96 850T uncommanded Revving MVSolved bad ECT

socalover · Post by **socalover** » 07 Apr 2015, 17:09

So yesterday on my way home I was at a light and the car started revving up from 1000 rpm to a little over 1500 rpm. Had to push hard on the brake to make sure I didn't hit the car in front of me.

Today at lunch I was going about 30 mph and it revved up again 3 times while I was driving and this time about 2000 rpm. I put the car in neutral when I come to a light so I don't run over anyone.

When I started the car after work I usually let it warm up for about 2 minutes. During this time it revved up to over 2000 rpm when it usually warms up to maybe 1500 and then drops to 1000 and stays steady until I drive.

This is pretty scary stuff.

Thanks in advance for your input.

Post by **erikv11** » 07 Apr 2015, 19:26

This sounds like the throttle cable and/or throttle linkage is sticking. Look that over carefully, for sure clean out the throttle body with carb cleaner.

Post by **scot850** » 07 Apr 2015, 19:35

Obvious stuff, like have you checked the floor mat isn't fouling the gas peddle?

As Erik says on the cable/throttle body as starters. Check the cable isn't frayed.

Neil.

socalover · Post by **socalover** » 10 Apr 2015, 13:06

It ended up being the Mass Air Flow. After posting here I went to leave work and while sitting with it in park it revved to 4000 rpm several times with in about 5 mins. I had it towed to a friends shop. It's fixed, codes are cleared. YAY!!!!

So I'm due for a smog and since this work just got done. How many miles should I drive it before I take it in? I'm guessing the computer needs to reset.

Post by **abscate** » 10 Apr 2015, 13:13

200 miles or so typically for the emissions monitors to all go ready.

Couple of other active threads on this at moment, too.

Post by **misha** » 10 Apr 2015, 13:20

Bad Maf will not rev the engine up to 4k rpm

When it goes bad...the idle fluctuates up & down from 600-700 rpm to 1000-1200 rpm and that is followed with black smoke from the exhaust and unburned fuel smell.Fuel consumption goes up to the sky.

That guy in the shop ripped you off for a new Maf,i can bet on it.
Your symptoms are leading to a bad iac(idle control valve)or,just like somebody mentioned in previous posts....to a mechanical problem of throttle cable.

Almost all of us had a bad Maf once.If just one of us can confirm that he had symptoms like you with a bad Maf....i will eat it along with air box and filter in it.

Post by **cn90** » 10 Apr 2015, 20:50

1+,

The accelerator cable is about $40 or so. Get it from Volvo.
My cable was replaced at 140K (seized).

Take the opportunity to clean the throttle too.

kaneelschep · Post by **kaneelschep** » 11 Apr 2015, 10:15

I had exactly the same with my t5. its very freaky and actually quite dangerous.
It just started to rev out of the blue for a few seconds to almost a minute.
It started with low revs but in a few weeks it went higher and higher. Braking or letting the clutch stop it works, but it feel terrible.
I searched everywhere on the internet and found someone talking about this exact problem.
he said a faulty temperature sensor next to the thermostate does this.
The warehouse guy at my local Volvo dealer confirmed he knew about the problem.
I replaced it and the problem was immediately gone and has not resurfaced in the 15000km I drove since then.

The parts guy said the sensor is very sensitive to problems. Even when you forget to use the washer on it, it will go in to deep and give more problems.

socalover · Post by **socalover** » 12 Apr 2015, 17:38

Well... It did it again this morning. Revved up to 3000 rpm while in park. So when my friend opens shop tomorrow he will be hearing from me. As far as the maf it hasn't been replaced since I've owned the car for 5 yrs and the code pointed to it. Ugh

socalover · Post by **socalover** » 12 Apr 2015, 18:12

How about the Baro sensor?