Renix MJ eratic idle?

[88jeep1]

88 mj 4.0 aw4 4x4. Did upgrade injectors new timing set, oil pan, rear main seal, water pump along Iac, Tps, coolant temp sensor, plugs,wires,cap,rotor, Upgrade factory computer to run renix system better. Also fuel pump is original to my knowledge with a new fuel filter if that helps at all. The truck has an eratic idle. It seems to respond well when I blip the throttle. What I notice is the engine comes back down after the rev back to an idle and  it seems to drop sudden. Then it catches itself and picks back up in rpm. If I don't touch the pedal it sits and idles. Just isn't smooth has like a roughness to it or like a miss.  

Any help with this would be greatly appreciated! I will do my best to do the tests you guys suggest and report back. I just need someone that knows these alittle better that can help me out on this project of mine. 

[Ωhm]

I'd start with cruiser tip #8 (TPS )

Renix TPS Adjustment

[88jeep1]

22 minutes ago, Ωhm said:

I'd start with cruiser tip #8 (TPS )

Renix TPS Adjustment

Thanks for answering. I will do this tomorrow and see what I come with. I also want to add I have an REM as well. If there's something on it I could tell you when it's plugged in let me know.

[Ωhm]

Make sure O2 sensor is switching and closed loop doesn't drop to open loop.

[cruiser54]

Yes, use the REM.

 

But, go to www.cruiser54.com and do Tips 1 through 5 anyway.

[HOrnbrod]

Does the Renix REM provide an air/fuel ratio display?

[cruiser54]

15 minutes ago, HOrnbrod said:

Does the Renix REM provide an air/fuel ratio display?

No. But it shows short term and long term fuel trims and oxygen sensor activity, MAP voltage, engine vacuum etc.

[HOrnbrod]

2 minutes ago, cruiser54 said:

No. But it shows short term and long term fuel trims and oxygen sensor activity, MAP voltage, engine vacuum etc.

 

So no live A/F display?

[cruiser54]

Not that I've seen.

[HOrnbrod]

Oh well, it can't have everything. I'd kill for a similar live monitoring display for an HO...........

[cruiser54]

20 minutes ago, HOrnbrod said:

Oh well, it can't have everything. I'd kill for a similar live monitoring display for an HO...........

Especially one that was part of the dash clock........

 

I wish more guys here would get one. for the price of a coupla unneeded sensors, you can own one. 

[88jeep1]

12 hours ago, Ωhm said:

I'd start with cruiser tip #8 (TPS )

Renix TPS Adjustment

I did the flat 3 wire and got 4.87 b to a. I did the b to c and got .763. what is my desired number suppose to be? It says move the tps till I have my desired amount but doesn't tell me what I'm shooting for?

[88jeep1]

Also I will add I cleaned the c101 with crc electronics cleaner couple months back. Just to rid it of all that black tar crap. I actually did as many plug in the engine bay as I could see with the cleaner. Then let them air dry before I plugged them back in.

[fiatslug87]

38 minutes ago, 88jeep1 said:

I did the flat 3 wire and got 4.87 b to a. I did the b to c and got .763. what is my desired number suppose to be? It says move the tps till I have my desired amount but doesn't tell me what I'm shooting for?

from Cruiser's tips:

1-KEY ON, measure voltage from “A” positive to “B” ground by back-probing the connectors. Note the voltage reading–this is your REFERENCE voltage.
2-KEY ON, back-probe the connector at wires “B” and “C”. Measure the voltage. This is your OUTPUT voltage.
3-Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts.

 

So in your case 0.828

 

And what does this mean? "Upgrade factory computer to run renix system better."

[88jeep1]

4 minutes ago, fiatslug87 said:

from Cruiser's tips:

1-KEY ON, measure voltage from “A” positive to “B” ground by back-probing the connectors. Note the voltage reading–this is your REFERENCE voltage.
2-KEY ON, back-probe the connector at wires “B” and “C”. Measure the voltage. This is your OUTPUT voltage.
3-Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts.

 

So in your case 0.828

Ok so I have 82 then the tps would be good right?  I just did the coil terminals cleaned and sandpapered. Plugs cleaned on it. 

 

Also a while back the grounds were upgraded to 0 gauge head to firewall the dipstick grounds were cleaned and a bigger ground added to a bolt near the engine mount.

[88jeep1]

Also when I got this truck the emissions container was missing as well. Could a vacuum/plug setup be missing from it not being on the firewall?? Like needing a signal to run better?  I have one on my donor 88 stick mj I could install. What do you think on that?

[88jeep1]

When the rem is plugged in running it says just after start up 15tps, 13.6-14.1map, 15.4-15.7vac, 14-15ign, 586-619 rpm, 14.0battery volts, 0.70-(4.96 on occasion)vO2, says Lean ex, open lp.

[88jeep1]

43 minutes ago, fiatslug87 said:

from Cruiser's tips:

1-KEY ON, measure voltage from “A” positive to “B” ground by back-probing the connectors. Note the voltage reading–this is your REFERENCE voltage.
2-KEY ON, back-probe the connector at wires “B” and “C”. Measure the voltage. This is your OUTPUT voltage.
3-Your OUTPUT voltage needs to be seventeen percent of your REFERENCE voltage. For example: 4.82 volts X .17=.82 volts.

 

So in your case 0.828

 

And what does this mean? "Upgrade factory computer to run renix system better."

I put a newer ecu in was told it would open a few more HP's up and mellow the idle out even more. It's a bendix 428 out of a newer auto XJ.

[87MJTIM]

23 minutes ago, 88jeep1 said:

When the rem is plugged in running it says just after start up 15tps, 13.6-14.1map, 15.4-15.7vac, 14-15ign, 586-619 rpm, 14.0battery volts, 0.70-(4.96 on occasion)vO2, says Lean ex, open lp.

If the REM is telling you the engine is Lean and in Open Loop, then either your O2 sensor is bad or possibly the O2 heater relay is bad.  Swap out relays in the box on the passenger side engine compartment.  Recheck the REM for Lean/Open conditions.

 

There are instructions on testing the O2 sensor as well.  Use the meter to test that before swapping parts.

[88jeep1]

1 minute ago, 87MJTIM said:

If the REM is telling you the engine is Lean and in Open Loop, then either your O2 sensor is bad or possibly the O2 heater relay is bad.  Swap out relays in the box on the passenger side engine compartment.  Recheck the REM for Lean/Open conditions.

 

There are instructions on testing the O2 sensor as well.  Use the meter to test that before swapping parts.

I have to go to work now. I will try that tomorrow to see what I end up with. I had a cracked exhaust manifold. When I got another used one I never changed the O2 out. Just reused the one that was in it. Testing on that stuff tomorrow thanks!

[87MJTIM]

A cracked exhaust manifold would trigger the lean condition with the 2 sensor - too much air getting to the O2 after combustion. 

 

[omega_rugal]

first, how many RPMs at idle?

 

second, does it happen cold, hot or both?

[88jeep1]

1 hour ago, omega_rugal said:

first, how many RPMs at idle?

 

second, does it happen cold, hot or both?

The rpm fluctuates on the rem from about 586-619. When it's cold my oil pressure is about 80 on the cluster gauge after first start if that's even a good thing to go by. Seems to mellow out after it warms up more. It never quite goes away. The other thing I noticed if I rev it alittle not alot of rpms it almost seems like it's going to fall on its face trying to recoupe from being rev'd alittle.

[88jeep1]

5 hours ago, 87MJTIM said:

A cracked exhaust manifold would trigger the lean condition with the 2 sensor - too much air getting to the O2 after combustion. 

 

I changed the cracked one out. I got another used one that was good tho it came with a used O2 sensor in it. I just through it back on the head with a new gasket and all bolts torqued.

[88jeep1]

21 hours ago, 87MJTIM said:

 

On 11/27/2017 at 11:04 PM, Ωhm said:

Make sure O2 sensor is switching and closed loop doesn't drop to open loop.

So I read somewhere about cleaning the I AT on the intake. I cleaned it and all of a sudden my lean/ open loop went to displaying closed and now lean/rich changing back and forth.  I believe I have uncovered alittle of my problem. It went to closed loop almost immediately after cleaning the iat.