Acura MDX SUV Forums banner

1 - 10 of 10 Posts

·
Registered
Joined
·
6 Posts
Discussion Starter #1
Hope someone can throw some guesses at me on this one.

I was driving my 02 MDX with 134K miles on it down the interstate at about 75mph into a 10mph headwind today. after about 30 minutes into the trip, the revs which had been locked in at about 2k rpm, jumped to about 2500 rpm for about 1-2 seconds and went back down... this happened repeatedly every 5-10 seconds or so. I took the next exit (5 miles later) and high tailed it back home for fear of boiling the AT fluid during the 3 hour drive ahead. This issue was not apparent when I drove in D4 on the way back home.

Cruise control was on (also got the same behavior with cruise off)
No hills
was not accelerating, passing, cornering
Trans flush was performed under 1 year ago (5K miles ago)
MPG was reading normal range
not towing, not carrying anything heavy
Check engine light is off... but havent tried to pull codes yet.

Also, FWIW, when the slip happened, the rpms didn't slowly build to 2500, they jumped up like I had just stepped on the accelerator and then the revs dropped sharply back down to 2000.

thanks!
 

·
Registered
Joined
·
1,156 Posts
Might just be the torque converter unlocking if you are right on the edge where the computer decides to unlock to maintain speed. Is it doing it even when you are not driving into the wind or at higher or lower speeds?
 

·
Registered
Joined
·
6 Posts
Discussion Starter #4
In that case, it was not close to a high demand scenario as I can routinely accelerate hard enough to get the MPGs down to 10 before it will unlock from 5th and downshift/rev-up.

This issue has also happened even when I am driving at about 60mph with no load/headwind...MPGs were reading something like 25-30 at that time.

Since the inner-workings of an automatic transmission is one of the last areas of the automobile that i am weak on I am at a loss. My instinct tells me that a dirty electrical connection could cause this issue but that *should* be causing a fault and a CEL or other error light to turn on.
 

·
Registered
Joined
·
348 Posts
Very hard to diagnose but to me at least, the good news is that it is not slipping out of gear completely but just to a higher rev (in gear I assume) and then back down. Do you think it is going into 4th gear when the "slip" happens? Hopefully this is not the tranny going but either an electronic issue or TC issue. Either is better than the tranny going south...Good luck with finding the answer!
Regards--Matt
 

·
Registered
Joined
·
6 Posts
Discussion Starter #6
I agree. I kind of have my hopes up about it not being a complete rebuild... although I suppose at 134K miles, its about due for one. I know these transmissions are not bullet-proof by a longshot.

It is not hitting 4th gear... at 75mph, 4th gear causes the motor to spin at about 3000rpm and when the rpm jump was happening, it was only going up to about 2500 rpm.

Thanks for the input Matt.
 

·
Registered
Joined
·
6 Posts
Discussion Starter #7
So I took it in to a local trans repair shop. Had the guy drive it with me in it while his scan tool was connected. No codes stored or pending. We logged about 40 miles without incident... of course.

He was very confident that the issue was not with the transmission. He said that the issue I describe is most likely a "command" scenario where the ECM tells the AT that a high demand condition exists but since it's caused by a faulty sensor or connection that it goes away as quick as it starts so it keeps cycling back and forth on the TC.

He noticed that the intake manifold pressure voltage and the MAF voltage delta was more than what he was used to seeing so the issue may be with either one of those or it could be any one of intake temp, throttle position, EGR (though probably not in this case) sensors acting 'twitchy'.

Since we had some time to chat I asked what he he has been seeing for transmissions by the way of the oddessy, Pilot and the MDX. He said that Honda certainly is "very upset" about this consistent weakness in their product lines. His shop has been seeing a fairly steady flow of these transmissions in for work. He said that the only reasonable way to rectify a failing trans is to replace it as the updates to the failed components cause a cascading effect of all related components in the transmission... in the end it would cost as much or more than just getting a different trans. He told me that they recently did a Pilot trans replacement for about $2800. Odessey trans for around $2500 or so. They use aftermarket OE transmissions as they have much better warranties than the Genuine Honda Transmissions. Interesting.

Back to the point. Looks like I will have to drive around with my OBDII scan tool connected so I can find the offending signal in the system when it happens again. I guess that's better than having to ride the VTX in the winter :)
 

·
Registered
Joined
·
6 Posts
Discussion Starter #8
Drove for about a mile in the freeweay and noticed that the tc didnt lock up in fifth gear at all. After about half a mile the cel lit up. Got the code and its the dreaded P0740. Ugh. :(
 

·
Registered
Joined
·
6 Posts
Discussion Starter #9
Trans shop performed checks on line pressures and solenoids and whatnot and determined the issue is internal to the trans so they are going to replace it. Total expected bill $3885.

140K on the clock.

A little note for everyone's enjoyment: I paid the balance of the loan off (a rather large sum of coin) the day before the CEL lit up. Point and laugh if you like.

Too bad everything else on this thing is still mint. Especially the motor. Otherwise, I would dump it back on the dealer in trade... but I love this SUV.

Wish my stock options weren't all underwater.
 

·
Registered
Joined
·
6 Posts
I am having a transmission slip problem. Sometimes when I first put it into D5, I press on the gas, and nothing happens. Back to Park and D5 again, all is well. That happened 5 or 6 times over the last few months. So I am driving back from Annapolis to Chicago, and on the open highway, the transmission slips out of gear. It is as if I am in neutral. The engine revs but nothing happens.

I came close to having to pull off the road. It did it like 4 times in an hour. And then I discovered this. If I pull the gear selector a little towards D4, everything is fine. And, from then on, each time I put it into D5, I pulled it a little more towards D4 so that it was more in the middle of D5. Since then, not a single problem.

Could it just be that it is just that when I put it into D5 that it is not fully engaging? Like there is just a mechanical adjustment that could fix everything? For now, I am satisfied to just keep driving the way I have been, putting it "all the way" into gear.

2004 MDX, 178,000 miles.
 
1 - 10 of 10 Posts
Top