JuLink

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Background: I've got a '93 GS300 with 145k miles on it. Had it for about five years. Great car.

I've been reading on this forum about how great a clean MAF is so a few months ago I used the CRC MAF cleaner on my 2000 Eclipse. At first it started stalling afterward but then I reset the computer again (overnight) and that went away and after a few days all seemed well. This last Saturday I did the same to my wife's 2000 RX300 and it didn't have any complications resulting from it.

After doing the RX300 I then moved on to my GS300. It's been running great (smooth, etc) but I figured that the MAF sensor was old (looks to be original) and has probably accumulated some kind of grime in it so why not.

So I sprayed it up generously, let it dry for about 30 minutes, popped it back in, hooked the battery back up and took it for a drive.

Initially it started fine and was revving smoothly at about 1250rpm while parked. All continued well until the engine was warmed up enough and I pulled up to the first stop light. I'm not sure for how long I was sitting there but after a brief amount of time the engine cut out and died (along with the CEL coming on).

The same thing happened when I cleaned the MAF on my Eclipse before so I thought "oh, I guess I didn't have the battery disconnected long enough to reset the computer" and I didn't think much of it, I just figured I'd be careful to not actually come to a stop anywhere.

But eventually it got bad enough to where just taking my foot off the gas would cause the RPMs to drop so low that it would shut down. After a somewhat dangerous trip back home popped the hood and pulled out the "MAF" again and both the ECU-B and EFI fuses and let it sit overnight.

Then, Sunday morning, I got up, put everything back in, and turned it on again. Just like Saturday, it started up fine, revved at 1250rpm to start and then started dropping as the engine warmed up. If I just left the car in the garage idling (door opened of course) it wouldn't stall but it would get real low (maybe 300-400?) and run rough. I decided to see for how long it would sit there before stalling and I let it run for about 15 minutes and didn't have any stall, despite the very low RPMs.

I then decided to try giving it a little bit of gas to see what would happen. It would rev up okay I suppose, and if I let off the gas slowly the RPMs would drop back down but still not quite stall. While doing this I noticed that revving/unrevving would release some white smoke out of my tail pipe occasionally.

I continued doing this for a while (revving gently, releasing slowly) and eventually the white smoke went away and the idle revs crept back up to 500 and the engine no longer seemed on the verge of stalling. A short time later the idle speed went back to 600-700 and all seemed well and I thought I had a happy ending to my journey.

Also, after turning off the car I found that a decent amount of small black soot had been kicked out of the tailpipe during this time when I was running it in the garage.

I drove it to work this morning, nothing out of the ordinary and everything seemed fine. Then, this evening, I drove it home and at one point, while going downhill a bit, I gave it a little extra gas. The tach jumped up to around 4000 and then dropped to 2000 and would oscillate. At one point (while moving) the engine completely cut out.

The rest of the ride home was pretty uncomfortable. The engine never cut out again, and I never felt in danger of stalling while stopped or slowing down, but giving gas often resulted in the engine revving up high and then dropping down and repeating a few times, usually ending at around 2000rpm with a feeling of minimal power (although the engine seemed to be running smoothly). Also, once this mess started, I noticed that the tach would drop low for a brief second now once I first gave the car some gas after coasting/stopping, which it was not doing previously.

Searching for MAF cleaning before it seemed all the threads that I came across were bunnies and rainbows for cleaning it, but now I'm finding several threads where people are saying that our GS's don't actually have a "MAF" but rather an "AFM" that operates differently and shouldn't be cleaned (but yet still more threads extolling the virtues of cleaning whatever it is that's in the GS).

So any ideas on what might be going on here? Have I totally tortured and killed my MAF/AFM? Might this be an issue that will sort itself out as/if I drive it more? Should I attempt another cleaning? Should I have reset something else that I didn't?

It kind of seems to me like the problem could be that the transmission is trying shift in a really stupid fashion, hence the high/low revving combinations. Or would this kind of thing happen if a hose somewhere were cracked and suction were being lost intermittently?

One final thing I should mention is that I tried starting the car with the MAF simply unplugged and the car wasn't starting at all (whereas it was starting fine with it plugged in).

If I do have to simply replace the MAF where would people suggest getting them? I've seen threads where people have mentioned MAFs ranging from $80 to $1000+.

I'm really hoping that somebody out there has some ideas for me. My background is engineering and I understand some about how a lot of this works but I'm no mechanic. Thanks in advance for any ideas!

Duds

Definetely sounds like you killed it, the only part of the afm I would ever clean would be the housing, never touch the actual sensor. I would suggest pulling one from a junker to see if it fixes your problem. What are your codes?

[ant]

just FYI an AFM is an air flow meter. An AFM measures air flow past it's element. The element gets to a certain temperature and senses the air flowing past it. They usually have mesh either end to prevent turbulence within the AFM and allow a good reading. If you have an AFM equipped car the AFM is situation normally just after the intake and is very sensitive to things like blow off valves as they release air before the throttle body which has already been metered for by the AFM.

generally AFMs can be cleaned but you really have to be very careful and use a very gentle and specific cleaning product. however they can get to such an age that they do die regardless and if trying to clean them. perhaps try to borrow one and try it to see what happens.

a dodgey AFM wil cause all kinds of issues as it will be giving bad signals to the ECU. Also the car probably doesnt start without it connected as it is vital to the engine mixtures.

Rising_Sun

iTrader: (2)

Toyota integrated an intake Air temp sensor in our MAFs. That sensor is very sensitive and the alcohol in CRC maf cleaners can cause them to malfunction. At cold start (High Idle) the ecu bypasses the MAF signal and no problems arise. When the motor is warm is when you will have the most problems. Borrow a MAF from another car and see if it solves you problem.

Kaiser

iTrader: (1)

It's a Karmen Vortex meter and it never ever gets cleaned. The RX300 is called a hot wire mass air meter which is the kind you can spray. The meter in your GS is shot.

JuLink

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I fear that the concensus may be correct in that I broke it, but I'm remaining optimistic and still curious about some of what I've seen.

Here's where I'm at now:

Last night before I went to bed I decided to give things one last shot. I figured that the car got me to work the day before and tricked me into thinking everything was fine so I figured I'd try that again.

I pulled the fuse on the ECU and EFI again, removed the sensor and made sure that the seal was oiled well enough (and then reinstalled it, of course). While I was there I took a look at my air filter and found that it was dirty enough for replacement (considering that I'd hardly had the car out of the garage since I put the last one in I didn't think that there was any chance that it would be dirty yet so I didn't check it before). It wasn't horrifically dirty and the side leading to the engine still looked almost brand new, but the intake side really had a lot of dirt on it.

Today I drove it to work and back (25 minutes city driving each way) and, while I didn't push the engine above 2500rpm, it ran great. The engine was very smooth. I felt like it was up-shifting a bit soon, but that could have been due to my gentle driving and it seemed like it happened less as I drove it more.

So my current plan is to drive it gently for a few days and see if any problems arise. If all goes well with that, I'll then try revving it a bit more and see what happens - who knows, maybe the problem will have worked itself out by then (like the low idle problem did).

I'll post back with updates on what happens.

Can anyone think of why my cleaning might have caused the white smoke/black soot and why the idle got better once I burned through that?

vtecthis1

i am having a similar problem on my 92 sc400 I thought i would clean the AFM, and filter with the "cleaner" and my cel came on.... i could not even accelerate past idle...i had to very gently depress the throttle or the car would nose dive and die...later, i removed the AFM and cleaned it again with the "cleaner" and this time, it ran with the cel on and i could drive just fine.... it just is running pig rich, and the cats smell horrible... i took it to the interstate and floored it... after about 4k rpm, the cel went off, and all was well, but i was going 90 + mph, so i had to let off... the cel came back on, and it is still on... since AFM's cost so much, i was wondering whether or not there is a higher volume meter housing that would allow more air to "lean" out the engine... b/c obviously, the AFM is sending a signal to the computer that there is too much air when there is not and causing an overly rich mixture...

Kaiser

iTrader: (1)

The computer is doing it's best to learn the correct mixture using only the O2 sensors as you guys have melted your karmen meters.

MEANDAFAKA

a lot of people have problems after cleaning cleaning their lexus.

Duds

Seeing as you most likely fubared your afm your running rich/lean (hence the black/white smoke), as Kaiser said your ecu is trying to figure out the correct air to fuel ratio but can't cause the afm is sending messed up signals.

Still what codes are you getting from the car? Stick a paper clip in E1 and TE1 in the diagnostics box under the hood then put the ignition in position 2 and count the blinking lights. The CEL will blink giving you your codes.

Example: blink blink blink pause blink would be code 31.

JuLink

iTrader: (1)

Thanks for the input guys. I hope to check out what that code is tomorrow.

With the first day of my test driving I couldn't tell anything was wrong. With the second day test driving the CEL light comes on when I start the car 100% of the time, but the first time when it came on (on my way to work) the CEL went off about 12min into the ride. It then stayed off for the duration of the trip but came back on when I started the car to come home and has been on since then.

Were it not for the CEL I would not suspect that anything were wrong. I revved a little past 2500 a few times and nothing unusual happened. I still haven't tried to go above 3000 yet but it also seems like the engine is working a lot less than it used to and I can't hardly find an opportunity to rev it up to let alone over 3000rpm.

I remember before it seemed like I couldn't do anything other than coast without revving over 2000rpm, and now the car seems to be effortlessly gliding uphill while only turning 1600-1900rpm (acceleration seems okay so it doesn't seem like the transmission is just upshifting early).

JuLink

iTrader: (1)

First off let me say how much I appreciate everybody's time and help here.

I pulled the code and it's 28. There did not appear to be any other codes stored.

According to the listing I found, that's Main O2S which I imagine refers to the main O2 sensor. Another thread indicates that the listing I got that from might be at least somewhat inaccurate though. Given the impetus for the problem and the experiences of others I was expecting 31 or 32.

So does this mean that it's likely that it's a different sensor that I would need to replace? (or clean if possible?) Are there any tests that I can perform to confirm that this other sensor is/isn't malfunctioning?

Duds

That would actually make sense because when an 02 sensor goes you will usually get a cel but not all the time, lit one day gone for a few and so on. You may have gotten lucky with the afm and it was just still wet from the cleaner at first.

JuLink

iTrader: (1)

Okay, so where is this main O2 sensor that the code is referring to? I searched all of the threads for "O2 sensor" and got a lot of interesting info but the only info I got for locating it/them was that there is at least one hooked up near/on the exhaust and one that's somewhere close to the radiator? It also seems like there are three total - two pre-cat and one post-cat. I have seen a few pictures of the sensor itself and I took a quick look around my engine bay last night and didn't notice anything that seemed to be it.

sebastian0

I would guess the main one is the first one in the exhaust system, but I'm not sure.