p.s. Also, while looking at the temperature sensor voltages at the LM I noticed that the signal ground line (which goes to multiple sensors and distributor) is connected to body ground (0 ohm). Is this the way its supposed to be? I didn't see any obvious connection in the factory wiring diagram.

 

ive had this exact problem as well

its been reported many times on the forum

and...I cant remember what causes it lol

is your logic module from an automatic? or minivan?

 

My LM is from an 87 Daytona Shelby. Manual, I ?assume? Recalibrated by previous owner.

Also, I have commitments that will take me off this forum from now through late Saturday night if not mid day Sunday. Please don't take my lack of response in this time period as disinterest.

 

When you release the clutch you are adding load so the idle speed will drop.
For whatever reason the AIS is not extending to idle when you release the throttle with no load.
The RPM readings you are describing are reminiscent of Cold Air/Winter time RPM levels.
Be sure TPS voltage at closed throttle is below 1.00 volts.

Circuit N5 is the Signal Return for All Sensors to LM Red Connector Cavity #25.
Circuits K5 and J9 are the Grounds for LM Red Connector Cavity #24.
Circuits K5 and J9 are the Main Controller Ground at that Ground is bolted to the Rear of the Fuel Rail.
Circuit N5 is Connected to Ground Internally from the LM Red Connector Cavity #25 to Cavity #24.

 

I've got the same issue with my 88 Daytona, ever since I pu the boost button custom SMEC in it. I'm pretty sure it's set up that way specifically so that when you're in between shifts the RPM stay high so that when you engage the clutch in the next gear the engine is already revved up a bit and doesnt bog down.

 

I have the same problem with my Omni. I'm just getting it back on the road and that is one thing on my list to try and fix. My car is an automatic with a lower stall convertor. You can imagine what problem that causes when driving slowly in a parking lot. I run a boost button cal also and I can adjust my idle with ease in mptune. But what I have not fixed yet is the idle up that occurs at exactly 5 mph. At 4 mph or less it idles where I set it, now at 800 rpm. But as soon as I get to 5 mph on the scanner it goes to 2200 or so. With my convertor it pulls me through every parking lot with me having to hold the brakes to keep from going 20+ mph. In my case I know its definitely a cal setting problem. As mentioned others have had the same problem. I have been watching another thread on the other forum with the same problem for a year now and have not seen a fix for it there either. If anyone has an idea what setting to change on the cal let me know and I will give it a try. My guess is the factory cal asks for so many ais steps up after 4 mph to prevent decel stall out on a quick stop. With any mods made to the car this setting becomes to high and causes the extra high idle many complain about. Hopefully we can find and answer once and for all to this problem.

 

it's in the code, the AIS opens under 3 conditions. You give it gas, the car is cold or the car starts rolling.

It's all done so the car doesn't stall and for emmisions. You blip the throttle the AIS will open a bit to let the revs hang and make sure their is no unburnt fuel. You start rolling the ais opens to help you get and stay rolling. Cold idle is self explanitory.

There's a couple different ways to stop it and it just depends on how much you hate the revs rising without your input.

1st is to go in and set the AIS vs TPS table to zero and the speed vs ais to zero. This helps a ton but doesn't completely eliminate it. Probably about a 1-200 rpm gain will still be there. I also adjust the temp vs ais table a bit as I hate a rediculously high cold idle when there is no oil in the system. This setup is all done if the car is to remain stock.

Auto's need a bit of a bump to the ais tables for shifting gears and a little more ais values when cold as they like to stall when cold and you're on and off the throttle.

Now for my personal modded 5spd cars which means aluminum flywheel, UDP, ported water pump, lighter clutch to get the rotational weight down and drive how I like (on top of the other usual mods for power) I take the AIS motor out of the TB, unscrew the pintle head, put a big glob of gorilla glue in the ais passage way where the pintle sat and put the motor body back on and let the TB sit at just the right angle for a couple days till that glue get's nice and hard and fills up the whole passage air tight. Trim off the excess that get's into the main airflow cavites too. Then put it all back together. In the ECU I set all tables to zero (just so the motor doesn't move much and I know what I'm starting with) then I bump the cold idle advance 2-4 degress under 110 degrees of motor temp.

Now when you hit the starter it fires right up into a 1200rpm cold idle and by 110 degrees is settled right down at your base idle setting. The revs drop instantly back to idle on a throttle blip or when you push in the clutch, pull it out of gear etc. I like it this way much better as my foot controls what the car does vs an ECU trying to guess what I want.

 

I have looked through mptune and the only thing I have found so far that makes reference to 4 mph is "SwitchPointForDecelIdleAisControl" under "Idle" then "AIS Decel". So what table is used at this switch point? Maybe "RollingAisHighLimit"? There are a few dozen choices that the computer uses to up the rpm speed and I'm sure its needed on my car as its an automatic and has working ac. Just fixing the extremely high idle that comes after 5 mph would fix mine and the op's problem too I think.

 

OK, sorry about the gap. I'm back. Had an adventure with the car today and in the end I might have a data point or two to work with in diagnosing this (in addition I'll take a look at what NAJ pointed to). I had an hour on the freeway, then 6 hours later another hour long freeway drive, this time (comically as it ended up turning out) to pick my mom up at the airport. She's 80 and doesn't have above average appreciation for GLHs. After I pulled off the freeway but before entering the airport I pulled off into a lot to mount the logic module which was splayed out in the passenger foot area and to put the trim on. Trouble was that after doing that I couldn't get it to start! Lotsa crank, no start. So knowing that I've previously seen stalling when I push on the red connector I tried flexing it every way. Then opened the LM case. There are a number of sketchy solder joints where the red connector connects to the board. They'll be getting re-warmed tomorrow, as well as some continuity checks in that area. Then I tried to remove and reset the red connector but couldn't get it disconnected, after 10 minutes prying on it I was only able to raise it 1/16". But it turned out that was enough to get it started. And then it idled at 3000 RPM!, much higher than before. By now mom's flight had landed so I told her I was screwed and enlisted my brother to pick her up. Then with more fiddling I removed the idle speed motor and saw that the pintle was off the seat by about the thickness of a dime. Dime added. Idle was then good. Cancelled brother. Picked up mom, drove her back to her house.

But the thing that I learned - Even with the idle motor unplugged and the air passage mechanically blocked with a dime the car still wants to and does idle high (1900 RPM) when rolling (but returns to near normal when stopped). So what does the LM have to work with? Ignition advance is the only thing I can think of that it is using to obnoxiously rev the engine. Huh? Baffling.

 

check the speed distance sensor in this case.

 

Check it for what? How? It seems that it must be doing its job well if the LM knows when the car is rolling and when its not.?.


WTB: Chrysler DTC - I've been running into a lot of wiring problems with this car, more than all previous vehicles I've owned combined. Its time, I need one of these.

 

I'd swap it, check the connectors to make sure they're tight on each other, probably crimp them down a bit to be sure.

A scanner is very helpful. The OTC 4000E or enhanced can be found on ebay fairly reasonable and will do everything you need/want with the pathfinder II cartridge.

 

Hmmm, Still chasing this. But thought - I have a GM style(?) 3(?) bar MAP sensor which is fed directly from the intake manifold through a very stout looking silicone hose, and hose clamped for good measure (all by previous owner) but the baro solenoid valve is not involved. The baro solenoid valve is connected electrically but not pneumatically (ports open). Is this the correct way or is this the (or a) problem?

Oh, and as for the TPS, voltage goes down to 0.7 and ramps up and down seemingly very smoothly. I increased throttle for about a minute and decreased for about a minute using a digital (would have preferred analog) volt meter and all looked good. But - But - It runs much better without the TPS connected. It seems as if the fewer sensors I have connected the better it runs. Probably forcing it into a pre-defined limp home mode rather than working with whatever bad information its getting.

 

If the Baro Solenoid is Not Properly Connected it will create a Fueling Issue, Not an Idling Issue.

 

So let me get this straight, the baro solenoid must be connected even when the map sensor and calibration have been revised / upgraded?

You know, one of the first most obvious things I noticed with this car is that the baro sensor isn't used, but I've just been assuming that was part of the way that people had learned to do it as the vehicles were updated.

 

As for fueling, I've not yet gotten the wideband in but in the three sets of spark plugs I've swapped through I've not seen anything unusual.

 

On all Injected cars Baro Info is gathered by the engine controller with initial key on.
On TBI cars Baro info is not updated again until the car is shut off and restarted.
Not so on a turbo car because fuel control is more crucial, Baro Info needs to be updated constantly while driving.
When driving at no load cruise the controller will use the Baro Solenoid to block all vacuum to the Map Sensor and Vent any Vacuum in the line between the Baro and Map so all that it is reading is Barometric Pressure.

How Much does this Affect Fuel Control???
IMO, Not Worth Going Lean in Boost and Having Detonation or Burning Down or Blowing Holes in Pistons to find out for the Sake of Two Vacuum Lines.

But, I Digress, it is Your Car so as the "Blind Faith"Song is Titled...
"Do What You Like".

 

On the speed sensor, that's the second recommendation I've had to try swapping in a known good one, crimp the wires tighter, etc. That's a messy project, isn't there a way to check it from the logic module (to check all wires, connectors, sensor at once) by rolling a wheel around slowly while probing the appropriate two wires? Isn't it just a reed switch sensor that opens and closes? Presumably 1000 times per mile or approximately 1/ wheel revolution?

NAJ, I'll re-plumb it back to the factory way the next time I get a session under the hood.

 

Chances are if there is not a Code 15 set the VSS is functioning properly.