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High Idle, No Converter Lockup Etc!!!!! Need Bigtime Help Please


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I have done so much to this truck I am just about to throw in the towel.  If some of you aren't aware of my build thread this is what I have so far.  

 

1987 renix comanche, 4.0L AW-4

Renix wire harness, computer and tcu from 90 Cherokee

'95 block '99 intake

Billet 63mm throttle body with Hesco adapter for renix sensors

Hesco adjustable fuel pressure regulator

Wideband O2

 

 

 

New sensors I've installed

TPS

IAC

O2

 

Now onto the problem(s)

 

The truck idles very high 1500-2100rpm when in park and the torque converter doesn't lock up.  At 45-50mph the tach is over 2K.

 

I have went through the wire harness and cut out the sensor crimp and resoldered the connectors.  I have upgraded the battery, body and block grounds.

 

Everything was cleaned and dielectric grease was put on the connectors.

 

Now I have tried to adjust the TPS a number of times in the past 8 months I have had this problem.  I cannot get the required voltage without the throttle plate stop screw adjusted so the throttle plate is cracked open.  This was today's activity.  So it used to idle about 1500 rpm and now it idles at 2100!!!  I pulled the "new" iac and the plunger came apart in pieces, it unscrewed and the spring and rubber piece was all in pieces.  I reinstalled my old one and no change.

 

I unplugged my MAP when the truck was running and it died.  I don't know if that's right or not.  I have not tested the MAP.

 

So I have no where to go, I have been working on automobiles for 20 years and this is the worst one I have ever worked on.  I can't seem to get it right and I really want to drive it to break in the motor.

 

So if Cruiser would be kind to work with me I would love it!!  I really need someone to come up to trouble shoot the problems with me because I don't have the patience to tinker with it blindly all summer.  Please help me get this right.

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I see you used the Jeepers and Creepers throttle body. That's the one that comes as a kit and you have to install the throttle plate by modding the shaft, si? Just looking at it, the plate isn't fitting well; way too much air gap. Also, I'm sure you did but I have to ask: did you use the Renix IAC and TPS on that HO throttle body? How did you adapt them? The Renix and HO have different outputs.

 

Also, since you have a wideband A/F meter, are you are still using the original narrow band O2 sensor output voltages to feed the Renix computer? That engine would be a good candidate for the TB-mounted 96 MAP sensor too. 

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Yeah I wasn't happy with the way the throttle butterfly fit, there is a gap around the whole thing.  It doesn't touch the sides at all.  That could be a BIG part of my problem.  I used what they sent me and followed the directions to a T.  (Whatever that means)  Yes I used the renix IAC and TPS, The IAC just bolts on no different.  I used the HESCO adapter for the TPS for what it's worth it doesn't allow me enough adjustment to get the recommended voltage.  That's why I had to adjust the mechanical stop and that compounded my problem.  It also whistles when I put my foot into it.  Which my wife can't stand!!!!  I am using a new renix O2 sensor to send to the computer and a second O2 for the wideband O2 digital readout in the cab.  I don't know if my MAP vacuum is good or if the sensor is good either.  I guess I could try a newer MAP to mount to the throttle body if they are no different.  That would clean things up for sure.

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I looked at those throttle bodies and decided against them. They claim they save the buyer $$ by not mounting the plate; I call BS on that. Even a .005" plate misfit can cause all kinds of idle problems. I have also seen a few complaints on their throttle bodies due to high/erratic idle, but assumed that was because of improper plate installation by the end user. I used a BBK TB and the fit and idle was perfect.

 

I know you don't want to hear this, but I'd junk the J and C TB (if the MAP checks out). Instead of buying a new 62mm-63mm TB, pick up a used HO TB at the yard or on Ebay - they are cheap enough. At least that way you could eliminate the J and C TB as a cause of the problem.

 

BTW, are you using the TB vacuum port for the firewall MAP? Check your 5VDC reference voltage at the MAP also?

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I looked at those throttle bodies and decided against them. They claim they save the buyer $$ by not mounting the plate; I call BS on that. Even a .005" plate misfit can cause all kinds of idle problems. I have also seen a few complaints on their throttle bodies due to high/erratic idle, but assumed that was because of improper plate installation by the end user. I used a BBK TB and the fit and idle was perfect.

 

I know you don't want to hear this, but I'd junk the J and C TB (if the MAP checks out). Instead of buying a new 62mm-63mm TB, pick up a used HO TB at the yard or on Ebay - they are cheap enough. At least that way you could eliminate the J and C TB as a cause of the problem.

 

BTW, are you using the TB vacuum port for the firewall MAP? Check your 5VDC reference voltage at the MAP also?

 

I am using the throttle body vacuum port for the MAP.  I haven't checked the MAP voltage out.  I wouldn't be opposed to trying a different throttle body, or maybe I can call the manufacture and have them do something for me, like refund my money!!!  I agree making the end user take a hack saw blade and assembling the part does sound crazy, I guess it would save money on their end, but I don't think it's nice for the customer to use old parts and modify them to use on their brand new casting.  I'll check out BBK.  Thanks for the advice Don, I will work on that.

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It's a Jeep Miracle!!  I bought a used OE '93 throttle body and exchanged my broken IAC for a new one and installed it.  I adjusted my TPS to spec and adjusted my Hesco adjustable fuel pressure regulator up to 39psi with the vacuum disconnected.  The truck idles beautifully smooth at about 500rpm or lower if that's accurate on the gauge.  It goes down the road awesome, the exhaust is much quieter if that makes any sense.  It had a nasty resonance at about 1700rpm that you go by.  It doesn't droan all the time anymore.  

 

I still don't think the torque converter is locking up, maybe I need to adjust my trans cable?  I don't know how to do that though (yet).  It seems to me that the line pressure can be increased because it shifts slow even in the performance setting switch.  It's an old trans, has over 200k on it.  

 

Thanks Don for the great advice!!!  I will call the manufacture of the throttle body and see what they can do for me.  I will get that BBK one for sure.  It seems like the engine could use a lot more air.  It has a tick on the top end I will have the engine builder listen for when I can get down there.  I just want to make sure it's ok.  I don't hear any valvetrain noise on my '99 so there shouldn't be any with this fresh stroker.

 

So I just need to figure out if the torque converter is locking up or not.  I will post a video of driving if it will help you with trouble shooting that problem.  Let me know what to do next guys.

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Have you checked resistance through the AW4 solenoids yet? The O/D (TC Lock) solenoid is #3. If the solenoid coil is open, the TC will never lock/unlock. Pretty common failure too.  You can check for 12-15 ohms at the 7-pin white connector on the cable that runs from the AW4 to the TCU along the firewall. Disconnect the connector on the firewall and ohm out the pins on the transmission side as follows:

 

Connector Pin Layout

 

E  F  G  H
    C  B  A

Solenoid 1, B to G
Solenoid 2, B to F
Solenoid 3, B to E

 

Solenoid resistance can also be checked from the TCU connector:

 

 

 

A bad or mismatched TCU can also cause TC lock up and/or shifting failures.

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Ok, from B to E I get an open circuit.  So it looks like I will need to replace the solenoid(s).  So a couple of questions, where should I buy them from?  Should I replace all of them or just the one?  I have another trans in the storage unit so I could source one from there to be cheap.  I looked online and can't find a good place to buy new ones.  Advance can't even order them and Autozone wants $329 for something that says solenoid.  I don't trust them.

 

Thanks for the advice again!!

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Ok, I was wrong in my initial measurements.  I probed the black connector.  After I re-read all the post I measured it again.

 

This time with the light gray or (white) connector.

 

I first measured all the above and got open on all.  Then I measured "B" to the battery ground and got an open.

 

So it looks like the wire that is supposed to be the ground for the solenoids is not registering.

 

So I measured battery ground to all three pins.  

 

G 12.7 ohms

F 13.8 ohms

E 17.8 ohms

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Ok, I was wrong in my initial measurements.  I probed the black connector.  After I re-read all the post I measured it again.

 

This time with the light gray or (white) connector.

 

I first measured all the above and got open on all.  Then I measured "B" to the battery ground and got an open.

 

So it looks like the wire that is supposed to be the ground for the solenoids is not registering.

 

So I measured battery ground to all three pins.  

 

G 12.7 ohms

F 13.8 ohms

E 17.8 ohms

 

AW4 manual says: Replace valve body solenoid(s) if resistance is not 11-15 ohms. But definitely clean up your grounds first. FWIW mine all read 14.0 ohms. You can also check the solenoids using pins C14, C15, and C16 on the TCU connector to ground.

 

Shift Logic

S1 ON + S2 OFF = 1st GEAR

S1 ON + S2 ON = 2nd GEAR

S1 OFF = S2 ON = 3rd GEAR

S1 OFF = S2 OFF = 4th GEAR

S3 ON = TORQUE CONVERTER LOCKED 2nd-4th GEAR/OD

 

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Guess where all the solenoids ground? Engine dipstick tube stud. Along with the shift logic ground and the TCU ground.

Well that won't matter if I am testing the plug disconnected from the trans anyway, right?  I haven't tested the engine harness pin to see if that has ground, but if the solenoids are working it should.  Maybe the harness for the trans is bad?  I will check into that, feel free to point me in any other direction otherwise.

 

Thanks again.

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This is true. All you are doing at the connector is checking the resistance of the individual solenoid coils. When they go bad, they usually open; no continuity. There are plenty of writeups to install a manual TC lockup switch on NAXJA and other places if you have to. I think your solenoids are okay. Why don't you check the solenoid resistance from the TCU connector next?

 

BTW, was your AW4 working fine before the engine swap?

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Great idea, I really couldn't tell you when it stopped working.  After I did the swap it never did run right and I put only a few miles on it.  I will check the TCU tomorrow if I get a chance.  I swapped the entire engine harness, drivetrain etc from a '90 Cherokee.  In the last week I changed the engine harness again because I wasn't happy with the way I did it last  time.  i went through the harness very meticulously.

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  • 2 weeks later...

I'm thinking it has something to do with my brake switch input.  I have a '96 brake booster and MC installed and I have an aftermarket brake switch.  The brake lights come on fine but maybe the computer doesn't show the switch input.  There are two of the exact same brown plugs under the dash and only one seemed to work with the switch.  I am going to get the wire colors and look in the manual to see if that's the problem.  

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