Rebuilding a throttle body? (1 Viewer)

[KLF]

Wow it's been quiet in this section the past couple of weeks... hope everyone is having a good New Years so far.

I'm still struggling with a very uneven idle, it's pretty annoying. Symptoms: After it's fully warmed up, often if I stop in traffic, the idle will be anywhere from 1000-1500 rpms. If I "blip" the throttle at the pedal, it will go usually go down to 900-1000 rpms. Sometimes, just sitting still, I can watch the idle creep up on it's own, till it hits the fuel injector cutoff point with the ECU, around 1300, then it drops down to 800 or so, then slowly do it again.

What I've done: The TPS is good and properly adjusted, there are no codes in the ECU, the IACV is brand new, as is the dashpot on the throttle. This is an '89 throttle body & intake. All vacuum lines have been replaced, EGR checks out, as do the EFI sensors. Throttle cable is brand new OEM. Timing and valve clearances have been set within the last 500 miles. Oil changed last week. Cam is an engnblr RV, new since the engine was started 3 months ago after a full rebuild.

I believe I've narrowed it down to a sticky shaft or butterfly in the throttle body, with a weakened coil spring. If the idle is fast and I hop out and open the hood, I can manually push the throttle fully closed, and the idle will drop to 750-800 where it's supposed to be. I also have a piece of duct tape on the idle speed screw now, as it seems to creep out on it's own.

Has anybody pulled the shaft & butterfly out of a throttle body? I thought about it, but the staked screws scared me off. I didn't want to mess anything up, as scarce as these things are getting. Junkyard replacement is a waste of time IMO, it will likely be just as bad (assuming I could even find one).

I'm aware of the TB boring & rebuilding that LC Engineering and 22REPerfomance.com will do, but I really don't see the value of having it bored out, without going to a lot of other trouble to tweak the intake and port the head, which I have no intention of doing. I just want a smooth consistent idle.

Thoughts?

 

[pappy]

I'm still struggling with a very uneven idle, it's pretty annoying. Symptoms: After it's fully warmed up, often if I stop in traffic, the idle will be anywhere from 1000-1500 rpms. If I "blip" the throttle at the pedal, it will go usually go down to 900-1000 rpms. Sometimes, just sitting still, I can watch the idle creep up on it's own, till it hits the fuel injector cutoff point with the ECU, around 1300, then it drops down to 800 or so, then slowly do it again.

If the idle is fast and I hop out and open the hood, I can manually push the throttle fully closed, and the idle will drop to 750-800 where it's supposed to be.

Thoughts?

Thoughts? Ya, let me know if you figure this out. Mine does the same thing ... except the idle doesn't creep up. It just sticks open slightly until I bump the throttle.

 

[Ctenosaurian]

I have had mine do the same thing as well. A simple blip of the gas pedal always fixed for me. I just assumed it was the throttle cable binding of being gunked up after driving down dusty roads a lot. It hasn't happened for about 10K miles now, so who knows.

 

[KLF]

I called the folks at 22reperformance.com for advice and to inquire about a rebuilt throttle body, they said "never heard of that happening". Hmmm...

 

[GRM]

I've had this happen to me too, but usually it revolves around the idle adjustment screw coming out, or the o-rings wearing out.

When the idle starts creeping up, is the dash pot engaged? Also, have you tried to use a heavy secondary spring to help keep the butterfly closed?

 

[Mudder]

may seem silly as it's a new one but check the idle/mixture screw O-ribng. I had my old 89 die on me on hills because it was unscrewing and screwing its self in on my. Would change the idle too.

 

[KLF]

I do believe the idle screw is moving on it's own, but I have a piece of duct tape on it now so it can't move anymore. Looks kinda redneck, tough...

I grabbed my old '87 TB, I'm gonna try to take it apart, see how hard it is. I may try to move an additional spring over to the one on the truck. But it's too darned cold to be working on it now, and now we're getting a storm.

 

[Mudder]

Wish I knew the part number but I got a bigger o ring then what came with mine. It was green. If I go down to my truck tomorrow I'll pull it and and measure it.

 

[MatS]

My old Hyundai Pony used to adjust the idle by itself while driving, countless times I would hop out at a light with my screwdriver and loosen the screw and be sorta normal again. That was carbed but same setup, once you've solved your issue and have your idle set, little dab of locktite will help keep it there.

I would be tearing into the donor TB and seeing what is possible and not, scary part about those staked screws is that if one comes loose.... bad day.

 

[snobdds]

I would start with a good O-ring on the idle adjustment screw. I know you have tape over it to prevent it from moving, but that screw is a controlled vacuum leak and the oring may be stretched and allowing air in that is not metered. If all the vacum lines are good, I don't know where else unmetered air is getting in to make the ECU cut fuel on idle. Then find out why the butterfly is sticking. As long as the spring is not totally stretched out...it should work.

 

[Oatmeal]

My 85 had the same problem.
With over 300k on the t/b, I narrowed it down to a worn throttle shaft bore not always allowing the butterfly to seat properly.
Couldn't find a repair kit but, was able to find a good used one at www.car-part.com.
Looking back now I could've probably rebushed it with some flanged oilite bushings (McMaster Carr)
Hans

 

[pappy]

I'm still struggling with a very uneven idle, it's pretty annoying. Symptoms: After it's fully warmed up, often if I stop in traffic, the idle will be anywhere from 1000-1500 rpms. If I "blip" the throttle at the pedal, it will go usually go down to 900-1000 rpms. Sometimes, just sitting still, I can watch the idle creep up on it's own, till it hits the fuel injector cutoff point with the ECU, around 1300, then it drops down to 800 or so, then slowly do it again.

Thoughts?

So, resurrecting this. I've had this persistent high idle problem as well. I pull up to an intersection, and the idle runs between 1200-2000rpm. I tap the gas pedal, and it comes back down. Finally, I'm sick of it and ... like I always say ... start simple.

I pulled the throttle cable out and sure nuff' I can feel it binding inside the housing. A new cable was ordered and installed. This seems to have solved the problem, and created another. My old cable didn't slide very well which created a heavy pedal. The new cable is slippery and is taking some getting used to at the pedal.

Also, I screwed up and ordered the wrong cable. I have the late plenum conversion and the throttle cable is longer than the 1985 cable. The '85 works, but it is shorter. The sticking cable was the longer cable, so at some point I figured this out.

 

[KLF]

My throttle cable is new OEM, and I lubed it well prior to installing, so I'm sure that's not my problem. It's been getting worse lately, really driving me nuts. I have to blip the throttle every time I stop, otherwise the idle is 1800-2000 rpm, very annoying.

Came home from an errand today and the idle was way high as I pulled into the driveway. Popped open the hood and carefully investigated. The throttle cable was totally slack but it felt like the damper dashpot was in the way and not compressing like it is supposed to. So I just took the stupid thing off. I'll let you know if it's any better now.

 

[KLF]

So, removing the dashpot on the throttle helped a lot, it is much better now. Not perfect, but better. No more high idle stickyness. Kinda pisses me off, that dashpot is new, I just bought it in November, and it wasn't cheap (~$50). But I still have an uneven idle, sometimes is it 1000-1100 rpm, sometimes 700. My plan is to live with it for now, then when it's warm out again I'll pull the throttle body off again and try to have it rebuilt. There is a carb shop about an hour from me that I have used in the past that does amazing work, I know they also clean and rebuild injectors now, so I'm gonna ask them if they also do throttle bodies.

Snowing like hell again today. Really sick of this. Another day of cancelled classes. I'm having to now look at cutting material out of my classes, there's no way I'll get it all covered. The only good news with this weather is I've been able to test out the lockers, which still work perfectly.

 

[pappy]

Well, my problem is also better ... but not solved. At least it doesn't hang up in the 1600-1800rpm range. Now it's around 1000rpm, and it consistently hangs there until I bump the throttle. Think I will look at my dashpot.

 

[KLF]

It's very easy to remove to test if it's the culprit. Two phillips heads screws.

 

[muddpigg]

X2 on Lce and 22re performance being spendy. Have you seen Maxbore prices seem reasonable compared. I've not had a TB rebuilt so don't have a comparison.
I recently swapped TB and upper plenum and had this problem. If i didn't blip the pedal I cound get out and tap the TB level and it would free up and drop idle. I gave the TB linkage a good spray of PB blast and it is fixed.

Hope you get it worked out, high idle annoys the hell out of me.

 

[KLF]

Hmmm... I wasn't aware of Maxbore.com. Thanks for that. I tried that local carb shop I mentioned, they don't deal with throttle bodies. I don't really want it bored out, I just want it all pulled apart, cleaned up, new seals, etc. I will see if Maxbore can do that.

 

[muddpigg]

Let me know what you find out. I'm riding the fence on having mine bored out. Just don't know if the "juice is worth the squeeze."

 

[KLF]

I'm gonna give the guy a call at some point and see what he says. His website is pretty cool, how he shows in detail how he does it. I'm impressed that he hand cuts every butterfly to fit.