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Renix TPS nightmare

A

adrago247

NAXJA Forum User
Location
Atlanta, GA
I bought an 89 xj renix 4.0 a few months back after someone hit my 87 and its had a bunch of issues since. I bought it not running, fuel tank was full of rust, injectors were shot, stuck valve w bent pushrod among other things. Ive got it pretty well driveable now but whenthe engine is up to temp and i slow down to get off the highway and stop or just stopping from cruising in 4th gear lockup, the engine wants to die. I have replaced the O2 sensor w a oe bosch unit, cleaned the iac from my wrecked renix that never had this issue. I have tried 4 different throttle position sensors now. The one that was on the 89 when i bought it, the one off the 87 which looks original, and 2 new ones from autozone now. None of them seem to want to adjust into range following cruiser54’s write up. I have refreshed the grounds and replaced both battery cables. The multimeter reads 0 ohms resistance from pin B to ground on the engine side harness. The reference voltage is 4.44 volts(which seems low to me maybe?) and all 4 sensors will only adjust the output voltage up to about 0.2 volts. When i do this the engine revs to about 2.5-3k rpm and doesnt come down until i turn it off and adjust the sensor back more towards the middle. What am i missing here?
 
cruiser54 said:
When installing the TPS, are you sure it's little tang is on the correct side of the throttle body linkage?
Click to expand...
I am. The output voltage does change as i open and close the throttle body. I also noticed that when it idles rough after coming to a stop I sometimes lose power brakes. I assume this is just from low vacuum idling low and rough. Is 4.44V low for the reference voltage? Could the stalling and idling rough be caused by like the egr sticking open?
 
Update: Last night i plugged all the vacuum lines going to the egr and it hasnt had the stalling or running worse at idle when coming down from cruising. I drove it last night for 30 minutes on the interstate and this morning again 30 minutes on the interstate and neither time did it try to stall when coming down to idle. It is still idling just a little rough and the idle is wandering a little bit
 
cruiser54 said:
Good find.
Keep in mind that the EGR can not completely seat even with the vacuum lines plugged.
You get an undectectable internal vacuum leak.
Click to expand...
Is there a source for a new egr valve? I do have one on the engine out of my 87. Would it be better to swap it on or just do a block off plate? If i run w the egr blocked off will i see a mpg difference or anything like that?
 
adrago247 said:
Also I still cant get the TPS to adjust. Is it normal for the engine to die when i unplug the MAP sensor?
Click to expand...


I had a problem like that with adjusting the TPS for years (never was to spec) and I was getting goofy limit data on the WOT voltage from the TPS, and after years, I one day discovered the metal arm attached the throttle body was bent (not factory bends) and the lower peak voltage, bent arm was also not letting the throttle body open all the way.

Having other Renix jeeps let me compare the bent arms. You can unsnap the arm off, engine off, and retest the TPS voltage for a first clue....

That simple fix solved a low power at WOT problem I had fought for what must have been 10 years.

My Snap on Red Brick data was what clued me into the problem.
 
I get a high idle on my '88 when I adjust the TPS to spec. I simply adjust it to idle correctly and it runs fine. I have a similar reference voltage. I don't recall the output.

Good catch on the egr. If the pintle doesn't seat, you'll "leak" exhaust fumes into the intake and the engine will stall. You can try cleaning it with some TB cleaner. Manually pull back the pintle or use a vacuum pump so you can clean the seat too. The egr also uses the transducer (the black plastic "UFO") attached to it. A new EGR is difficult to find. Legally, you can not delete the egr unless the vehicle is off-road only. Good thing you have another Renix. :)

I do have a bit of a wandering idle. The total swing is less than 100 rpm. It's even less in gear. Off idle, the rpms are steady in both park/neutral and in gear.

Yes, my engine dies if I disconnect the MAP sensor.
 
Looks like we got "ghosted". OP hasn't been back since August.
 
Not sure what you mean. If I'm cruising along and come to a complete stop (like a traffic light), yes, the idle will fluctuate slightly. If I shut it off and restart, no gas pedal movement, it will start after a few cranks, idle about 1000 rpm for a few secs and then drop down to about 650-ish with the slight fluctuation. If I hold the throttle even slightly off idle, like say 800, it's rock solid. Cruising at any speed shows the tach steady.

It's been doing this for quite a long time. It has a Standard IAC, replaced about 3 1/2 years ago (for smog test), and I keep the TB clean including the IAC passage. My egr is OK too (again passed smog).
 
Finding an EGR for a RENIX 4.0 is a formidable, and fruitless task. All I've ever been able to find is one for the 4 cyl. I suppose I could research this, but will the 4 banger work on the 4.0?
 
The gaskets for the 4 cyl and 6 cyl are the same so the EGR from the 4 cyl should fit. However, it doesn't use the transducer so I don't know if it will operate the same.

I do have a brand new Standard EGV 608 I bought a few years ago, when I thought my egr went bad. No one locally had it but I found one at a parts store not too far away. I have not seen it available since.

Another website shows these as substitute numbers. None of them show available

Factory Number
Forecast 9188
WELLS EGR365
AIRTEX 4F1412
CARQUEST 70-5864
CHRYSLER 53004867
ACDelco 214-1305


Since then, I've managed to salvage one with the transducer from a local yard. I don't know if it really works but it seems to be OK.
 
I didn't think that the renix EGR had a transducer in it, I thought it was controlled by the solenoid on the fender mounted by the airbox.

The Standard EGV580 looks identical to the one on my 87 4.0. That's not to say a previous owner didn't put on a 4-cylinder EGR. I bought the truck about 17 years ago. Don't know. It is always past smog (CA) with flying colors.
 
Bent said:
I didn't think that the renix EGR had a transducer in it, I thought it was controlled by the solenoid on the fender mounted by the airbox.

The Standard EGV580 looks identical to the one on my 87 4.0. That's not to say a previous owner didn't put on a 4-cylinder EGR. I bought the truck about 17 years ago. Don't know. It is always past smog (CA) with flying colors.
Click to expand...


It is, but the transducer operates off of exhaust backpressure as well.

When the engine is running, vacuum is applied to the solenoid from a vacuum port in the throttle body. If the ECU has energized the EGR solenoid, vacuum will not flow through the solenoid or the transducer. If the solenoid has not been energized by the ECU, vacuum will flow through the solenoid and the transducer. If the exhaust back pressure is high enough to close the vacuum bleed in the transducer, vacuum will flow to the EGR valve. If the back pressure Is not high enough the vacuum will bleed off. When the vacuum reaches the EGR valve, the diaphragm is pulled up causing the EGR valve pintel to move off it's seat allowing exhaust gases to enter the intake manifold and finally the combustion chambers.

Having said all that, if it passes, it PASSES!! The smog folks only care that there is an EGR, it functions and passes the sniffer.

Here's the EGR and Transducer from my '88.

GoKrjTdl.jpg


Here's the guts of the transducer.

mHFtNZ5l.jpg
 
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