Chrysler Repair: Rough idle 88 labaron, vacuum leak, vacuum line


Question
Roland,
       i have a 1988 labaron with a 2.2 liter engine with single port efi, my question is when i turn on heater/ ac control the engine, when i come to a stop it has a rough idle once i get going it quits  ,it dosent matter if i have the a/c on or the heater. i have did a vacuum leak test and i come up with no leakage.  thanks,  jim

Answer
Hi Jim,
The vacuum leak is always good to investigate, and a couple of lines you might want to check are: the line between the power brake cannister vacuum connector and the heater/ac control unit in the cabin (which is a very thin tube that goes thru the fire wall and that might have a crack or be disconnected; the manifectation of that would be poor on no control over the air distribution controls), and the line from the control unit in the cabin to the heater by pass valve located in the cooling system tubing in the engine compartment which also is vacuum controlled.
The other routine rough idle cause is an egr valve that is leaking (it should be closed when at idle, so check the vacuum line between the intake manifold and the egr valve vacuum control unit) and also rev the engine and notice whether the stem inside the egr cage moves up and down freely, it has a groove so you can observe it move).
Other than that, the most useful thing to do would be to try to get the fault codes that may stored in the engine controller memory to readout. Try using the ignition key: turn it "on-off-on-off-on" and leave it "on" (doing this quickly, no longer than 5 seconds). By "on" I mean just the normal position when the engine is running, not the cranking position. The 'check engine'light will remain on when you leave the key in the "on" position with the engine still not running. But then watch the 'check engine' light to begin flashing, then pause, flashing, pause, etc. Count the number of flashes before each pause and keep track of the numbers. Repeat the readout and verify the counts are correct. Then group them in pairs in the order that they came out, thus forming two digit numbers. You may notice that the pause is shorter between the digits of a given number, and longer between the numbers themselves. Then send me a 'follow-up' question telling me the results of your readout. By the way, 55 will be the last number (two groups of 5 flashes each) and that is the code for "end of readout".
I have the troubleshooting manual for the 2.2 engine and we can look up the possibilities of what is wrong based upon what fault codes you show.
There is also an essay on fault codes at the site:
http://www.allpar.com/fix/codes.html
which gives the meaning of the code numbers. But then you need to get specific info for what exactly might be the diagnostic tests or parts to replace to complete the repair.
Roland