@Extinct ooh that. Thanks. I’ll do a time based graph when I can.

If I understand it correctly, the upstream O2’s should cycle and the downstream O2’s should have constant voltage?

I’ll try to graph fuel trims as well. If fuel trims are still sub optimal, what would y’all suggest looking into next?



On an unrelated note: I’ve decided to swap out my Severe Duty Hayden fan clutch for a Heavy Duty - the Severe Duty did help stabilize my temps, but the noise is excessive and makes it hard to hear and feel the motor.

 

The downstreams move a little bit but not much. They are basically there to monitor cat condition and efficiency. If it is running without codes I would stop chasing it. Hell I run my DD with all the oxygen sensors dead and it gets 16.5 mpg on the highway going 75. Truck is registered in a non-inspection state so no worries there.

 

Gotcha - no SES yet. I'm in Alabama, no inspection here either so I am good to go.

With all of the issues this truck has had, entirely due to the poor work from the PO, I've been a little weary of driving it without trying to diagnose every little issue.

When I was getting Lean Codes my fuel mileage was abysmal. 11 mpg cruising at 65 on the highway. I'm confident it's better now with new injectors and all the vacuum leaks we found, but I think mileage is one indicator of getting the problems solved.

I still have an uneven shake at idle. I've mentioned this before here. It's smooth when I first start it and the engine is cold. As the engine heats up the idle gets a little more rough - it seems to be correlated with RPM. The lower the idle RPM, the more the truck shakes. I know we're talking about a 20 year old V8 powered vehicle here, so this is not conclusive, but it seems a little excessive to me.

I say all of that - I rode in my friends new Camaro SS last weekend and it shakes more than the Disco at idle by a long shot and it's a few years old. I am probably looking too far into that "issue." My mechanic has driven the truck several times and never mentioned that, so I assume it's pretty normal. Just seems to me like that could be an indicator of a misfire or poor fueling etc.

 

Quick update for those of you following along.

• I've put about 70 miles on the truck since the last post. Still No SES! I put a new starter on yesterday.
• My fuel mileage is still worse than it should be. I am thinking the cats are getting clogged, but not bad enough to throw codes yet. Most of my driving is stop and go around town, so hard to say that 6-8 mpg avg is bad when it's all slow speed, start/stop. That number is based on the Ultragauge, might not be accurate.
• I have yet to graph fuel trims and O2 voltages, but I will try to do that soon.

I installed a Hayden severe duty fan clutch a while back (thanks for forum members support). After having a misfire I learned how hard it is to hear the motor with the severe duty fan clutch. I enjoy the sound of the Rover V8, and would like to be able to notice misses and running issues easier. I pulled the Severe Duty off and bought a Heavy Duty Hayden unit to replace it with.

I drove around yesterday with no fan clutch to feel the difference and listen to the motor. For those that say the Hayden does not rob much power, I strongly disagree. It's a noticeable difference, granted, I was running with no fan clutch at all.

Also, my cooling system seems to be in good shape. Until you drive the truck it will idle under 200 degrees with no fan clutch easily. I drove around for probably 20 minutes before temps got over 204. Hottest I saw was 206.5. It obviously needs the fan to stabilize temps, but that was a good proof of concept that my cooling system works well. Any time I would idle the temp would slowly come back down. I also could hear the motor really well and it sounds very healthy. I think the cats are making some noise as you hear a ticking from under the truck that is not present in the engine bay, but hey, I won't complain...

The saga continues... Thanks for the help so far.

 

Heat shields frequently come loose on the cats, you might want to check that for your noises.

 

Okay, sorry for the delay on this. Here are my fuel trims as of today.

Fuel mileage on the ultra gauge is still showing pretty poor mileage. 6-9 mpg’s around town.

But the engine isn’t toast so I can’t complain.

I can hear the cats ticking after shutting the truck off.

Video: