C70 S70 V70: aw50-42le auto gearbox and rpm

[nettiwolfi]

Hi

I'm new to the forum, and spent now days looking through it but couldn't find the answer.

I have a Jan 2000 volvo c70 2.4turbo with the aw50-42le aut gearbox. What happened is when I pulled up today to refill, I noticed the rpm rhythmically moving between 900 and 1100, and I could also feel a really-really slight engage-disengage type of thing in my backside, although the car didn't actually move back and forth. The gearstick was also a bit harder to move than usual. I then got home, and it still did it. I stopped the engine, and about a few hours later went to see if it is still happening, but at a cold start it was all fine, rpm stable at around 1000. Then went on to test drive, gear changes as smooth as before, no jumping between gears or anything. Then stopped again, and noticed when breaking from 70mph rpm goes down to around 800ish, whereas if just step off the gas and let the car roll at 70mph rpm is around 1500. Then when I came to a stop, still in D, it was around 800rpm, and then also in N it remained at the same rpm. Then turned the engine off, 5 minutes later restarted, and the rpm jumped from 800 to around 1500 and back to 4-500, it felt like it was going to stall. Put it in D, started driving, drove another 10 miles, nailed it, did emergency braking, engine off then on again, could not reproduce the problem, although the rpm drops with breaking, goes below 1000.

Transmission fluid looks light red(ish), doesn't smell burnt at all.

Question 1: is it normal for the rpm to drop below 1000 when braking? Also, it feels like it is dragged down rather than normal fall when foot off the gas.

Question 2: is it possible for the gearbox not to be disengaged fully when in P? I checked the gear selector cable and it appears to be ok.

Would appreciate any help or suggestion, idea.

Thanks a lot

[fungus]

It might not be the 'box....
With my V40 auto, when in D warm and stationary the revs would rise to 1100ish and fall to 700, this would cause the car engage the TC and move forward if I didn't have my foot hard on the brake pedal.
I cleaned the idle control valve and throttle body and idle control was good again and hence not engaging the TC.
The cleaning task took one hour, my engine was the same as yours with one less cylinder!



Sorry havn't answered your Q's though...

[Luxobarge]

Originally Posted by nettiwolfi

whereas if just step off the gas

I'm confused... I assume it has a gas conversion, does it do this when on gas or on petrol, or both???

[fungus]

Originally Posted by nettiwolfi
whereas if just step off the gas.

Methinks foot of the accelerator, i.e over-run. I blame American-English for the confusion!

[nettiwolfi]

thanks for the messages guys, been to have the fault codes read out, there was only one, the intake air flow mass sensor said it was "out of range" (whatever it means), which apparently could cause uneven idle or stall like effects.

I'm not 100% sure that was what happened, but will give it a go, it needs to be replaced anyway, so I'll get it done next week. I'll keep everyone posted.

btw: foot off the gas = foot off the accelerator (confusing, sorry sorry sorry

[Luxobarge]

Right - MAF fault then.

You could try cleaning it - this often doesn't last for ever but might help confirm diagnosis, they're pretty expensive if you get a proper Bosch one - and you should!

Yeah - I get confused by the use of the American language....

Cheers,

[nettiwolfi]

it's running perfectly ok now, I'm now thinking of not touching it until it actually becomes a regular thing