Stop Motion

Hi,

Here's what's happening to my tranny:

Especially at low speeds/rpm's, the transmission seems to be slipping - BUT - more than that, occassionally it seems to be hunting, like it's trying to shift and getting caught between gears.

It definitely seems to slip at times, and other times it seems as though it is trying to shift - the engine rpm's drop regardless of pedal position, and the auto tranny seems to disengage. This happens for a second or two, then it locks into gear again (in the appropriate gear where it usually was).

So there are two things happening - the gear-hunting (where it seems to be disengaging and dropping the throttle), and general slipping, where the engine revs up without the resistance of the tranny and I have loss of acceleration.

It doesn't seem to be happening as much at the higher speeds. I checked the diagnostic codes - wound up getting a 14 for the ECU (Idle Air Control Valve), and a 15 for the TCM - the MSS.

Where might the Mainshaft Speed Sensor be located? The repair manuals for this year Accord have been lost/stolen at my library, and another copy is days away - I am borrowing this car from some friends, and would like to get it back into good running shape for them (and for me). I haven't yet disassembled the TCM to see if it's got any blown resistors/diodes, etc., but it doesn't seem to have the typical problems associated with a hosed TCM (2nd&4th gear only, stuck in 3rd, etc.), but I haven't ruled that out yet. I'd like to take the diagnostic code at face value, first, and check the MSS, then go from there. Transmission Fluid level/color are fine, BTW.

Thank you!

Schmitey

On my 96 EX (could be completely different, really not sure) the mainshaft sensor is a magnetic sensor on the bottomside of the crankshaft BEHIND BOTH the timing belt cover and the balance shaft sprocket. There's gotta be a way you can test it though withough going through all the hastle of taking things apart. If I remember correctly the wires snaked up the firewall side of the timing belt cover, start there. Good luck man! Hate to say it but that's why I got a stick, I just completely dismantled my transmission so I could go in reverse again...wouldn't even try on an auto.

You're not talking about the vehicle speed sensor are you? That's on the transmission itself, not to be mistaken with the backup switch. Since you're talking about erratic shifting not engine misfire that sounds more likely. Could be different lingo between the years.

Also from my understanding the idle air control valve shouldn't have anything to do with your transmission, only like the name says...how the engine idles. Now that you've recorded the codes have you tried resetting the ECU?

Alright my third and final edition! Do a search for the Helms repair manual (the end all be all DEALER repair manual). I was lucky enough to find the Adobe Acrobat files online and print off what I needed. You might also try Ebay.

And don't give up on the library. Every library I've ever been to has reference (non-removable) repair manuals IN ADDITION TO the small Haynes that you can check out. Huge ugly Mitchell catalogues for anything that burns gas and has moving parts. Worse case scenario buy one for $20 at an Advanced Autoparts or something similar (or when no-ones looking cut it open and play dumb to read what you need).


Modified by Schmitey at 12:35 AM 10/15/2004

Stop Motion

Thanks for your reply.

Actually, as I drove the car tonight, I came to the conclusion that I am experiencing two discreet problems, but that they occassionally occur at the same time - one is the acceleration dropping off in spite of the pedal being depressed, and the other is the random decoupling/half-shifting that's occuring in the transmission. Together, they give the ride an unwelcome gently-lurching quality. I wonder if the transmission isn't the root - perhaps it's sending a signal to the engine to decelerate so it can switch gears, which it sometimes does and sometimes doesn't follow through with...

It's not my car, unfortunately. I am interested in buying it from our friends, though - and I do usually prefer manual trannies (though changing clutches, like the one I'm working on in my '92 Cherokee, is a nightmare). The transmission in my '87 Toyota van has over 205k miles on it, has (sorry to say) NEVER had its fluid changed, and still runs like a freakin' champ. I am going to change the fluid this weekend, though.

I may try to reset the ECU and the TCM. I'll search for those procedures on the board. Still, I think I need to give the MSS some attention, and at least check the wires and connections. This car has 190k miles on it, so it wouldn't surprise me if this has broken or worked loose.

Schmitey

Shoot, we might as well by PM'ing seeing as how we're both on but you're a trial member...

You seriously want to buy this car, friend or not I'd be careful! This is really becoming out of my league, but definitely check your connections, relays, fuses, etc. I suck at electrical stuff.

Check the transmission mounts too, I had a family car do some weird stuff to me due to a cracked mount. I don't know how but it affected the shifting. Then again it was a Ford!

As far as the 205k miles without the fluid changed... Not that I would suggest that but I've had mechanics tell me that the grit in your fluid in some cases helps it to grip, and after changing your fluid it may start to slip. I'm not a mechanic but if it runs now don't fix what's not broken. I've gotten myself into more trouble trying to do extreme preventative maintenance (replacing perfectly good seals etc).

And to be reassuring Jeeps are a pain in the *** to work on from what I hear. You got the old inline style?

Stop Motion

Hi,

Now you've got me having second thoughts about messing with the fluid on my Toyota Van's transmission. I could always keep the old fluid, just in case, if I did decide to change it...

I put the Honda in neutral, and rev'd it - when I pressed the accelerator down a medium amount, it would rev up to 2400 rpm, and immediately cut out, and the revs dropped to 1100 - it would cycle like this again and again when I held the pedal down. When I really "stepped on it", it would zoom up to ~5000rpm without the fuel/revs cutting out - I'm thinking that this is related to a faulty signal from either the TCM or perhaps the MSS, since it seems to be trying to prepare the engine to shift, by cutting out the accelerator/gas. I will try to find the Mainshaft Speed Sensor tomorrow when there's more light out. I found the 1992 Accord Factory Service Manual for download on http://www.honda.co.uk - they seem to call the MSS the NMSS... it would make sense that the sensor might be the problem - I'll start there, and if that doesn't work, move on to the TCM.

Yeah, 4.0l inline 6 on my Jeep...'92 Cherokee Laredo - the engine itself isn't too hard to work on, but the tranny's a hog, and all my bolts are siezed up...grrrr.....I don't want to round off any more bolt heads.

hawkmgc

On the AT its not the same as the MT, but I have found that the causes seem to be close to the same. If you say the speed sensor is going then I would start there first. As on my MT it would cause the same issues with idel and accel. and would act goofy even after the ESL lights up.
I changed the Speed Sensor, and now no problems at all.

That is what I would do, but then again I knew that part needed changing.
Good luck

Stop Motion

Okay, I thought I knew where the Mainshaft Speed Sensor was, but when I lifted up the hood, I couldn't find it!

Does anyone know where this thing is in a '92 Accord?

Schmitey

on my 96 with a manual transmission its on the bottom side of the tranny, money says its on the tranny

hawkmgc

its under the air tube on top of the trany right next to the shift link support bolted to the block on the right side.

They love to hide things like this on honda's, more they have to move (or make you think they have to move) to replace it. I replaced mine without removing all the crap that the REPAIR book said you had too. I just used a crows foot wrench 10 mm and took out the two bolts and pulled it up after unclipping the clip from HELLo .....

Took longer to unclip it then it did to unbolt and rebolt the thing.

Happy hunting

Stop Motion

Thanks for your responses. I'll check it out later this pm, after I work on my Jeep some more.

Stop Motion

I'm still having trouble locating this thing. I was able to get the Chilton's manual from my library, but the speed sensor's location is only shown for the 6 litre, which has a different setup - the diagrams for the 4 litre engine don't show the Mainshaft Speed Sensor.

I have a diagram from the factory manual, but it isn't very high resolution, and is sort of a "cut-away", so it's difficult to actually discern its position.

grampsvantruk

The last post I see to this thread is from 2004... it is now 2011 and I have a 1990 Honda Accord with the exact same problems as described in this thread. Are there any pictures out there for where to find the NM and NC speed sensors? I'm having a really tough time finding them... Any advice would be appreciated.

poorman212

A manual helps....search for one online.


http://techauto.awardspace.com/transmission.html

Just about halfway down....you'll find the answer to your question.