Yes, i have searched around but i still have the problem.
Specs: 1989 toyota truck with 94 22re.
Whats wrong: idle screw is turned all the way in and idles around 1500 rpms whether its warm or cold. when driving the truck and you come to a complete stop at a light or stop sign with your foot on the brake, the engine will surge and almost act like its going to die. when you dont have your foot on the brake it just surges and sounds like its running good. I was told it could be the brake booster but the motor did the same thing when it was in a different truck.
things i have checked: timing, air flow meter, air intake tube, vacuum lines.
From reading around on the net, i figured i should check the fuel filter and the egr valve. Any other ideas?
It's not going to surge with it unplugged; I'm going through the same exact issues as you and I'm stumped.
You've checked everything I have - The last thing I need to check is the EGR. Don't bother with the fuel filter, that's not it. Don't forget about the Dash-pot either - that's prone to sticking and will cause the throttle to hang open.
EDIT*
Another thing; Mine will actually idle the way it should after a long period of idling or if I'm out wheeling at slow speeds. (I actually have to turn the idle screw back out to where it should be for it to idle at 900 or so).
I have had the same issue.. it was the AUX AIR VALVE under the intake.. It faces the twords the front.. it is held in place with 2 ten mill. bolts.. water runs through it..
You are one of those special "throw money at it Mechanics" Eventually you will replace enough parts to accidentally fix the problem. Fawking test shit before you spend money.
I'm taking away your posting privileges if you make another throw money at it without testing it post. :shaking:
Pull the rubber hose off the dash pot diaphragm (the gold disc) and confirm the throttle closes all the way to the mechanical stop. If it closes all the way then put the hose back on. The part at the end of the hose is a bleed valve. The dash pot just keeps the throttle from slamming shut. It should let it slowly close to the Mechanical stop. If so then there is nothing at all wrong with the dash pot.
Did somebody mess with the adjuster on the mechanical stop? that being open to much will prevent the throttle from fully closing and allow enough air past the throttle plate that the idle bleed screw will become ineffective.
If the truck has A/C there is a a A/C idle up device on the intake. It has a white plastic adjusting screw. Turn that screw and see if the idle changes. If so the idle up circuit is on. Does the A/C work? if it doesn't work but the A/C button is on it would cause this.
There is also a cold Idle air bypass under the plenum. If it was stuck open it would cause these symptoms.
A wore out throttle plate shaft could also explain this.
By a FSM this stuff is all covered in depth in the factory manual.
sounds like a vacuum leak or an issue with the iac valve. you can plug off the hole in the throttle body with a piece of duct tape to verify.if at operating temp,the idle drops when you have it taped off that would indicate an issue. just be carefull not to suck the tape up into the engine. you may have a sticky throtle or worn throttle plate? it seems as though your getting too much air into the intake from what you describe. does it have a misfire at any certain rpm? if you cant figure it out and you dont have a vacuum leak you can tweek the afm a bit but that would be covering up the problem unless thats the problem. i dunno but you have some testing to do! look in the 93 fsm here for specs.
There was a dude on Yotatech that found that there was a piece of logic in the computer that will cause the idle to surge when the brakes are applied. Computer senses the brakes are applied, so raises the idle to compensate for vacuum loss, then IAC sees high idle, so lowers it, round and round again.
He cut the wire from the brakes to the computer. He had a write-up on what he did, but I don't have the link handy. Haven't tried it, can't vouch for it, but something to look into if you get stumped. I'll post the link later when I'm home...
There was a dude on Yotatech that found that there was a piece of logic in the computer that will cause the idle to surge when the brakes are applied. Computer senses the brakes are applied, so raises the idle to compensate for vacuum loss, then IAC sees high idle, so lowers it, round and round again.
He cut the wire from the brakes to the computer. He had a write-up on what he did, but I don't have the link handy. Haven't tried it, can't vouch for it, but something to look into if you get stumped. I'll post the link later when I'm home...
a lot of efi's with a high rpm at idle has a vacuum leak, or a bad base gasket (same thing really). get the carb cleaner, or find a mechanics fog machine and start at the intake.
I have a truck that when you came to a moderate to hard stop, the engine would do just like you mentioned. After a little research, I found that a faulty or inaccuate speedo (which is what I had) could create such problems. Whether it was beause you had larger then stock tires or it didn't work all together, it could cause problems. I replaced the faulty speedo, and the problem was fixed. Apparently, the ECU makes adjustments to the intake based on the RPM/MPH readings.
Just something to chew on.
I guess you could call that another throw money at it method though. :flipoff2:
ok so let me get this straight from all the info gathered, its either caused from the idle being to high or a vac. leak, or the egr is plugged?
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Related Threads
?
?
?
?
?
Pirate 4x4
18.7M posts
366.4K members
Since 2000
A forum community dedicated to custom off-road vehicle owners and enthusiasts. Come join the discussion about trail reports, builds, performance, modifications, classifieds, troubleshooting, fabrication, drivetrain, and more!