On my way back home outside of Atlanta GA I was towing my gf's MR2 on I85 when all off a sudden we had to stop due to a traffic jam. My brakes were very hard to stop and I had to shove it in neutral because the idle was stuck at 3400 RPMs. I pulled onto the shoulder and take a look at the throttle valve. I cleaned up the throttle plate and still had the same results high idle. Next I examined the throttle cable mechanism and noticed all 3 cables were very slack and the spring must not have been strong enough to cut the idle down. Anyone have this problem before? I did not find anything on my search other than adjusting the cable. I know the cruise cable is broken so I'm going to replace it.

 

Hard brakes and high idle at the same time. That would lead me to think the brake booster went bad or you have a leak in the brake booster vaccum line somewhere. Usually the cable sticking won't make the brakes hard. hard brakes has to do with a vaccum leak or bad brake booster. I would check those as well.

 

I can't believe I didn't think of that, you may absolutely be right. I still need to adjust my cables and fix the cruise control cable as well. Thanks Trx!

 

not sure if this applies to your engine, but on the 22RE, those are classic symptoms of the dashpot sticking.

 

Dashpot? Please excuse my ignorance here but what is that?

 

bear in mind this is all from my 22RE experiences, but other motors work similarly, so it prolly applies...

the dashpot is the little plunger like thingie (sort of a shock absorber) that keeps the throttle body butterfly from slamming shut...

serves two purposes...prevents backfiring and keeps the truck from stopping too quickly when you let off the gas pedal. (at least in theory...in reality, my truck and others trucks seem to behave the same even with the dashpot removed completely, so it seems it might be solving a non-existent problem.)

anyway, on the 22RE, at least, it is on the outside of the TB where the accelerator cable hooks up to it. it has a little rubber boot that gets torn and then gunk gets in there and the plunger sticks and won't close all the way...thus, holding the butterfly open and causing the high idle (which also makes it hard to brake because you are fighting the increased power made by the engine at the higher RPM level).

when this first happened to me (at 2AM out in the middle of nowhere), i just took the dashpot off...problems solved. i have since put it back on and just spray it with silicon lube every now and then and that seems to keep it working fine.

(that could also explain why your cables have slack in them...if the linkage on the TB is not closing all the way and the gas pedal is not depressed, there is a shorter distance than expected between the pedal and the TB.)

 

If this is a 3.4L, there is no dashpot on there......not sure if this is a 2.7L.

What motor are we diagnosing BTW?

 

Checked the brake booster line and vacuum. Everything checks out normally. I cannot find the dashpot you are talking about. I have a '98 4RUnner with a 3.4l engine. I will have to get back to it.

 

I beleive they are supposed to help with emissions as it allows the gas that was being pumped in at full throttle to burn when you suddenly let off the gas, because you are right taking it off cause no ill side effects that I can see.

 

i guess 3.4s don't have one...might have some other "thingie" to serve the same purpose, though...or maybe the butterfly is just sticking partially open for some other reason...dunno, just something to check out.

 

Update:
I wound up finding some type of hose that feeds into the air intake box to somewhere on the back of the engine had a nice long split on the bottom so I never saw it during my initial check. Went and replaced the hose and it worked again.

edit: Finally saw what it was on Alldata... it was an idle air control valve hose. That explains the high idle and no power. Thanks for your input guys.

 

this just happened to me i am going to lube up the dashpot and check if any air lines are not connected and just check out everything to do with the air flow system

 

Vaccum leak I figured as much that is usually the symptoms! Glad you found the problem!

 

Yeah came to figure out that the IAC bumping up the idle and the brakes are having a hard time to fight the increased power so it made them just about worthless. It was scary too since I was hauling a trailor with my gf's MR2

 

Humm... this would explain my NO power breaks and idle at 2200....... i need to check the vacuum lines before i replace teh break booster and dashpot...