RENIX ballast resistor, TPS adjustment questions?

Specs;
90' 4.0(newly rebuilt), AW4, NP 231, swapped in 29 spline 8.25
All RENIX inputs/outputs are new;
IAC, MAT, CTS, fuel pump and reg., TPS, O2, Reman dizzy, injectors, CPS, Knock sensor, I probably missed something but trust me its new!(this is a restoration project)

OK I have had some detonation/valve pinging issues on acceleration, and it just seems to lag. Idles fine but low(350-450 rpm) cruises fine, no hesitation misses or stumble. It just seems lean on accel. I had originaly thought it was the EGR, but I ran it blocked off with a plate for a week or so to try it and no difference. The EGR/solonoid is new as well. So I decided to clean the ballast resistor contacts this a.m. and check the resistance. The resistance was 1.8 ohms!

Could this cause my pump to run slow/low pressure and lean out to cause the detonation?

Can I run it without the ballast resistor? I don't mind the noise.

TPS adjustment issue; I can only get it to about 81% on the tranny side and .75 on the flat connector side. If I try to get one side dead on the other goes out of whack! My input voltage on the square connector(tranny side) is 4.72. Is that normal?

The issue that I am having that I think is TPS related is the tranny upshifts when I let off the gas unless I'm at highway speed, even if I am going down hill. The tranny shifts fine and is a solid shifter otherwise.

Give me some advice/opinions.

I don't have any experience with the auto trans TPS's, but the 4.72 seams a little low. It should be 5.00vdc--down to ~ 4.85. The .13vdc difference may, but not likely, cause problems. Check your MAP base voltage--should be the same as your TPS base--both use the same 5v output of the ECM.
You can bypass the ballast resistor. It's only function is to slow down the pump speed to reduce noise; however, unless the pump has another problem, bypassing the resistor won't cure your pinging. I'd be suspicious of the rebuilt distributor, or how the timing chain, gears, CPS, and "dizzy" install were done. Sounds like your base timing is advanced.
If you think it's running to lean, due to the fuel pump, check the fuel pressure and flow rate.

xjbubba said:

I don't have any experience with the auto trans TPS's, but the 4.72 seams a little low. It should be 5.00vdc--down to ~ 4.85. The .13vdc difference may, but not likely, cause problems. Check your MAP base voltage--should be the same as your TPS base--both use the same 5v output of the ECM.
You can bypass the ballast resistor. It's only function is to slow down the pump speed to reduce noise; however, unless the pump has another problem, bypassing the resistor won't cure your pinging. I'd be suspicious of the rebuilt distributor, or how the timing chain, gears, CPS, and "dizzy" install were done. Sounds like your base timing is advanced.
If you think it's running to lean, due to the fuel pump, check the fuel pressure and flow rate.

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What can I do to increase the voltage output of the ECU if its low?

The engine was built locally by a well known machine shop that specializes in Jeep engines, I feel that the internals are together good. I put the dist. in and it took several shots at getting the indexing right. Should I pull it out and move it up a tooth? I still have the original dist. and have tried that as well, no difference. CPS is a direct bolt in OEM unit I would love to be able to move it to try to change the timming but there is no adjustment. I'm still on the original ignition coil but my spark is strong(will jump about 2' when the plug wires are pulled).

So far it sounds like the distributor is off by one tooth on the install, something many of us have had to fight with at one time or another. It is real easy to install it one tooth advanced or retarded. When this happens it runs, but runs just like you detailed below. There are a few excellent threads posted earlier this year in the OEM forum on how to get it on the right tooth. Seems it's a bit of an art to installing it. Try marking the postition you have it in, then try reinstalling it a tooth forward and or a tooth backward from the mark to see if moving it one tooth one way or the other solves the problem.

If that fails, then I would ohm out the harness wires on both sides of the TPS sensor with power off, then again with power on check the voltages, both with the TPS disconected. I found problems in my wiring harness and had to replace the ground wire on one side of my TPS.

Also make sure the MAP sensor vacuum line to the intake manifold is not loose!

Others here have reported low voltage feeds to their TPS sensors (as low as 4.5 volts IIRC) and they used the percentage rules for setting and calibrating the position of their TPS with no problems.

My money is on the dizzy being off one tooth based on the recent rebuild. The manuals I have read are real vague on the exact proper possition of #1 on the rotor once it is installed.

Ecomike said:

So far it sounds like the distributor is off by one tooth on the install, something many of us have had to fight with at one time or another. It is real easy to install it one tooth advanced or retarded. When this happens it runs, but runs just like you detailed below. There are a few excellent threads posted earlier this year in the OEM forum on how to get it on the right tooth. Seems it's a bit of an art to installing it. Try marking the postition you have it in, then try reinstalling it a tooth forward and or a tooth backward from the mark to see if moving it one tooth one way or the other solves the problem.

If that fails, then I would ohm out the harness wires on both sides of the TPS sensor with power off, then again with power on check the voltages, both with the TPS disconected. I found problems in my wiring harness and had to replace the ground wire on one side of my TPS.

Also make sure the MAP sensor vacuum line to the intake manifold is not loose!

Others here have reported low voltage feeds to their TPS sensors (as low as 4.5 volts IIRC) and they used the percentage rules for setting and calibrating the position of their TPS with no problems.

My money is on the dizzy being off one tooth based on the recent rebuild. The manuals I have read are real vague on the exact proper possition of #1 on the rotor once it is installed.

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Thanks, as soon as I am able to drive it and see if the ballast resistor was part of it or not I will pull the distributer next, and I think I will go one more tooth and see.

xjtrailrider said:

Thanks, as soon as I am able to drive it and see if the ballast resistor was part of it or not I will pull the distributer next, and I think I will go one more tooth and see.

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If it does turn out to be the ballast (which shouldn't be ruled out. I think the OEM ballast resistors were open on the backside of the ceramic case...) you can run safely without it.

The ballast was added in late 1987 as a "voluntary recall" for NVH, and got added in 1988 production. The timing may be a bit off - it was probably added by Chrysler in mid-1988/1989. However, here's what I know...

I had a 1987 that did not have the ballast - worked fine.
I've got a 1988 that had the ballast added - worked fine.
I've had two 1989s - I had to remove the ballast on one and install a bypass - both worked fine.

(If the damn City hadn't stuck their nose in my business, I'd still have all the rigs. Bastages...)

I'll be removing the ballast in my 88 when I get it into the garage to overhaul the engine management and clean up some electrical work, and I'm not worried about the idea. Use at least the same size of wire that comprises the rest of the circuit - I don't have my notes handy offhand, but you can probably find it in the wiring diagrams I've got up at RENXPower (groups.yahoo.com/group/RENIXPower) without too much trouble.

5-90 said:

Use at least the same size of wire that comprises the rest of the circuit - I don't have my notes handy offhand, but you can probably find it in the wiring diagrams I've got up at RENXPower (groups.yahoo.com/group/RENIXPower) without too much trouble.

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Thanks 5-90, I found a brass 3 bladed conector that is used in marine applications to hook up multiple accessories to a battery post(Made by a company called Johnny Ray) I clipped off the extra connector and insulated the whole thing real well. So basically the 2 wires are directly connected by a solid brass connector. I'm hoping to go on a test drive this evening.

I think the timming is at least close, I get good gas mileage and have no issues with stumble or misfire but I'm not ruling that out due to the fact I had issues when I first dropped the motor in a year ago getting it indexed. My only issue really is it just seems a little sluggish(on hard accel) and the detonation. I forgot to add that the knock sensor is hooked up so it is retarding timming I'm sure when the dtonation occurs.

If I want to retard the timming one tooth I will move the dist. one tooth clockwise....correct? Just want to get my thinking straight before I pull it out and move it.

I doub't it is the ballast resistor. Correct me if I am wrong, but the Jeep ballast resistor just drops the voltage to the fuel pump once the engine is running, and increases the fuel pump life and reduces its noise level. When it goes bad its an open circuit, not 1.8 ohms, thus when it goes bad the engine starts and then dies as the fuel pump circuit switches from the start mode (bypasses the ballast resistor) to the run mode, goes through the ballast resistor. If the jeep runs, it is not the ballast resistor.

My old 76 Dodge lean burn was another story, it had a ballast resistor that I believe was involved in the ignition circuit somehow. It had a start and a run resistor in the ignition circuit somewhere.

xjtrailrider said:

I think the timming is at least close, I get good gas mileage and have no issues with stumble or misfire but I'm not ruling that out due to the fact I had issues when I first dropped the motor in a year ago getting it indexed. My only issue really is it just seems a little sluggish(on hard accel) and the detonation. I forgot to add that the knock sensor is hooked up so it is retarding timming I'm sure when the dtonation occurs.

If I want to retard the timming one tooth I will move the dist. one tooth clockwise....correct? Just want to get my thinking straight before I pull it out and move it.

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I not sure which way to move it. In the past others have just marked where they had it, reinstalled it one tooth one way, tested it, then one tooth the other way (back two teeth at that point) from the original mark if the first try did not work. The results were usually obvious.

How good is your mileage right now?

I had numerous problems with accleration with mine, and the last fix to that problem turned out to be the TPS, which I think you know already. It was the tranny side of my TPS that was off, it was making my tranny shift up at 2000 rpm at WOT instead of 3400 to 3800 rpm.

Ecomike said:

How good is your mileage right now?

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14 in town, 20 highway, 16-17 mixed.

Is the fuel filter new/recent?

Slo-Sho said:

Is the fuel filter new/recent?

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Within the last year(8k miles), It wouldn't hurt to replace it again I guess.

Try setting the ECU side of the TPS to .50v at idle, atleast 4.70v at WOT. Don't worry about the trans side. On my 90, I couldn't get it to run right at spec so I had to figure in a little voltage drop at the ECU under the dash. Now it hauls like a champ.

Slo-Sho said:

Try setting the ECU side of the TPS to .50v at idle, atleast 4.70v at WOT. Don't worry about the trans side. On my 90, I couldn't get it to run right at spec so I had to figure in a little voltage drop at the ECU under the dash. Now it hauls like a champ.

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Ok I'll try that, its at .75 now. You think it should be lower at idle? I'll try it!

xjtrailrider said:

Ok I'll try that, its at .75 now. You think it should be lower at idle? I'll try it!

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Actually the 89-90 FSM says to use the TCU side of the TPS to set the idle for AW4 automatics. Being the last year(s) Renix was made I am guessing it was an improvment over the prior year FSM procedure. There was a good discussion on this in one of the earlier threads this year on the Renix TPS. As I recall the 87 year said something like 0.70 volts for the ECU side, then the 88 year said 0.72 to 0.73 volts on the ECU side for the idle voltage, then the 89-90 said something like 87 % (IIRC) of the input voltage to the TCU side of the TPS should be the idle setting, thus leaving the ECU side to end up varying from jeep to jeep, and switching to the TCU side of the TPS as the side to calibrate the idle.

If I had known that and done that sooner I would have found out my TPS was defective on the TCU side of the TPS 2 years sooner, as I could not get it over something like 45% of the input voltage on the TCU side of the TPS at idle.

Personally I would use the TCU side for calibration of the TPS idle, and then check the ECU side to see if the idle voltage makes sense on the ECU side, and if it does not, I would get a new TPS.


Oh, and I am currently, getting the same mileage you are.

Fuel filter should be good for at least 50,000 miles.

Thanks, I haven't monkeyed with it yet, I have it set at 82% on the TCU side and its .74 on the ECU side, that was the best balance I could get! My RENIX manual says 83% on the TCU side. I'll try it and see.

Ecomike said:

Actually the 89-90 FSM says to use the TCU side of the TPS to set the idle for AW4 automatics. Being the last year(s) Renix was made I am guessing it was an improvment over the prior year FSM procedure. There was a good discussion on this in one of the earlier threads this year on the Renix TPS. As I recall the 87 year said something like 0.70 volts for the ECU side, then the 88 year said 0.72 to 0.73 volts on the ECU side for the idle voltage, then the 89-90 said something like 87 % (IIRC) of the input voltage to the TCU side of the TPS should be the idle setting, thus leaving the ECU side to end up varying from jeep to jeep, and switching to the TCU side of the TPS as the side to calibrate the idle.

If I had known that and done that sooner I would have found out my TPS was defective on the TCU side of the TPS 2 years sooner, as I could not get it over something like 45% of the input voltage on the TCU side of the TPS at idle.

Personally I would use the TCU side for calibration of the TPS idle, and then check the ECU side to see if the idle voltage makes sense on the ECU side, and if it does not, I would get a new TPS.


Oh, and I am currently, getting the same mileage you are.

Fuel filter should be good for at least 50,000 miles.

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Question - as I recall, doesn't the TCU side of the RENIX TPS work in the opposite direction from the ECU side? I seem to recall that from somewhere, and I'd like to make sure of that...

xjtrailrider said:

Thanks, I haven't monkeyed with it yet, I have it set at 82% on the TCU side and its .74 on the ECU side, that was the best balance I could get! My RENIX manual says 83% on the TCU side. I'll try it and see.

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Those numbers sound reasonable, and good! What are the numbers on both sides at WOT?????? That is where I found mine to be bad it should get close to 17% at WOT on the TCU side. OH, and 82% sounds correct too, not 87% as I said earlier. I knew it was eighty something....but my memory is not what it use to be.

5-90,

The answer is yes, your right, they do work in opposite directions. From idle the ECU side increases, and the TCU decreases.

Ecomike said:

Those numbers sound reasonable, and good! What are the numbers on both sides at WOT??????

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I'll post them tomorrow, gettin late here in eastern time!

Thanks for everyones help!

Ecomike said:

I knew it was eighty something....but my memory is not what it use to be.

5-90,

The answer is yes, your right, they do work in opposite directions. From idle the ECU side increases, and the TCU decreases.

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Neither is mine - been hit in the head too hard too many times. Thanks for the confirmation on that!