got a 91 tracker and its running rough please help

[welderdoug]

I just bought a 91 tracker only has 40,000 miles but it starts somewhat hard then starts to miss under power. It doesn't seem to do it as bad when it warms up, but if i unplug the iac it runs fine. I don't even know where to start with the sensors, but it does have a fresh tune up also, and new wires.

[jtgh]

i bet it rooled over and is 140k. 2k a year is very low) mine rolled and shows 65k
"unplugged the iac, it runs fine."

Did this cure the miss or the the hard start.?

the iAC , works under all modes.
cranking it opens fully to allow fast idle and proper mixture.
and for idle.
and for deacceleration air cut
cold start fast idle too.

unplugging it , cause it to open tad. allowing more air.


if the Iac is stuck or commanded closed, during start, it will be a hard starter.

tune up , = rotor,cap, wires and plugs? at least?

i bet dollars to donuts, you have at least 2 problems on this EFI system.

common other fail is ECT sensor, Engine coolant sensor, with 2 pins.
if it reads, higher (ohms) it will force a false richer starting , AirFuelRatio .

The other fail coud be the fast idle dash pot not opening when cold.
look on side of TB(rear) see dash pot, see it hold open the throttle?
it must. or starting will be real bad.

your car has 5 paths of start air. ( all 5 contribute to a good start)


missing on 8v engine is almost always.

bad tune up, cap rotor wires and plugs.
or running lean,do to fuel pressure too low. (among many )

[welderdoug]

it actually cured both, once i unplugged it it fired right up and ran like a top. it has had a tune up including new fuel filter. i'm not getting a check engine light but it doesn't even light up when u turn the key, some im thinking someone pulled the bulb.

[jtgh]

ah, lamp is bad or ecu is failing self test diagnostic.

it runs self test every boot.
no lite = fail.

my IAC is bad too, it is siezed. for 1 year, but i found one at a wrecker.

one way to get extra air is to unscrew that screw on the end of IAC.

I have a new test for the iAC , coming out tonight, including how to test it
and to calibrate it. with a video showing the live test.

cheers.

[welderdoug]

should i try a new iac??

[jtgh]

Originally Posted by welderdoug

should i try a new iac??

i cleaned mine.

remove it .

read this.
IAC-e testing

see video of it working the 12v battery applied.!

then fill the hole with carb cleaner and wiggle the plunger till it frees up
then let it dry.
once it is free , it can work.

it might need calibration.

cheers

ps. it is very expensive.