Choke issues! - High RPM.

choke is electric.Sounds like from ur description above that it is working ok as far as the position when cold is concerned.If it doesnt completely open when warm.spray some carb cleaner on the pivot popnts of the choke butterfly and see if that helps.Also the carb has a fast idle cam that should disengage when the truck is warming up just by blipping the throttle.If it isnt disengaging,that could be the problem.The choke itself is the black round mechanism on the rear of the carb.some of the old ones could be adjusted but if u r running the Nikki that came off my 92,i dont think it can >BJ

...OHHH Boy!

Ok I'll try some carb cleaner and what not but I don't think thats the only problem because even with the choke just stuck on should it really be up near 2500rpm?

Anyways I tried a few things and had some interesting results.

So here is a pic of where the choke butterfly is sitting pretty much all the time except when I was doing the cold test.



Ok so then I found the push rod that moves the butterfly and noticed a few things. Ok first off, the 'fast idle cam' or what I believe it is does not allow the choke to open all the way however if I push down the choke rod only it will open all the way.

See this pic:



And in this one you can see where I was pushing to open the choke.



When I did this the engine basically did not change at all. However while I was doing this if I blipped the gas it dropped down to a regular rpm. At this point I could release the rod I was pushing down and it would be fine. Now while it was idling fine if I blipped the gas the choke plate would go back up to the same in the pic above and the idle would shoot back up.

I don't know if this gives you any more insight... Ideas?

Zac

So after playing around with it more I discovered this.



So in this pic you can see the metal part thats being pointed at. The choke rod attaches to that. When I simply click this part down the choke is open and truck runs normal. When I click it up the choke goes back to that half closed position. Its kinda like a switch to my problems lol. However if when it is clicked down and truck is running normally when I blip the gas it once again returns to its original half closed position.

So I don't know if this means that the mechanism that makes that piece switch is broken or if doesn't mean anything at all but I thought I'd post it.

So from the sounds of it do you think the fast idle cam is not disengaging?

Zac

i have the same problem and i had it narrowed down to the choke too... i just zip tied the linkage so it was at a manageable rpm for the trip i was taking at the time (to reso) since we got home its been in the garage with an oil pan leak and needing a few things before it gets back on the road. hope we can find a solution to our problem!!!!

that last pic... almost like there's a spring or something missing that holds it in place so the idle is good

The fast idle cam works this way. Listen carefully and you will fix your very simple problem.

With engine cold and not running, when you blip the pedal, the fast idle cam will be locked at the throttle shaft raised section by the pulling action of the electric choke being cold. This will close the choke.

As the engine runs, the alternator will supply the power to the electric choke. Verify that you have about 6-7 volts DC to the back of your electric choke and ground. As the choke heats up, it will push down (green arrow down) on the linkage you were talking about. When you blip the gas pedal again, the fast idle cam will be released from the throttle shaft through the pointed section riding on the fast idle cam. At this time, the choke should fully open and the idle should drop to your idle screw setting.

zach lube all the moving parts very well i noticed yo have a lot of dirt and grime on theses pivot poits carb clean them then get some good lube...not w-d 40 and try that...sounds to me like your just getting hung up

From looking at ur pictures,all the parts look ok and I dont see any bent or damaged pieces.Do as 892200 said-verify that u have the correct voltage at ur choke terminals-clean the pivot points with carb cleaner -then use a good silicone spray and lube all the pivot points.In full closed position it is not unusual for a Maz truck to rev to 2000 rpm on a cold am.Give it time to warm a bit and blip the throttle and it should fall off on the fast idle cam to 1000-1200 rpm until warm.BJ

So today I decided to drive my truck and ended up broken down. I parked my truck and when I came back to restart it it barely was limping to life and when it did the headlights were out and my head unit was all messed up. But with all of this, the truck was actually idling at a normal idle. I then parked the truck again and it would not restart.

After getting CAA to come pick me up and drive me home I discovered the alternator is actually shot! This alternator is only a few months old and only has like 4,000km on it. Now I just tried calling the place I got my alternator at and it kept saying the number is out of service. Turns out their shop burnt down! I think they are out of business now or at least a while.

So I put on a spare alternator I had off my 1989 b2200 that was fairly new (2004 after market) And after installing it I realized it is missing connections. So there is a pretty big wire that clips into the back its I think beige or black? and the biggest one. This alternator does not have a hook up for it. Do I need it? It is still working without it.

So now with the new alt working I hooked up the voltmeter to the choke wire and the voltage would not read, it was jumping from 8 to 20 to 14 to7 and everything in between. I tested it on my battery and its reading a constant 12 or 13. Did I have this hooked up right maybe? I just had the volt meter hooked up to the choke wire with the unit basically running inline. To choke wire from alt, into the volt meter, out the voltmeter, and into the choke. Is that the way it should be hooked up?

I'm gonna keep checking things out and have to go pick up some grease for all the connections in a bit but if you have any thoughts let me know. What do you think about the choke volt reading?

Thanks for all your suggestions so far everyone.

Zac

I had the same problem with my choke on my truck a few months ago, I tried oiling everything and it would work for a week and then it would start acting up again,so i went to canadian tire and they sell a kit that converts it to a mechanical choke.