Misfire at 3000

My girfriends 93 1.9 has a slight misfire at about 3000 rpm, but only when the ac is on, otherwise it has plenty of power. It has new wires, new fuel filter, new air filter and platnium plugs but the misfire was there before I changed all this. It is only slight but anoying and usually only in 2nd gear.

JM

My girfriends 93 1.9 has a slight misfire at about 3000 rpm, but only when the ac is on, otherwise it has plenty of power. It has new wires, new fuel filter, new air filter and platnium plugs but the misfire was there before I changed all this. It is only slight but anoying and usually only in 2nd gear.

JM

my car would buck when in second gear turned out the plug wires were leaking spark. Although you say they are new I'd recheck they arent arcing or grounding. BTW my car has a big differnce when my a/c is on also.

The misfire was there with the old set of wires so I don't believe they are grounded or leaking and this only happens when the ac is on. It runs excellent otherwise with plently of power and there is only a slight loss of power when the ac is on. Are there any real mechanics here?

JM

The misfire was there with the old set of wires so I don't believe they are grounded or leaking and this only happens when the ac is on. It runs excellent otherwise with plently of power and there is only a slight loss of power when the ac is on. Are there any real mechanics here?

JM

There ARE real mechanics here, but I'm not one of them. :rolleyes:

Still, it occurs to me that there's a solenoid for the A/C that actuates to keep the idle steady when the A/C is on - if that was dirty or had sticking issues it might cause a miss at higher speeds. Its on the throttle body. Just a thought... :2cents:

There ARE real mechanics here, but I'm not one of them. :rolleyes:

Still, it occurs to me that there's a solenoid for the A/C that actuates to keep the idle steady when the A/C is on - if that was dirty or had sticking issues it might cause a miss at higher speeds. Its on the throttle body. Just a thought... :2cents:

would that be the Idle air control valve you are thinking of?

The misfire was there with the old set of wires so I don't believe they are grounded or leaking and this only happens when the ac is on. It runs excellent otherwise with plently of power and there is only a slight loss of power when the ac is on. Are there any real mechanics here?

JM

You seem to have all the answers already but I stilll suggest checking the plug wires, plugs and maybe the coil (pack). If you are chasing the slugging from the a/c that my car (and others on this forum) have good luck if you find it please share with the rest.

would that be the Idle air control valve you are thinking of?
That's the one...sorry, just trying to help.

That's the one...sorry, just trying to help.
ohh ok thought there was something else that i didnt know about I'd like to find the answer to the same probllem

Missfires That Only Occur Under A Load (3,000) Rpms Are Ignition Missfires. Spark Plugs, Ignition Cables, Coils, Etc..

Your problem might stem farther then your plugs wires and pack. You said that there was a slight loss in power from the A/C turning on. This should not happen, when the A/C butom is pressed the rpms should jump to a higher ldol for the added power use.

That said there might be a problem with the charge thats being held in your battery (try just cleaning your posts) or from the alternator itself. Try putting a volt meter on it. The idol for your alternator should be around 12 but when the rpms get higher they should be about 14 to keep up with the power usage.
For your battery try taking it into a Part Source or Auto Zone or Canadian Tire or what ever you have. Get them to give it a charge, they will also be able to tell you if the battery itself is still good and able to hold a charge or if it needs replacing.

Your problem might stem farther then your plugs wires and pack. You said that there was a slight loss in power from the A/C turning on. This should not happen, when the A/C butom is pressed the rpms should jump to a higher ldol for the added power use.

That said there might be a problem with the charge thats being held in your battery (try just cleaning your posts) or from the alternator itself. Try putting a volt meter on it. The idol for your alternator should be around 12 but when the rpms get higher they should be about 14 to keep up with the power usage.
For your battery try taking it into a Part Source or Auto Zone or Canadian Tire or what ever you have. Get them to give it a charge, they will also be able to tell you if the battery itself is still good and able to hold a charge or if it needs replacing.

My '99 2.0 does a sagging with the a/c (or fan) on. The A/C has been checked by a service center. My battery has been checked (actually replaced) I personally did that voltage test and all voltages checked out fine (only didnt check the amps dont know how)

I think you may be right about the idle control valve. Sometimes after a long drive the idle sticks and I have to turn the vehicle off and restart, then everything is back to normal. I hear an arching noise when I turn on the AC every once in a while so something must be grounding out. If that doesn't work I will replace the coil pack. The battery was checked and it is ok as well as the output amperage from the alternator.

Thanks,

J

I think you may be right about the idle control valve. Sometimes after a long drive the idle sticks and I have to turn the vehicle off and restart, then everything is back to normal. I hear an arching noise when I turn on the AC every once in a while so something must be grounding out. If that doesn't work I will replace the coil pack. The battery was checked and it is ok as well as the output amperage from the alternator.

Thanks,

J

Do you know how to clean the IAC?

No I don't know how to clean it but if you tell me I could probably manage it.

Thanks,

J

No I don't know how to clean it but if you tell me I could probably manage it.

Thanks,

J

This valve is mounted on the throttle body by two bolts and a wire plug, and it can be removed (Be careful not to damage the gasket) and cleaned with spray can of carburator cleaner. Then before you reinstall it lube the gear inside (you'll see when you have it out and look at it upside down) with wd-40 or 3-1 oil.

You also can plug it back in (before you install) and leave it on the throttlle body turned toward the windshield and get in the car turn the key on and watch to see if it is moving to conferm the part is working)

Not all under 3k rpm problems are ignition. I have a '90 LX that wouldn't rev past 3k. I replaced the coil, and it still had the problem....turned out the fuel pump was bad.

You seem to have all the answers already but I stilll suggest checking the plug wires, plugs and maybe the coil (pack). If you are chasing the slugging from the a/c that my car (and others on this forum) have good luck if you find it please share with the rest.
You can also develop a misfire with a faulty fuel injector. Try performing a noid light test first, to make sure you have a good pulse to the injectors.
another thing to try is changing to A/C relay and the WOT relay (wide open throttle) Ford had a lot of problems with those relays. They are located on the fire-wall passenger side top of the engine compartment.

My girfriends 93 1.9 has a slight misfire at about 3000 rpm, but only when the ac is on, otherwise it has plenty of power. It has new wires, new fuel filter, new air filter and platnium plugs but the misfire was there before I changed all this. It is only slight but anoying and usually only in 2nd gear.

JM
If your car has a misfire, then it should set a code in the computer.
Also a faulty fuel injector can cause a misfire. But it would happen all the time not just with the A/C on.
Ford Escorts had a terrible time with the A/C relay and the WOT (wide open throttle) relays, not working properly. Try changing them. They are located on the fire-wall,passenger side, engine compartment. One is Gray and one is brown. Replace them in pairs.