B4000 IAC / idle problem

[dangus582]

To blogpost or not.

B4000
4.0 manual M5OD
Post sep

Bought a 94 B4000 (manual) gem for $1500 on valentines day. The weird problems are starting to best me.

Recently changed the IAC since the idle was a bit choppy (+/- 5% or so) and would hunt. Occasional stall on rapid stops, gear directional change and slow turns. Loses power at about 10 min into driving. Sometimes spews so much coolant I have to give it a break. Think that's a coil pack issue.

Transfer case motor fully detached, 4x4 isn't working properly. ABS light on. Friend trying to troubleshoot that.

Feels like trans shifts a 2nd time. Like a rough shift but with no clutch and no hand on the knob. Pressure plate sticking?

Anyway, coolant and stalling: Figured its either electrical or vacuum.

Changed IAC.

truck starts, but zooms up to 2500-3000rpm, turns the crank once and turns off. If I tap the throttle, zoom back up to 3000, and shut off without more throttle tapping. After about a minute of throttle tapping, she starts to idle. Idles high at 1100. No more spontaneous turnoff as aforementioned

Changing PCV today. Tried starting fluid spray, didn't see a vacuum leak near EGR.




Egr Is blocked (1/16 hole)
Vapor canister is deleted (tubes recirc fuel excess)
No muffler, still has cat
Entire coolant system replaced with new parts
Custom 3" intake
New fuel filler line, was totally dryrot

++tons of Random.problems

 

[franklin2]

With the engine fully warmed up and idling as good as it can, unplug the IAC wiring plug. If it keeps on running, turn the idle stop screw back till the engine is barely idling. When you unplug the wiring on the IAC, if the engine stalls, turn the idle stop screw in till the engine runs without the wiring plugged in. If you unplug the IAC and the engine keeps idling high, and you turn the idle stop screw all the way back and it's still idling high, you have a vacuum leak somewhere and it's sucking air into the engine.

Spewing coolant out of the radiator? Take the radiator cap off when it's cool, and check the brass washer right under the cap. See if it has a crack in it.

 

[dangus582]

Thanks for the suggestions. Will try those.

IAC procedure in your post - except "idling high" means "idle hunting" is identical to the last IAC now replaced

Don't think its the rad cap but I will check. Think it may be the seal on the reservoir.

Replaced some parts on the cold air filter system and the idle issue seems to be gradually improving. Is that a thing even with Odb1?

 

[franklin2]

These old systems do take several starts and stops to relearn when you change something.

 

[dangus582]

Would it be more fruitful to just do the whole idle re-learn process again? Haven't got around to playing with the idle screw yet per your suggestion, had some other pressing things that needed tending to. Got some better seals on the cold air so if the radiator goes tits up, I'm not getting coolant/water in the intake. Also changed the PCV which looks like it was the original ('94) and burped the radiator which got a buttload of bubbles out. Engine seems very happy with higher radiator pressure.


Anyway, started looking into doing what you'd recommended and I can't find the "idle screw" for the life of me; only the throttle adjustment screw. Is Finkle, Einhorn? (Are they the same)

 

[franklin2]

It's the idle stop screw that the throttle rests against when you are not pushing on the pedal. And there is no use doing a "relearn" if you do not change anything. Once you change something, you can take the battery off, or just drive it for several days and let it figure it out by itself.

 

[dangus582]

My B4000 absolutely wants to be named Officer Murphy. He lays down Murphy's law all day.

Still haven't got down to adjusting the idle, but I did find out why I'm running so lean on turnover.

EGR got carbon deposits, which started spewing smoke from spark plug #6. After changing EGR, smoke (exhaust) billowed from the EGR recirc tube. Scratched head for a few days.

Found that I completely misunderstood how the MAF/TB work for "unmetered" air, moved some of my intake vac lines around and the RPM increase to hard stall problem is almost gone.