# 1989, Idle way high, or very rough



## squarepeg (Mar 23, 2005)

NEW here. Read a few dozen searches.................1989 4cyl, 5 spd, 230K. Last year had 8 new plugs, wires, and fuel filter. Two months ago out of no where....when coming to stop sign, it started idleing way high or so rough it almost stalls out. Runs fine going down highway.

No CEL, dont smell any gas. My 81 did the same thing but I learned to live with it (dummy). .....1-Is there a usual common fix for this ......or as my searches indicate....multitudes of things to look for?

2- is there somewhere to go for picture locations of emissions parts etc....like MAF, EGR, solenoids, etc for the 1989 pickup?.....thank you


----------



## zanegrey (Dec 5, 2005)

read the codes...


----------



## NicHB (Mar 5, 2008)

could be several things. I'd check all your vacuum hoses for leaks and replace your PCV valve. My '95 HB was idling a little high as well. I found a cracked vacuum hose going from the throttle body to the brake booster and replaced a bad PCV. I also ran some Sea Foam through the TB and now everything is is smooth as budda.


----------



## BLOX (Mar 11, 2008)

I own a 97 HB and my truck recently running rough, check your TPS sensor, might be that


----------



## NicHB (Mar 5, 2008)

Well... I spoke too soon.

Now my truck idles high (about 1500rpm) again and it seems to be at random times.

Also, after my truck warms up, I'll be cruising in 3rd or 4th gear and it'll "bump" when I let of the gas to coast. It feels like a load it being placed on the engine a little and I can make it go away by hitting the gas again. But it bumps again as if releasing the load. Any ideas?


----------



## BLOX (Mar 11, 2008)

My 97 HB does that also, the letting off the gas and clunking kind of motion. I believe all that is is your RPM's dropping down because u just let off the gas, i wouldn't worry to much about that. Are you doing your annual maint. to the truck, that could also be why.


----------



## NicHB (Mar 5, 2008)

BLOX said:


> My 97 HB does that also, the letting off the gas and clunking kind of motion. I believe all that is is your RPM's dropping down because u just let off the gas, i wouldn't worry to much about that. Are you doing your annual maint. to the truck, that could also be why.


I did everything listed above in my precious post...PCV, fuel filter, engine oil, replace cracked vacuum hose, air cleaner. I'll most likely do the dist. cap, rotor, wires, and plugs too.

I just don't like the way it idles high at random times even after it's warm.


----------



## zanegrey (Dec 5, 2005)

you are wasting your time and money..

just read the codes...


----------



## Willz7 (Mar 11, 2008)

Squarepeg...
Had the same problem on my 88 4x4... Mine turned out to be the "AB" valve... (the annoying fat hose that hooks to the back bottom of the air box) Was creating a constant vacuum leak. This may not be your problem but my first guess would be that its vacuum related.
Willz


----------



## NicHB (Mar 5, 2008)

zanegrey said:


> you are wasting your time and money..
> 
> just read the codes...


only code I get is for the speed sensor, which I replaced but didn't fix the problem. I reset the computer and I'm getting the same code and a non-working speedo.


----------



## squarepeg (Mar 23, 2005)

Thanks for insights......PU belongs to neighbor lady who is barely making it each month. Her starter went out today so I towed her back 20 miles. Now have time to check it out some more in next few days.
Previously had a 4 cyl that one day it just started bucking. Accelerated fine, but as soon as you let your foot off the gas to de-accelerate, you had to have both hands on the wheel as it would buck so bad I thought my head was going to hit the windshield. Quickly accelerate and bucking went away.
Dealer said I needed a $400 carb. I dont know if I was too cheap, stubborn or both, so I just kept foolin' with it each night. I know you are supposed to check the PCV valve like the book says. I rattled it and sucked on it several times, semed OK. After the 3rd time looking at it I noticed on bottom that a little piece of the plastic that the ball seats against was chipped out. Spent $2 on PVC valve and solved problem....thanks


----------



## Nightrunner (Mar 12, 2008)

Noob here, and kindred spirit. I have an 89 HB Special with about 275K. Long ago I had the same problem of rough idling. It turned out that I neglected to keep the valves in spec and the clearance had dropped to zero. Yup, the Nap-Z is solid lifter. Pull the valve cover and check the clearance. They adjust with screws and lock nuts so its easy. I do not recall if it caused a fast idle but definitely a rough idle. Ran fine at high speed though.

The other thing that occurs to me on high mileage engine is gummed up fuel injector. Try a couple cans of injector cleaner.

Let us know.
Cheers
Scott


----------



## squarepeg (Mar 23, 2005)

I'll be working on the PU tomorrow.....When coming to stop light, sometimes it idles way high, sometimes almost dies. You never know which one its gonna be. Its 50/50 deal. thanks


----------



## Nightrunner (Mar 12, 2008)

Hmmm. Bad O2 sensor maybe? Anything that controls the fuel mix or throttle opening could be causing this.


----------

