Throttle Sticks!!

jcgranato · 12-14-2014, 12:36 PM

I have noticed with my 3.2 the last two days that the throttle sticks a bit. After driving, as I come to a stop with the car in neutral, the throttle will stick at about 1300rpm. If I blip the throttle it then drops back down to 850rpms. Any of the experts here have any suggestions? It hasn't been a problem but I don't want it to get worse. Thanks.

Quicksilver · 12-14-2014, 02:55 PM

Obviously you will want to look at the butterfly and see if it is consistantly returning all the way to the idle position...

But...
I'd check and see if the idle position switch is working consistently. If it doesn't get triggered the DME won't know that you are at idle.
Also the "Idle Stablizer" (IAC valve) could be acting up and letting too much air through. Lots of threads on checking that out.

Arne2 · Arne2's Garage

Also check the cable for the cruise control. I understand these are a problem area. Mine has been safety-wired.

Tippy · 12-14-2014, 03:42 PM

Your idle microswitch is probably wearing out. It's on the backside of the throttlebody.

cjannelli · cjannelli's Garage

As Arne said. My 3.2 did this very suddenly. The fastener holding the cruise control cable to the heater shroud broke. Easy fix thank goodness.
Chris

jcgranato · 12-15-2014, 02:09 PM

I have another observation from driving today that may help a diagnosis. Between shifts and once clutch is depresses and held down the RPM's drop much slower that usual. They drop slowly at first down to about 1500 then drop suddenly to 750. Does this shed any light?

LjH · 12-15-2014, 02:58 PM

I chased this problem for about a year. I replaced the TPS, IAC, bushings on the transmission, and modified the cruise cable clip. Nothing provided a long term solution.
Then I noticed lost motion in the bell crank on the transmission.
Purest stop reading here..
So I went to Advance Auto and bought a selection of throttle springs.
I attached a spring at the transmission and the problem stopped.
The spring selection was less than $5.00.

See attached......

tshebib · tshebib's Garage

Here's my return spring solution. I fabbed a tab and installed it on one of the side plate studs.

jcgranato · 12-15-2014, 05:31 PM

Excuse my ignorance but what is happening that make the need for an additional spring necessary ?

DRACO A5OG · DRACO A5OG's Garage

Here you go:

THE FIX: Binding Accelerator, NOT Pedal or Bell Housing BUSHINGS, not even @ Tunnel

Jim

Tippy · 06:17 AM

Quote:

Your idle microswitch is probably wearing out. It's on the backside of the throttlebody.

With engine OFF, disconnect the idle microswitch and probe the contacts with a multimeter with the settings on for continuity. Without touching throttle body, the continuity should "ring". When you barely crack the throttlebody, the alarm for continuity should go off.

Also with engine OFF, you should also hear a light clicking sound at full idle and just barely cracking open throttlebody while rotating back and forth.

Lastly, with engine ON, you can verify by using a timing light. With no movement, I believe idle timing is 5 degrees. Just barely crack open throttlebody, and the timing should jump to around 20.

jcgranato · 12-17-2014, 05:52 PM

Don't have the equipment yet to test the continuity but I have a new observation. I found that the idle is still a bit high even with the throttle cable pulled back all the way, so I do not think it is a sticky cable. I did also notice that the revs dropping slowly only happens once the motor is warmed up. Revs and drops as well as idles normal when the engine is cold. Does this now narrow things down?

Tippy · 12-17-2014, 06:04 PM

The engine when cold will rev a little higher as all EFI systems do this AFAIK. It should be down to 880RPM (IIRC) when warm.

So does it rev to 1300 when warm, or only cold?

DRACO A5OG · DRACO A5OG's Garage

On our 3.2s when cold start, for the 1st 45 seconds there is a warm up idle, which is higher the normal. After that it will drop to normal idle speed, if not chipped, it it 780-800 RPMs (84-85), if chipped or 86-89 3.2s it will be 880-900 RPMs

jcgranato · 12-17-2014, 07:00 PM

Quote:

Originally Posted by Tippy

The engine when cold will rev a little higher as all EFI systems do this AFAIK. It should be down to 880RPM (IIRC) when warm.

So does it rev to 1300 when warm, or only cold?

1200 for about 45 seconds then drops down to 750-800. drive for 10 min and all is normal. once temp gauge moves out of first white mark, the revs drop much slower and stop at 1100-1200 unless i blip the throttle then they drop to normal 750-800.

Tippy · 12-17-2014, 07:04 PM

I suspect the contact tip on the idle microswitch may be worn. Listen for the "click" rocking throttlebody with engine OFF.

No click, no idle timing and higher revving.

Tippy · 12-17-2014, 07:06 PM

The switch is adjustable BTW.

Redbarnman · 12-18-2014, 02:02 PM

I had exactly this problem a couple of years ago and messed around with extra return springs which worked for a while but then the problem returned. So I traced the accelerator mechanism from pedal to engine and found the problem was no more than a rusting pivot bearing on the bell crank which sits down on the side of the gearbox by the drivers side drive shaft (on an LHD car). Unfortunately it is difficult to take this off for a good clean as it fouls the bodywork but undo the nut, apply some oil, work it back and forwards a few times wipe off the oily/rusty mess and put a bit of grease over it. Problem solved in 5 minutes. (After reading all about the engine management system and the expensive parts involved, a spot of oil was a welcome result)