High idle in gear - 96 Explorer manual

[FredB69]

G'day one and all, I have a 96 Exploder with manual transmission. When pulling up to a stop with a gear engaged it will idle at 12-1300rpm. This will settle if I select neutral, work the clutch and reselect a gear. It sometimes chooses to be difficult to select a gear from a standstill and causes the engine rpm to increase as I try to engage a gear.

I haven't seen anything in the forum yet that is of a similar issue . Any advice greatly appreciated.

Cheers and have a bonza day.

[BroncoJoe19]

I thikn that your perception that there is a connection between moving the shift lever, and changes in idle speed is innaccurate, and is most likely not related at all.

You porbably have a surging (going up and down) idle, or perhaps just a high idle.
Surging idle is ofthen caused by vacuum leak/s, dirty, sticky IAC, and sometimes a dirty MAF sensor. Could be other things, but those three are good places to start, and are easy, and inexpensive.
Check for vacuum leaks, clean your IAC, and Clean your MAF.
Here in America there is a chain of auto parts stores that will pull diagnostic codes for free as a service. You may call around and see if any in your area do the same.

One other sensor that will cause a high idle is a faulty TPS.

What does the IAC do? How does it work?
Ford Fuel Injection » Idle Air Bypass (IAB)
Check and clean your IAC
Ford Explorer IAC Fix .: Articles

Checking for vacuum leaks.
Some of the sensors and some of the actuators either read the amount of vacuum, or use vacuum to move controls, therefore it is important to the proper functioning of the engine that your vacuum system is fully intact. Otherwise one may get codes falsely indicating that there is a problem with a controller/actuator, or a sensor when in reality it is caused by a lack of vacuum.

Look at your rubber vacuum hoses (they are about 1/4 - 3/8 inches in diameter, if they are dry rotted or cracked, replace them. IF they slip on/off of their connectors too easily, they may have stretched out a little bit, cut the ends off, and put them back on.

You may listen for a leak. Sometimes using a cut off piece of garden hose is a good aid to listen with. Sometimes a cardboard tube (like from gift wrapping paper) is helpful. Just remember that whenever you stick your head inside a running engine compartment, that you are not wearing any loose clothing or jewelry that can get caught.

Another suggestion is to use a spray can of carb cleaner and spray around the bottom of the intake manifold, and the base of the throttle body assembly. IF there is a leak, you should hear a change in your engine.
Keep a fire extinguisher handy, or use water instead of carb cleaner (it works, but not as well.) Be aware that if you use water and the wires get wet and it runs worse... your wires may be bad, and the water is allowing them to arc instead of jump the gap of the spark plug.

Another suggestion is: to take a propane torch, turn it on (but don't light it) and move it over the vacuum hoses and connections. The engine RPM's will increase if there is a leak and the propane gets sucked in.

Courtesy of TheOldWizard ford-forums... Don't forget to remind folks to check the PCV valve, hose and grommet !

[FredB69]

Thanks BroncoJoe19, I noted that you are one of the guru's in the forums and I thank you for your time and knowledge. Re my issue, I definitely have an increase in rpm at times when selecting a gear. At the same time it is difficult to shift into gear and usually wont go in. This is most probably an issue with the clutch slave cylinder and sigot bearing. I have gleaned that info from the forums and links. I agree that the IAC could be a contributor as it is dirty but I will get some cleaner to rectify that and will then see how its going. Overall, the issue could be 2 problems occurring at the same time.

There is one broken vacuum line in the heater circuit where the tube disappears under the blower box. I will block that off as well in the fault finding process.

I am not sure where to find the MAF sensor. My local Ford dealer may be of assistance but on a previous visit they checked for vacuum leaks and said it was good to go. They also mentioned that they had only seen one manual Exploder before....

I will check our auto dealers for the code reading service but I have not heard of that service being provided here in Australia.

Thanks again and have a bonza day.

[BroncoJoe19]

I haven't done a clutch since about 1976. It was mechanical, not hydrolic, so I am not familiar with yours. However I had thought that perhaps the synchro's are going bad in your trans which would make shifting a little more challenging (hence some grinding of gears). IT still does not make sense to me that there is a correlation to shifting and engine RPMs going higher.

Let's just throw numbers around. lets say it should idle at 800 RPM, and that when upshifting you would run it up to 4,000 rpm, then sift to 2nd. at that point perhaps it would slide into gear at 1,000 RPM, but when you depress the clutch the engine goes to 2,000 because that is where it is idleing (due to the vacuum leak). Well at any rate we'll see.

BTW... it doesn't matter how dirty the IAC is on the outside, you must remove it and clean the internals.

Your MAF sensor is located on the air intake tube just after the air cleaner box.

[FredB69]

G'day again, its not the synchros (no grinding). The suspect items are the slave cylinder/spigot bearing. The IAC is dirty on the inside (already checked, just didn't have spray cleaner..) and thanks for the MAF location, however not stepping outside to check that just now (4:23am here). Back to the shifting problem, it only occurs when coming to a stop. It's not noticeable during normal shifting, there appear to be no issues there. Like I said, working the clutch causes the rpm to drop back to normal.

I have looked at the clutch mechanism and inside the vehicle is the clutch depressed switch block (the one that senses if the clutch is depressed for starting the vehicle) and to my mind there is a greater number of wires coming from that block than what would be required to just detect the clutch depressed (about 6 as opposed to 2 I would think). It's an interesting problem and if I had a wiring diagram I could figure out what is in the associated circuits.

Do you have a link for electrical circuits (always good to have)?

[BroncoJoe19]

which engine do you have?

[FredB69]

SOHC 4.0L fuel injected