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Well, after being told by "Ford mechanis" that there was nothing wrong with my car and that the rough idle was just the "nature of the Beast" I set to work myself. 1. Checked air filter - almost black, box has dirt, leaves etc in it. 2. Clean box & replace filter. 3. Install Tickford snorkel. 4. Buy 2 y.o. IAC from low mileage wreck, clen and install with new gasket. 5. Remove, clean, and reinstall throttle body with new gasket. I would say 80 - 85% of the problem is gone, BUT, the engine seems to fluctuate from 750 - 900 or 950 rpm in idle. Any ideas on the possible cause. I didn't touch the TPS other than disconnect the electrics and hook back up clean & dry. Will be fitting EF lid with mods over weekend, but need to sort out this new problem. What think ye guys? You all come back now - hear!
 

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How U going? I'm an ex ford mechanic and have worked on shitloads of AUs with rough idle.. Here is a typical fix au idle list( need access to NGS or WDS diagnostic systems) Check IAC % is 30-35%..base idle screw is adj to obtain IAC %. Check and adjust TPS to voltage reading of 0.7v. check pcm for updates.. there was always pcm software updates. check leads resistance.. this can be done easily by leaving leads on coil pack. should be approx 10000ohms/30cm of lead. (leads 3&4 were always likely candidates for open circuit) check spark plug gap 1.3mm exactly!! this is important on AUs. check carefully spark plug insulation for the tiniest cracks and replace if needed. Another amazingly common thing to find is loose inlet manifold bolts..(about 95% of AUs I think!), this will cause her to run lean of course, the oxygen sensors detect the lean mixture and compensate by telling the pcm to squirt fuel a bit longer thus stuffing your fuel economy too.
check & tighten all manifold bolts (even the bottom ones!). take the entire airbox out, (6 bolts) and that will make things heaps easier!!! & a long 10mm spanner is handy.
After all that, if it still idles rough or erratic, a pcm re-learn for base idle can be carried out. Disconnect battery for 5 mins. Reconnect battery. Start car. Now 4 steps... 1. Have A/C on & in Drive(foot on brake) for 2 min.. 2. now A/C off, still in drive for 2 min... 3. now A/C back on in Neutral for 2 min... 4. and finally A/C off in Neutral for 2 min. Turn Ign & re-start. Should be like a new one!!
 
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