i recently finally got this car to run and now it runs crappy when cold and idles too high....put a GM code scanner when it was running and it came back with code 34...now thats either mass air flow (MAF) or manifold absolute pressure sensor (MAP) any ideas as to what i should look at first? or has anyone else had a similier problem? any help would be great thanks!

 

Had the same exact problems. My throttle body was not closing all of the way which caused the really high idle. Then the car would still idle above 1000 rpm's. To take care of that I had to adjust my throttle position sensor (TPS). This may take care of you MAF sensor problems as the reading of the MAF sensor with the reading of the TPS determine when the ECM throws the dreaded code 34. If this does not take of the code, check wiring around the MAF relay and sensor. If it still throws code, change relay. If still throwing the stupid code, you may have to spend $200 on a MAF sensor. If the above does not fix the idle, you may need to look at the idle air control IAC solenoid.

 

Remeber to adjust the TPS when the car is at running temp. You can do this with a voltmeter or by ear. With a voltmeter set the TPS between .56 and .70 volts. By ear, have the car running and at running temperature. Adjust the TPS until the idle changes. The temperature of the car must be at running temperature to adjust by ear.

 

alright thanks ill try that and see what i get...i was considering replacing my IAC anyways...you think this would help? or be worth it?

 

If you are broke and love your car, take it out and clean it. If you are going to keep the car for a long time and the sensor is twenty years old, a new one, from a trusted parts store, would be a better choice. In other words, cleaning the OEM IAC is better than buying a cheap piece of junk.

 

yeah i can fully understand that...i love these cars and never wanna get rid of this one...how would i go ab cleaning it? i had it out but there isnt a whole lot to look at..

 

This is a tuned port injected motor right? The pintle, which is the tapered piece at the end that goes into the throttle body, should be clean. I.E. you should see metal and not cruddy build-up. If there is crud, get it off without damaging the thing. The passage where the pintle meets the throttle body should also be free of crud. Have you gotten anywhere on idle issues?

 

yeah well i replaced it anyways cuz it was cheap enough...i also replaced the TPS (throttle position sensor) and now im gettin a code 22...which is TPS sensor...im thinkin it just needs adjustment...is there an easy way to do this?

 

The TPS has three wires on it. The bottom one supplies voltage to the sensor, and the top two send a voltage reading back to the ECM. When the throttle is moved, the voltage between the top two will increase with increasing throttle and decrease with decreasing throttle. At idle, or when the throttle is not depressed, the voltage between the top two wires should read anywhere between .56 and .70 Volts. How to decide exactly where is whatever makes your car not throw the code but still idle somewhere around 800 RPM. At full throttle, the TPS should read over 4 Volts. The voltage between the wire at the bottom and any ground (battery or frame of car) should be 5 Volts. After adjusting, disconnect the ECM power supply for thirty seconds and then reconnect it. This is the sensor lookin' thingy by the battery. I believe it has one orange and one black wire. This will reset the computer. Now start the car drive over 30mph for at least a half of a mile. If your car has a manual transmission, when you push the clutch in, the RPM will drop quickly down to around 1200 RPM, after you completely stop, the RPM should go to somewhere around 800. If you have an automatic it is probably something like 500 RPM in drive and 800 in park or neutral. (Don't quote me on that) Whatever transmission you have, mess with the sensor, reset the computer, drive it a little bit, then check the idle. Hope this helps

 

If it is the original motor and you want it to run a lot better, change the timing chain and gears. That alone will help tremendously. What I mean by "that alone" is you will have to pull off the fan, water pump, harmonic balancer, spark plugs, etc, and you can put all of these back on or replace them. This is a time-consuming job and should be done with care, but the results are amazing.

 

really? i changed the timing chain and gears in my 85 before and it didnt really seem to make any difference at all..and my 87 i have now only has 89k

 

It really depends on how the 89k got there. If it was driven by a granny on the highway, then they do not need to be replaced. If it has been raw-dogged by a teenager against every mustang in sight, they need to be replaced. In either case, if you are sure the gears and chain are tight and have no play, then play with the timing. The way I set my timing is as follows:
1. Put a fresh new knock sensor on.
2. Make sure the distributor (dizzy), the module in the dizzy, the button, the cap, the wires, and the plugs are all in tip-top shape.
3. Loosen the dizzy nut so that the dizzy can be turned with some pressure, but not so loose that it can turn freely.
4. Start the car and let run until it is at running temp.
5. In the engine compartment, quickly race the throttle.
6. Turn the dizzy until you have the quickest response from the motor.
7. Drive and make sure this setting works for all RPM and loads.
i.e. drive normally, punch it while at low RPM, punch it while at high RPM, yada yada yada, so on, so forth.
The knock sensor is $35 and makes or breaks the motor.