Yep, this one car is a pain. Thought I'd throw out some more symptoms to see if anyone has any ideas. It's also started with the steering wheel shimmy thing. :-( So, I thought I was going to tell that the code appears immediately, as soon as it starts, because it seems like that when I was driving it yesterday on the interstate coming back from Dallas. But just went to check and no, it took several minutes of idling then 3 miles of driving to set as Pending. It turns on the CEL the next time I start it. I've replaced the injectors, upper ox sensor, air filter, and MAF with no change. Took it to a buddy's shop because my TorquePro won't read much data. He's not a hybrid guy, but this seems to be an ICE issue so I thought he'd figure it out. No luck. He says that all of the sensors/events that would set a 0172 are sending the appropriate data. A weird thing: immediately after changing the injectors, the MPG meter went haywire - it shows mileage in the 80mpg range. Seems to be working as far as the meters going up and down, registering electricity generated, etc. but always shows mpg in the 80s. The only things I didn't check from the diagnostic list are the fuel pressure and coolant temp sensor. Buddy said it's not likely fuel pressure since the code is for too rich, and the coolant sensor reads accurately. So, it drives fine as long as I keep clearing that code. When I got it back yesterday from my buyer, the CEL was on and in addition to the 0172 it had misfire codes for all cylinders, so I assume those will set if I let the 0172 code set and keep driving it for a while. My buyer had no way to clear the codes. Anyway, that info probably won't help y'all, so maybe the better question is what happens if I keep driving it like this - just clearing the code every time the CEL comes on. Again, it drives fine like that for hundreds of miles. No misfire codes, just the 0172, and it runs seemingly fine although I'm not getting the MPG data to confirm. Need to do that manually the next time I fill up. I guess what I'm hoping is that whatever is causing the DTC will get worse and finally self-identify. But, of course, I don't want to burn up valves, pistons, whatever. The coolant temps are always normal at 182ish so I don't see an imminent threat. Just throwing the shimmy out there, in case anyone has heard a way to fix it without replacing the steering gear. It's just hard to invest that much effort in these old cars. I got steering gears on my parts car, but taking it off, and taking the one off this car, then installing is more than this old man wants to do. But worse, after getting this car back home, I discovered lots of rust underneath from that Minnesota snow. Trying to remove the steering gear, breaking all those rusted bolts, is not something I'd try. What's weird is this car didn't have the shimmy when I bought it. Drove it all the way from Minnesota to Texas to LA and back to Texas with no problems When we got to Texas, and finally hit rain, I found out the filler tube was rusted through, and I assume water got in the tank from the storm, because it started missing horribly. And that's when the shimmy started too. I stuck the car in storage for about a year before I got around to swapping in another tank/fuel pump, and when I got it running again, the shimmy was gone. I've not driven it a lot since then, maybe a thousand miles over the last year, but it never shimmied again, until now. It almost seems like the shimmy happens when the engine starts missing. I'd be interested to fix the 0172 and see if the shimmy goes away again. I know, dumb, but why'd it go away the first time? I remember the posts about using low voltage to "burn the fuzzy hairs" off the magnets in the steering gear. Did anyone ever try that? Do those "hairs" go away on their own eventually, like when you park the car for a year?
My son's '01 (used to be mine) is posting a similar P0171, but it seams to drive okey and we haven't attempted to troubleshoot it. The only known issue is the vacuums controlled valve on the cat is rusted and no longer functions. You mentioned in post that the exhaust assembly isn't hard to remove, so when the weather gets warmer, we may try to grease the valve linkage and try to get it working again. Perhaps that will help.
Had a 2000 Ford with a similar issue. Intermittent CEL/fault code. Took it to a Ford master mechanic and he eventually found (after several "Nope, that didn't fix it" trips) that ALL the vacuum control solenoids and valves had some defect - they were either leaky or nonfunctional. Solution: replace all the solenoids and valves. I suspect that your P0172 (too rich) is because the system can't get the air/fuel mixture where it wants to be. Nothing to do but buy the parts and replace them all, including the rubber hoses (they're 25 years old now). Vacuum system diagnostics are hard. Good luck....
Yeah, difficult to fix. I left it sitting now for a few weeks and when I tried to start it, got the orange triangle but no code except the 3191. Goes to Ready, and I drove in from the driveway as I was trying to do, but every time I clear the code and restart, it immediately comes back. aaargggh. Thanks for the suggests. May be vacuum related. This car has the OEM cats replaced, so no VAV exhaust recycle.
If you can't get the linkage to free up, yeah, I think you might be able to just hack it with the substitute vacuum reservoir trick. I've only done that when installing a cheapo aftermarket cat, so not sure it works the same with the old valve still in place, but can't imagine why it wouldn't. probably need to choose whether to leave the valve stuck open or closed or partially? IDK. Depends of your outside temps, I expect. Not sure how much it operates in a warm weather environment like here in Texas.
SYK, there's one code for stuck open and one for stuck closed, I forget which is which - 1436 and 1437, IIRC.
Can't help specifically but many turbos were needlessly replaced on VW TDIs because of clogged vacuum solenoids/actuators/tubes. All caused by EGR.
I missed the "jk" and had to look up the site. Thanks a bunch. How do you know anyway, lol. The answer is no, lol. The name derived from a quote from a German hypermiler years ago. I started using it in my tdiclub.com days, in the Y2K timeframe.
