RRC Won't Idle in Gear

[jhawk]

While replacing my alternator I noticed a leak in the hose from the MAF to the throttle body. I replaced it and now the truck won't idle in gear. It runs great and will idle in park. I've replaced the stepper motor and MAF, set base idle, cleaned everything I can think of, checked for vacuum leaks, etc. I'm at my wits end. Please shoot any and all ideas my way.

Absolutely no issues before I replaced the hose.


Jim

 

[ptschram]

Year? CEL/EFI lite on?

When it is idling, if you put your hand over the air filter inlet, does the engine die?

 

[jhawk]

It's an 89 and no CEL. It dies with your hand over the air cleaner inlet. It's way worse when cold so I changed the ECT yesterday with no changes.

It idles best when warm and the stepper motor bypassed. I can get it to idle nice and steady at about 900 via the dash tach. Once the stepper is reconnected it wants to idle in the 1200 range. When it is cold in the morning it doesn't want to idle.

Thanks,
Jim

 

[kk88rrc]

When you say it doesn't want to or won't idle… what do you mean? It's high, low, surging, hunting…..
How was it before you touched the base idle?
Try your old stepper… new one may be bad.
MAF…. new or used?

 

[jhawk]

The idle is pretty close to the video below when cold. The MAF is used. Adjusting base idle really hasn't made a difference and it's set back to where it was before the issue.

I'm starting to think it's the signal to the stepper motor.


https://www.youtube.com/watch?v=dAIQKptf_mY

 

[SLC99Disco]

FYI, I was just dealing with a similar issue on my 90 RRC. I was scratching my head as to what it could be, I went through everything and some things twice. I had replaced fuel pump, plug and wires, cap and rotor, stepper motor, cleaned MAFS, set base idle, replaced 02 sensors, still could not figure it out. Finally I checked the air gap on the distributor pick up and discovered it was way out, I adjusted it within spec and it has cured my idle issue.

 

[rover4x4]

I've been dealing with a similar scenario on my 91 I adjusted the air gap (way out of spec) and it seemed to help for a bit. I drove it for a weekend and it started surging in gear. I have not tried a new stepper only a "good" used one from another truck. spraying areas that might be leaking air with ether ddidn't affect idle so I've ruled out vac leaks for the most part. It is a really frustrating problem.