Car runs smoother/quieter after clearing memory...am I delusional?

[jessman1128]

'96 GASE 2.4L

This past weekend I pulled the ignition coil cover off to check the coils, replaced the plug boots, and re-gapped the plugs. (This was done because I'm trying to figure out the cause of some driveability issues I've been having - that thread is here (http://www.gaownersclub.com/forum/showthread.php?s=&threadid=76859).)

My car runs somewhat loudly, it sounds like the exhaust, and I've always assumed it was from the couple of small holes in my muffler.

After doing that work, the car ran smoother and quieter (exhaust noise was there, but noticeably quieter) for a couple of days, then started acting up again and running louder. I initially thought it had been running better due to the replaced plug boots and regapped plugs.

Since it had started acting up again I decided to check the plugs/boots again just out of curiosity, since they're easy to get to, and take pictures of the plugs to post them here (I thought they looked okay, but I'm not experienced in reading plugs, so I figured it wouldn't hurt to have somebody else look at them). I unhooked the battery last night before going to bed (something I also did last weekend when working on it), intending to pull the plugs this morning before going to work. Well, I overslept and didn't have time to check the plugs, so I just hooked the battery back up and drove in to work.

To my surprise, the car again ran smoother and quieter, like it did last weekend.

The only code that my car has been throwing is P0141 (the rear O2 sensor). The code did get thrown again a couple of days after working on it last weekend, but I don't remember now if the code reappearing coincided with the car starting to run rough/loud again. The code hasn't been thrown again so far today, but I'm sure it will after a few more drive cycles.

The car running smoother for a time after clearing the memory seems plausible to me; if a sensor or something is defective it might take it some time to re-adjust itself improperly and start running rough again. I really don't understand how/why it would be running quieter though. Is there some other noise that sounds like exhaust noise but really isn't?

It's certainly possible that I'm imaging all of this (sort of like the placebo effect), but I've been paying pretty close attention to how my car has been running and sounding while I try to figure out what's going on and I'm quite positive that I'm not imagining all of this.

I've checked the details for the P0141 code to see if it alters how the car runs in any way after it's thrown, and it doesn't.

So my questions are these. Does what I have just described sound possible/plausible, or am I delusional? And if it does sound possible, any ideas on what would cause something like this?

[rixGAphx]

And folks think I'M wordy.

:D :D

Summary:
'96 4-cyl, 11-yrs old, 208,000 miles.
We don't know which tranny, manual or automatic, since Jesse refuses to answer despite several requests :roll:

Problem:
Engine sometimes runs rough at highway speeds, seems low on power, *possibly* bad fuel consumption.
Sporadic SES, only code is P0141 O2 Sensor Heater Circuit Malfunction (Bank 1 Sensor 2), indicating a problem with the rear O2 sensor (which should be checked/replaced eventually, but is not causing the present problem).

Plugs recently checked and gapped; were replaced 1.5 yrs ago; tops of plugs showed some 'flaky white stuff'.
* What brand/model of plugs do you have in there?
You have no 'plug wires', just the 'boots' with (as I understand it) a metal spring that is acting like a wire to carry the power from the coil to the plug.
White flaky stuff' is almost always some kind of oxidized metal, specifically, zink-oxide or aluminum oxide, produced by the metal in the presence of high heat.
So I *guess* that your springs aren't touching the plug fops tightly, and there's some arcing of the current. That would reduce the energy avilable at the plug electrodes (inside the engine) and result in poor ignition.

If you have a 'couple small holes' in the muffler yet can't replace it, try not to poison yourself with carbon monoxide.
At least seal the holes with 'muffler bandage' (a special epoxy and fibreglass cloth patch kit from Checker/AutoZone/etc.).
I think they sell it at the convenience store checkstands in MI, land of the salted roads and dragging mufflers :eek:

Come to think of it, your P0141 code could result from general rust/crap at the back of the cat.
And your rough-running could be caused by a nearly-clogged cat.
Take your car to Midas and have them inspect the exhaust, including checking the cat for clogging (which is different from a worn-out cat that doesn't clean the exhaust anymore).

The computer on the '96 is pretty sophisticated, and you're right that it 'forgets' its 'learned behaviour' when it's been disconnected from the battery for a while.
But it's a relatively dumb old 'puter, and doesn't really have that much to forget.
It doesn't store information about its sensors' readings; it samples the readings anew every time you start the car.
And it doesn't 'adapt' to readings of sensors as they deteriorate.

What you are *prolly* experiencing is the 'run-rich' mode of the engine that happens EVERY time you start the engine 'cold'.
The 'puter stays in 'open-loop' and adjusts the fuel injection and ignition by default, until the coolant warms and the 'puter starts to make adjustments based on data from the front O2 sensor (closed-loop).

Hope this helps,
-Rick

If you have an auto tranny, it REALLY needs the fluid level checked, and prolly a change of fluid.
Midas does that, too.

[jessman1128]

Originally posted by rixGAphx
And folks think [B]I'M wordy.

:D :D

Yeah, I've been accused of being too wordy on occasion myself. I'm sure you're shocked. :)


Summary:
'96 4-cyl, 11-yrs old, 208,000 miles.
We don't know which tranny, manual or automatic, since Jesse refuses to answer despite several requests :roll:

Well...I hate to tell the guy that's helping me that he's wrong...but I did say it was an automatic in the 2nd post of my original thread. That info is buried about halfway through that extremely-wordy post though, so I can't fault anyone for missing it. :)


* What brand/model of plugs do you have in there?

Ac Delco platinum plugs (p/n 41-942) (same as OEM, I believe). I pulled my maintenance notebook out the other day and found out I was wrong about how many miles I've put on the car since I bought it. I estimated 30k in my original thread. It's actually 45k. Probably wouldn't be a bad idea to go ahead and replace my plugs now regardless.


If you have a 'couple small holes' in the muffler yet can't replace it, try not to poison yourself with carbon monoxide.
At least seal the holes with 'muffler bandage' (a special epoxy and fibreglass cloth patch kit from Checker/AutoZone/etc.).
I think they sell it at the convenience store checkstands in MI, land of the salted roads and dragging mufflers :eek:

I tried that a few weeks ago, and was mostly unsuccessful because one of the holes is towards the top at the front of the muffler, and I didn't have the car jacked up at all so I couldn't really see what I was doing. I'll probably jack it up this weekend and try to patch it better.


Come to think of it, your P0141 code could result from general rust/crap at the back of the cat.
And your rough-running could be caused by a nearly-clogged cat.
Take your car to Midas and have them inspect the exhaust, including checking the cat for clogging (which is different from a worn-out cat that doesn't clean the exhaust anymore).

I took it to Muffler Man yesterday for a general exhaust system inspection. They told me about the holes in the muffler (which I obviously already knew about), said the rest of the system looked fine, but that they don't have the equipment to check my cat. Being a muffler/exhaust shop first-and-foremost, I thought that was rather odd, but that's what they told me. So I still need to get my cat checked out.


The computer on the '96 is pretty sophisticated, and you're right that it 'forgets' its 'learned behaviour' when it's been disconnected from the battery for a while.
But it's a relatively dumb old 'puter, and doesn't really have that much to forget.
It doesn't store information about its sensors' readings; it samples the readings anew every time you start the car.
And it doesn't 'adapt' to readings of sensors as they deteriorate.


I obviously want to get this thing figured out and fixed, but in the meantime is there any harm in disconnecting the battery periodically if in fact the car runs better for a day or two after the battery has been disconnected?


If you have an auto tranny, it REALLY needs the fluid level checked, and prolly a change of fluid.
Midas does that, too.
Definitely. While I still haven't checked the fluid, I have been doing some reading about trannies and have realized that it is way overdue for a fluid change, at best. Do I want a fluid change and flush? Or just a fluid change? I've heard bad things about high-mileage trannies with unknown histories being flushed, that's why I'm wondering.

Ok, I'm going to stop putting this off. I'm heading out on lunch now. I'll drive it around for a bit first - 15 min, I think my owner's manual says - and then stop to check the tranny fluid.

[rixGAphx]

Originally posted by jessman1128
Well...I hate to tell the guy that's helping me that he's wrong...but I did say it was an automatic in the 2nd post of my original thread.
That info is buried about halfway through that extremely-wordy post though, so I can't fault anyone for missing it. :) My bad.

Been lookin' all OVER for this, "It's an automatic transmission."

:banghead:

[rixGAphx]

Originally posted by jessman1128
So I still need to get my cat checked out.
Checked for CLOGGING, not for efficiency.

DIY:
* Get a drill and 3/16" bit, and a #14 (or 1/4") stainless steel sheet metal screw from the Ace Hardware or such.
* Jack and support the car.
* Drill a hole in the exhaust pipe, about 3-4" in front of the catalytic converter. Drill the hole in the side, not bottom.
* Start the engine and let it warm-up.
* Seal and un-seal the hole with something heat-resistant like an oven mitt.
* There should be very little, if any, change in engine tone/idle quality between sealed and unsealed.
* * If there's little difference, then exhaust is not being impaired by a clogged cat.
* * If the idling engine runs better/stronger/more smoothly when the hole is open, then the cat is clogged. Get a new one.

* Just screw in the stainless steel sheet metal screw to seal the hole; the stainless will never rust or corrode.
The edge of the hole will rust *slightly* over time, but not as much as it would if the hole were in the bottom of the pipe where condensed water collects.

* Inspect the wiring and connector for the post-cat O2 sensor while you're there; unplug/replug the connector several times to somewhat clean the pins/sockets of corrosion (this may well restore the operation of the heater circuit).

I obviously want to get this thing figured out and fixed, but in the meantime is there any harm in disconnecting the battery periodically if in fact the car runs better for a day or two after the battery has been disconnected?No harm whatsoever.
Just be sure to connect/disconnect the ground/black (NEG) terminal first (actually, it's the only one necessary to disconnect, as it will STOP all current).
Do I want a fluid change and flush?
Or just a fluid change?
I've heard bad things about high-mileage trannies with unknown histories being flushed, that's why I'm wondering.When 'power flushes' were first introduced, the machines had their own built-in pumps and often used too much pressure, and sometimes were mis-connected for reverse flow :eek:
So there are lots of horror stories and old-wives tales out there about blown seals and whatnot.

Nowadays, everybody just disconnects the hoses and dips them into the 'exchange machine'. The machines pump is just for recirculation within itself.
The system uses the tranny's own pump to exchange old fluid for new, so excess pressure never occurs (nor does backward flow).

A fluid/filter change will only change about 1/2 the fluid, since gravity can't remove the fluid inside the torque converter and some fluid is trapped within the tranny body via checkvalves.

If your fluid is reasonably clear and red, then a basic 'change' would do you.
If it's brown, or black, or nearly opaque; or smells well-burnt (as badly as toast that you wouldn't accept from a Denny's) or is gritty, then a complete flush is in order.

...then stop to check the tranny fluid. :bigok:

[jessman1128]

Tranny fluid level was towards the lower end of the hash marks, but definitely within the hash marks. I looked at my owner's manual again after checking it and realized it said drive for 15 miles, not 15 minutes. However, I'm fairly certain I drove it enough to get it warmed up enough for a decent reading, and I followed the rest of the instructions exactly.

Not sure about the quality - forgot exactly what I was looking for, so I'll probably have to check this part again. I didn't have a paper towel handy so I used a cheap fast-food napkin; placed a drop or two on it and waited about a minute. The color was a really light pinkish-brown, and it did spread out some on the napkin. I didn't think to smell it.

Thanks for the instructions on checking if the cat is clogged. I've been wondering if there was any way to check that myself. AllData talks about using an exhaust backpressure gauge that you temporarily replace the front O2 sensor with. Sounds easy enough, but I don't have an exhaust backpressure gauge.

[GatorGA]

Wow, I think Rick finally has some competition with long-winded posts! :lol:

[rixGAphx]

Originally posted by jessman1128
Thanks for the instructions on checking if the cat is clogged.
I've been wondering if there was any way to check that myself. AllData talks about using an exhaust backpressure gauge that you temporarily replace the front O2 sensor with.
Sounds easy enough, but I don't have an exhaust backpressure gauge. Neither did Muffler Man, nor most DIYers or small shops, since:
* It costs $150 and has only one use; and,
* Can be substituted by yer thumb in a heat-resistant glove using the O2 sensor hole (which is pretty easy to get to on your engine, but not so on the GA V6 and other engines).

The gage must be precise since the pressures involved are low (about 2 psi for a nice, open exhaust; mebbe 7 psi before the engine just won't run at all), but it must also resist the 350*F temperature of the exhaust.

http://www.sjdiscounttools.com/otc7215.html

Not even 'Actron' makes a cheaper version, and they make cheap versions of EVERYTHING :roll: .

IMO only a NASCAR shop would need this gage, for precise tuning of huge carbureted race engines.
And their concern is to create ENOUGH backpressure (since their huge pipes are so free, while an engine needs a *little* backpressure for proper flow).

[rixGAphx]

Originally posted by GatorGA
Wow, I think Rick finally has some competition with long-winded posts! :lol: Sometimes I hafta edit heavily.

Did you know that PM's max-out at 3,000 characters? :eek:

:D :D

[jessman1128]

Time for an update...

I don't necessarily have a question exactly; just providing updated info and symptoms in case it sheds any additional light and somebody feels like responding.

About 2 weeks ago I finally got around to patching my muffler again. I discovered a nice hole on the top of the muffler that either wasn't there last time I patched it, or I didn't notice it last time. It was a little larger in size than a quarter. I patched that as well as I could and it quieted the exhaust noise quite a bit. I had forgotten the car could run that quietly. (The patch has since started to come off, so the exhaust noise has returned a little bit, but that's irrelevant at this time.)

With the exhaust noise diminished I was then able to hear the rest of the car once again. I quickly realized that at least some of my issues were transmission-related (just as you suggested, Rick). I'm a complete tranny novice, so I might be explaining this incorrectly. I've been noticing the tranny not up-shifting at the proper times (delayed shifting?), shifting hard at times, not down-shifting properly when trying to accelerate from a highway cruising speed, etc. By not up-shifting at the proper time I mean that I can hear/see the RPMs rise higher than I believe they're supposed to before it shifts. If I had paid attention to how it shifted prior to all of this I probably could have noticed this before just by watching the RPM gauge; but I didn't, so I didn't notice it until I could actually hear the engine/tranny again. It also seems to be slipping at random times, I think.

I've also started experiencing more of what I described in my first post as "when I start to slow down, sometimes the car almost imperceptibly jerks and the engine sounds like it's going to cut out on me for a split-second, and then it's fine after that." Except it's getting more noticeable now, and doesn't just do it when slowing down after turning off cruise control, but also sometimes while accelerating or driving at a steady speed. After doing some more research the past couple of days I'm thinking it sounds like it's a TCC issue (and the engine isn't actually cutting out on me, I just thought that's what was causing the jerking before).

I finally scheduled a transmission fluid change for tomorrow night. However, I'm a little hesitant about dropping 109 bucks on a tranny fluid change if my TCC actually is going bad, because a fluid change won't help the TCC at all from what I understand of what I've read. And fixing the TCC requires going into the tranny, so it will be rather expensive. And if that is the case, then I'm looking at an expensive TCC repair as well as an expensive water pump replacement. I'm thinking I'd probably be better off just junking the car and looking for another inexpensive junker to drive until it too falls apart. (I'm on a rather limited budget, and I can't afford car payments, so getting a newer vehicle is out of the question.) Unfortunately I don't think there's any easy way to confirm that it's a TCC problem, so in the next 24 hours I have to decide if I want to take the risk of dropping $100+ on changing the fluid and have it not help at all.

[HornetGT141]

Well you may have been looking at my post when you saw the TC/TCC issue. Except when my TC was going out I wasn't having any noticeable problems when accelerating but rather when I was decelerating like you said.

Rick informed me that when the engine was getting ready to die the TC was very quickly shutting off right before hitting 0. Almost right before the engine would stall. The noticeable thing I saw about the TC going out was when I would pull up to a stop light/sign and upon driving forward the car would have somehow shifted itself into neutral. I would then have to shift into park and back into drive to disengage the TC (which Rick also informed me of). Is your car doing that?

I had the tranmission taken in to get a partial rebuild and it was $1700 (warranty covered $1000 :D ) but it doesn't have how much the TC was alone with labor. But my reverse gear blew out and some of my 1-2 and 3-4 pistons were also on the verge of failing.

I'm not sure on the car wanting to cut out while going steady speed because that sounds to be another issue. I have read in some cases problems with the engine cutting out while driving may be fuel pump related, but I'm probably just speaking out of my butt on that one as it has never happened to me before.