I recently tested to see if my fuel pump and the pump in my fuel tank were working via jumping them with fuses 4 and 6. Confirmed that they were both working, however when I started my engine again the engine would was idling high as though I were pressing the gas to the floor. I disconnected the idle position sensor, and it still ran at a high idle, when I pulled the hose that goes to the idle valve control the engine would die, but I noticed that the suction was high. My cousin suggested cleaning the throttle body may solve it, but considering that the problem began just after checking my pumps via the fuses I am thinking it may be something to do with the computer.

 

Not likely to be the computer. Checking the pumps like that should not cause high idle, may be you have an air leak somewhere causing more fuel to be metered out... Check for air leaks in the hoses around the intake manifold, and the gasket itself. Check the throttle spool alignment too, may be it got twisted-- the idle you describe is very high (gas to the floor)...

 

Lev, Thank you for your fast response. I can say that I never experienced a vacuum leak that increased the rpm of my engine. That said I did just recently test for vacuum leaks with a homemade smoke machine and hose and found no leak. I will check again, but visually I could find nothing. The throttle spool alignment was fine also. No matter what gear I am in it runs at a high idle. I was thinking it could be the throttle position sensor, I have never done anything to that.

 

sounds like you have done a lot of troubleshooting. did you ever just disconnect the battery wait a while then reconnect and
see if any changes? a few weeks ago someone had a simiiar situation which turned out to be a bad TPS.

 

wait, pulling those idle air hoses serves NO useful purpose, that would let unmetered air into the engine, undoubtably causing a nearly immediate stall....

When you unplugged the electrical connection to the idle air control (IAC) it idled too high, then your issue is very likely the throttle body or IAC being gummed up and not closing properly. I would clean both the throttle body and the IAC. if you remove the throttle body for cleaning, you should use a new paper gasket before reinstalling. and if you remove the IAC, you should probably have new hoses on hand as 35 year old IAC hoses will likely crack.

Use liberal amounts of throttle body spray to clean both. The IAC has a solenoid actuated 'shutter valve' , this should move freely, and if you apply 12V across the pins of the electrical connector, it should snap open, disconnnect and it should snap closed rather quickly.

For LH 2.2 cars like yours there's a specific procedure for adjusting the idle, but they should only be done after everything else is working correctly. From memory, you unplug the IAC, shut off all electrical accessories, start the engine and let it warm up and it should idle about 600 rpm. there's a sir bypass screw on the throttle body to adjust this. once adjusted, you plug the IAC in and the idle should be about 700 rpm. with the IAC connected, putting the car in gear, or turning on the A/C, or any other heavy load like headlights, the idle should at most dip a tiny bit for an instance and come right back to 700 rpm once fullywarmed up. a cold enngine should idle at like 1200 rpm or so until it starts warming up then descend to the optimal 700-ish.

newer LH2.4 car owners who read this, (thats 1989+), theres' no such adjustment, its entirely computerized.

 

Good idea, I will give that a try also. Cleaning the throttle body and replacing the hoses probably wouldn't hurt. Unfortunately, I have to wait for Saturday to try anything.

 

I was crossing my fingers that it might be that, but ufortunately no go.

 

Alright so I final managed to get a few days to work on her. We cleaned the throttle body and Idle air Control valve, IAC, with lots of throttle body cleaner and it seemed to do the trick. Although for the first 40 miles or so the idle surged slightly when stopped. I am still paying close attention to how she drives, as I always do kind of a habit. I added seafoam cleaner when I filled her up, hoping that will help maintain as we enter into colder months. Just happy to have her back on the road! Thank you everyone for your advice!