High idle in park; stumbling upon

Bob O'Neill has been plagued with this problem on his 1986 base Daytona for several years on and off. He cleaned all the connectors, tapped out continuity and resistance readings. The root of his problem came down to fractured or relaxed contacts at the ECM, where the TPS signal feeds in from the harness.

Unfortunately, Chrysler used a horrible contact design at the computer connection:
http://www.molex.com/molex/products/datasheet.jsp?part=active/0008500030_CRIMP_TERMINALS.xml

These terminals will embrittle and crack with the slightest exposure to any caustic compound such as ammonia fumes (read - windshield washer fluid).

I think you will find that these terminals are either broken off, or have lost their springiness, at least for the TPS signal.

Can the terminals be replaced without swapping in a new ECM?

Edit: Upon reflection, if it is a contact that has lost its springiness, could I simply shave some of the plastic (a mm or so) off the plug to compensate for the loose fit?

No. These contacts are on the harness side. The problem is that they mate with pins that slide against the 'ramp' of the contact. So there is only contact on one side of the pin, instead of 2 or 4 sides with "good" contacts. Removing material off the housing will not help and will only make it more likely to lose contact. But you should be able to see if any are damaged by shining a light in the plug.

Double and triple check for a vac.leak. Check those hose connections and especially those plastic lines at the rear of the valve cover. An idle that high sure seems like air is getting in where it shouldn't. Check the line going to the brake booster and the line nylon line that goes inside to the HVAC control head.

Good general advice, but the presence of another code 24 after clearing the codes, says that it is still an electrical problem. Those contacts are garbage, we no longer use them in new designs at work.

Yes, I'm convined its electrical too. I've been having trouble getting the car to start since I replaced the TPS as well.

Bob, is it advisable to carefully crimp the female ends of the connectors? Short of purchasing and splicing in a new harness, it's all I can think of to solve the problem.

If replacing the TPS changed the behavior, you may be getting close. A direct OEM replacement TPS might be an important consideration here. Many aftermarket sensors will 'fit', but might have a different internal calibration.
Always use OEM parts for best results. This one covers 4 alternate Chrysler part #'s. See if one of them is the # of your original TPS:

http://www.rockauto.com/catalog/moreinfo.php?pk=41493&cc=1097726


Clean out the old die-electric grease from the PCM connector with compressed air for a good look at the female terminals. Does disturbing the electrical connectors/harness while it's running affect the engine idle speed at all? I'm thinking that your female PCM terminals may look more like this:

0900c152802514e0.gif

images

IC, in 1986, Chrysler was using the KK terminals. It's very possible that they continued into 1987. Regardless, my money's on that area for the trouble.

And while the idle and WOT voltage may vary slightly in different brand TPS', the code 24 is tripped if the output goes out of min or max range. That's not going to be the result of a different brand sensor. The limits that trip the code are something like 0.2V or less and 4.8V. So it really is only an open or short that will trip a code.

starfire, there is nothing that can be crimped in that terminal design, in the contact area. It's a spring-loaded ramp. The only crimp is the connection to the wire. You could try gently bending the ramp upward, but I predict it will break off or bend back down and be intermittent immediately. If you have these contacts, best to rework at least the contact that brings the TPS signal in.

My car had all kinds of idle problems until i when i put in spark plugs and gapped them in the middle of the range . Runs perfect now.

.045 is too wide a gap for these engines. .035 is the factory spec, and they don't tolerate more than .040. So re-gap it to improve the idle, or it will not run well.

I'm not sure which AIS is used in 1987. The older one from 1984-86 vintage is a cylinder about 3 inches long and maybe 1 1/2 inches in diameter. These are notorious for sticking, and when people try to disassemble them to clean or repair them, sometimes they won't go back together correctly or can break. The newer AIS is stubby in comparison. I don't recall if there is a spring.