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Old December 1st, 2007, 12:33
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Ecomike Ecomike is offline
NAXJA# 2091
Join Date: Dec 2006
Location: MilkyWay Galaxy
Posts: 15,367
Re: 96 OBD II engine misfire codes and rough idle

What is really weird is that it almost immediately throws a misfire cyl code on cold start up, at ECT = 60 F. Then if I clear the code after it warms up and restart it, I can not force it to throw a misfire code again, even with multuiple restarts until it cools down to say 70 F.

The Coolant temp is running about 210 F with out any fans on at all. Takes about 20 minutes of idle at 80 F ambient just to trigger one elec fan to run for about 30 seconds, which drops the ECT from about 220 F to about 190 F in just 30 seconds. One electric fan runs on the ECT switch through the PCM, the second electric fan is operated with the A/C on. There is no fan clutch, or mechanical fan on this beast. I see no signs (yet) of coolant / head gasket leaks in either direction, and the misfire code switches between at least 3 (or 4?) cylinders so far. It has not thrown any other codes at all after 16 restarts and about 60 minutes of idling during those start run operations.

I did find a disconected vacuum hose to the fuel pressure regulator during the first test, fixed that, but the codes did not change, except for the freeze frame data which went from Fuel sys #1 reading "CL" to reading "OL" now, ????

Fuel sys #2 in the freeze frame of the missfire code is always reading CL-Fault, but I have not been able to find any references yet that tell me what " CL, OL, or CL-Fault" in the Fuel Sys means, nor why, or what the 2 fuel systems are, like what is the difference between fuel sys #1 and #2?

Thanks for all the replies and help guys!

I am going to run fuel pressure and vacuum tests today.
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