1988 carrera fast idle when hot issues

[tshih]

Recently when in stop and go traffic my 88 carrera 3.2 (144,000 miles) idle speed has been rising to 2-3K rpm. Normally I just blip the throttle and it would go back to 900-1000 rpm as when cold.

I did the usual check of the throttle linkage, listen for the micro switch actuation and measured the resistance (open switch is overlimit of multimeter, when closed is .002ohms). The CHT was just replaced because it was a single wire one. Now the throttle position appears to bind at just before the microswitch is engaged (closed).

The engine would be at 3000+rpm when I released the gas pedal and opening the engine lid and pushing the linkage closed brings the rpm back down to 1100.

So the conclusion is there are mechanical as well as initial idle speed problems to remedy.

Looking in the workshop manual for the 3.2 under section page 24-2 which shows the diagram for lubricating the ball socket connectors of the throttle linkage (near the gearbox housing) and a photo of the upper throttle body assembly with the advice of "Never lubricate upper bearing on operating linkage regardless of circumstances, since a special sleeve is installed." I had earlier sprayed that area with a lubricant so I think the block sleeve connector has swelled and needs to be replaced. Anyone has replaced that piece before to be able to tell me what's involved? Also on the next page 24-2a Adjusting full load setting of throttle valve, how is that done? By shortening or lengthening the linkage rod distance?

[tshih]

Upon looking at the linkage I've been able to answer my own questions. The block connector was held in place by a circlip, easily removed and cleaned. The throttle position was messed up by the previous person who worked on the car (I assume from finding his past handiwork that he is a bad mechanic (sparkplug #6 had backed out or wasn't properly seated under his care). The clamping screw of the F.I. boot was positioned to interfere with the full travel of the throttle mechanism. After moving the band clamp, I see what the manual means by having at least 1 mm clearance between the throttle and housing upon full depression of the accelerator.

Moving on to adjusting the position of the throttle switch and idle setting.

[Venetian]

I had the identical symptoms as you describe. A change of oxygen sensor and adjusting the air flow mixture appears to have solved the problem.

[kidrock]

First things first. When the weather warms up, our 3.2's are notorious for sticking linkage...particularly at the point where the linkage connects at the driver's side of the transmission. Get underneath her and clean and lube her real good, then see if you still have any further issues.

[tshih]

Will do as suggested about cleaning linkage at bottom. However I have a sneaking suspicion that the plastic bushing on the throttle body itself is swelling from the sprayed on lubricant. Looking at the parts diagram doesn't show this to be a replaceable piece by itself. Buying the whole throttle body assembly is $500. I'm thinking that maybe I can substitute a bronze bushing of the same size like the 914 pedal cluster rebuild bronze bushing solution to sticking pedal bushings fix for this problem that nags all older 3.2 owners.

[tshih]

Problem solved !

The linkage at the bottom of the car where it pivots around the bushing near the CV joint on the gearbox was quite dirty. cleaning and re-lubricating that part and replacing the return spring under the intake manifold cured the fast idle when hot (sticky) problem. The idle when warmed up to operating temp is still a touch high (1100 rpm) but that should be a simple adjustment after bridging the idle circuit as the instructions given in the workshop manual.

[tshih]

Problem solved !

The linkage at the bottom of the car where it pivots around the bushing near the CV joint on the gearbox was quite dirty. cleaning and re-lubricating that part and replacing the return spring under the intake manifold cured the fast idle when hot (sticky) problem. The idle when warmed up to operating temp is still a touch high (1100 rpm) but that should be a simple adjustment after bridging the idle circuit as the instructions given in the workshop manual.

[kidrock]

I love a cheap, easy fix

[dshepp806]

Good!!!!!!!!!!!!!!

[tshih]

Actually the problem later returned after a few days! The definitive final fix was changing the swollen plastic bushings at the bell crank housing sleeve of the accelerator linkage (near the gearbox in front of the drive shaft CV joint) with the bronze bushings sold by Pelicanparts. The correct size of the sleeved bronze bushes are 10 mm ID and 13 mm OD bush sizing by 15 mm long. That's for a 1987-89 Carrera 3.2. Earlier models may use the 914 part number sized bronze bushes same as for the pedal cluster bushing replacement of the plastic bushes there.

[Buzzard95]

I had the engine out of my 88 Carrera 190K miles to replace fuel lines and rebuild my G50 transmission. While out I replaced plugs, cap, rotor, alternator, clutch & hydraulics, flywheel, O2 sensor, DME relay, cylinder temp sensor, sent my injectors out for test & cleaning, adjusted valves, & checked vacuum lines. Started right up after the 7 mo. project, but is running @ 4K rpm with no pedal, and revs from there with pedal. Can't find any mechanical blockage so don't know where to go next. Have a Bentley manual but need a systematic trouble shooting tree for this specific problem, since I can't find any posts with the same issue. Any help will be much appreciated.