Yours is an L98 mine is a LT1. Any difference in the test? My FSM is for a 1992 specifically.

 

More of a setting than a test but AFAIK it is the same thing. If the IAC is at 0,it still means it has too much air.

 

Your bbk throttle body will flow more air than the stock 48mm at idle. So adjust throttle plate for minimum idle while watching tps setting. TPS still needs to be close to .55. Then see where you IAC counts are. 92-93 are speed density it won't pick the increase air flow of the larger throttle body. It will cause IAC to have 0 counts. You may need tweak it several times.

 

IDK about LT1 motors but I normally set IAC first then TPS because you're constantly adjusting the screw in and out, Rev and repeat till it is right. After that, I would adjust TPS.

 

It's not a BBK TB. It's a Rochester. As far as I Know it's original. It miked out at 52mm.

 

Same thing 52 mm isn't 48 mm.

 

Not sure how it will matter, either way. I have a 58mm 1000 cfm TB and that is how I set minimum air rate

 

aklim:
Don't have a scan tool. Do you mean an OBD I tool. No way to check pulses as mentioned in the FSM. You mentioned a "set screw". What set screw? The only set screw is on the throttle cam, and it's sealed. No adjustment on my IAC or TPS. Could you be more specific? A little confused.. Well, a lot confused.
Thanks for your patience, Dave.

 

Actually, I mean a scan tool that can read live data. If I was owning this car for any length of time, I'd buy a scan tool. Not sure what the OBD 1 tool is. If it is a code reader, you can do it with a paper clip for a lot less.

If your TPS has no adjustment, you are good. All you need to do is start the car and it takes that voltage as "base voltage".

As to the set screw, that is the sealed one. Many people take it out unless you need the car to be original as possible. Reason I like to use the IAC counts, and you do need a scanner to read the data is that it doesn't rely on the system being perfect, which you are not certain of at this moment. Here is what I do. I get the engine to operating temp and with everything but the motor off, check what the IAC counts are. Usually about 20-30 counts. This means that the ECM feels it needs more air than with the throttle blades closed. So if it is 0 counts, it means the ECM doesn't need any more air. Then I turn the screw out and close the TB a bit. Rev and check the IAC counts. If that doesn't change, turn more. Once the screw is no longer in contact with the "lever", it means the blades are closed all the way. If it still reads 0 counts, it probably means that there is an air leak because the ECM doesn't want any more air. If it is higher than 30, it means the ECM does need more air. So I turn the screw in which opens the blades more and lets more air in. This now means I don't have to rely on a suspect tach and it also tells me that there is no air leak.

I would get a bluetooth scanner from 1320 Electronics. There is an ALDL Scan program that is free. This makes it a scanner for you and you need one to work on these cars.

 

Did this bench test:
Removed IAC and probed the harness with key on there are two 12v pins and two grounds.
Re-attached IAC to harness. Key on or off pintel does not move or click.
Removed IAC to bench.Using a Power probe, hot to ground, hot to ground, no detectable pintle movement.
Bad IAC?
Dave

 

Not the best way to test an IAC. A good way to break it. Since IAC is out use light pressure and walk pintle back reinstall. Ground aldl ECM will command IAC closed. Disconnect IAC connector. Start engine is slow or won't idle normal? Way too fast IAC maybe sticking. Key off reconnect IAC cycle key 2 times IAC should be a 40ish steps. Disconnect connector IAC start engine should be at fast idle.

 

Kev.t

Pintle does not move in or out. Even with strong pressure, or 12v applied. Seems to be frozen. I'm thinking it's toast.
All I have for testing is a DVO meter, a Power Probe, and a 12v test light. No way to test the step thing. So,cave man stuff. Did I mention it's not throwing any codes?

Dave.

 

IF it is frozen, it's probably toast. I guess you are going to have to try replace it to see. This isn't going to be the last problem. Might I suggest buying a scanner to make life easier in future?

 

I've had this since 1998.First time something like this has come up. More the mechanical type. Rocks and clubs.
Can you suggest one that a cave man can plug into a laptop?
Thanks, Dave.

 

1320 electronics has a Bluetooth unit. Pretty cheap

 

Turns out it was the IAC. Rough idle gone. But, however the very next day it throws a C22 code, TPS signal low. I had checked this previously and it met specs. Replaced it and code went away.
And then, and then, the engine put out this horrible loud whirring sound. Idler pulley bearing toast. Lately this cars' got it in for me. Maybe an exorcism is in order.
Thanks for all the help guys. Drive on.
Dave.