Low Idle Problem Help..? Options

[detoxcowboy]

I have a 74 2.0

Idle stays low (verge of stalling) and Idle screw has no effect.. Jump on the throttle a few times and the Idle stays High.. Turn it off and restart the Idle is low again.. What is the vaccum supposed to be in the system? I reset the timing and that helped a little. Idle is steady. Is my TPS mal Adjusted. Wher and how to I start to search for what is wrong?

After 2500 rpm the car runs and climbs but try to hold at 2500 rpm in the driveway and the rpm starts to drop slowly..

Things I recently changed..

New control NOS unit (matches the car year and the mps)
New Vacumm Hoses and Fuel Lines..
New Cylinder Heads (valves etc.)
3 New Engine Harnesses (Ignition, Alternator and FI)
New Cold Start Vlave
New temp 1 and temp 2 sensors..
Had Serviced the Injectors too

** I DiD change the New decel valve hose routing to Match what is discussed in THE ECU link which differs from pelican parts..

ANy help is goo help..

[SLITS]

On your brain, try richening the idle mixture by rotating the adjustment knob a couple of clicks clockwise. Generally, you don't want to move it more than one click at a time and let it stabilize, but you can always lean the mixture by rotating one click at a time counterclockwise.

[detoxcowboy]

I tried that helps a little..

When you set the timming on a 74 2.o do you have to plug the vacumm advance..

I ran it to 3500 evn and set did not plug the advance..

[SLITS]

As I remember, not plugged but disconnected.

You can also richen it more and see if the idle comes up. Generally, with all else working correctly, the idle will come up and you can adjust it with the idle screw on the throttle body.

Also, what's your fuel pressure? Should be 29.4 lbs at all times. If low it will run lean and not idle correctly.

Car will also idle low if your timing is retarded. Make sure you timed to the correct mark.

[Jeffs9146]

I would check to make sure you have the correct CHTC on the passenger side head!

Also check the threads....mine were stripped when I bought the car and it took me two weeks of trial and error to figure out that the CHTC was not making good contact with the head.

[detoxcowboy]

I would check to make sure you have the correct CHTC on the passenger side head!

Also check the threads....mine were stripped when I bought the car and it took me two weeks of trial and error to figure out that the CHTC was not making good contact with the head.

New Heads And New cht 012 which worked correctly prior to all my changes..

[detoxcowboy]

As I remember, not plugged but disconnected.

You can also richen it more and see if the idle comes up. Generally, with all else working correctly, the idle will come up and you can adjust it with the idle screw on the throttle body.

Also, what's your fuel pressure? Should be 29.4 lbs at all times. If low it will run lean and not idle correctly.

Car will also idle low if your timing is retarded. Make sure you timed to the correct mark.

I never checked my fuel pressure as I had bought a new pressure regulator.. good idead.. I ahev read some people bump it up a few pounds..

ON THE ECU How MANY Clicks to Richen Is to far? I read 3 or 4 clicks max from factory point, but I also see they did not put a stop at that point..

SO BASIC UNDERSTANDING IS I DO NOT HAVE A VACCUM LEAK CORRECT? I KNOW OR THOUGHT VACCUM LEAKS ARE AT HIGH IDLE..CONCERNED ABOUT VACUMM WHEN IDLE WOPULD NOT COME BACK DOWN AFTER A FEW REVS..

[detoxcowboy]

As I remember, not plugged but disconnected.

You can also richen it more and see if the idle comes up. Generally, with all else working correctly, the idle will come up and you can adjust it with the idle screw on the throttle body.

Also, what's your fuel pressure? Should be 29.4 lbs at all times. If low it will run lean and not idle correctly.

Car will also idle low if your timing is retarded. Make sure you timed to the correct mark.

I WILL RE-TIME IT WITH IT DISCONNECTED AND CHECK THE TIMING MARK IS TRUE..

[SLITS]

How many clicks? I figure the car is 30+ years old and if it was still at the "factory setting" I would be amazed. I usually start at midpoint of the range and go up from there until the exhaust smells "gassy", then start backing down till it I am happy with the idle and starting characteristics.

Otherwise, obtain and LM1 and set the air/fuel ratio at 14.

If your deacceleration valve is working correctly, your idle will not immediately return to "normal" after chucking a few revs.

You can bump your fuel pressure by a couple of pounds. I don't know exactly at what pressure you can over-ride the return spring in the injector causing it to leak. Bumping the pressure up will also richen the mixture to a degee. I don't think I would run much higher than about 32 psig.

I also check the function of the AAR (Supplementary Air Valve) while playing with the above. From cold start, it takes some time for the valve to close. If it doesn't close, it's a pretty big "vacuum leak".

[detoxcowboy]

Alright problem solved!! The decel valve that i recently hooked up "correctly" according to the ecu document was "working" extremely well.. too well (my decel valve is brand new just for anyone thinking something else.. so I re hooked it in the manner according to Pelican Parts which is "wrong" and bypasses it and its vacuum.. just like i had it prior to the new heads.. Now the idle drops back to where i set it.. right away the air bleed screw starting working again which was drivng me crazy as I did not really have a vaccumm leak but needed air and starving for it.. anyways thankd slits..