failed smog with all very high numbers SOLVED

89 xj 4.0 renix manual

southern california, mid december 2011

about 190,000 miles

failed smog in every category except 25 mph NOX

besides failing smog, engine was hard to start hot and always smelled a little too gassy. never felt very peppy.

tested inlet and outlet temps of catalytic converter. outlet was significantly higher than inlet (indicating it works to some extent)

compression on all cylinders is 140 to 150 psi.

spark plugs look great with no fouling and they must have about 20k miles on them.

passed smog 2 years ago.

connected DRB II and ran engine test. returned with fault 1065 , which is O2 sensor running rich. the troubleshooting chart for that fault involves disconnecting the o2 sensor, and then monitoring the o2 sensor voltage while shorting various terminals on the harness. im not sure if i was doing this wrong, but my drb ii never showed anything but 0V (shorted or not) during this test, even when the actual pins on the harness measured 5V (not shorted).

i measured the voltage for the heater of the o2 sensor, and found it was 0V. This is because its only 12-14V for about A SECOND after you turn the key on. once i discovered this, i found the voltage to be about 12V for the o2 heater.

while running, the O2 sensor voltage (monitored via DRB 2) clearly swang between 1 and 4V like it should. it appeared to be working.

so now I began to believe the fault 1065 was real, and there was something causing the system to run rich at some point during the engine test, and the O2 sensor was probably working ok.

measured fuel rail pressure. 33psi at idle with vac hose, 40psi idle without vac hose. if engine is shut off, loses pressure at about 1 psi every 7 seconds.

removed fuel rail to observe injectors for leaking. noticed that tons of fuel would leak if i moved injectors around. it was leaking past the fuel rail orings. the intake manifold orings looked okay, but the fuel rail orings were hard as rocks. replaced all. now the leak was fixed, so i could actually observe the injectors outputs for leaks. none seen. suddenly i noticed that there was fuel dribbling out of the fuel pressure regulator vacuum line nipple.

so I'm assuming that was the whole problem. the intake manifold was sucking gobs of fuel through the fuel pressure regulator because of some internal leak. note that i observed the leak while the engine was off. im not sure if the dribbling would occur with the engine running. although it seems like it would.

if only i had tested for this first i could have skipped everything above...although it was good i found those old orings on the injectors. all you need to do is disconnect the vac line from the regulator and look for fuel dribbling.

Yep, start with the easy stuff first, like the vacuum line to the FPR!!!

Good write up!!!! I had that problem on the 89, 8 weeks ago. I got lucky, and found it in about 10 minutes, LOL.

On mine if you test the temp of the inlet pipe right before the cat it is much hotter then right after the cat. Does that mean the cat is bad?

What are you using to test the temperature, and are the surface colors different?

No it does not confirm a bad cat, if the engine is running too lean, IMHO. But it might be a Cat. You need more info to confirm a bad Cat.

Infrared themometer. I sanded my rusty downpipe so it was the same color as the cat and after pipe. Just wondering becasue of comments made by the OP. I have some checking with my multimeter to do anyways as soon as it stops raining.

okay guys..there is more to this story..

since i had found the fuel regulator dribbling gas into the intake manifold through its vacuum port (see first post), I celebrated in my mind (cautiously) that I had the problem fixed.

wrong o...

so what happened next?

well, I didnt go straight to get it re-tested.

i wanted to make sure that fault code from the DRB 2 went away.

it DIDNT.

i still got the fault code that indicated "oxygen sensor indicates rich".

shortly after startup, the O2 sensor voltage (observed with DRB 2) would swing rich and lean like it should...but after several minutes, it would hang at near 5V. (i believe that is actually LEAN, but maybe during the system test the DRB does something that causes the sensor to ouput RICH constantly). thats not good.

so...since I had already tested pretty much everything and fixed a major fuel leak, i figured that my O2 sensor was bad and just went out a bought a new one for about $50 from autobone

the new sensor swang MUCH faster and did not peg out at 5V. it kept swinging all the way along the 15 minute drive to the smog place.

I also tested the EGR system. heres what you need to know:

this jeep, an 89 4.0, has a black plastic flying saucer "egr transducer", as well as the actual egr valve.

the transducer works like this, it allows engine vacuum on the VAC port to reach the EGR port (they are labeled) ONLY when exhaust backpressure is present on the third port. therefore you cant test the black plastic transducer by seeing if it holds vacuum on the EGR or VAC port, unless you supply positive pressure on the third, bottom port, SIMULTANEOUSLY.

you can do that by leaving it connected as it normally is, and then unplugging the EGR port and connecting a vacuum gauge to it. blip the throttle, and you should see a very brief spike of vacuum on the EGR port.

i believe you CAN test the actual EGR valve with a vacuum source. make sure it holds vaucum and that the pintle of the valve moves when you apply vacuum. also, the engine should die if you do this at idle.

and, the DRB did not show the fault code during the engine test.

BUT I STILL FAILED SMOG, with very high numbers still. i dont have the exact numbers because the test was run in manual mode. i know they were high, maybe even as high as I originally ran before the o2 and leak fix, but its possible some of them may have been fixed, in fact, i think maybe only NOX was still high. MAYBE. dont take this as fact. i just dont remember.

So....DAMN...the smog tech suggested the cat, and I figured it probably was too. it looks like the original cat, which must now have 187000 miles on it. running super rich for 15000 miles probably killed it. problem was my two cat tests SEEMED to indicate it was okay:

test 1: exhaust backpressure. measuring the exhaust system pressure with a vacuum/pressure gauge on the EGR backpressure port showed less than 2 psi while blipping the throttle. thats good as far as I know.

test 2: the outlet temperature of the cat measured 150+ degrees hotter than the inlet temperature. this is also a good sign...hmm.

well, i crossed my fingers and bought a cat. i installed it and did a couple tests.

the outlet temperature was about 150F hotter than the inlet, like before. hmm....

i could see through the old cat okay. it didnt look blocked or plugged up..it did look black though.

oh well...lets go get tested.

PASSSED!!!!!

with UNBELIEVABLE numbers, check them out in the pic.

so, to recap:

the actual problem appears to have been a leak in the fuel pressure regulator, allowing fuel to pass through the diaphragm into the vacuum side of the regulator which is connected to the intake manifold.

running rich for who knows how long (up to 15000 miles), may have killed the O2 sensor AND the catalytic converter.

yay!

blubullett said:

On mine if you test the temp of the inlet pipe right before the cat it is much hotter then right after the cat. Does that mean the cat is bad?

Click to expand...

not neccessarily..if the cat has had plenty of time to warm up and measures a few hundred degrees, it could indicate a problem.

yes i did the test with an infrared non contact gun..

make sure you drive around for a bit

then test it right away.

test in a few spots as near the element inside the cat as possible

thats way cool you passed with such good numbers. one thing i dont understand though is why the MIL/check engine light visual test says pass. i dont think the 89 had a check engine light. what is the MIL?

The old cat may have been doing some additional combustion and thus was still getting hot, but may have been overheated enough to damage the surface catalyst chemistry such it that no longer works as designed.

These catalysts have three different active catalysts along the path from inlet to outlet, and each one has a different step in the process that is critical to the next step. It also works in a complex swing cycle very rapidly, rich to lean back to rich that has an average 14.7:1 ratio, but the swing process is part of what makes the Cat work, so a slow to respond, slow swing from rich to lean and back, O2 sensor adds to the low efficiency of the Cat problem. It takes both being at top efficiency to do the job.

2stix said:

thats way cool you passed with such good numbers. one thing i dont understand though is why the MIL/check engine light visual test says pass. i dont think the 89 had a check engine light. what is the MIL?

Click to expand...

anytime i refer to a fault code or test i am talking about the chrysler DRB II scanner i had hooked up to the renix computer. youre right, there is no mil/check engine light on the renix system.

acannell said:

anytime i refer to a fault code or test i am talking about the chrysler DRB II scanner i had hooked up to the renix computer. youre right, there is no mil/check engine light on the renix system.

Click to expand...

Does the DBR-II show the Renix ECU storing any codes, or running data?

Ecomike said:

Does the DBR-II show the Renix ECU storing any codes, or running data?

Click to expand...

hmmmm...i wondered the same thing given that renix isnt supposed to store things..i forget if you go to the "fault codes" menu item if it says "not supported" or not..sorry im too lazy and too tired of dealing with the jeep lately to go hook it all up and find out..next time i do ill check and report back..

the faults I am talking about are from running the "engine test" on the drb 2... i am not sure what the drb 2 does when you run the engine test, but it asks you to press the throttle to certain positions while it measures things, then it tells you if any faults happened...

there is a powertrain diagnostic manual with the dozens of fault codes you could get and very detailed troubleshooting flow charts for each one, with relevant schematics and diagrams, its incredible.

so with the drb 2 and the diagnostic manual, im INVINCIBLE!! muhahahhahah!!

although really i dont know if i trust the drb 2 fault codes yet, although i have no reason not to, and so far its not lead me astray..

you CAN get running sensor data with the DRB 2 on a renix. from my memory:

o2 sensor voltage with rich/lean
throttle position
coolant temp
air temp
RPM with sync signal status
closed loop or open loop o2 status
a few internal variables regarding the fuel trim
injector pulse width
battery voltage
map sensor (vacuum, baro, and i think voltage)
relay statuses (egr, baro, AC etc..)

maybe something else too i forget..