VX bucking bronco
 

Sure wish I'd found this forum BEFORE things started to go wrong with the VX. I live in Ohio where big pickups rule the road, and small gas savers are definitely a minority. Always nice to talk with like-minded folks.

I've had this gal since she was new; she's now at 172,000 miles. For about the last 15,000 or so she's been developing a noticeable miss at steady speeds. That means *any* speed - 25mph, 65mph, anything in between. It's gradually been worsening to the point where the miss has become a buck.

Fuel efficiency has dropped too. I seldom got the EPA 56 highway even when she was new, but in mixed driving I mostly got 46-48. That fell to around 42-44 when the roughness started, and has been more like 38-40 lately.

Until recently she always smoothed out when I accelerated, with a little stumble at the start of acceleration. Lately the engine stays rough under acceleration, too, and the stumble has become a trip-and-almost-fall.

Through all this, the CEL hasn't come on (except when I've been tinkering and deliberately disconnected something). No codes are set by normal driving. Bridging the diagnostic connector produces a steady CEL, no blinks.

Plugs and air filter have about 10-15K on them. I replaced them early in the game, shortly after the first slight roughness appeared; no dice. I put on new plug wires (NAPA, IIRC) about a year ago; again, no change. Have I forgotten anything?

I ran the oxygen sensor tests in this forum and elsewhere. When I spray ether into the air horn the voltage jumps to -1.39 (or therabouts; hard to read) as the engine almost stalls. Pulling an injector plug off sends it to +.42. Both of those seem about right.

The spool valve seems to be working OK. I connected it to B+ at idle and engine speed dropped a bit. (Is that what should happen?)

Checked the TPS with an ohmmeter; I don't recall the exact resistance, but it changed smoothly with throttle position, no jumps or dips (I was hoping for a big glomph at about cruising position, but no such luck).

She runs tolerably well in open-loop mode - during warmup, or if I disconnect something like the oxygen sensor or spool valve. But that probably doesn't mean much.

It sure does feel like she's running 'way, 'way too lean. But why?

Can anyone offer more suggestions for what to try? I'd be most appreciative. Many thanks.

distributor cap and rotor should be replaced... maybe the distributor itself is going out... have you checked the timing?

jpciii makes good suggestions.

Honestly, if you have 170K+ on that engine and havn't changed the o2 sensor, you REALLY need to. I suspect it may actually have something to do with your problems.

FYI, you can get them brand new on ebay for $170.

Hmm. I had a highway breakdown recently, and the shop they towed me to put in a new ignition control module and a coil. Come to think of it, she seemed to run a little worse after that. I don't think it's usual to pull the distributor when changing the ICM, so I wouldn't think that would change the timing. Still, it's worth a check.

I remember changing the cap and rotor, but I can't think when. Maybe 30-40K miles ago?

Thanks. That sounds better than the $300+ I was quoted at a couple of local places. I don't see any new ones on Ebay right now though, just several used ones.

The OxS passed the test in this forum (see above). But you still think it's worth trying a new one?

Is there an OxS failure mode in which the OxS tells the ECU that there's less O2 in the exhaust than there really is? That is, could the OxS be lying to the ECU, telling it the mixture is richer than it really is?

If the OxS were flaky, wouldn't the engine run poorly all the time, including at idle? It idles smoothly, though sometimes faster than it used to. (1100 rpm falling to 700-800, compared to the 500-600 it used to idle.)

So many questions! :confused:

when I took my vx to the dealer about a year ago to help me truble shoot my exact same problem, they said they didn't have a reliable way to test the o2 sensor, but I had the same problem you had, only I managed to get 210,000 miles on it befor it died, but about the same number of years, so it makes sense, it seemed as if the problem is that it's fallen out of calibration, and that just happens when it gets as old as it is.
Have you replaced the timing belt and water pump yet? it's a good idea to do every 100,000 miles.

Sounds like a bad valve to me.

Thanks for the reminder. I changed the water pump & timing belt at 87,000, and timing belt alone again at somewhere around 160,000 miles.

The bad valve scenario is pretty scary. I really don't think I want to get into pulling the head, and paying a shop to do it is going to be mighty pricey. But if I can find my old compression tester, I'll make 'er breathe into it this weekend.

Replacing a valve isn't all that bad, just follow the instructions, :)

I would advise a compression check also... if you come back with one low cylinder, get it leak-down tested. Also, check over the EGR system. When doing my swap, I had it hooked up incorrectly so that the valve was always open and the engine ran terribly. (Though that should throw a code for the valve lift sensor.)

Just checked the timing, found it a bit retarded, maybe 5-7 deg off. (Hard to see the marks on a rusty, pitted flywheel, had to find TDC with a dowel.)

Still runs lousy.

But #1 plug is black and turns out I had Bosch in there (what was I thinking?). You could just about drive an Expedition through the gap. I'm going to try new plugs, whatever I can get today (probably Champion) and then dig up the NGKs Monday. I'll check compression as I change the plugs.

Compression looks good - 210/210/210/220. New plugs, cap, and rotor helped a little, but not much. I think I see an oxygen sensor in my future.

I found one on Ebay at $197 with shipping. Anybody have any experience with these guys? Their price is $185, no extra charge for shipping.

https://www.oxygensensor.net/parts/o2parts/L1H1.html

oh95vx -

Not sure about them, but I asked the same question as a favor for my wife's mechanic :

Civic VX LAF sensor price?
https://www.gassavers.org/showthread.php?t=2121

CarloSW2

Cfg88, good catch. Thanks for the thread ref - I appreciate its report on oxygensensor.net.

The folks on Ebay who are getting $190 are the same ones who were getting $170 back in December. Not a surprise I guess, as the US dollar has mostly been getting weaker on world markets, sorry to say.

Running open loop is likely to knock off a couple of my cat's 9 lives, and it's probably lost 3 or 4 already. So I don't think I'd better do too much shopping around.

BTW, all the plugs were black. I thought black carbon normally indicates a RICH mixture. But she runs more like she's lean, bucking and surging. Maybe they're black from all the misfiring?

Hmm, if the plugs look like that, what do the inside of the head and the tops of the pistons look like?

oh95vx,

Your problem sounds somewhat similar to the problem I had w/ my VX. Mine stumbled and almost died when slowly accelerating. When I accelerated hard, it was ok. As soon as I let up on the gas it bucked and stumbled. Turned out that the EGR ports were clogged w/ carbon. To test, I unplugged the hose to the egr valve control assembly and blocked it off. All symptoms went away. The only thing different from your problem is I was getting a check engine light. I never ended up cleaning the ports because I would have had to remove my intake manifold. Instead, I kept the hose blocked and never had a problem after that. See the following links for info about blocked EGR ports:

https://home.comcast.net/~em-engineering/T2T013.pdf

Hope this helps.

Steve

I wonder why that would set a code. The diagnostics in these 92-95 VXes don't seem all that smart. It appears to me that the ECU does a minimal test on each unit, and if it seems to be there and responding, it kinda shrugs and says "OK." But maybe I'm missing something ...

Thanks for the suggestion. Pulling off the hose to the valve is an easy test to try, so definitely worth it.

I have to pass I&M here. However, the NOx limit is 1240 ppm, which seems pretty high, so it might pass even without the EGR. (Her last test, 2 years ago, she did 46.3 ppm.)

I have a new oxygen sensor on its way, and we'll see what that does to the situation.

Thanks to everyone for the ideas and help so far. If I may bother you a bit more ...

Does anyone have a suggestion for an oxygen sensor installation and/or removal tool?

Most of the oxygen sensor wrenches I see advertised are 7/8" and say "fit all US and many import sensors." I'm not sure they'll do the job for this one. A 7/8" open end wrench fits pretty loosely on the hex. It's been living in that manifold now for 12 years, and it's not going to want to leave. I'm just about certain to round it off trying to remove it if the wrench doesn't fit perfectly.

I have some deep impact wrench sockets (no impact wrench, but a sturdy breaker bar and about 3' of galvanized pipe can bust loose some pretty tight stuff). The 22mm socket seems to be the right size, though it's not quite deep enough to fit over the old OxS, so I can't seat it to be sure. Besides, I'm not quite ready to cut the connector off yet.

I could chop off the top of the old OxS, or go buy a deeper 22mm socket, but I still wouldn't have any way to install the new OxS.

What do you use? Are the "crowfoot" wrenches any good for installation? Will an extra deep 22mm socket (preferably 6 point) do OK for removal?

If you need to remove the Oxygen Sensor and it's been in their that long, it is probably going to be stuck pretty tight. If you get a tornado porpane torch it puts out a very hot flame, which you can use to heat the exhaust around the Oxygen Sensor. You want to heat the exhaust till it's as hot as you can get it, or to where it starts to glow red, if you can.

For a wrench I purchased a 7/8 inch box wrench and then used a cutoff wheel to cut a notch in it, so I could use it to remove and install the Oxygen Sensor. You need to get a 8 sided box wrench, not a 16, so that you have all of the steel you can get, holding the wrench.

I would definitely put in all new plug's, but if they are all black like you described, then I'd go ahead and replace the Oxygen Sensor.

On the propane torch, you can also get a bottle of MAP gas, which burns hotter than propane, but attaches to the same torch head. Mine comes with about a 6' hose, which makes it real handy, but I've also seen them mounted to the bottle adapter.

They look similar to a regular propane torch, but they look like they have a silencer, like on a gun, attached to the end. They can be used for regular soldering, but you need to use the lower side of the heat range.

oh95vx,

I used the special O2 sensor socket with the slit on the side. Not sure of the size...I can check it for you if you want. I put plenty of torque on it to get my 13 year old O2 sensor out and didn't have any problem. I actually used a breaker bar to break it loose. FWIW

Oh, you'll definitely want to get the car fully warmed up at a minimum before trying to break it loose, that's what I did. Or take the advice of the previous poster.

-- Scott

I've taken some old ones out and been shocked by how easily they actually did come out. Yeah for stainless.

Thanks for the tips. I've never seen a 6-point box end wrench. I probably don't shop for tools in the right places.

There's not much detail on the d15z1 engine's OxS in my Haynes manual, but in the "general instructions" it does suggest running the engine for a while to get the manifold hot before trying to remove the sensor. So Gary's idea makes sense.

I just want to make sure I don't round off the hex on this critter. I've done similar dumb things too many times and ended up having to take heroic measures. Or worse: there's nothing more humbling than calling up a mechanic first thing Monday morning to ask if you can have your basket case towed in.

I don't think the humungous 8-pin connector on this sensor will fit through a box end wrench. I might be wrong. That doesn't matter for removing the old one (just cut the wires off), but it does for installing the new sensor.

I couldn't find a single o2 sensor wrench that fit snug when I had to replace my o2 sensor, I think I went with the 22mm socket and cut the wires, leaving a pig tail, incase I had to solder them back together.
Most auto parts stores will rent inpact wrenchs, I own one, and spent alot of time waiting for the compresser to fill up to a high enough presure to run it, but after about half an hour of it impact wrech rattling away, and heating the manifolt with the torch in between, I got it loose.
I recently saw some spray for removing rusted parts that sounded like it freezes the part (shrinking it), you might try something like that, or something that just lubs it, and removes the moisutre from the rust like heat, then you will have a bit of work, but it's well worth it.

The o2 sensor crow's foot wrench worked the best for me. I have a crow's foot and the socket type.

Ryland called it. Gave 'er a new oxygen sensor and she runs like new. Well, OK, not quite like new, but pretty darn good for her age.

I grabbed the Sawzall and beheaded the old oxygen sensor (to fit into my not-quite-deep-enough 22mm "deep" socket). It was suffering anyway, so that put it out of my misery. Whacked the breaker bar with the heel of my hand a couple of times, and out it came. Didn't even need to heat up the manifold. Put the new'un in with a shiny new Craftsman 22mm open-end wrench.

Nice diagnostic work, guys! Many thanks.

Sweet! Good call, Ryland. That was a nice easy fix.