Performance Nightmare Ended(Thank God)

meteg · Post by **meteg** » 30 Aug 2009, 09:55

Yes my peformance nightmare with non turbo 95 850 has ended.the knock sensors were the culprit.. even there werent any check engine light on I removed the intake manifold, 4 hrs and installed the new sensors had to do some modification because the older sensors have two plugs on them.. but the new ones didnt instead the new ones came with a common connector at the cable end which has 3 pins. anyway I modified the cables of the old sensors and installed the new ones.. and I cant believe this is the same car..

the power, perfomance everything is amazing..

Post by **Ozark Lee** » 30 Aug 2009, 12:23

I am curious. With no codes what led you to the knock sensors as being bad? Those are odd parts to actually fail.

It is great to hear that your car is back running well again.

...Lee

meteg · Post by **meteg** » 30 Aug 2009, 15:38

Hello Lee,

I know it sounds odd like I said there was no CEL light on however after the replacement the car really runs strong. there was no other possibility left since many components on the car(engine,tranny, other sensors,distributor cap, rotor, plug wires) are new and injectors are cleaned.. so it was kind of a gamble but it has worked.. I was almost going to sell the car if the problem persisted..

I can finally enjoy the car and hope to use it for many more years if there are no accidents or health problems I may have..

Post by **misha** » 30 Aug 2009, 17:47

Congratulations!The risk has paid off!

As Lee said...very strange that the check engine light wasn't on.
Anyway...glad that you solved your problem,enjoy in your car!

Post by **findude** » 31 Aug 2009, 04:54

Regarding the CEL not coming on. I'm having this problem now with my 1996 n/a 850. After querying the OBD II with a scanner, I discovered that the sensors were not ready (the monitor read out is "inc"). I'm trying to get the ECU to "learn" again so that the ECU will recognize the monitors from the sensors, but I haven't managed it yet.

Research suggests a common cause is a shorted sensor, so I'm starting to troubleshoot that.

I even had a Volvo dealer look at the problem: they told me there were no codes (which I already knew) but never told me that the monitors were not ready. From the scanner I borrowed, one has to drill deep into the menus to actually check the monitors. In other words, the lack of an error condition (CEL) is sometimes just an indicator that the monitors associated with the sensors are either not reporting or the ECU is not interpreting the signal. I suppose you could also have a bad CEL light bulb inside the instrument cluster.

Anyway, it's a frustrating problem. Especially when you know the car has a problem (mine is obviously running rich) and the on board diagnostic system can't help.

Post by **Ozark Lee** » 31 Aug 2009, 09:25

There is a specific drive cycle to set the readiness monitors. You may need to pull the battery and start from scratch.

https://www.matthewsvolvosite.com/forums ... 6234#56234

...Lee

Post by **findude** » 31 Aug 2009, 12:09

I've been working on this drive cycle for a couple of weeks now with no luck (after disconnecting/reconnecting the battery). Prior to that the car had run several months when I used the OBD II scanner and got the incomplete test response.

I'm going to give the drive cycle a few more tries, query the OBD II again, then resort to troubleshooting sensors for ground, short, etc.

Meanwhile, I'd appreciate any and all ideas/insights. Thanks.

janwolff79 · Post by **janwolff79** » 19 Jun 2010, 11:54

Hi ive just come accross youre post and wonder what the performance problem was? I have a 1996 volvo 850 2.5 20v and every time i start the car it judder and there is no power sounds like ther is no presure then the power kicks in. is this anything like the problem you had? Knock sensors.
Thanks for reading Jan, Manchester UK.

Post by **JDS60R** » 19 Jun 2010, 12:23

When I see that studder on startup it usually turns out to be a leaking headgasket or a failing coil/plug.