Rough idle (Page 1/1) Fierojor33 OCT 09, 03:22 PM First off thanks for letting me join, always have wanted a fiero and now my luck has changed and I have one. Now for the question I have, I just got a 1985 fiero gt 2.8l and I am having trouble pin pointing an issue. When jumpering the aldl system and doing the timing I can just about get everything in line and once I go to start the car back up without aldl jumper it has a misfire and #5 cylinder barely sparks most of the time missing spark. I shut the car off and now is where the weird part comes Into play, I jumper the aldl system wait 30 sec and then disconnect the iac vavle and when I start it up the vehicle runs as smooth as smooth can be without any issues. Possible bad map sensor? Also with everything in normal operating mode the car likes to backfire if you barely touch the gas pedal. Patrick OCT 09, 03:50 PM Welcome to the group. One thing to be aware of with these cars with the 2.8 is that the outer ring (where the timing marks are) of the harmonic balancer can start to slip (due to failure of the rubber in the balancer). As you can then imagine, that completely throws off the ability to time the ignition properly with a timing light. To check to see if this has happened with your balancer, remove #1 spark plug and use something like a plastic straw to put into the hole. While rotating the crankshaft by hand, determine where top dead center is. When TDC is found, the widest of the three timing marks on the balancer should align with 0° on the timing scale. Fierojor33 OCT 09, 05:35 PM Yes I just verified that #1 is at top dead center and on timing the wide mark is at 0. Patrick OCT 09, 06:13 PM It's difficult to diagnose something like this from afar as we don't know variables such as fuel pressure, and the condition of spark plugs, spark plug wires, coil, ICM, etc. Check the TPS for dead spots. Also check that both injector fuses are good.