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99 Wrangler Running Rough with AC on

I have a 1999 Wrangler which normally runs great. I have been having a very intermittent problem where the motors starts to run rough, causing the Jeep to shimmy. I think that it is related to the AC and the problem seems to be more pronounced when the weather is extremely hot. Yesterday was a really problematic day as it was very hot in NJ and I dove for many miles in stop and go shore traffic. I have also noticed that sometimes when it is running rough and shimmying, if I take it out of gear it returns to a normal idle.

I had it in the shop once already and they replaced a bunch of sensors and a cracked distributor cap and didn't improve the situation at all. Would be very grateful if someone had some guidance or any ideas.

Reply to
Kevtrane
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Your Idle Air Control valve is dirty. You can clean it but best is to get a new one.

Lynn

Reply to
Lynn McGuire

I'd stay away from that shop. The shotgun approach to solving issues is only a last resort.

IAC as Lynn said,

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I also had some rough run, also some sudden downshifts on the highway when I let off the gas. This was the TPS (Throttle Position Sensor) also on that page.

Check for any loose or broken vac lines, those will cause stammering.

Did they replace the coil? If you have a weak coil the engine will complain under load. And that problem will get worse with temperature. Even bad coils can ohm out ok. You need one of these to actually test them.

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Also be aware that multiple sensor faults can be caused by bad battery terminals, wires, engine ground, or a bad battery. Any time you see lots of sensor faults the first thing to check is the battery.

Reply to
DougW

Thanks for all the input, really appreciate the assistance.

Quick question about the Idle Air Control Valve. The mechanic who looked at it before says that they replaced the Idle Air Control Motor, is that different then the valve?

The shop says the replaced the Coil, Cap, Rotor and Wires

Now I am embarrassed, my battery terminals are caked with crud. This weekend I need to clean them all up and make sure I don't break anything else.

Reply to
Kevtrane

Same thing. The motor is part of the assembly so if they replaced it they should have also cleaned the valve body.

Plugs too?

I had a real problem with the check engine light coming on while driving. Tested everything, tightened everything. Finally decide to pull the battery off and have it looked at. The positive terminal snapped off when I was prying up on the battery connector. :/

A real quick check for bad ground is putting a jumper cable between the engine block and battery negative. If your idle smooths out then check the ground strap. On the I6 it's usually off the bolt that holds on the ignition coil. Not sure where it is on the V8. Also check between battery negative and frame. If that clears things up then it's the battery ground lead.

Any time you take the battery off it's a good idea to retrain the computer. Turn the ignition to run (leave the engine off) then slowly s.l.o.w.l.y cycle the throttle body between full open and closed about four times. Holding it wide open for a few seconds. This helps the computer set the sensor range. Otherwise it's going to set itself over a few days and give you some odd feelings. power sag, etc.

Reply to
DougW

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