Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

I was hoping to solve this issue on my own using the huge amount of data from similar threads, but after reading them all twice and doing the steps I am still not getting anywhere. So, here I am, another poor bastard with a RENIX running rich (in California, of course :shiver: )

A little over a year ago I bought a 1988 XJ. It had about 185,000 miles and ran alright. Of course it was leaking everywhere but the price was in my range, and I was looking to increase my mechanical knowledge while building a reliable offroad rig for overland/camping excursions.

Here were it's passing SMOG numbers at time of purchase:


Here are it's failing numbers now:


In the year between those two tests I touched pretty much everything except the bottom end in my process of fixing the XJ up and learning about it. Obviously somewhere I screwed something up because it's running very rich in the CO% dept.

1988 XJ Pioneer 4x4, AW4, np231. Bone stock when I got it.
Since then:

~3.5" lift w/ 1" tcase drop
Replaced stock D35 with a 29spl 8.25 from a 2001 (3.55) (replaced driveshaft at that time with a correct, kastein-reccomended length)
31" Cooper ST MAXXs on stock wheels.
Head was pulled and taken out for hot-tank/valves/deck (new felpro 530HD head gasket + new head bolts torqued in sequence to spec)
Every goddamn gasket replaced new with FelPro. Freeze plugs replaced once, and one again when one failed.

Sensors I have replaced & How They Tested according to LungHD testing numbers:

New cap, Champion copper plugs, wires, ignition coil. New 2AWG battery cables cut & crimped to fit. She starts right up without struggling (at least by renix standards). It's had several oil changes, but currently running Castrol GTX high-milage 10w30 + 1qt MMO. Doesn't burn any oil that I can see since I changed it 500 miles ago.

New radiator, hoses, HESCO high-flow waterpump/thermostat housing. (Jeep runs steadily at 210 on streets in 95degree weather, ~215 under load uphill, and ~190-200 coasting downhill.

Transmission cooler installed (bypassing radiator heat-exchanger).

When I pulled the head, I noted some hairline cracks on the exhaust manifold in the usual collector area - wirewheeled them clean and had a friend booger-weld them. Removed all the sensors from the intake manifold and had it high-temp pressure washed clean (inside & out). Reinstalled both with a new gasket and torqued new bolts in the proper sequence to spec (front and rear bolts present/not sheared off). Muffler had some leaks and was replaced at a local shop.

At the time of the failed smog check, the only fueling/engine modifications I was running was 703 injectors and a 60mm bored throttle body from StrokedJeep. After the fail, I swapped back my original OEM injectors (w/new o-rings) and it failed again with essentially the same numbers ( left the bored TB on....mistake?).

I did almost everything but the head rebuild myself, and was relying heavily on archived threads/various jeep forum renix-specific searches. With that in mind and to answer your next question, here's the relevant Cruiser54 tips I have completed:

(disclaimer: I am a complete novice at electrical systems and multimeters. Please let me know if you think I'm screwing up a test)

1 Grounds refreshed + new grounds added: fuel-rail>firewall, Batt Neg>radiator support, Instrument panel
2 C101 refreshed Cleaned that thing meticulously, but haven't eliminated it
3 Connectors/Relays cleaned
4 Coil replaced, contacts cleaned
5 Checking sensor grounds TPS B terminal to batt. neg. = 4ohm @ 200ohm multimeter dial setting ( no variation while wiggling harness)
6 Sensor Ground Upgrade Began this today. I was able to find the brown/white wire splice near the MAP sensor, but there were no wires with that color code near the harness side of my MAT connector?
7 CPS Testing Sparks easily, haven't tested
8 TPS Testing/Adjusting resistance tested fine, adjusted as per instructions. Also tested TPS for dead spots with analogue multimeter; needle swept smoothly
9 ECU connector refresh Done, everything was already clean as a whistle
10 Trans Plug refreshing refreshed engine bay connectors, have not done glovebox connector
11 IAC Cleaning Replaced with new IAC
12/13 TDC + Distributor indexing Set to TDC, windowed a spare cap, reinstalled and examined it. The rotor tip was already dead-on with the trailing edge leaving #1.I figured it was good there - do I still need to pull out the whole distributor/cut locating tabs/etc?
14 Throttle butterfly Adjustment Done, and cleaned perfectly by Jeff @ StrokedJeep when the TB was bored from 52 to 60mm. This is currently the only modification done to the fuel/air system - maybe that's enough to cause the system to run rich but I doubt it?
16 Vacuum test for exhaust restriction Haven't done
18 Improving instrument panel ground done
21 RENIX EGR valve test New valve, tested OK
22 RENIX vacuum harnesses new front harness, rear OK
I've shot starter fluid at every vacuum hose junction I can think of with no change in idle.

:banghead: Sorry about all that text but I know that's the stuff you guys are gonna want to know. Here's some purely observational stuff I think is important:

When starting on a cold engine, the Jeep turns right over and idles nicely at the desired 750rpm for about 10-15 seconds. After that, over a period of about 5seconds or less it drops to 500 RPM and begins stumbling/seeking for approx 2minutes. RPM at idle remains fairly consistent at 500 in P or ~600 in D after that. Exhaust does smell very rich and plugs turn black rapidly. It does this pattern no matter what combination of 703/stock injectors/bored or stock TB I give it. The damn thing runs great aside from the low idle. This seems like an open/close loop situation to me, but I don't have one of those Snap-On bricks to read things.

Fuel milage on the 703 injectors was consistent at 10.5 city - I don't do much highway, but the one time I tracked it I was getting 19mpg. I don't have any relevant numbers since I put back in the stock injectors.

I love this stupid Jeep more than any of my other vehicles. I've got 2 months before I have to pass, but it depresses me every time I look at it so I really want to figure this one out. My only remaining ideas are to eliminate the C101, replace the cat (my smog guy doesn't think it needs a new cat), maybe find some stock-size shitty takeoff tires for the dyno test to reduce load on the engine under acccel? Do I need to track down a spare ECU? I know I have to be missing something here for the numbers to be so far off after an overhaul.

:hang:

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

There is a commonly overlooked sensor called the air charge temp sensor. It has a direct bearing on how rich or lean the engine runs. It is mounted on the intake just to the rear of the throttle body.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

old_man said:

There is a commonly overlooked sensor called the air charge temp sensor. It has a direct bearing on how rich or lean the engine runs. It is mounted on the intake just to the rear of the throttle body.

Click to expand...

Thanks for the reply! That sensor is a.k.a. the Manifold Air Temp/Intake Air Temp, right? Looks like this?



I don't think you can get those new anywhere, as far as I can tell in my searchings. I usually snag them when I see them at junkyards and clean them out carefully with throttle body cleaner. I've tried swapping mine around with no result. Mine reads 480ohm resistance @ ~200deg, which I think is within range for a good sensor?

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

When I replaced my iat I used a newer style, like a HO and the appropriate pigtail.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

mtbxj87 said:

When I replaced my iat I used a newer style, like a HO and the appropriate pigtail.

Click to expand...

I was considering doing that, but other threads like this one said the HO sensors put out different readings/aren't compatible with RENIX ECU. In that (4-year old) thread someone also says the dealer told them the RENIX pigtail part was discontinued... Ecomike chimes in to say the last time he got one in a parts store was 3-4 years before that, so I'm not holding high hopes. Yours runs well though? Might be worth a try...

The closest thing I could seem to find was this one but I'm not sure if the resistance numbers are right and they want more in shipping than the part costs. 5-90 does mention using them here though, so that's a good sign. It's a $30 minimum order, anyone else need one/group buy?

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

Mine runs great. No issues. ~20mpg on highway. The scanner shows correct readings too

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

Do you know what part number/year sensor you used? I might swing by the junkyard tomorrow and grab the right harness connector.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

I don't know. I believe it was 1st gen HO.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

http://www.jeep4x4center.com/omix-i...7221-01.html?gclid=CJ_LgoDZhccCFcRlfgodKs8A1Q

It was like this, I bought one from napa tho. Have you tested the old one to make sure it is bad? Work through cruser54 tips or lundhd is pretty good.

Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

Catalytic converter

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

mtbxj87 said:

http://www.jeep4x4center.com/omix-i...7221-01.html?gclid=CJ_LgoDZhccCFcRlfgodKs8A1Q

It was like this, I bought one from napa tho. Have you tested the old one to make sure it is bad? Work through cruser54 tips or lundhd is pretty good.

Click to expand...

Thanks. My current sensor tested within ohm range (assuming I did the test correctly) but I'm running out of other ideas. I've done almost all of the Cruiser and LungHD tips (listed which ones in the OP).

Jeepity Jeep said:

Catalytic converter

Click to expand...

I wondered about this because as far as I can tell the cat is original, with 190,000 on it. It has an intermittent rattle to it as well, but I can't replicate it by smacking it with my hand so I figured it might be the heat shield. I suppose the best way to test it is to take it to an exhaust shop and have them do a pressure test or something? My smog guy helped me run some tests on the dyno trying to figure out the problem, and he didn't think it was the cat for what it's worth. The plugs also blacken rapidly so I still think it's running pretty rich.

Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG de...

Your catalytic converter needs to be replaced. You'll enjoy not only better emission readings, but improved performance, as well. Mine rattled first 5 minutes or so after start up, as well. A place like Midas will just replace it. A place that performs the smog test will be able to tell you the before and after measurements. My smog place is just next door to Midas, so it's a 1-2 punch, for me

Yes, based on your high emission readings you likely have multiple trouble spots. Mine were a quarter or so of your measurements. Replacing the converter and then retesting will enable the smog tech to continue troubleshooting.

My rattling converter caused more than one issue. Once replaced engine coolant temperatures behave better, more power when the engine is under load, better fuel mileage, etc. etc. etc.

Jeeps (especially those running trails) are hard on catalytic converters. It is not unheard of to replace the converter once every two years just to pass smog as the vehicle gets older.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG de...

JeepityJeep said:

Your catalytic converter needs to be replaced. You'll enjoy not only better emission readings, but improved performance, as well. Mine rattled first 5 minutes or so after start up, as well. A place like Midas will just replace it. A place that performs the smog test will be able to tell you the before and after measurements. My smog place is just next door to Midas, so it's a 1-2 punch, for me

Yes, based on your high emission readings you likely have multiple trouble spots. Mine were a quarter or so of your measurements. Replacing the converter and then retesting will enable the smog tech to continue troubleshooting.

My rattling converter caused more than one issue. Once replaced engine coolant temperatures behave better, more power when the engine is under load, better fuel mileage, etc. etc. etc.

Jeeps (especially those running trails) are hard on catalytic converters. It is not unheard of to replace the converter once every two years just to pass smog as the vehicle gets older.

Click to expand...

Great info, thank you. I'll find a good shop. Being that the cat was okay a year ago I figured it would still be good, but I didn't take trails into consideration - I've probably driven it harder in the last year than the old thing had seen in it's other 26 years. :yap:

Did you pick a CA-approved cat in particular or just go with whatever the shop suggested?

Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG de...

I too didn't at first consider replacing my catalytic converter when I failed smog test, as my converter had only 10k or so miles on it. I think something caused the converter to go bad, rattling being a key symptom in both our cases.

The Midas that I go to already had a 2.5" Magnaflow high flow catalytic converter sitting on the shelf I've heard there could be some issues if you choose to install it yourself, but I confirmed from my Midas that claim is not true, at least not in my location - doesn't seem to be a concern with my smog shop either. So, if you'd like I can take a photo of the new converter, which has the part number, etc.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

A new converter installed at a shop will probably run about 150-220$ including the cat. The place you took for smog, was it only smog or a repair shop. A lot of times shops will re-test for free if you use them to repair your vehicle.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

I think the 703 injectors you had in there fouled up the o2 sensor.

When I put the 703s in my 89 and scoped results on my snap on brick, the motor would go into closed loop but quickly reduce the STFT (short term fuel trim)
values to the point of Open Loop

The 703s dump too much fuel for the Renix to handle.

If you had them in for a while they probably messed up your cat converter too.

Look on Ebay for a Snap on MT 2500 .

Its they only way to check your Loop Status and other data

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

my2monkeys said:

I think the 703 injectors you had in there fouled up the o2 sensor.

When I put the 703s in my 89 and scoped results on my snap on brick, the motor would go into closed loop but quickly reduce the STFT (short term fuel trim)
values to the point of Open Loop

The 703s dump too much fuel for the Renix to handle.

If you had them in for a while they probably messed up your cat converter too.

Look on Ebay for a Snap on MT 2500 .

Its they only way to check your Loop Status and other data

Click to expand...

What injectors are you running now?

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

A direct fit, CA approved CAT is in stock at RockAuto for $157. I put one on my 88 last year when it failed.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

I run 703's in my Renix MJ. No ill effects, I average 20+mpg in my average DD scenario.

Re: Rebuilt & tuned up RENIX running very rich - help me save it from the SMOG demons

Perhaps the "new" injectors are bad?

Volvo 746s work great in the Renix Jeeps.

NEVER a bad idea to eliminate the c101.