http://tc.wagoneer.net/sblog/index.php ]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100729-132431 last time, and had exactly the same fiasco as last time.

First test wasn't accepted. Hose fell off on the second test, and the "driver" miserably failed to maintain speed on the second test. Just... like... last time!!

How is that POSSIBLE?!

Only this time the second test was accepted by the manager. Despite how badly the "driver" blew it in the highway driving section, no doubt making my numbers much worse than they should have been.

To top it all off, despite leaner jets, the truck failed worse than before on CO and HC!

Last time: HC=3.8015, CO=62.2980, NOx=6.5254
This time: HC=4.7772, CO=82.9261, NOx=4.7884

I'm in a quandary about what to do next. I can go another two stages leaner on the jets, but I suspect the accelerator pump -- and the "driver's" gratuitous use of it -- is hurting the most. For that matter, the power valve might be the biggest source of trouble and may need replacing.

The hot temperatures probably aren't helping either. I could take it in during the early morning hours. To a different facility in hopes that I get a competent driver. Should I take it into the testing facility tech center for diagnosis? Or to a local carb specialist? Or just install the fuel injection system that's ready to go in the garage?

What boggles my mind is that last time TC passed two years ago, the truck posted outstanding numbers. This time around I'm on my fourth test failure. What gives?! I mean, besides the fact that NOx and HC limits got stricter...]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100703-091649
And it is a long road trip and we've not really tried taking Violet on extended drives like that. So I think we'll end up throwing in the towel and trying for a four wheeling run a little later on.

Meanwhile, the set of #50 and #48 jets I ordered arrived from Carbs Unlimited while I was away on a business trip for the week. At some point I'll give those a try and see if I get any closer to getting through emissions.]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100618-120037
I did a few tweaks to make the truck run and idle leaner and advanced the timing a little.

The third try was decidedly not a charm. The inexperienced driver had to run the test three separate times before it was accepted. First try, the hose slipped off the exhaust... right at the end. The second time the guy still couldn't match the required speed so the test wasn't accepted. I guess driving a carbureted vehicle was a new thing for him. His third attempt was accepted but the truck was over the limits on CO and NOx.

I thought it'd be interesting to try and analyze the IM240 graphs to see what might be wrong with the truck that's causing the emissions test failure.



Oxides of Nitrogen (NOx) was just over the limit of 6.000 at 6.5254. When NOx is high that is usually a sign of high combustion temperatures, either due to a malfunctioning EGR, a device that lowers combustion temps, or because of too much spark advance for the mixture.

Because I increased the timing, I suspect I went too far. According to the printout, acceleration contributes 57% to the NOx readings, where cruise is contributing around 15-20%, suggesting the problem isn't isolated to part throttle acceleration (vacuum advance is controlled by ported vacuum on this truck). Base timing is probably too advanced. When vacuum advance is added under part throttle load (acceleration), even more NOx is generated. You can see from the chart that the driver was punching the gas way too frequently causing NOx spikes. It's possible that if the mixture is too rich, less advance is needed. So the mixture contributes to the problem.



The HC (hydrocarbons) chart shows spikes on acceleration indicating unburned fuel because of an overly rich mixture, undoubtedly. HC spikes on deceleration too; typical for a carb'd vehicle (computer controlled cars lean the mixture severely during deceleration). Maybe I can do something to improve that issue, I don't know. The numbers on the printout show a 58% contribution by acceleration to HC and 23% by deceleration.

It's also possible that the AIR system isn't diverting (enough) air to the catalytic converter to aid in converting the exhaust gases under acceleration. I might see about working on the ignition system, too, in case it helps more completely burn the air-fuel mixture.



Finally, Carbon Monoxide (CO) is pegging out on acceleration, contributing 80% of the overall CO output. The power valve clearly works only when it is supposed to, but is delivering way too much fuel. I'm not sure if a new power valve would fix this, or if I just need to adjust base jetting of the carburetor for thinner, hotter summer air.

Last time I passed it was pretty cold outside. I am leaning towards switching to #50 jets or smaller, then adjusting the aneroid again. I might need to replace the power valve after all, though. If there were a way to adjust the amount of fuel delivered in power enrichment mode, that'd make this easier to solve. On a Quadrajet, Edelbrock Performer, Motorcraft 4350, and others, the carb uses rods to meter fuel in power mode; one can select rods with wider diameters for power mode to deliver less fuel.

The 2150 is stuck with two-stage power valves. Supposedly 1-stage valves can be used but when I tried this last time, the valve wouldn't fit; not enough threads to engage properly. If it worked, one could select a power valve that engaged at a lower or higher vacuum to suit the application. This is the same concept as changing rod springs on an Edelbrock Performer.]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100608-210126 http://tc.wagoneer.net/sblog/index.php?entry=entry100606-220143
Got the replacement glass with a perfect lifter track from one of the original CFSJA members. After vacuuming out most of the remaining glass shards, removing the rotted guide rubber out of the side channels, I installed the window using the original snap clips, and tested it out.

Oddly, the window started going up on its own when I shut the tailgate -- key wasn't in the switch! The tailgate switches on these trucks are pretty unreliable. Anyway the window goes up and down effortlessly, now. I won't be able to hear that sweet AMC V-8 exhaust sound quite so clearly, but I much prefer having glass in the back.
]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100604-000000 Last time, I aced emissions after some tweaking. That was just two years ago so I thought maybe with an oil change and air filter I'd pass, or at least come close.

Uhh... not quite. CO limit 40, TC blew 327!!! Crap.



The driver was very careful to drive smoothly with the throttle (carburetor equipped vehicles send a lot of gas down the intake when you punch the gas a lot).

I suspect that the power valve has, once again, failed. Having to spend $60 on a kit every two years to rebuild the carburetor is stupid. Especially when one considers that a Qjet can retain its emissions-friendly calibration for years without any maintenance. I now officially hate Motorcraft 2150 carburetors.

The numbers and graphs suggest an extremely rich mixture -- leaving unburned gas (Hydrocarbons) and lots of CO in the exhaust. While acceleration counts for half of the emissions results, the contribution of cruise is way too high, suggesting a problem that isn't isolated to one circuit (e.g., idle or cruise or power).



The CO graph is pegged out across a wide range of driving scenarios, which is typical of a power valve that is permanently engaged. (Can you tell I've been there, done that?) You can see CO is pegged during cruise, light acceleration, and heavy acceleration. That shouldn't happen.



The HC graph shows problems on acceleration, primarily, but also shows a lot of unburned fuel pretty much all the time.



Before I shell out the money for a rebuild kit, I need to verify the choke is pulling off correctly and that the aneroid isn't stuck closed. If those two things check out, I'll try to find a power valve separately but most likely will have to get the rebuild kit.

It's probably just as well that they rescinded the collector plate exemption here. I'd rather go through this every other year hell than pollute all the time.

Now that Ethan finished setting me up with the right gear for fuel injection, I'm installing it as soon as I can, believe me. I'm sick of carburetors.]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100602-230148
Unrelated topic: one of the backyard bunnies got severely injured somehow, back legs paralyzed, one injured, flies already buzzing around him. Just an absolutely awful sight. I suspect a particular neighborhood cat is to blame. This cat killed and partially ate another rabbit a few weeks ago. I felt I had to put the rabbit out of his misery. Never had to do that before. Ugh.]]> http://tc.wagoneer.net/sblog/index.php?entry=entry100526-221514