Well guys after almost a year of siiting I finally have it running and driving, much better than befor I might add. I had a real bad hunting idle and a bad rich condition. I found that minimum idle was never achieved so IAC was trying to do all the work!! I have now fixed the problem(s) I was after and I have a few new one?? I cant seem to fix the idle (too HIGH) coming to a stop or light, if I have time or wait it will come down to where it should be but down shifting at 2K is a little to high for me! Whats causing the delayed idle down? Think the IAC is weak or am I missing something else? Also how can I determine a lean condition on a TPI car? I have a backfire @ the 1/2 shift @ wot. Im running the stock FPR cap with 29lb injs, I have about 40/42 lbs of fuel (no vac) should I try the adj cap or what? Any help would be great

 

OK, first off, you have a speed density system?? 1227730 computer with NO MAF sensor or not.....

at any rate with the SD system, you have to have a vechicle speed sensor hooked up, or the engine hunts at idle at traffic stops...
don't ask....

also you have to clean the idle air motor assy....just a rapid squirt with carb cleaner...and an air jet blast is fine...screw it home with a dap of WD for lube in the snout/shaft....

turn on the key, hear the fuel pump run for a second then quit...short out the two test point to see codes...the fan should turn on...
pull the 4 pin plug to the IAM (idle air motor)......start the engine, if you have trouble running it, you have to fight it untill you reach the absolute minimum idle speed of your cam....say 700 rpm or so...engine maybe not happy..but set the idle there with the throttle bolt up top on driver's side...the stop screw...i'ts a Torx....

so when it's warm and idle is about 1/2 way fine at ~700 rpm or so....
kill the engine, and plug it in, to restart the car.....

IF still troubles....pull the timing check wire/clip in the brown/black of the harness, set the timing at 8* lock it down....then plug it in and restart the car....

if all of this don't work....lemme know...PM as I may miss the post....

had a TPI on my shark for 12 years now....BTDT...

 

Another possibility of the hanging high idle could be a worn throttle shaft. The IAC may close completly, but the worn throttle shaft is allowing a vacume leak causing it to idle high.

Do you have any trouble codes, or is the SES light on?

The back fire under load indicates a lean condition Have you checked for vacume leaks? A simple way to check is by spraying starting fluid or WD40, or propane around the intake gaskets, and vacume connections while the engine is running. The engine rpm will increase when you spray around a leak.

Is your MAP sensor vacuume referance attached to the correct port?

 

Yes, Speed density with the weather tight ECM no MAF also no EGR or Smog. I have set base idle, base timing set to 8* I have a rebuilt throttle body 52mm off Flea bay so the shaft is not worn and the IAC passage is clean! The car is running and driving but the idle is kiling me at the stop light or while shifting. It will come down but not to fast. I also have a VSS for a manual trans, Im fairly certain it works because at first I had a chip for a auto and every time I came to a stop the car died, changed the chip and no more. I have the MAP vaccum off the port next to the fuel p. reg vaccum. I also just installed a new set of intake gaskets

 

I just took a look at MAP vacuum I is coming off the plenum @ the the two small ports. The Heater control is also getting vac from a Y fitting on the same port. Any chance the Y to heater control is messing with the signal? Also is a max lenghth on vac line to MAP? right now its about 10" long. Ill try the easy fix and pull the y fitting

 

OK, now I know for sure you have the exact same symptoms I have tolerated for a long time with my install....I find cleaning the IA motor sometimes helps...but not for long....

I think I am going to put another relay in the brake release circuit for my auto TCC, and short out the input to the speed sensor...so that computer thinks the car is actually stopped, then drop engine speed....

lie to the computer, essentially....not gotten around to doing it yet...

I going to put a say 200 ohm resistor in the circuit hot side, and put my switch on the computer side of that resistor so the magnetic pickup never sees a direct short circuit...but the computer sees NO voltage input, so thinks the car is stopped....I been playing with this for about 12 years now....dunno why it does that, but so yours does too....

did you do your own wiring harness??? if so, pay particular attention to the ground and exactly how they are run....SHARE NO GROUND LEADS FROM ONE CIRCUIT TO ANOTHER...ALL RUN INDEPENDANTLY...DON'T ASK.....

 

Sreet & Performance made a harness for me and set me up with the ECM and custom chip. What do think of the MAP sharing a vac source for heater control via a y fitting? The heater control was never hooked up before this repair. I cant remember if I had the same sympton before I replaced intake gaskets?

 

The map sensor needs to be on it's own port, don't tie anything into it. If you need to get vaccum for the heater controls do it on the brake booster side.

The length should be ok, my map sensor line is about 10" from the port and seems to be working ok. I wouldn't go much more than that, the closer the better.

 

My car was running rich and the vaccum was fine, what it ended up being was an exhaust leak near the oxygen sensor. It was making the ECM think the car was running lean and compensated by adding more fuel.

I installed new gaskets in my exhaust (center dump manifolds) and that fixed the problem

If I'm not mistaken, I think that caused a high idle too, can't be for sure though.

 

MY MAP sensor is on the firewall about 8" from the mani got it's own line....so does the adjacent fuel press reg.....

the accessories and other BS are run off the throttle body large port on the pass side....

I have HB brakes so the power brake booster input on driver's back end there is to the PCV....

 

I will move the vac for the heater control valve. I mounted my MAP sensor in the stock location on the fire wall, hope thats close enough. And now that you mention I have a exhaust leak on the O2, seemed pretty minor. Looks like I have a couple of easy fixes ahead of me

 

That minor leak will make a HUGE difference I had a leak at my doughnut gasket, I didn't have those sleeves in my exhaust and the gasket got a little sideways and I crushed it......air was coming in through there. I bought the sleeves and a pair of sintered metal gaskets, best thing I ever did.

Here is where I mounted my map sensor