89 XJ RENIX low rough idle

[Ecomike]

OK, so it's in a Renix Manual but what YEAR is that manual?


My Renix Fuel Injection FSM, dated 1987 just says about 0.80 volts, end of story. Says nothing about manual versus automatic, or percentages, just "about 0.80" on the ECU side of the TPS.

I am just trying to figure out what the different Renix years and sequence of changes were on the setting of the TPS instructions. I am also curious now what the OBD-1 and OBD-II instructions are for this. Looks like it is an item that evolved year to year!

Of course the next question is why did they change it, and what else did they maybe change, like did they upgrade the software in the Renix ECU between 87, 88, 89 and 90? Hmmm!

8Mud, what are your thoughts on this?

Guess I need to check 5-90s Yahoo Renix page and my own archives to see if I have an 89 FSM in pdf. I know I don't have a 90 FSM yet.

straight from the renix manual, step 4, page 32:

Divide the output reading by the input voltage.
the desired value is 4.15V.
Example: If the input voltage is 5V and the output voltage is 4.15; divide 4.15 by 5=.83=83%.

So, you need to set the TPS for an auto at 83% of the input voltage on terminal A.

 

[Ecomike]

This is straight out of the 88 FSM.

"1) Turn ignition on. Check throttle position sensor input
voltage. Connect voltmeter negative lead to terminal "B" (M/T), or
terminal "D" (A/T) of sensor connector. Connect voltmeter positive
lead to terminal "A" (M/T and A/T) of sensor connector.
NOTE: On (A/T) models, connector terminals are identified by
letters molded into back of connector. On all models, do not
disconnect TPS harness connector. Insert voltmeter test
leads through back of wire harness connector. On some
models, it may be necessary to remove throttle body from
intake manifold to gain access to sensor wire harness.
2) Move and close throttle plate completely (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Input
voltage at terminals "B" and "A" (M/T), or terminals "A" and "D"
(A/T) should be 5 volts.
3) Return throttle plate to closed throttle position (M/T
and A/T). Check sensor output voltage. To do so, disconnect voltmeter
positive lead from terminal "A" and connect it to terminal "C" (M/T),
or terminal "B" (A/T).
4) Maintain throttle plate in closed position (M/T and A/T).
Ensure throttle linkage contacts stop. Note voltmeter reading. Output
voltage should be .8 volt (M/T), or 4.2 volts (A/T).
5) If output voltage is incorrect, loosen bottom sensor
retaining screw and pivot sensor in adjustment slot for a coarse
adjustment. Loosen top sensor retaining screw for fine adjustments.
Tighten screws after adjustment."

So it must have changed in 89 or 90?

 

[87manche]

don't have any idea.
I used the procedure listed in that renix manual to set it on my 87, fixed my low idle problem.

http://pirate4x4.com/tech/billavista/PDFs/index.html

in there, under the jeep section, renix manual.
it's actually a pretty good read, explains all the sensor inputs and when they're used.

 

[Ecomike]

Page 1 says it covers 87 to 90 years, so it would have to be a 1990 manual. So I guess it is an update for all renix years that came out in 90.

 

[87manche]

Page 1 says it covers 87 to 90 years, so it would have to be a 1990 manual. So I guess it is an update for all renix years that came out in 90.

that would be my guess, since it has the pentastar logo on it as well.

 

[badgator]

Set mine to .80 volts, on various posts and in manual. Today I tried a different ECU, no change. (Luckily u-pull-it has a 31 day no hassle return policy!) Also tested wiring between Latch relay and ECU, about 1 ohm, 12v to relay. I does run smoothly after I increased air bypass, but still turn on AC, RPM decreases 150-200 rpm.

 

[Ecomike]

I wonder if the prior owner monkeyed with the air bypass and throttle stop screw or throttle stop ear to lower the idle while fighting a high idle problem. If so the IAC may already be wide open with no room to open further. Try adjusting one of then to raise the idle, then if needed reset the TPS (if you move the throttle stop ear or screw).

Only other possibilty I can think of is a damaged IAC that can not physically open wide enough the give it the extra air it needs to boost the RPM/power needed to handle the AC.

Have you tried a good or new IAC yet?

Set mine to .80 volts, on various posts and in manual. Today I tried a different ECU, no change. (Luckily u-pull-it has a 31 day no hassle return policy!) Also tested wiring between Latch relay and ECU, about 1 ohm, 12v to relay. I does run smoothly after I increased air bypass, but still turn on AC, RPM decreases 150-200 rpm.

 

[87manche]

I wonder if the prior owner monkeyed with the air bypass and throttle stop screw or throttle stop ear to lower the idle while fighting a high idle problem. If so the IAC may already be wide open with no room to open further. Try adjusting one of then to raise the idle, then if needed reset the TPS (if you move the throttle stop ear or screw).

Only other possibilty I can think of is a damaged IAC that can not physically open wide enough the give it the extra air it needs to boost the RPM/power needed to handle the AC.

Have you tried a good or new IAC yet?

he said he tried 2 other IAC's, so I think that your first guess may be right. Under normal circumstances you should never have to tinker with the throttle stop, but I think you're out of options on this one.
The only other way to find out would be to have someone with a IAC excersiser check it, and that means a trip to the dealer most likely.

 

[badgator]

My XJ ran fine until about a month ago, I have been driving my Mercedes since I bought it about 2 months ago. The air bypass still had the welch plug over it.

 

[Ecomike]

Maybe the synch sensor in the distributor?

 

[badgator]

Luckily I bought/begged/stole plenty of parts, trying coil, distributor w/cam sensor next.