Idle a little rough

[88LTDCV351]

OK, Marauder just hit 122,700 miles and it seems like the idle recently has gotten rougher. Otherwise, car runs good. What things do I need to do to smooth out the idle?

Thanks,

[jstevens]

clean MAP and IAC. May need new COPS.

[screamn]

When was the last time you replaced your spark plugs????

Check plugs & replace if needed.

[88LTDCV351]

I replaced my own spark plugs at 100,000 miles with Autlite X-103s I think. What does the idle air control motor look like on the 4.6?

[burt ragio]

It is a small round cylender the size of a pill vial. It is bolted to the front of the upper intake manifold.

[Blackened300a]

I replaced my own spark plugs at 100,000 miles with Autlite X-103s I think. What does the idle air control motor look like on the 4.6?

It wouldnt make it idle rough unless it's leaking. Check your vacuum lines. Is it rough like a miss or just slight vibration?

[Smalldogg/03mm]

It wouldnt make it idle rough unless it's leaking. Check your vacuum lines. Is it rough like a miss or just slight vibration?

It's not a miss it does it at a cold start bad.. And when it's warm everytime when I come to a stop it die down to about 2-3grand.. With the heat on worst.. Like u guys are saying I'm thinking vacuum leak

[Blackened300a]

I had a similar issue when my intake tube was loose. I also noticed a surging rough idle when I had a crack in my lower intake manifold. The line that comes off the PVC into the upper intake lid was leaking on mine and caused similar issues. I ended up having to put a clamp on it. If its really loose or pulling air the engine would have hard starts and stall.

[88LTDCV351]

Its nothing so serious. Just more of a slight vibration at idle than seemed normal. Have had the car for 6 years but recently the idle just seems to have more vibration than usual. I've put a lot of miles on it these last two years after prevously babying the car. Before I got the VV carb crown vic, I remember my 88 LTD Crown Vic 302 and my brothers 88 Grand Marquis used to require constant cleaning of the idle air motor to keep the idle smooth. I think I'll try that first on my Marauder. I'm not sure if my VV 351 has an idle motor since its carbed but its always had some vibration.

[88LTDCV351]

Cleaned the idle air motor with the spray cleaner. Now idle is too high. What did I do wrong?

[Blackened300a]

Cleaned the idle air motor with the spray cleaner. Now idle is too high. What did I do wrong?

Make sure the gasket is sealed.

[88LTDCV351]

Just tightened everything. However, one of the bolts broke. Darn.

[88LTDCV351]

OK, idle has gone down a bit but still seems high. Managed to get what was left of the broken bolt out. Tried to match it up at Autozone but the closest one seems too big. Anyone know the correct bolt size or the Ford part number?

Thx