Auto Computer with Manual Transmission

[shr3dd3r 09]

Some of you may be following my build thread, but I decided to post a new thread concerning this issue so I can hopefully get some feedback and get the problem resolved ASAP.

I am running the Mountaineer's auto computer with an m5r2 manual transmission and I have a few issues.

1. Unsteady idle. When I depress the clutch to shift gears the rpm's shoot way up instead of going down, and then take several seconds to come back down. At stop lights it sounds like I'm flooring it and then it dies down to an extremely slow unsteady idle after a few seconds. I don't understand why idle speed is affected by having a different transmission, I just assumed it was a nonadjustable computer parameter.

Can this be fixed without a tune? I can have the CEL codes removed, but as far as an actual tune goes they are wanting to charge way more than I want to spend at the moment.

2. Occasional hesitation. It's almost like it misfires once every couple of minutes.

Any ideas? I know the computer wants OSS, ISS, and TCCS so how best can I tackle this? Anything I should try before resorting to a tune? If I can get this resolved without a tune then all I'll have to worry about is getting rid of the CEL's.

 

[dangerranger83]

An auto trans puts a load on the engine when its in gear so the computer is programed for that and factoring that in.

When I had the old 2.8 under my hood I converted it to TBI and it was running an auto computer and had the same high idle issue when pushing in the clutch pedal. I "fixed" that problem buy unhooking the idle speed controller actuator and manually setting it myself. But soon after that I durasparked it then even later put the 5.0 in.


Does taking your foot off the gas pedal but not pushing the clutch for those few seconds then pushing the clutch help prevent the high idle thing or does it happen no matter what?

 

[shr3dd3r 09]

An auto trans puts a load on the engine when its in gear so the computer is programed for that and factoring that in.

When I had the old 2.8 under my hood I converted it to TBI and it was running an auto computer and had the same high idle issue when pushing in the clutch pedal. I "fixed" that problem buy unhooking the idle speed controller actuator and manually setting it myself. But soon after that I durasparked it then even later put the 5.0 in.


Does taking your foot off the gas pedal but not pushing the clutch for those few seconds then pushing the clutch help prevent the high idle thing or does it happen no matter what?

No that doesn't help. I can be coasting at 1500 rpms and when I depress the clutch it will shoot up near 3000 rpms for 3 seconds or so. Then it slows down so much that it nearly dies and stays like that for a few seconds, and then shoots back up to around 3000. Of course this reading is a tad high since I haven't rewired the tach for v8 use so I don't think that's even right either. At least it doesn't sound like it is.

It drives great though when I'm giving it gas but it does NOT like to idle. It makes it a little awkward to shift gears when the rpms shoot up when I depress the clutch. Also the occasional hesitation it has I've heard is caused by the auto tranny functions but I don't know what.

I am just trying to find out if I can solve the problem by disconnecting a couple of wires so I at least know what to tell the guy to take out whenever I have a tune written.

 

[Teddyzee]

You can manually delete the IAC function like danger mentioned.
The clean-hands Mustang guys will have a fit, however

Two options I've done are make a new IAC gasket with much smaller holes (I used sheet metal and tiny 1/8" holes, you can adjust to taste) to limit IAC function, but my Mustang currently has a solid gasket in it. I set the idle to a very low 600rpm and it drops the moment I touch the clutch.

Having the the trans functions deleted my improver the idle function for you.

And contrary to the pocket book racers of the world, you certainly can set the idle speed on a Ford EFI with the TB set screw. It's called hotrodding

 

[shr3dd3r 09]

You can manually delete the IAC function like danger mentioned.
The clean-hands Mustang guys will have a fit, however

Two options I've done are make a new IAC gasket with much smaller holes (I used sheet metal and tiny 1/8" holes, you can adjust to taste) to limit IAC function, but my Mustang currently has a solid gasket in it. I set the idle to a very low 600rpm and it drops the moment I touch the clutch.

Having the the trans functions deleted my improver the idle function for you.

And contrary to the pocket book racers of the world, you certainly can set the idle speed on a Ford EFI with the TB set screw. It's called hotrodding

I assume the IAC valve doesn't know what to do without the auto tranny, so should I disconnect the electrical connector and adjust the idle speed manually and see if that works? Will leaving the connector off for a while do any harm? I just need to figure something out until I have a tune.

 

[Teddyzee]

You could definitely do that. Not sure if unplugging it has any drive issues of it's own. That's why I did mine the way I have. But it's easy enough to try!

Manual cars do that, too, as did your stock Ranger- raise idle when speed gets below 5mph (that' what Fox body Mustangs do, anyway) and whenever the clutch is pressed or neutral selected. It's normal, but being exaggerated in your case.

As for you miss, that could be anything from plugs, plug wires, could be very simple.

 

[shr3dd3r 09]

You could definitely do that. Not sure if unplugging it has any drive issues of it's own. That's why I did mine the way I have. But it's easy enough to try!

Manual cars do that, too, as did your stock Ranger- raise idle when speed gets below 5mph (that' what Fox body Mustangs do, anyway) and whenever the clutch is pressed or neutral selected. It's normal, but being exaggerated in your case.

As for you miss, that could be anything from plugs, plug wires, could be very simple.

I'll try it. I guess it must be looking for signals from the auto tranny and clutch and whatnot to determine idle speed. Without them it's just going haywire. Maybe that's all I'll need to have deleted besides the CEL's in the tune.

 

[shr3dd3r 09]

You could definitely do that. Not sure if unplugging it has any drive issues of it's own. That's why I did mine the way I have. But it's easy enough to try!

Manual cars do that, too, as did your stock Ranger- raise idle when speed gets below 5mph (that' what Fox body Mustangs do, anyway) and whenever the clutch is pressed or neutral selected. It's normal, but being exaggerated in your case.

As for you miss, that could be anything from plugs, plug wires, could be very simple.

Also, another thing that could be contributing to the idle speed problem is the coolant temperature sending unit. The gage on the dash hasn't worked since I did the swap, and I think the PCM uses this info to help determine idle speed. I suppose I should check that as well.

Does the temperature gage have to be rewired like the tach does? I don't remember anyone saying there was any difference between v6's and v'8s as far as the temp sender wiring.

 

[Teddyzee]

There are two coolant temp senders. One is for the dash gauge, and one for the ECU. You may want to make sure you have them correct, or even plugged in at all.

 

[shr3dd3r 09]

There are two coolant temp senders. One is for the dash gauge, and one for the ECU. You may want to make sure you have them correct, or even plugged in at all.

They are both plugged in, but the gage is not working. Disconnecting the IAC connector I was able to adjust the idle, but after a bit the rpms still drop down too low. When I test drove it the same thing started happening. The rpms still shoot up when I depress the clutch. The effect isn't as severe now as it was with the IAC connector on, but it is still very annoying.