I'm new to the site so Hello. I have a 95 22re manual trans w/ 145,000. My problem is when I start the engine cold the rpms go to about 2000 and after about 10 minutes the rpms begin to bounce rythmically up and down. On the low end almost sounds like it's going to stall.Then after this cycle which lasts about fifteen minutes it stops. And as long as the engine is warm never does it again. Can anyone offer some advice. I thought vaccuum leak, but then figured it would do it all the time.https://www.yotatech.com/forums/imag...lies/alert.gif

 

I have a 92 22re with close to the same miles.. Mine gets worse when I push the brakes too. It's not dealing with vacuum because I plugged the vac line from intake to booster and it did the same. I have been searching around and have decided to block off the cold idle air valve. It's on the bottom of the throttle body. There is a coolant line running to and from it. The valve is open with the engine coolant is cold and increasing coolant temperature gradually closes it. I have also read that once the engine is warm and the ecu is in closed loop, it will cut the idle down if the rpms are too high at closed throttle and once they're cut down they're restored. This causes the loop of high idle low idle. From what I've been able to put together, I'm guessing that the cold air valve is being lazy and keeping the idle up too long as the engine warms. At a certain temp the ecu switches from open loop (cold, ignores input from sensors) to closed loop (reads from O2 among other sensors), but the cold air valve is lagging behind with the idle a little high for the ecu's liking. It then cuts fuel to drop idle, restores it, idle raises, cuts fuel again, over and over again.

I now have mine fixed to where it DOES NOT do this when I first start it or once it gets warmed up good. I adjusted the idle down to get his far. However, like you, there is a short time in between where it does the dumb stuff. Above is the only explanation I can think of. I am going to remove my throttle body when I get home and plug the holes in the throttle body that the cold idle valve uses to route the air when cold and just set my idle to where it will behave itself. Hope this helps..

 

Your idle is to high. Back your idle screw out. It sounds wierd but when the computer comes out of closed loop (warm) there is to much air bypassing the throttle plate and the computer starts bouncing the idle.

 

Not necessarily.

My '94 truck had the same problem that Injected1 is describing above. I bought the truck used from a dealer and after about 5 weeks of owning it the problem started. I took the truck in to have it fixed under warranty because everything I tried (adjusting idle, etc.) wasn't working. After a couple trips it was determined that the cold air valve described above was clogged. It was cleaned out, and it's been a year now with no problems.

 

Update: Plugging the air passage the the cold air valve uses to route the air around the throttle blade while cold worked. The idle stays where I put it with the screw now. Now I just have to figure out wtf to do about the brake causing the idle fluctuation while the a\c compressor is kicked in. :pat: If I don't figure that one out soon I'm just gonna bypass the ecu with the brake wire and run the wire directly from the brake light switch on the pedal to the brake lights. I see no reason for the ecu to have to know when I push the brakes anyway.. Grrrr...

 

The ecu wants to "know" when you step on the brake so it can reduce the fuel going thru the injectors. Its a emisions/mileage thing, if your stepping on the brake you only need enuf fuel to maintain the idle. You don't accelerate when braking, so it cuts the fuel. The problem starts when our idle screw is set higher than the ecu can recognize. Idle set to high, ecu thinks your accelerating, and cuts fuel. Hence, vroom cut vroom cut etc etc

 

Its not the ecu changing the fuel. Its the vacuum booster pulling vacuum causing your idle to screw up. The ECU knows when your AC is on though and bumps your idle up because your compressor is taking more power to run. Sounds like you may have a vacuum leak if it is not your idle. It should idle with no AC at 700-800 when warm. If it is more like 1000 then when your AC compressor comes on you run into the problem that I described earlier.

 

I completely agree with you to an extent. The high idle DOES cause this problem. However, I had my idle set LOW when warm.. However, when cold the cold idle air valve would not fully close before the engine switched to closed loop. (engine warm) The vrrrooom cut vrrooom cut would only happen after the engine was in closed loop operation and the idle was still high because the cold idle valve wasn't shut yet. So, in a sense, it was caused by high idle, but I had NO control over it. If I turned the idle bypass screw down to where it wouldn't do this for that short period of time, it would barely run once the cold idle valve closed. So, I just ended up blocking the darn thing off..

I now have adjusted the a\c idle screw to idle slightly lower with the compressor kicked in and so far I'm not getting the vrrrooom cut vrrooom cut with the a\c on and brake applied anymore. I'll let you know how that turns out. I'm leaving my thread I created about the a\c brake applied open for the time being because I would like to know what suddenly caused this and if it's a sign of another problem.

By the way, the problem WASN'T vacuum related because it wouldn't do it with the brake light fuse removed, brake light fuse installed with brake booster capped off, or with the transfer case in 4wd. I took all of the measures so I could take vacuum out of the equation and isolate it to be an ecu\electrical issue. The ecu's in these things are on crack.. LOL

 

there is alot of info available if you search on google. Just search google, type in------22re idle truck brake---- etc This brake/idle problem is pretty well documented..

 

as I said in another thread ther are many things that cause the idle to bump up, a/c, p/s, 4wd there might be another but I cant think right now. Hope this helps..

 

Yeah, I've found a very small crack in the top of my radiator that is allow a small amount of coolant to escape. The overall problem probably has to do with that and the coolant temp sensor, but I won't know for sure until I get it fixed. I wonder what the best stuff to fix the plastic would be?? Think JB weld or twin cylinder epoxy would be better?