[rowdhawg]

With appologies to the SVO purists I need some direction with a problem I am having with a swap I made. I swapped a 1985 SVO engine into a 1983 Ford Ranger PU. The engine and wiring harness (vane meter, MAP sensor, ect.) came out of a 1985 Mustang and I have a 1987 LA3 computer. I checked the wiring harness to make sure all the pins hav econtinuity and go to the right sensors.
The engine runs good with the exception of the idle. It will surge (run to 2000 rpm then almost stall) when I connect the IAC, and idles with it disconnected. The TPS is set at .8 and I have 5 V reference voltage to the sensors.
If anyone has informationon what voltages I should expect I would appreciate it.

[sleeper_inc]

You know you have to rewire the harness to use the LA computer right?

[rowdhawg]

Yes thanks... The only changes I saw was to switch the VAT (pin 25 in the 1985 to pin 43 in the LA3 and the VAF pin 43 in the 1985 to pin 27 in the LA3). When I did this I lost 5V reference, and the car did not start (no surprise). When I change the VAF to pin 25, the 5V comes back and the car runs but will only idle with the IAC disconnected.

[sleeper_inc]

Hmmm... I have really no idea what could be causing this. Your best bet if you question isn't answered is to post this on turboford.net

[NavySVO]

To set the TPS you will need the following tools.
1. Small Phillips screwdriver
2. Digital Voltmeter
3. Analog Voltmeter

The base idle needs to be set properly prior to setting the TPS. see below for instructions on setting base idle

The next thing to do is hook up the analog meter to the green and Black wires. With the key on open and close the throttle body slowly, you should see the needle move in a smooth arc without jumping around. If the needle jumps there is a dead spot in the TPS and it will need to be replaced.

The next step is to set the TPS to the proper voltage with the key in the on position. Using your digital meter, connect to the same wires as you did in the above. The TPS voltage should be as close to .90V with the TB in the closed position. At full open (WOT) should be around 4.5V to 4.75 V. If the TPS is not within the above settings, loosen the 2 phillips head screws and rotate the TPS until you get to .90V at closed throttle. Tighten the screws, and recheck your settings again.



To set your base idle you will need to have the car running, at operating temperature, all accessories off.

The next step is to disconnect the IAC (Idle Air Controller). The engine speed should slow to around 750 or it may stall. The proper setting is listed on the emissions decal on the cover of the coil.

With the IAC still disconnected set the idle speed using the adjustment screw on the front of the TB. Operate the throttle a few times to make sure that it is set properly.

Turn off the engine and reconnect the IAC and start the car. After a few minutes the idle should set itself around 950 to 1025 RPM. After doing this procedure, it may be necessary to reset the TPS.

[SvoScott]

I had a similar problem on my 88 turbo coupe. The dealer spent many hours attempting to figure it out. What finally turned out to be the culprit was a bad harness at the TFI. They installed a new pig tail and the problem was solved.

[NavySVO]

Originally Posted by rowdhawg

the car runs but will only idle with the IAC disconnected.

Take off the IAC and clean it. I used Fuel Injecton cleaner and sprayed it in the IAC cavity, filling it up with the cleaner.
Then I put it on the workbench so the holes were facing up and let the FI cleaner soak overnight. The next day I poured out black crap you wouldn't believe. Idled smooth after that.