'02 3.0 A/c On = Rough Idle

[J.HYATT]

Hi all...

I've got 2002 Ford Ranger Ext. Cab 3.0 v6 automatic. If you put it in gear and turn on the a/c the engine lopes / idles badly. Whenever the compressor kicks in, it drops to 500rpm and tries to cut off. If AC is off, it idles fine.
Any Ideas???

Problem #2: Runs great down the road until you give it gas to down shift while going up hill. It will down shift but it kicks in and out like it's starving for fuel. Fuel Pump??? Filter?

Any info greatly appreciated.

Thanks,

newbie...........

[J.HYATT]

BTW

Scan Tool shows no codes.

[bikerboy]

Check your Idle Speed Motor. It's two bolts mounted on the top of your throttle body. just clean it out with some gum-cutter. Clean your throttle body while you are there. Also when is the last time you did a complete tune-up, including plugs, wires, pcv valve, fuel filter,air filter?

[J.HYATT]

Thanks. I'll give it a try. As for tune up I'm sure its due - just bought it. I got a good enough deal on it to put a little extra in it if needed.

[J.HYATT]

Well I cleaned it and it seemed to help .... for a minute. So I replaced it, Still does the same thing. It won't do it when it first starts up and the idle is higher. What else would affect idle speed with ac on? Would an over charge on the ac system cause it?

[Ranger44]

Check your throttle position sensor (TPS). It is strictly a driver input sensor, and affects the fuel injector pulse, something like 500% override, and well if you do stomp on the gas and it's not working properly, it'll basically seem to bog out.

[J.HYATT]

Thanks for the tip. So far, I've replaced the IAC Valve, and the TPS. Neither have fixed the a/c Idle issue. I've also cleaned the MAF. This one's got me stumped.

As for the problem cutting in and out at highway speeds, it's getting worse, so I think it's almost got to be fuel pump/ fuel filter.

Any further idea's on the a/c idle issue. Is it possible to just dial up the idle a few hundred rpm?

[Ranger44]

Have you checked for a binding A/C compressor? It may just be on it's way out. It'd put a load on the engine. Unplug the A/C compressor and see if it makes the difference. BTW, new parts can be DOA. Do you have a manual and multi-meter? I'd actually check the sensors.

[almostclueless]

Torque convertor clutch problem?

[J.HYATT]

Yea I thought about the TCC. But it down-shifts smoothly and then starts cutting out. Just to be sure, I thew it into neutral and revved it. With out fail, it will cut out at 3100 rpm. I put a fuel pressure gauge and revved it up and the pressure would drop slightly at the same instant it started cutting out. It never dropped below 50psi. I think that's more than sufficient on a flex fuel. If someone doesn't agree please let me know. It would be a releif to know that it's just the fuel pump. I know they're in the tank and it sucks a little to change em, but I'm tired of trouble shooting.
I'm afraid the a/c - idle issue is most likely what was mentioned by Ranger44.

[almostclueless]

Originally Posted by J.HYATT

It never dropped below 50psi. I think that's more than sufficient on a flex fuel. If someone doesn't agree please let me know. It would be a releif to know that it's just the fuel pump. I know they're in the tank and it sucks a little to change em, but I'm tired of trouble shooting.

Um, the spec on my 98 is around 70psi.


I can understand why youre tired of troubleshooting.....and you should consider a solid diagnostic by a good dealership. Ends up being CHEAPER than throwing parts at a vehicle.

[bikerboy]

If you think it might be due of r atune-up then i would do one before you spend more money to have a dealership or personal garage diagnose it. Replace the spark plugs, wires, fuel filter, air filter and pcv valve.