96 850T uncommanded Revving MVSolved bad ECT

socalover · Post by **socalover** » 14 Apr 2015, 14:21

He sprayed cleaner under the area the black L shaped rubber hose that's attached to the metal tube.

Post by **misha** » 14 Apr 2015, 15:22

In injector area?
Could be that you have bad injector seal(s) or fpr vacuum line.That L shaped metal pipe which goes into rubber hose is fuel return line from fpr.Check vacuum line at fpr which goes to vacuum tree.

socalover · Post by **socalover** » 14 Apr 2015, 22:29

Would that cause the revving issue or just something else that needs fixed?

I've started the car 3 times since the vacuum lines were replaced a couple of days ago and it hasn't revved up to 3000 rpm like it did before. I haven't driven it around yet but I will on Thursday.

On Friday I'll have the 3 items on the list taken care of.

socalover · Post by **socalover** » 29 Jun 2015, 17:26

Well I'm back to the same issue.

Vacuum lines replaced: drove fine for 2 months then it started acting up again.

New IAC installed: mine was the original so the resistors were bad. Started to drive home and about 2 miles down the road it started acting up again. Accelerating up to 2000 rpms while driving and sitting at a light. I did happen to look at my temp gauge and it was fluctuating up and down between cold and normal.

I asked the shop to look at the sensor under the thermostat as suggested in here.

They test drove it for at least 10 miles after the IAC was installed with no issues so they are scratching their heads.

Post by **misha** » 29 Jun 2015, 18:40

socalover wrote:...I did happen to look at my temp gauge and it was fluctuating up and down between cold and normal.

That indicates bad ect sensor.

Do not install anything but oem.It's made by Valeo.Only aftemarket ect which will work on these cars is Vernet.
While you're in that area...replace thermostat too.87 for turbo and 90-92 for non turbo.
Before replacing ect,check it's connector for corrosion.
Iac valves NEVER fail on these cars.They can become clogged from oil and gunk and car can idle higher or lose idle completelly,but good cleaning with solvents or carb cleaner makes them to work like new again.

socalover · Post by **socalover** » 29 Jun 2015, 19:52

Geez I am starting to think my car hates me. When they test drove it was it didn't act up after changing the IAC. I don't like looking like I'm crazy. Ha ha ha!!! In my defense I never noticed the temp gauge issue until today.

Sommerfeldt · Post by **Sommerfeldt** » 30 Jun 2015, 06:56

Just chiming in here in the "don't overanalyze" spirit... The servo motor for the cruise control went bad on my old T5-R. If that thing plays up or has electrical issues, it'll pull on your throttle. That said, you'll feel the pedal disappearing on you when it revs up if that servo motor is the issue.

Good luck - I see you've already got a bunch of guys more knowledgeable than me helping out.

- S

socalover · Post by **socalover** » 30 Jun 2015, 11:20

I thought the cruise control but mine was disconnected before I got the car.

socalover · Post by **socalover** » 01 Jul 2015, 15:37

So just got my car back and it all seems good. He said when they checked the ect it was marginal at failing but there was some corrosion that they cleaned up before putting the one in. Also the mechanic said he never realized how sensitive they are on Volvos.

Post by **abscate** » 02 Jul 2015, 02:08

They aren't sensitive and for every good diagnosis of a failed ECU we have about 100 bad diagnoses.

Connections and cleaning are usually the extent of the problems and even those are very rare.

Hope it fixed it!!

late edit - poster of above must have been smoking dope when he wrote this - please ignore

ECTs are sensitive on these cars
ECUs give very little trouble

96 850T uncommanded Revving MVSolved bad ECT

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