Occasional rough running when cold - Have to reset MS

[TrumpetRhapsody]

I'm having this bizarre issue occasionally while the engine is still very cold. Usually within 5 minutes of starting, with the clt around 40-50 or less.

 

Most frequently it's right when I back out of a parking spot, and go to start driving off. The car will be idling very roughly due to no IAC, and i'll be having to give it some throttle to keep it from stumbling. When I increase the throttle to drive off, the motor hesitates and won't leave idle rpms (usually under 1200 or so). The motor has no power, and sounds like it might not be running on all 6.

 

I'm usually not datalogging, since it happens infrequently, so it's hard to track. I think I did get one loged once, but nothing looked strange. PW was good, all sensors were reading normally, the motor just wouldn't go above 1200rpm or so. Power cycling megasquirt solves the problem every time.

 

 

 

Along the same lines, I think I may need to play around with simultaneous instead of alternating injection. The car fires off very well, but no matter the warmup settings, I have to give it throttle to keep it running above 500rpm, and it's still rough till it warms up. Even introducing a vacuum leak as a manual IAC didn't help much.

LatestTune120108.zip

[X64v]

Along the same lines, I think I may need to play around with simultaneous instead of alternating injection. The car fires off very well, but no matter the warmup settings, I have to give it throttle to keep it running above 500rpm, and it's still rough till it warms up. Even introducing a vacuum leak as a manual IAC didn't help much.

 

 

I'm not sure what's causing the first problem you describe, but as for what's quoted, switching between simultaneous/alternating injection will have no effect on your idle speed or warm-up characteristics. When I switched from simultaneous to alternating I made no adjustments to my warm up or idle speed settings, and the way it runs cold didn't change at all. If you have no IAC or fast idle (I don't, either), it's simply going to idle very low while cold, plain and simple. I have my hot idle set at 1000rpm, and it won't idle above 500rpm until the water temp is above 80 degrees or so.

[TrumpetRhapsody]

I see, I'll read up more on simultaneous vs. alternating.

 

Well I know it will idle low, but with hot idle set to 950-1000, it won't even idle properly with no throttle. It sputters around below 500rpm and usually eventually dies if I don't give it some throttle.

 

The vacuum leak method hot idles around 1100-1200, but makes no difference on the cold idle.

[TrumpetRhapsody]

Ok, so I'm a fool. Just found out on the way back that the warmup table isn't live. Have to burn it for it to make a difference. Clt was at 80, but I think I had the whole thing too rich. That should help cold startups some. Guess we'll see tomorrow morning.

 

Now back to the original, weird problem...

[naviathan]

Sounds like you're getting power spikes. Could be a faulty voltage regulator. If you can datalog it check the voltage.

[TrumpetRhapsody]

Voltage is one issue I HAVE fixed. I'm using a ZX internally regulated alternator from Autozone now (so newish/reman), and have VERY stable voltages (only about a .6v variation in the logs).

 

I'm definitely getting noise into the system, but this feels different. I get small spikes on stuff like the clt and iat, and rather large ones on the MAP that are definitely noticeable... This is a prolonged problem though, not a quick blip. Only goes away with a MS powercycle.

[TrumpetRhapsody]

Had it happen again yesterday. This time it was as I was going from a stop, I let the rpms bog very low, and it almost seems like it got stuck in crank mode or something. As soon as the rpms bogged the sound of the motor changed as if It wasn't running on all cylinders, and no matter how much throttle I gave the rpms wouldn't change. Once again, a MS powercycle brought it back to life.