I have just Installed a new IAC, and had the TB of and cleaned it .

I have set Base idle, but couldent reach more the ca. 500 rpms
I then set the TPS
The car idles fine at 700@neutral 600@Ingear

BUT when i start the engine, it will run very rough, and I have to give it like 2000 rpms to keep it alive... Then the "service Engine Soon" light will come on, and I can get the car to settle on the 700 rpm idle

The car drive just fine after i have done this "start procedure" with the gas, and wait for the Serice light to come on, and it will idle fine at 700 rpms.

The code im getting is "33" a MAF code
What is the real probelm here.. what is comon, and what should I check

regards

 

Check your MAF connector and make sure its seated correctly on both ends, you might even check the IAC spindle and make sure its set correctly when installed.

 

Here's the Chilton codes: Code 33 Manifold Absolute Pressure (MAP) sensor - signal voltage out of range, high or Mass Air Flow (MAF) sensor - signal voltage out of range, probably high.
Let me do more research. The Chilton manual does recommend testing all connections/hoses for frayed wires, loose connections, broken wires, split hoses, etc. You can clear the code by disconnecting the battery for 30 seconds (this will cause you to lose your radio presets though).

 

Something with the connection to the MAF sensor has gone awry. Go through and trace its wiring back.

Otherwise, its probably the relays behind the battery on the firewall.

 

Here's something I found in my notes about Minimum Air Set on 1985-91 L98s. This is from Gordon Killebrew's class notes. I'll keep researching the code 33.

Normal idle voltage is .54 to .26 for 1985-89 cars.

1. Jumper across pins A and B in the ALDL connector under the dash, and then, turn on the ignition key (DO NOT START THE ENGINE). You will hear the coolant fan come on and the CHECK ENGINE indicator will start flashing. This is normal.
2. WAIT at least 30 seconds with the ignition on, then open the hood and unplug the idle air control (IAC) solenoid. It is located on the right side of the throttle body. This will not let the extended IAC motor pintle move out of the shutoff bypass air position. Remove the ALDL jumper wire.
3. Unplug the single wire connecter on the harness wire by the wiper motor. It has a tan/black striped wire. This is the 5-volt distributor bypass wire that diverts the engine to base timing when it is open.
4. Start the engine and set the base timing to 6 degrees BTC.
5. Remove the idle screw plug on the left side of the throttle body assembly. Using a 15 Torx tip adjust the idle to 450 rpms.
6. Reconnect the IAC connecter to the throttle body.
7. Check the TPS (throttle position sensor) voltage. Loosen the 20 Torx screw and set it to .54 to .56 volts. Using a digital volt ohmmeter across terminal A (black wire) to terminal B (dark blue wire) to set the switch, or use a scanner. The engine does not have to be running; only have the ignition turned on.
8. Remove the battery cable and then reinstall after 10 seconds. This erases the code 42 that was set due to the disconnect of the 5-volt bypass distributor wire.
9. Start the engine and vary the rpm's. After the engine is warm, hold the engine at 1500 rpms for 2 minutes. This cleans the O2 sensor.
10. Shut the engine off, then restart it. It should now idle correctly.

 

I think the power and burn off relays behind the battery are the same P/N; if so you can just swap them.

I suspect the problem is in the connection to the MAF (assuming you did not drop the MAF) since you had it disconnected to access the TB.

BTW, what is the TPS reading at 600-700 RPM??

 

Just found a paragraph in Chris Petris' class manual where he says the L98 fuel control system is sensitive to vacuum leaks. If a vacuum leak occurs the idle speed will be increased because the MAP sensor recognizes the vacuum loss and adds fuel as necessary (my note: causing a gasoline smell out of the exhaust?).
Check those vacuum hoses!

 

OK, just found the Code 33 Troubleshooting guide in my GM 1987 Corvette service manual. I can scan these and E-mail them to you. I co not have a copy machine so I must go to the local Wal Mart to use theirs. I have to wait for my wife to get home though as I am watching a couple of the grandkids.
I can only scan loose pages so thus the need to copy the book first. I should be able to do this within the hour.
Hang in there. We can figure this out!

 

0.71V

 

A code 33 Troubleshooting guide!!!

That would be cool!

 

I have just visualy checked the MAF burn of. But dont know if i found anything...

At idle the MAF was Very bright RED, when the engine was turned off it dident change, the red just went out...


the MAF at idle.

 

PM sent. Need your e-mail address.

 

PM sent

 

Is there a reason why you set the TPS to .71? I know when ever I went over something like 65 or so it would set a code on mine.

BTW, while I'm not sure whether the wire should be red hot at idle, it is my understanding that the way the MAF works is that the amount of voltage it takes to maintain the wire at a set temperature is extrapolated into airflow gm/sec. MEaning as more air passes over the wire, more voltage is needed to maintain the set temperature. Unfortunately I have never looked at mine with the hose disconnected so I don't know what's normal.

 

When setting the TPS after during the base idle...I have 0.65 v at idle and 4.78 full throttle...

When the engine is idling with the IAC back into plave i have 0.71v at idle

 

I would try and set the tps below what you have. I don't set my TPS while it's in base idle. I set it afterwards with it idling with the EST wire connected. I would try and get it down below .65 with at regular idle.

What are your IAC counts at idle? Is it possible it's too far closed.