Idle Speed and Error Code Question

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Feb 24, 2006
I just purchased a 94 LC with 147,000 gentle miles. One of the things that I first noticed was a high idle condition (1900 rpm) after starting a cold motor. The idle would slowly creep down to the 600/800 range within 3-5 minutes of start and then run relatively normal (that is to say somewhat rough).

Because I wanted to do some of the work on the engine myself, I cleaned it up with an engine degreaser and water. Predictably, the engine ran poorly afterward and since I was having my mechanic replace the front axle seals I asked him to address the rough running issue. He blew the water out of the appropriate nooks and crannies and I thought that would me the end of the problem.

However, when I picked it up (on a friday, after business hours) it was still running rough. I took a peek under the hood and discovered that his tech had not attached the distributor cap and that the rotor had slightly damaged the cap. I attached the cap and he agreed to replace the rotor and cap after his tech took a look. Since he wouldn't have the parts in stock until the next day, I left, but on the way home I got a CEL. I checked my Chilton manual and followed the instructions for acquiring the error code (No. 71). I started by checking the components of the EGR system, which was the system that corresponded with the error code and low and behold I found 2 detached vacuum lines to the VCV and VSV for EVAP (I believe). I reattached the lines, cleared the error code and turned on the ignition (didn't start). At this point I realized that I had not disconnected the jumper. I turned off the ignition, and unhooked the jumper and started the engine. I noticed two things, one, the engine was running smoother and two, the idle problem had gone the other direction.

The engine does seem to run smoother, but if I don't keep my foot on the accelerator, the engine idle will drop and it will eventually stall. I tried resetting the ECM by disconnecting the battery for 30 seconds, but that did not immediately fix the problem.

One thing I am worried about is that I have somehow damaged the ECM by keeping the jumper attached and turning on the ignition. However, I have read posts that would suggest that this should not have damaged the ECM.

I have also read posts that suggest that the ECM needs time to relearn after the battery is disconnected.

Did I damage the ECM and if not how long should I wait to see if the ECM relearns the proper idle speed and given the circumstance does anyone have any suggestions?

I apologize for the wordy post, but I thought the history would help in Dx'ing the problem. Needless to say I also beg your indulgence for any portion of my question that may have resulted from my own ignorance.

This is a test
You might want to introduce yourself. You'll probably get a little help and shake off the cold shoulder. Welcome to the forum! :flipoff2: Thats the Mud welcome by the way!
After checking code and pulling the efi fuse, my 94 LC took about 2 to 3 starts (10 - 15 miles of actual driving) to start idling correctly (~600-650 rpms). I still get the 71 code and plan to start with the egr modulator (it was full of carbon-dirty filter) and work my way around the entire egr system.


PS: Welcome to the forum :flipoff2: (that is my first official welcome)!
Thanks you guys for the quick reply. I think the problem is resolving itself. The idle is still low, but it is no longer stalling when I come to a stop. Now if I can just extract the code for the radio security system from the prior owners I will be able to drive AND listen to music.

Thanks Hog Head for the heads up (poor pun intended) regarding the introduction.

My rig is pretty much stock and in excellent condition. I purchased from the original owner who maintained the vehicle, kept the service records and gave them all to me. It has never been taken off road, although I plan on correcting that situation as soon as possible. Reading this forum has already pointed me in the right direction on the birks and the front door speakers. I belong to a similar forum for my Honda Element and they are lifesavers (as you know). I live in the southen San Joaquin area of southern California and I work as a government attorney.
Thanks again for your help!

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