Volvo 850 O2 sensor troubles

Krisemann · Post by **Krisemann** » 30 Dec 2019, 06:45

Hello! I've recently replaced my O2 sensor as my old one failed on me, and the new one works... To some extent. The car runs well for the first 30 seconds. After that the new O2 sensor kicks in, and it suddenly struggles to keep its idle, sometimes it outright dies. When I drive, it has a hard time accelerating; I have to floor it in order to get up regular hills, for instance. However, if I let the car idle for 10-15 minutes before driving, the car runs perfectly.

The sensor I've installed is a Ridex O2 sensor, from here: https://m.autodoc.co.no/ridex/13629202

I've tried resetting the ECU and running it through tests which users have posted on here (fuse, discharging wires, holding brakes for 2 minutes, leaving the battery unplugged overnight) and other boards, but nothing has helped. I've also tried WD-40 on the contacts. I did get an error code A2-512 once (rich fuel mix), but I haven't been able to replicate this error - usually I only get 111, so no errors.

My car is a 1994 Volvo 850, 2.5L 144hp 10v (no MAF, Titania sensor). Any help would be greatly appreciated

Post by **RickHaleParker** » 30 Dec 2019, 13:28

Krisemann wrote: ↑30 Dec 2019, 06:45 However, if I let the car idle for 10-15 minutes before driving, the car runs perfectly.

In other words: No power when cold.
Check for intake manifold leaks when the engine is cold.
A defective Coolant Temperature Sensor could throw off the Air/Fuel mixture.

Krisemann · Post by **Krisemann** » 30 Dec 2019, 14:35

Thank you. Will check out those parts ASAP.

EDIT: Note that the engine runs fine the first 30 secs after startup (no matter hot or cold) - so I doubt it's the manifold. I'll look at the temperature sensor, though.

Post by **RickHaleParker** » 30 Dec 2019, 14:48

Krisemann wrote: ↑30 Dec 2019, 14:35 EDIT: Note that the engine runs fine the first 30 secs after startup (no matter hot or cold) - so I doubt it's the manifold. I'll look at the temperature sensor, though.

Engines start on a rich Air/fuel mixture then lean out.

Post by **misha** » 30 Dec 2019, 15:15

The main problem you have is that brand of sensor...RIDEX.

These cars runs ONLY on OE & Oem Bosch sensors.
Aftermarket sensors are useless in Volvos.
The car would probably run better with old o2 sensor than with new aftermarket one.

Also....when you buy a replacement sensor...it MUST have the exact same Bosch part number like old one.

Krisemann · Post by **Krisemann** » 30 Dec 2019, 17:22

Hmm, that's odd. I'd have to test the old sensor again, see if I get the same error.

Post by **misha** » 30 Dec 2019, 17:32

There is nothing odd.
They are manufactured from cheap materials,not calibrated properly to satisfy demands of the car's management like OE and OEM parts/brands.

Krisemann · Post by **Krisemann** » 30 Dec 2019, 17:39

Well looking into it really doesn't make it easier - check this thread out: viewtopic.php?t=45356

I don't think the sensor is the problem, but I'll test the old one tomorrow just to be sure (I replaced it because I'd get sudden power losses with thick black smoke and backfiring in surges lasting 5-10 seconds).

Post by **misha** » 30 Dec 2019, 18:42

What brand was the old sensor and what part number is stamped on it?
It should be Bosch as far as i know.
The only differrence is the type...Titania vs.Zirconia.
Titania sensors have different values....resistance...as far as i remember...
as opposite to Zirconia ones which uses voltage values.
10v cars doesn't have Maf sensor...they have IAT (intake air temperature)sensor at air filter housing.
Don't remember if 10v cars have MAP sensor...if it have...check it's vacuum line.

Krisemann · Post by **Krisemann** » 31 Dec 2019, 03:46

Yeah, it's Titania (10v), I wrote that in OP. MAP sensor seems to vary on where it was sold new rather than model, so I'd have to check. The IAT seems to be fine.