810; shut down
815s; re-start..now MAP working
827s ,934s, 946s, 1048s; revved up engine

[Matt Cramer]

The stall might be preventable by lowering the Cranking RPM number; this will keep it from applying cranking fuel levels to a running engine.

Are you able to check the MAP voltage when the signal locks?

[23tbucket]

Well...something strange happened today! I went to start the bike and "no go"...I had no tach signal. I opened the side cover to inspect the pulsers and gap...it was all okay. I wiped down the magnets and the little tit...engine started right up after? I wonder if I need to upgrade my ignition? Would an ignition "blip" cause the MAP to freeze up?
I ran the engine for quite some time today and the MAP signal worked like it should...engine never slowed down and stalled like it did the other day. I had a voltmeter on the MAP sensor...the voltage stayed at 4.497 and never wavered a bit.
I keep the cranking quite high....I have a fairly big battery...the engine cranks over about 750 rpm.

Here is the datalog from today: ( I don't see anything abnormal)

2013-01-10_13.00.33.msl jan10,2013.zip

[Matt Cramer]

The code you're running does use MAP crank angle sampling, but I'm not sure how the sampling behaves if there's an RPM input hiccup. It is possible the sampling may freeze up.

[23tbucket]

I strongly believe I have an some ignition issues.....things never quite seemed right form the get-go. Apparently this engine series did have ignition problems. I am going to order and replace the complete ignition system with one that uses an optical sensor for triggering. This new system has a "built-in" tach output signal ( a perfect square wave).

I/we can only hope the new ignition eliminates the MAP freezing problem? Regardless..the ignition needs to be working correctly and reliably.If the ignition upgrade solves the MAP freezing...great!.....if not...plan "B".....lol

It will take a few weeks for the new ignition to be shipped and get installed. I'll post my results....

Thank you; Clifford