TBI Idle mixture

[krmiller07]

I have an 89 Pathy with the 5 speed. My question is, have any one had any issues or experince with adjusting the idle mixture on the engines ( V-6 ). My truck idles a little rough, or rich on start up, sounds like a carbed motor with the choke partly closed ! I'm getting piss poor gas milage both on the hiway and in town. It still smells rich even when the temp comes up to operating temp and idles kind of rough even though I have new cap, rotor, wires and plugs.I run a factory type K&N air filter, and have no Cat converter. The ECU doesn't pull any codes, and I replaced the 02 sensor with a new Bosch unit about 1500 miles ago. I'm running out of ideas. Someone told me theres a larger (slotted) screw on the passenger side of the TB that adjust the idle mixture and to some degree the "fast idle" speed, when the A/C or fan is running. This screw is normally covered or plugged from the factory for emissions reasons. Mine is not covered. and moves freely.

has anyone encountered this issue or have any suggestions on this topic ?

 

Thanks,

 

krmiller07

[MY1PATH]

untill completley warmed up the tbi retards timing 5 deg and enrichens the fuel.

Idle mixture is set byt the MAF & ecu.

once the engine is warm check your timimng, 15* should get you some help, stock is 12~13

 

then run ecu diagnostics and see what codes you get(guide is in the how to)

It wouldn't hurt pour a bottle of gummout regain in your tank. might clean up an injector issue or gunked valves.

Edited June 13, 2010 by MY1PATH

[krmiller07]

untill completley warmed up the tbi retards timing 5 deg and enrichens the fuel.

Idle mixture is set byt the MAF & ecu.

once the engine is warm check your timimng, 15* should get you some help, stock is 12~13

 

then run ecu diagnostics and see what codes you get(guide is in the how to)

It wouldn't hurt pour a bottle of gummout regain in your tank. might clean up an injector issue or gunked valves.

 

Thanks,

 

I have my timing set @ 15* at operating temp, and I've just recently cleaned my MAF by taking it out of the TB and carefully cleaning it with denatured alchol and a clean q-tip. all of this helped a bit, but I don't remember it ever idleing this rough then warm or on start up. I'run all of the injector cleaners, seafoam, techron etc..

[jj big shoe]

Someone told me theres a larger (slotted) screw on the passenger side of the TB that adjust the idle mixture and to some degree the "fast idle" speed, when the A/C or fan is running. This screw is normally covered or plugged from the factory for emissions reasons. Mine is not covered. and moves freely.

Yup, that screw adjusts the idle when the A/C is on. The FSM doesn't mention anything about it adjusting the idle mixture. That'll be controlled thru the ECM based on sensor inputs. Have you checked your vac hoses yet?

[krmiller07]

Yup, that screw adjusts the idle when the A/C is on. The FSM doesn't mention anything about it adjusting the idle mixture. That'll be controlled thru the ECM based on sensor inputs. Have you checked your vac hoses yet?

 

 

Yes, I've performed all of the "common sense" diagnostic's and haven't seen any codes show up on the ECU. I'm obviously stummped ! Motor has about 45,000 miles on it with good compression and minimal leak down.

 

Thanks

[Scaramoche]

Yes, I've performed all of the "common sense" diagnostic's and haven't seen any codes show up on the ECU. I'm obviously stummped ! Motor has about 45,000 miles on it with good compression and minimal leak down.

 

Thanks

 

Check parts of your emissions system because i have seen similiar issues with mine. Basically after i rebuilt the motor i noticed that i idled like hell. So being the rocket scientist i am, i removed all my emissions parts, capped all vacuum lines etc, and it ran great(a bit rich though). Either way over the last 2 months ive been reinstalling, repairing, cleaning parts, replaced all vacuum lines. Either way At first it ran like hell, then slowely i got everything done correctly and idling is stable(still a little erratic) I still have an issue with the AB valve(ie when it's connected my idle goes to hell again), may need to replace.

 

either way if all else fails test your emissions components.

 

 

UPDATE: i just finished passing emissions, and noticed my gas milage has improved dramatically, I think the bigest culprit was my O2 sensor. I also fixed my AB valve(seems it was seized, so i dumped a ton of bolt penatrater, let it sit for about an hour, then sprayed with 2 cans of brake cleaner) either way i cant beleive how that improved my milage. Note: also i added a new cat, not sure if that helped or not, but it sure as hell helped me pass emissions hehe

 

my 2 cents

scara

Edited June 21, 2010 by Scaramoche