jmedeiros808

All,

My brother picked up his 1993 Pickup. 22RE, 5-speed. Since the day he got it, it's had an idle surge under braking while at temperature. After some reading, we were pretty convinced it was the brake booster. So, $166 later, we had a new brake booster in and some freshly bled brakes. No surging, for about 10 minutes, and then the dreaded surge came back. We've gone through all of the hoses and vacuum lines to no avail, and finally found a (potential) root cause. A deeply-buried thread said that if the idle is adjusted too high, the engine will have a hard time under braking and surge the idle. It was a hunch, so we tightened the idle screw (also teflon taped the threads earlier, but that didn't help). Coming down to 850 or so, from 1100 revs at operating temperature, we stepped on the brakes and it didn't surge! However, tapping on the gas brought the RPMs up and for some reason when the idle came down, it went back to about 1100. Hitting the brakes again caused the idle to surge. So we looked for what was keeping the idle from returning to 850.

We tried actuating the throttle with the forward pulley, mounted to the throttle body, and learned that it will safely bring the revs back down after being opened. Using the rearward pulley, mounted to the intake manifold however, would bring the revs down but not all the way; it would take a small pull on the forward pulley again to bring it back down to 850. For some reason, the linkage on the intake manifold isn't quite pulling the forward linkage back where we need it. We'd considered the throttle position sensor holding the pulley from returning, so we pulled the throttle body off and cleaned absolutely everything inside and outside of it, hoping the butterfly valve wasn't getting caught on carbon or gunk inside. It seemed to return fully closed before and after. Next, we mounted it back on and disconnected the linkage between the forward and rearward pulleys, then ran the truck without using the gas pedal at all; still, the forward pulley seems to be working great, bringing the idle down just where we need it....it'd be fantastic to just tie the throttle cable to the forward pulley and call it a day, but we know that's not a proper fix.

I noticed the linkage between the two has some threads on it, and was wondering if that was adjustable; we'll need to find a vise to clamp it in, but we should be able to get a tighter pull and perhaps return the pulley to a better idle? Alternatively, we could get a new throttle body, TPS, IAC, etc...but if the intake manifold side linkage and pulleys are the real problem, they may just transfer the issue over. We tried the shotgun method with the brake booster and don't want to make that mistake again. It would hurt my pride if we got all of these shiny new things only to find out the problem started with a 3" linkage.

Option 1: Tighten or change linkage
Option 2: Figure out why pulleys act wonky toward each other
Option 3: Remove everything passenger-side of the valve cover and start new
Pre de-crapping

Post de-crappin

Friend opened the oil cap....notice the two pulleys in question on the left side of the picture.


Any feedback is wholly appreciated!

-John & Jason

jmedeiros808

Update: Autozone, NAPA, O'Reilly's don't have throttle bodies for sale. Nor do they have throttle linkage assemblies. Through craigslist hunting we've found someone willing to ship us some components. We'll be changing them one at a time to determine exactly where the problem is and will update within the week. Before we receive the parts, we'll try experimenting with dashpot removal or adjustment, pulling and lubing the linkages and other simple fixes.

Terrys87

iTrader: (1)

Have you tried burping the system. Raise the front end as high as you can and let it idle with the radiator cap off to get the air out of the cooling system. Let the thermostat cycle 3-4 times.

The dashpot can keep the idle high if it is not letting the throttle close all the way. Usually hitting the accelerator hard and fast will let it snap the throttle closed to where it needs to be get the idle back down and in most cases is because the dash pot is being sticky.

It is good to get the carbon off of the throttle body but as long as it is not keeping the flapper open, it really isnt a problem at this time.I have seen worse carbon on throttle bodies the had not caused any issues.

gsp4life

I agree with Terrys87.

I just disabled the dash pot on mine by setting the stop screw to where it won't push in the plunger anymore.

​​​​​Simple test: set the dash pot adjusting screw at a couple different places and see if the idle sticks at different rpms on test drives. If it does, the dashpot's no good and should be bypassed.

jmedeiros808

Pulley linkage

The nut spins, the head of it won't

Assembled

Disassembled

All,

Thanks for the replies. I'm not quite understanding how the cooling system could do that much damage to an idle; I'll definitely burp it this afternoon. Thanks Terrys87.

Furthermore, as gsp4life mentioned, the dashpot; I know it's only held on with two screws and I could see how if it were gummed up at the bottom of the throw, it would hold the idle there; if I were to remove it completely, could I rule it out as a worn part? With no dashpot, the revs can immediately snap back to idle. If it's still sitting high, the valve is sticking somewhere else. If it improves, we may have found the culprit.

In the meantime, I pulled off the linkage between the two pulleys and tried to shorten it, get a tighter throw between the two. The nut will come loose just fine, but even under heat, the head of it won't turn on the threads. I didn't want to risk squeezing it around the threads and ruining something, so I stopped after about 10 minutes with a torch, vise and pliers.

I also removed the linkage on the intake manifold side, pulled it apart completely, soaked it in Brakleen (except for the nylon/plastic split bushings), lubed it in oil, and reassembled it. Though it pivots on the pin a little better, it didn't solve the problem after a short test drive. Either it's not the problem or it's worn beyond reconditioning.

This afternoon I'll do a full coolant system burp, on an incline, Then take it for a test drive to see if that's our fix. If it isn't, I'll pull the dashpot completely (depending on replies) and see if we still have a sticking idle.
If the problem persists, I'll go ahead and order in the replacement throttle body, pick up a new IAC valve, TPS and give the whole thing a thorough cleaning beforehand.

I said I'd do this truck up right, put it back together and undo the ridiculous butchery that the previous owner had done to it. For laughs, here's what we've had to undo:

1. Ridiculous cold air intake ziptied to the fan shroud, where one end of the inlet wasn't big enough in diameter and thus wrapped in tape; the tape immediately got sucked into the piping and restricted most flow to the butterfly valve.
2. Wooden home siding acting as a battery tray reinforcement block
3. Bungee cord tying the battery to the battery tray reinforcement block
4. Random wire that we found to be the tachometer signal lead, pushed and wedged into the ignition coil connector

Next on the list:

1. Figure out why the speedometer (and odometer as a result) don't work
2. Repair the e-brake cable, which is snapped under the dash
3. Replace blown shocks
4. Figure out why passenger side door does not open from the inside, despite both door handles moving when pulled. Opens fine from the outside.
5. Undo the rat's nest of wiring left behind as the previous owner broke the heater control switch off, and then decided to rewire his own instead of finding a replacement switch.

You guys have been great help, even the lurkers lend moral support; if anyone's got fixes on either of these lists and problems, I'd love the insight. My brother is heading to the city (from Klamath Falls to Portland) and it's about time he's had a vehicle that runs properly on him. He had a 1993 with a 3.0, and surprisingly the head gasket held tight; since then he's owned a 94 Cherokee XJ and an 01 Subaru Forester. He's had worse luck with the Forester and its constant overheating problem, and scrounged what he could to afford this pickup. It's a bummer that he got basically robbed through the nose, despite it seeming like a good deal at the time ($3000). I just want the kid to have something he can rely on to drive without issue, for once in his short life, jesus christ.

Any help appreciated.

-John

gsp4life

I hear you loud and clear. Found I'd been screwed 6 ways till Sunday shortly after I bought mine, but it's all good now.

Sure, either reset the dashpot for a test or remove it altogether if you want, you'll know real fast if that was the problem. It's a well-known cause of idle sticking. I never figured out if the plunger or dangly valve was to blame, but I don't care anymore it works fine without.

I think our trucks speedos are just controlled by a spinning cable. Maybe it snapped?

Front half of the e-brake cable's not that hard to replace but while you're at it, I'd bet the rear drums have something stuck that caused the cable to snap in the first place. Check the bell-cranks, they like to fill with crud and seize. Should pivot real easily and I bet they don't.

Shocks are a breeze to replace on these trucks. Only annoying thing is the fronts probably bent a lot at the top threads, but some oil and ratcheting box wrench make it bearable. Or cut off with a grinder. I threw on a set of kyb excel-g few weeks ago. They're a little stiff, but not bad. While you're under there, check the steering dampener. Mine was original with 240,000mi and wasn't doing anything at all.