All Things Fiero > Tech Tips, Tech Questions
Idle issues...
crash_out:
I guess as a way to help others, I can share what HASNT corrected the issue. Of course barring a new component that was bad from the beginning. Also, the car did idle properly initially. I parked it in the garage while I worked on the interior-about 6 months without running. That's when it started surging and stalling.
The car has fresh plugs, wires, dist cap and rotor button. New IAC, fresh fuel, fuel filter, O2 sensor. New injectors. New high pressure pump for my 3800 swap.
I never messed with the timing from when it was running OK.
Fuel system wise, the only not new component is the regulator, and it seems to be functioning. Sensor wise, the the only ones I haven't replaced are coolant, TPS, and MAP. They all SEEM to be functioning. Ignition wise, I can only think of the pick up coil, ignition coil, and IC module. The exhaust fumes will burn your eyes if you stand back there long enough, but I kind of attributed that to lack of cat and the aftermarket exhaust. I haven't messed with the screw on the throttle body. From everything I've read, there's no reason to unless someone else has messed with it. And I'm not inclined to think that would be an issue since it was fine when I got it.
This kind of leaves only the ECM module. I'm honestly not willing to throw any more parts at it since I'll start the swap in November. If I knew exactly what I needed, I would but that one part. But not randomly throwing any more at it hoping it will fix it.
Fierofool:
You can check the TPS for correct voltage setting before swinging for a new one. 0.5 Volts at idle position and approximately 5 volts at wide open throttle. The engine doesn't need to be running. If it's not at the required voltage, you can carefully bend the tab to get it at the 0.5 volts idle.
The other thing that I believe could cause the problem, since you say it's running rich enough to burn your eyes and nose, is the coolant temperature sensor. It can fail without throwing a code. It can cause the other sensors to try to correct the rich burn by trimming fuel. Also check the vacuum connections underneath the MAP sensor.
I think I replaced my CTS. I did replace the IAC but that doesn't mean that one of them wasn't bad from the get-go. I think our problem is on the fuel side and not on the ignition side.
crash_out:
I checked the tps voltage, and came up with 0.63. That's well within tolerances. I have a new CTS ,not installed, but seemed to be getting proper readings through the data port for it. I have gotten the car to go into closed loop as well, which should mean it's getting up to temp. At that point, it really tries to idle at 900, just stalls out at anything less than a rough 1200.
Fierofool:
If Idle voltage is at 0.63 it's telling the ECM that the throttle is open and thus it's adding fuel. Could be the reason for the rich burn. Mine didn't run right at 0.53V. Adjusting it down so that it bounced between 0.49 and 0.50V did smooth it out when it warmed up. My fluctuation is while it's in open loop.
Raydar:
Sorry. But have to ask... have you verified timing, after using the "short the pins" method to adjust?
Whenever I had mysterious idling issues, I removed the throttle body, and removed the IAC and TPS, and everything else I could, and cleaned and brushed everything in the throttle body that I could. I did not remove the throttle plate, but I did clean the bore of the throttle body. Lots of build up behind the plate.
Think I used brake-kleen (red can) and a brush. Also sprayed through all the hose fittings and such. Be careful, Some of those internal passages just loop around. Easy to squirt brake-kleen in your eye. Don't ask me how I know that. :P
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