OBDI Code 33

[twiget]

I recently got my 'burb back up and running after a couple months as a paperweight. The distributor failed and I had to replace it. I set the timing at 0* TDC when I installed the new distributor. Now the truck starts up, but it idles rough for a few seconds, and occasionally it will die. If I give it a little gas, the idle will smooth out and the CEL comes on and my reader tells me it is code 33 for the MAF/MAP. It will also stall when I come to a stop if I dont keep my foot on the gas, and it also hesitates and almost stalls when I try to accelerate.

The truck is a '90 454 TBI, and after doing some research on code 33, I think the problem the timing. I found a reference indicating that the ECU needs to be disconnected from the distributor when setting the timing. When I unplugged the ECU connector from the distributor, the motor would crank but not fire up.

Is there a connector I am missing that disconnects the ECU from the distributor? Is the timing even a viable culprit for my fault?

 

[4X4HIGH]

The wire that needs to be disconnected is called the EST wire and is located near the brake booster. It should be a single wire that is brown in color.

 

[mudbuggy]

Egr valve or egr silinoid look there

 

[twiget]

I found the problem. The vacuum hose came off the back of the MAP sensor. I reconnected the hose and the code went away. Then I unplugged the wire 4x4 mentioned and set the timing correctly. Now it runs like a champ.

 

[mudbuggy]

Well good. Your symptoms sounded like my egr issue I had a few weeks ago. My egr failed to move what so ever, through the process of alldata I learned the the computer has no way to verify the egr has moved other then from the map sensor data hence my reply but good to know that your rolling again.