94 850 base NA with sluggish acceleration

ChillyOne · Post by **ChillyOne** » 27 Aug 2013, 20:47

This is my first post so please forgive me if I don't provide enough info. My 94 850 is normally aspirated with 122k miles. Just finished timing belt/water pump/pcv system/rear main seal work. All parts purchased from FCP. Idling, car sounds great but sluggish when accelerating. A-6 diagnostic socket reveals code 4-3-3 for knock sensor. No other codes. Tried erasing but same code returns. I heard that 850's had problems with knock sensors but this is the first time I've run across this. I was wondering if this sounds like a problem consistent with a bad knock sensor or something else causing the code like bad spark plugs. Also, there are 2 sensors. Is there a way to test the sensors? When I change the sensors, I will have to take off the manifold. Should I change the manifold gasket after only 200 miles? I appreciate any feedback and advice.

Thanks,
Bob

jdt1249 · Post by **jdt1249** » 27 Aug 2013, 21:37

did you unplug the knock sensor during the pcv repair?

Post by **jblackburn** » 27 Aug 2013, 22:35

Manifold gasket is fine to reuse.

The knock sensor will definitely cause slow acceleration as the car is backing off ignition timing/advance as far as it can in a "limp" mode.

You'll have to go through the whole process again to get down to the knock sensors, I don't think they can be reached from the bottom. It COULD be a bad or unplugged connection, but just to be on the safe side...get some knock sensors from a junkyard and just change them before you go back in. They're not a common failure item on the 850 to my knowledge...at least I haven't heard of it in the 7 years I've owned one.

Post by **abscate** » 28 Aug 2013, 04:12

Bob..maybe use a torque wrench on the manifolds to make sure you get them both even and tight?

Sorry you have to repeat the manifold drop, but Justin has hit your problem on the head, I think.

ChillyOne · Post by **ChillyOne** » 29 Aug 2013, 09:12

I want to thank all of you for the prompt advice. I'll torque the manifold bolts and reset the diagnostic. If the same code returns, then my fate is set. I'll check the knock sensor connection and replace the sensors if needed. I'm just dreading the fact that I have to remove and then reinstall the manifold each time to test it. Debating about just buying new sensors and replacing them just to save the hassle vs saving the money and spending the time.

Thanks,
Bob