engine idle rises and falls when cold. does fine when warm, but even then sometimes at idle, it will go up and down every second. i can hit the gas pedal and it evens out. ive also noticed that when driving, i can lift my foot off the gas pedal and the car will kind of jerk back and forth until i put my foot back on the gas pedal to keep the rpms up.

what ive done - cleaned TB, crankcase vent ports to intake, egr, iac, reset computer and base idle. worked for a moment but then started acting up again.

what confuses me is i tested the tps and it turned out with very bad readings, but unplugged it, tested it again and turned out perfect, plugged it back in and worked good again = problem? should i be testing this when the car is warm? with it running?

also, when the air conditioner kicks on, the engine drops and sputters for a second, and then jumps back up.

also hesitates while accelerating, and hesitation slightly goes away when my food comes off the gas pedal a little bit, and i can floor it and have full power again.

any thoughts or ideas? what should i be checking?

 

Sounds like the car has some issues with dirty connections. Those TPS connection readings could be part of the problem with the hunting.

My 94 had remnants of an old oil leak at the rocker cover when I got it, oily dust over a bunch of relays at the firewall, had intermittent a/c and weird o2 sensor behavior until I cleaned up all the pins, sockets etc.

If you don't have a small vacuum leak, I'd say it's the plugs and sockets from the intake sensors with less than perfect contact. TPS plug is worth checking first but may as well do them all, MAF, Coil plug etc. Contact cleaner, tighten up pin sockets, dielectric grease etc. Can't hurt, right?

good luck

 

Jagnoob,

I'm sure there are many people here on the forum that would like to help you get your Cat running smoothly so that you can enjoy yours as much as we all enjoy ours. Having multiple threads on the go at once makes it very difficult to follow and offer advice.

Ok, lets start with the basics;

How many miles (kilometres) has your Jag done?

Have you replaced your fuel filter?

Have you replaced your air filter?

Have you pulled out the old spark plugs, inspected them and compared them to a diagnostic chart? Have you replaced your spark plugs, leads, rotor and cap?

Have you done a compression test?

Have you done an oil change? both engine and transmission?

Have you inspected and cleaned your fuel injectors?

Do you have the Haynes manual?

The answers you give will greatly help narrow down the problem(s) you are having.

 

i have a haynes and ive done all of that. 138k is on the car. i just dont know what else to check, and i like to ask questions. sorry if that offends anyone

 

Asking questions is what this forum is all about. It's just easier to follow if you do it in a single thread so we all know where you are at.

Have you disconnected the MAF completely from the air intake, leaving the wiring attached, then run the engine to see if it makes a difference? then try the same thing but this time disconnecting the wiring? It's the big round aluminum cylinder between the air box and the intake with a brown/black square connector on top.

 

Having done a little more research, it's possible that you may have a vacuum leak at the intake manifold gasket... a common fault in a low mileage Aj6 engine.

 

i fixed it. the air conditioner was unplugged to where only the ground wire was attached. i was doing yet another wiggle test and pulled on the pigtail and noticed the power wire was just hanging there, so i plugged it back in and reset the iac. now it idles better and has a lot more power. i went to the jag mechanic for a brake issue, and he told me that the reason why it was doing that is cause the air conditioner was causing the engine to bog down and hit the rev limiter and the idle would bounce back up. makes total sense. he said it'd be a good idea to change the tps and the iac anyway, just because they are original is probably the cause of the acceleration hesitation.

now, to fix the reason why the air conditioner was unplugged.... vacuum leak behind the dash. time to take it apart! yay... not. anyway, thanks for your effort to help me and again, i apologize for asking so many questions!