RENIX Confused AF!

So, I had a bad engine in my '89. I swapped in an HO motor, did ALL the usual upgrades along with enhanced grounds. Every sensor has less then 1ohm of resistance. Brand new Exhaust manifold, Front pipe and 02 Sensor. All new gaskets and vacuum lines.

With the Snap-On MTG2500 hooked up, I follow the guided testing for all of the parameters.

MAP : Good (1.5- 2v)
IAT : Good (Rises from ambient to about
CTS : Good (Rises from ambient to 86-90c)
TPS : 0.69v
Idle : 680-700 rock solid
02 : Fluctuates between 2.9 - 4.9v (When pumping throttle)

HOWEVER.. The ECU only swaps between open and closed loop on cold start, then pegs the O2 at 4.9v and stays in open loop. The ECU reports a "Lean" fuel situation and I think this is the reason. But why?

I have run a small hose and propane around all the intake flanges and ports with no fluctuation in the idle. Same with the hoses. No vacuum leaks. Which is also supported by the rock solid idle and the MAP.

I cannot hear an exhaust leak, I cannot see one either. I have used a stethoscope to listen, and a cold mirror to check for condensation and look. For the LIFE of me I cannot find the issue, and its costing me $20 to drive 30km. Shes running RICH RICH RICH.

Any suggestions? :badpc:

I would probably try swapping in a different O2 sensor. This is the key sensor that the ICU relies on to manage the AF ratio and it not doing its job would result in the car running continuously in open loop

Make sure you have the correct O2 sensor. The Renix does not use the typical universal type.

^^ These 2 posts.

O2 should switch from .1 to 4.9.

The O2 sensor ingot was the NGK sensor Lordco (Local BC Parts Shops) Gave me, part number was correct. I will swap it out with a new sensor, perhaps that's been my problem all along.

I believe these two will work:


NTK 23553
Bosch 12009


If you look at the RockAuto site you will find that (as lawsoncl said) the 1990 model year uses a different O2 sensor than later models like the 1993.


HTH
Todd

I have ordered up an other 23553 Sensor. Two days ago, I disconnected the front pipe from the manifold. Those GOD DAMN connections suck... I put some Ultra Copper in there just incase there was a leak there and buttoned it all back up.

Last night, after a good 48 hrs of cure time (Its chilly here now), I fired it up with the MTG2500 connected again... and again.. during warm up, it cycled between 2.5 and 4.9v as well as open and closed loop. When it hit operating temp (86-ish C) it rested at 4.9v and stayed in open loop. The smell of gas was AMAZING...

So, I will pop in the new 23553 sensor tonight to see if THAT changes anything.

The smell of gas screams running rich, but the O2 sensor is claiming lean. Yeah, I'd suspect the sensor or the wiring to it.

Exactly, when I say rich.. I mean.. it costs me $20 to go 30km...

Checking the resistance is Less then 1ohm even with pulling on the wiring harness.

I belive its getting good voltage as its hitting 5v. But I have not checked the 12v (Orange) wire.

As I recall, the renix o2 sensor acts like a variable resistor. Whereas the typical O2 sensor generates a voltage that the ECU measures.

Just had a thought, what temp stat are you running? I don't know about renix but on my obd1when I had an improperly working stat it would never get out of warm up mode and my mileage was crap. Put in a stant and gained like 25% better mileage!

Something to look at is where the O2 harness runs up the front of the motor. It is easy to route the harness wrong and it will cook on the exhaust manifold. The spot where it cooks is really hard to see, I've had to disconnect the O2, engine temp, and knock sensor (on a Renix) and pull the harness up eight inches to see the melted spot.

It sounds like you have some sort of O2 issue but anytime mine ran that rich it was something t do with the MAP. How is the vacuum line to the MAP? Hairline cracks in the MAP vacuum line can be hard to see.

If you are running a Renix TB make sure the MAP vacuum line is plugged into the right hole in the TB, one is vacuum the other a blind hole.

Just a couple of things I've seen in the past.

I'm running an HO throttle body. I'll post up some pictures this afternoon.

Renix runs a lambda O2 heated sensor. The output toggles back and forth significantly in normal operation. It is not going to be stable.

old_man said:

Renix runs a lambda O2 heated sensor. The output toggles back and forth significantly in normal operation. It is not going to be stable.

Click to expand...

Right, but pegged at 4.9v when at operating temp is NOT fluctuating.

on cold start, it fluctuates between 2.9 and 4.9. But it all goes to shit when it hits normal operating temp.

New NTK sensor is installed, and working perfect.

The old sensor only had 300km on it, so I returned it.

I took the XJ on a good 4 hour spin in the woods. Did about 100km on only 1/4 tank of gas. Only $25. It used to cost me $40 to go 70km. So I have almost doubled my milage...

Thanks for all the help gents!