High idle, stuck adjustment screw
01-27-2011, 06:57 AM
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High idle, stuck adjustment screw
I've suddenly developed a high idle. This is causing my idle to lope when the brakes are applied. The idle adjustment screw it seized and I am at a loss as to what to do next. Any tips? And what might cause the idle to suddenly increase itself? Thanks
94 Yota truck 22r
94 Yota truck 22r
01-27-2011, 07:20 AM
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Thanks for the quick reply. In November I had my clutch replaced. My mechanic opted to change out my t-stat as well. When I picked it up he mentioned a high idle and stuck idle adjustment screw. So the screw hasn't been changed, I assume, from factory settings. It was running fine prior to that. Afterward for one reason or another the TB butterfly began stick so I cleaned off the gunk without removing the TB. It was a few weeks later that I noticed the loping idle. So those are the only changes to the truck. Coolant was a little low so I topped it off, put on incline and hopefully got out any air that was stuck in there. It's so cold outside that I haven't been able to really dig around. Guess it's back to the hoses in hopes of finding a leak.
01-27-2011, 08:04 AM
#4
Do you have a 22RE or 22R? I wasn't aware that they made the 22R (carbureted) as late as '94.
If it's fuel injected, when the thing is acting up and idling high try pushing the throttle body closed manually (under the hood) to see if your idle goes back to normal. On the 22RE's, it's fairly common for the throttle body dashpot to start sticking. I've always just pulled the dashpot off with no ill effects, some people say you can clean and lube it to make it work properly
LINK
Notes:
Dash Pot:
The GREEN CIRCLE shows the dash pot (DP) which is there to slow the closing of the throttle to prevent backfiring. It consists of the round air bellows, a spring loaded plunger, and the air vent line that attaches to the fitting at the base of the bellows. The vent line has a check valve in-line and an air filter to keep dirt out. The check valve lets air into the bellows then the throttle opens and extends the plunger. When the throttle closes, the stop screw contacts the plunger and pushes it in. The check valve closes to slow the air escaping the bellows and thus slow the closing of the throttle.
To troubleshoot the DP, make sure the air filter is clean and make sure the check valve is not clogged or stuck open. You should be able to blow air into the bottom easily (filling the bellows) but it should be hard to suck air out. Both the filter and valve can probably be cleaned with a mild solvent. Also, the plunger can stick. I find a shot of silicone spray applied to it periodically helps keep it moving freely. Lube it the push it in and out fully a few times to work the lubricant down into the plunger. And you can simpy back the adjuster screw all the way back to keep it from contacting the throttle linkage as a test. This way it is eliminated from affecting the throttle operation, in case you think it may be causing a problem.
To adjust the DP, I find setting the stop screw to depress the plunger about 1/2 of it's travel works well. If set too deep, you have more spring force to overcome and that can cause the throttle to not fully close. Too shallow and the DP can't really do it's job.
If it's fuel injected, when the thing is acting up and idling high try pushing the throttle body closed manually (under the hood) to see if your idle goes back to normal. On the 22RE's, it's fairly common for the throttle body dashpot to start sticking. I've always just pulled the dashpot off with no ill effects, some people say you can clean and lube it to make it work properly
Originally Posted by 4crawler
LINK
Notes:
Dash Pot:
The GREEN CIRCLE shows the dash pot (DP) which is there to slow the closing of the throttle to prevent backfiring. It consists of the round air bellows, a spring loaded plunger, and the air vent line that attaches to the fitting at the base of the bellows. The vent line has a check valve in-line and an air filter to keep dirt out. The check valve lets air into the bellows then the throttle opens and extends the plunger. When the throttle closes, the stop screw contacts the plunger and pushes it in. The check valve closes to slow the air escaping the bellows and thus slow the closing of the throttle.
To troubleshoot the DP, make sure the air filter is clean and make sure the check valve is not clogged or stuck open. You should be able to blow air into the bottom easily (filling the bellows) but it should be hard to suck air out. Both the filter and valve can probably be cleaned with a mild solvent. Also, the plunger can stick. I find a shot of silicone spray applied to it periodically helps keep it moving freely. Lube it the push it in and out fully a few times to work the lubricant down into the plunger. And you can simpy back the adjuster screw all the way back to keep it from contacting the throttle linkage as a test. This way it is eliminated from affecting the throttle operation, in case you think it may be causing a problem.
To adjust the DP, I find setting the stop screw to depress the plunger about 1/2 of it's travel works well. If set too deep, you have more spring force to overcome and that can cause the throttle to not fully close. Too shallow and the DP can't really do it's job.
Last edited by corax; 01-27-2011 at 08:07 AM.
01-28-2011, 12:11 AM
#7
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It would be a good idea to remove the throttle body and give it a good cleaning, also check the vacuum ports and make sure there not plugged. Don`t get any cleaner in the TPS or you will damage it. It may look clean from the front, but once you get it a part you will see that its not.
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