Chemical

So I recently picked up a 1991 GXL that does not run properly. It starts fine but does not hold an idle and shakes really bad while backfiring etc, especially under 3k, and will die if I don't keep it revved.

The ECU spat out code 33, port air solenoid, so I decided to trace it all the way back to the ECU itself. Sure enough, the 3.9 ohm resistor for the port air solenoid is fried.

Now for the question, even though the resister fried, and the diodes next to it are fine...would this be enough to fry the entire ECU and cause poor running conditions?



Thanks alot!

BlaCkPlaGUE

I doubt it. I would think that if the ECU did get fried, it would either throw the car into limp mode, or it would not work at all. We'll wait to see what others have to say before I keep flappin my bullshit mouth heh..

Thats interesting though, how did you find out what resistor it was within the ECU?

Icemark

pretty common ECU and solenoid failure. I see a lot of ECUs with that burnt.

Mint87RX7

does the port air solenoid affect idle after its warmed up? i thought it was just the BAC

Chemical

Thanks for the reply

I used the ecu pinout diagram in the FSM to figure out what the burnt resistor did..

What are the symptoms of limp mode?

HAILERS

The PORT AIR SOLENOID is disabled after the first twenty thousand miles. Disabled in that it will not pull in anymore after twenty thousand miles. It's in the free, online, fsm. i seriously doubt the car would go into any *limp* mode over a solenoid that is non functional after twenty thousand miles (did I already mention that? Yes).

BlaCkPlaGUE

why is it only used for 20k? I was told this as well when I talked about mine when I first joined here.. The FSM doesn't show any routing diagrams as to where the ACV routes and controlls air, it just has tests to see if its working. ANyone with a diagram as to exactly what it does with air?

HAILERS

When your car turns to 100,000 thousand miles ......the Port Air Solenoid is once again enabled and will work for another twenty thousand miles. This is a TRUE statement for a series four car and has been verified by MYSELF. So now you KNOW it is a true statement.

What all that gibberish above means , is this. Next time your car reaches the hundred thousand mile increment, go out to your car and put a LED on the Input wire and run the LED to the inside of your car. Watch the light as you drive the car. Then you'll KNOW when the Port Air Solenoid opens and supplies additional air into the PORT AIR PASSAGE which is called the PORT AIR PASSAGE because the airpump air on the whole goes to the EXAUST PORTS of the engine.

Chemical

i'm going to replace the ECU regardless, as they are pretty cheap...

I'm thinking its a vacuum leak causing the poor running, but i'd like to rule out the ECU anyway. (I've already done a compression test and it checks out fine)

thanks again for the input