[leolonewolf]

I've been trying to track down this issue for a few months now. I have a 2004 focus svt eap with 190k on the clock.

While at idle my rpm's fluctuate between normal (900) and as high as 2900 rpm. I just replaced my tps switch today, thinking maybe I had an issue with it. No luck, what was mild lately is now back in full force. I did reset the computer by pulling the battery cable for an hour while I cleaned up the headlights, stupid oxidation, and have been driving around town on errands for a hour or so. Other symptoms are very rough/jumpy throttle response when I let off the pedal. Almost like something is stuck and then breaks loose letting the engine drop to normal idle. Anyone have any ideas?

 

[leolonewolf]

Oh and vacuum at idle (850-900) is 18-21 on my obd reader

 

[sailor]

Moved to General Tech Chat for more looks.

 

[FocusKnot]

Have you ever cleaned or replaced the Idle Air Control (IAC) valve? Lots of idle problems show up with it sticking.

 

[leolonewolf]

No, I haven't. I'll look into it

 

[leolonewolf]

Ok, latest update.

Put in a new IAC. Same stuff still going on. In the last six months I've replaced the alternator, battery, IAC, and plug wires. I bring these up because I've discovered an anomaly with this idle issue.

Anomaly: when idling high, around 1500-2000 rpm, I turn off my heater/fan blower and the idle will drop back down to normal range of 8-900 rpm.

Still getting the random jerky feeling while driving too, like a stuck cable or something releasing. Occurs even when the fan is off.

This plus the new anomaly I found is suggesting to me an electrical current/voltage issue.

Your guy's turn, thoughts and input appreciated.

 

[iminhell]

Oh and vacuum at idle (850-900) is 18-21 on my obd reader

There is no MAP sensor. So this data is useless and false.


Repair your intake couplers. I'll bet at least one of them is torn on the bottom.
To test me, pull up on the manifold and watch the engine race.

 

[leolonewolf]

How would turning off my fan affect the idle though if it is just torn couplers?

 

[iminhell]

You said it doesn't:

Still getting the random jerky feeling while driving too, like a stuck cable or something releasing. Occurs even when the fan is off.

But I guess I'm wrong and I won't bother to help further.

 

[leolonewolf]

I can see the torn coupler affecting drivability when going down the road, I may be seeing two separate issues though and associating them as one.

 

[JFrye]

Long shot here, but is there any carbon buildup on the butterfly inside the throttle body?

 

[leolonewolf]

Nope, cleaned it out before I replaced the tps.

 

[focusdaily]

Try the fan on different settings, as in feet, chest, or windshield. I was diagnosing my car last year on a revving issue and was able to isolate it to only rev up when it was on the windshield setting. What I found was my ac charge was so low it would kick the compressor on and off which would cause the idle to jump up and down. Recharged the ac and it held a nice steady idle with the fan blowing on the windshield. As for the jerking on takeoff I have no idea, when's the last time you changed the fuel filter? Good luck.

 

[leolonewolf]

Try the fan on different settings, as in feet, chest, or windshield. I was diagnosing my car last year on a revving issue and was able to isolate it to only rev up when it was on the windshield setting. What I found was my ac charge was so low it would kick the compressor on and off which would cause the idle to jump up and down. Recharged the ac and it held a nice steady idle with the fan blowing on the windshield. As for the jerking on takeoff I have no idea, when's the last time you changed the fuel filter? Good luck.

It's not jumpy on take offs, just when I'm varying the throttle during normal driving. I'm going to grab a can of starter fluid this weekend and check the intake couplers as suggested and check my vacuum lines while I'm at it. I'm guessing my ac does need to recharged at this point too.... Seriously been eyeballing a new ST though.... Just don't want the payments LOL.