My 3.4 out of a '96 Limited is revving out of control. It was swapped into my '91 5sp. The ECU is for auto, but I don't think that's the problem.

For the past couple of weeks, the idle has been around 400 RPM, I finally wired in my post/cat O2 sensor, and re-tightened all exhaust bolts, that fixed the low idle. But now it starts at 1800 RPM, and the longer it runs, the higher it starts to idle, like to 3k. I need help now, I can't let this truck go down for any length of time, it's a dd.

 

engine codes are for multiple cylinder misfire, then a code for a misfire on each cylinder, and bad O2 sensor. Can a bad O2 cause this?

 

since nobody is answering I will take a stab at it. IAC messing up?

 

I have no idea what it could be but Cliff over at Toyonlyswaps is an awesome guy and may be able to help you out. They are really good with wiring and what not.

 

This website write up may be helpful for the misfire....
http://www.aa1car.com/library/misfire.htm

 

Longshot I know but.......mine did a simliar thing when i first fired it up. First i would check all the vacuum lines for leaks. Grab some starter fluid and spray everywhere. Increase in idle indicated a leak.

Mine was not a leak but the throttle cable. I at first, tried to use the 3.4 throttle cable and no matter how I adjusted it, it would never work correctly. I swapped the 3.0 stock cable back on and had no issues.

 

Are your ignitor wires connected correctly? Is your cat glowing?

 

the truck has been running fine for over 3 weeks, this just started, and come to find out that I hadn't tightened the throttle cable to the bracket. I adjusted that and my idle returned to 450 after warm up. I still need to replace my post/cat O2 sensor, but would it cause the misfire codes?

 

Doubtful. I ran mine for 6000 miles without any oxygen sensors and it never threw a misfire code.

 

my 95 idled high like that when the water pump was going out. any antifreeze leakage?

 

nope, runs fine except for the now low idle and bad O2 sensor.

 

check the ignition moduls one might be bad but i think the stuck throttle might have caused the computer to go ape trying to get it down i don't think a bad O2 sensor would be the problem

 

Check the idle adjust screw on the throttle cable bracket. Do you have an OBDii scanner that can read real time data? Check the throttle position. It should be around 10%.