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Renix power and mpgs problems

Is yours automatic Transmission???? I am going to assume it is, from your shifting comment.

Mine (AW4 Automatic) had no guts and no power (and other issues) when I bought it 12 years ago, my 87 Wagpneer.

Over the years I found one thing after another, some by shear accident that were causing the problem.

When I first bought it the Cat was clogged up. Took me three years to discover in my R&D that the category and aftermarket had no idea how to properly test a Renix TPS. Google "Ecomike RenX Files" for the 1 year story.

Turns out the TPS has 2 separate sensors. If they get out of sync the transmission may shift fine, but can shift late or too early. Mine never got over about 1200 rpm at WOT, took 3 minutes to get to 60 mph at WOT. I would be in 4th gear in 30 seconds doing 25 mph at WOT!!!! So yes it can have a huge effect. The problem was the Tranny side of the Renix TPS on mine only had about 30% of the span of a good TPS so shift way too soon and never got into the power range at 1500 to 3000 rpm

But the TPS passed all the various known versions of testing and calibration. A New TPS fixed the early shifting problem, I could now get up to 60 mph in reasonable amount of time, but it still had no real power like my other Renix rigs when I would go WOT doing say 35 or 55 mph.

Fast forward 11 years and by shear accident using my Snap-on MT-2500 I discovered the TPS did not have a complete % open span from min to max. The TPS was not the problem, it was good. The damn 90* rod on the side of the throttle body was not shaped properly anymore (PO issues) and was stopping the throttle body from getting past 58% of WOT according to my Snap on MT-2500 scanner. Looked tat the rod on my other 2 Renix jeeps and sure enough the 90 degree bend was about 70 percent on the problem jeep, and so the TPS sensor was not sending WOT data to the ECU and the throttle plate was only 58% open at WOT as the gas pedal could not push it further as the linkage could not move any farther due to the bent rod. It was the 90 degree rod with the black past press on grips on the side of the throttle body that was partly straightened out, limiting its movement to shorter path. Figured that out just 3-4 months ago.

Makes me wonder how many seemingly gutless engines got swapped over the years to replace a bent $1 (junk yard pull) rod, LOL.

Mine is 135-150 psi compression 292,000 miles and had as much power as any Renix I ever drove once I bent the rod back to its OEM shape using one from my other rigs as a guide. Real Dirty air filter can hurt power too, but I doubt you have overlooked that.

Too little fuel at high demand from a leaking hose on the output of the fuel pump inside the tank can cause low power too.

Smog test does not test acceleration and power, it is a static rpm test. The MAP signal is supper important when the throttle moves a lot real fast!!! So is the TPS signal!!!! In fact if the ECU side of the TPS can only from 17 to 50% of WOT, due to it being bad, it can cause low power and running issues as well.

MPG problems are usually the O2 sensor, but my bad TPS and bent rod cost me about 4 mpg each, and my bad O2 sensor was another 4 mpg lost!!!! I was getting 6-8 mpg at the worst before I replaced the TPS and O2 sensor.

I didn't think the TPS had that much effect on power. I knew it effected shifting, which is fine. Last time I checked it it was fine. And if the MAP was bad it would run like poo which I would think would show up on a smog test
 
That is not even close to good for the proper readings for a Renix TPS at WOT!!!! That sounds like a dead short at WOT.

What about the TCU Side readings? You need to measure both!!! And they need to be in sync!!!!

IIRC you should have 17% at idle and 87% at WOT of the feed voltage on the ECU side, and the opposite on the TCU side.

Check my old "RenX Files" thread here, or the Renix factory manual spec....

*TPS sensor: 4.88 volts and .87 volts. moving the throttle by hand engine off- 1/2 open measured 2.8 volts and wide open measured 4.8 volts
 
Update:

i got fed up with problems that i knew were electrical and over spring break at school i pulled every wire out of the car and deleted everything i did not need and then deleted many connectors, bad sections of wire, and rerouted a lot of the wiring. So all in all i redid all of the wiring in the jeep and ditched a full buckets worth of unneeded wiring. It runs great now aside from normal ticks or very minor piston slapping. The gearing is off for my tire size so i dont have ideal power or mpgs but i gained a lot of power back and it just generally runs better than before. I came across many bad sections of wire that would have been very hard to find with a multimeter, so im not sure what sensor exactly was sending the wrong signals. I know from the factory the wiring was fine but after almost 30 years, heat, corrosion, mice, water, brake fluid, whatever is putting a hurt on a lot of peoples wiring and its the last thing most people want to do. Testing every wire or unwrapping wire looms to inspect is horrible but when you run out of all other options sometimes you just have to do it.
 
Yes my jeep is auto. I will check that rod coming out of the TB after testing the TPS itself and going from there. Can you post a picture of how it is supposed to look possibly so I can determine whether or not the rod is the issue?
 
Better idea, take a volt-ohm multi meter and test the TPS on both sides at WOT. The ECU side should hit about 87% of the input voltage. Then test the TCU side at WOT, it should be about 17% of the input voltage at WOT. The Cruiser54, Lundford, and Jeep 1987 and 1990 multi port injection manuals tell you test the input voltage (test both sides of the TPS!!!), the ground (test the ground on both sides, they are not the same ground wire!!!!!, every one forgets that), and test and calibrate the idle position voltage but only the Snap on MT-2500 measures and reports the WOT % setting and voltage, and none of the write ups or manuals say anything about testing both sides and testing WOT. They all act like testing and calibrating one side is all there is to do. Wrong!!! One side can work fine and the other side be way off. Sensor or wiring!!!!

Do that first. If they are OK then the throttle body 90 degree rod must be OK. If there is an issue, then it could be the TPS sensor, the TPS sensor wiring, the TPS sensor connections/connectors (at the sensor or the ECU) or the throttle ROD!!!!

Oh and one last thing, mine is always gut less when the rug gets caught under the gas pedal!!!! Took me forever to figure it was also causing my fast idle one day LMAO.:doh:

When I got my Snap ON MT-2500 scanner I found out my TPS voltages were like 60% instead of 87% at WOT on the ECU side (the MT-2500 does not report the TCU side of the TPS readings :( ), but that is how I knew there was a throttle body or linkage problem as I got the same problem with two know good TPS sensors!!!! Once I found the TPS WOT voltage issues I disconnected the throttle rod and bingo the TPS data was OK. I could also see the butterfly plate opening much wider. The rod with the black plastic ends is the rod I had to fix, in the photo below.

images



You can see it attached to the throttle body on the right center below. The top bend is 90 degrees, mine was about 60 degrees.

Z


Uncle body must have adjusted mine (LMOA) before I bought the rig. Hope this helps?


Yes my jeep is auto. I will check that rod coming out of the TB after testing the TPS itself and going from there. Can you post a picture of how it is supposed to look possibly so I can determine whether or not the rod is the issue?
 
It does with regards to testing both sides of the TPS. I always do the WOT test per cruisers instructions. I'll test it again. Last I checked the throttle butterfly opened all the way so I don't think that's the issue.
 
TPS tests fine at both sides of the flat connector. Getting 90% of the reference voltage at WOT and have the proper 17% at idle. It smoothly rises to the 90% value at WOT, except for a quick spike to about 6.5v somewhere around 80% throttle. It doesn't stay there but it's consistent. I don't know what issues a quick spike in output voltage would cause. Ground is good there as well 0.7ohms with no spikes while wiggling wires
 
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6.5 volts? That is not possible with a 5 volt or less input.

Sounds like a bad spot on the TPS guts which is a sign it is bad, unless you have a short on the input wire to a higher voltage wire?

The square connector is the one that tells the TCU when to shift gears.

How bad is the MPG?

Have you verified that the AW4 transmission has TC lockup?

You might want to start a fresh thread for yours? The OP has fixed his.

TPS tests fine at both sides of the flat connector. Getting 90% of the reference voltage at WOT and have the proper 17% at idle. It smoothly rises to the 90% value at WOT, except for a quick spike to about 6.5v somewhere around 80% throttle. It doesn't stay there but it's consistent. I don't know what issues a quick spike in output voltage would cause. Ground is good there as well 0.7ohms with no spikes while wiggling wires
 
A spike on that side, the ECU side would cause a surge and then hesitation.

TPS tests fine at both sides of the flat connector. Getting 90% of the reference voltage at WOT and have the proper 17% at idle. It smoothly rises to the 90% value at WOT, except for a quick spike to about 6.5v somewhere around 80% throttle. It doesn't stay there but it's consistent. I don't know what issues a quick spike in output voltage would cause. Ground is good there as well 0.7ohms with no spikes while wiggling wires
 
Which I don't have or at least notice. My problem is consistent. I may just swap it for a new oem unit given the surge. Mpg are around 10 but I'm more concerned about the overall lack of power, especially on the highway
 
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Can you either start a new thread or list everything you have done and tested and tried and the history in a fresh new post here please? Then I can get a fresh start on ideas.

Which I don't have or at least notice. My problem is consistent. I may just swap it for a new oem unit given the surge. Mpg are around 10 but I'm more concerned about the overall lack of power, especially on the highway
 
Which I don't have or at least notice. My problem is consistent. I may just swap it for a new oem unit given the surge. Mpg are around 10 but I'm more concerned about the overall lack of power, especially on the highway

Have you pulled the dizzy, inspected it, and indexed it on installation?
 
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