Car acts funny when AC is on...

[MarlboroMan]

Its quite noticeable when the AC is on that the car "hiccups or has a "hitch". I guess thats the best way to explain it. Almost like a slight kick. Like you have watery gas or gunked up fuel system. And its consistent as long as the AC is on. I dont notice it when the heater is on. I notice too even when the engine is warm that the idle tends to stick sometimes around 2000 RPM, then drops down to normal after a few seconds. This seems real odd. It doesnt seem to be anything major. Just curious of to why it is doing this.

Also I dont know if this is a coincidence or not but at about 2100 RPM under easy or heavy acceleration it tends to have a little "hiccup" or "hitch" with the AC off or on. Almost similar but worse than the feel of when your IMRCs open up. I say a coincidence because I just recently changed my plugs (went with Autolites, which I dont like) and thats when it started. Wonder if it has anything to do with the plugs I changed?

 

[Red98CobraStang]

try the ngk tr55's. I like them much better than autolites. for the A/C hiccup issue, its normal. The engine hiccups because the compressor clutch is cycling on and off, drawing power from the motor. nothing to worry about.

do change out those crap ass autolites tho. ngk tr55's gapped at .054

 

[MarlboroMan]

You sure about the AC advice? Im not trying to insult your knowledge. Ive just never noticed it on any other car ive owned or driven, even Mustangs. Or is it just this particular generation that the AC is so damn monstrous it bogs down the engine performance that much?

 

[Red98CobraStang]

mine does it real bad sometimes too, like it takes the idle down to 300-400 rpm. my buddies 03 does it too. I wouldnt worry about it.

 

[SNAKEYE]

If it is hiccuping that bad due to the A/C compressor cycling off and on it is an A/C problem. It's probably low on R134 gas and kicking the compressor off on low pressure. Pickup a charging kit and (2) cans of R134 and DIY.

 

[coolguy10786]

Well if it does it with the ac off having it on is only going to make the problem more noticable. Make sure you got the right plugs. I went to schucks and got autolites and the gave me the wrong spark plugs. They were about 1/2inch too short. Thank god i didn't drive it. It was a mistake in the computer, so its a possibility that it could of happend.
Also you may have tugged on one of your spark plug wires trying to get them off to change the plugs. So you may need to change the wires because thats what im betting is your problem. You don't want to pull on the wire, only the rubber boot part.

 

[grandestang]

Mine has the exact same hiccup at 2100 rpm with the A/C on as your describing. Definitely a very noticeable almost like IMRCs opening. Its done it as long as I've owned the Cobra with both stock Motocraft platinum plugs and new Autolite 764s. Its totally normal and you shouldn't be concerned about it.

Paul

 

[97SVT#777]

Mine car has the hiccups with the a/c on. I've been wondering about this for a while whether it was normal or not. It's been like this for over 2 years, ever since I bought the car, and I've never thought about putting in more freon.

 

[JasonSnake]

AC in some cars will have it on 100% while ours cycle on and off. And since our cars have no balls in low rpm's, the power loss is very noticable.

 

[STAMPEDE3]

First off, Autolites arn't crap, they're almost identical to motorcrafts (At one time they were made on the same line) and people have been running for years without issues, they are very proven.

2nd, the hanging Idle is a dirty or bad IAC.

3rd, the hiccup when the compressor kicks in and out should not be as noticiable as the IMRCs opening. ?You may notice it but shouldn't be that bad, Sounds like compressor is loading really bad.

4th if the A/C at idle takes it down to 300-400RPS, that again is a IAC issue.
The IAC is supposed to increase idle when the A/C kicks in.

 

[nckissfan]

I second the comment about Autolites being a good plug. They are in my car, and have not had any problems out of them.

 

[MarlboroMan]

If it is hiccuping that bad due to the A/C compressor cycling off and on it is an A/C problem. It's probably low on R134 gas and kicking the compressor off on low pressure. Pickup a charging kit and (2) cans of R134 and DIY.

Dont think it is a AC problem right now. If it gets worse in time I might consider it being that.

 

[MarlboroMan]

Well if it does it with the ac off having it on is only going to make the problem more noticable. Make sure you got the right plugs. I went to schucks and got autolites and the gave me the wrong spark plugs. They were about 1/2inch too short. Thank god i didn't drive it. It was a mistake in the computer, so its a possibility that it could of happend.
Also you may have tugged on one of your spark plug wires trying to get them off to change the plugs. So you may need to change the wires because thats what im betting is your problem. You don't want to pull on the wire, only the rubber boot part.

I got the 764s. Gapped everyone as good as I can and with a feeler gauge. Only thing I can think of is maybe a gap too big or small on a plug. Since its such a minor miss. I never pull on the wire so it isnt that. Plus I inspect every wire. How hard is it really to change plugs? Ive changed many on many vehicles. Im not going to be conceded and say its not my error but I think these plugs just really suck. Im going to go back to OEM plugs here in a month or two. Im pretty sure its just the cheap ass Autolites. I was skeptical at first buying them but everyone talked wonders about such a great cheap plug. I differ with you guys. You live you learn.

 

[MarlboroMan]

Mine has the exact same hiccup at 2100 rpm with the A/C on as your describing. Definitely a very noticeable almost like IMRCs opening. Its done it as long as I've owned the Cobra with both stock Motocraft platinum plugs and new Autolite 764s. Its totally normal and you shouldn't be concerned about it.

Paul

See mine just recently started doing it. Thats why I asked. I dont think its anywhere of a major problem or a problem at all. Just curious if maybe a little tweak might get rid of it. Thank ya. :beer:

 

[STAMPEDE3]

It doesn't take much to damage these wires.
If it just started and started after you changed plugs, that's where my bet is.

 

[cobra331v1]

Uuummmm....I've used autolites in my 331 w/10 pounds of non-cooled boost. NO problems.