Hello everyone. I have an issue that I need some help diagnosing. I purchased my '96 850 GLT about a month ago and two days after I bought it from the guy the check engine light came on. He, of course, won't answer my calls nor respond to my texts. I presume he had just reset the light prior to selling it knowing that there was something wrong and now he has vanished. He told us that he had just replaced plugs, wires, distributor, belts (timing & serpentine) and not too long ago replaced the fuel filter & fuel pump.

So the sequence of symptoms and codes that I have gotten. At first, the codes were P0300, 302, 303, 304 & 305. I reset them and the CEL stayed off for a day and came back on the next day. This time it showed P0335, 0300, 302, 303, 304 & 305. Up to this point, I could not feel any engine missing...it was idling and running very smoothly at all rpm's. I have since begun to feel a jerking from the engine every once in a while and it is always between 2000 & 2500 rpm's. It is usually either during acceleration in first/second gear or while driving at 2500 rpm's. During full throttle, it does not do it and when the rpm's are above 2500 it does not do it then either.

I read on here that a guy had a similar experience and replacing the Crank Sensor solved the problem, so I ordered and replaced the crank sensor. When I was replacing the sensor, I went ahead and checked my plugs to see if any of them were fouling out and noticed that a couple of them were not gaped properly, so I went ahead and gaped them to the proper .028 (they are aftermarket...not Volvo plugs). After putting everything back together, I started the car and let it idle for a bit and noticed that it was still misfiring a bit...rpm's going down and back up every once in a while; like a strain was being put on the engine and released. I test drove it for about 1.5 miles and during that time, it wasn't missing or jerking as bad as it was before but the CEL came back on after 1.5 miles. I have not yet checked what the codes are.

This morning, on the way to work, it only misfired and did the jerking 3 times and every time was as I described earlier, around 2500 rpm's. I spoke with Robert on here last week before replacing my crank sensor and he mentioned fuel pressure. I have not replaced the filter or pump yet. Is there any way I can test the fuel pressure without just replacing them? I really don't want to just start replacing things if it's not the issue.

Any guidance would be great.

Thank you

 

Could possibly be a knock sensor since your getting the misfire on all cylinders...

 

If it were the knock sensor, would it not throw a code for that as well? Cylinder 1 has actually not ever shown a misfire code...which is also unusual about this situation. How would I test the knock sensor?

Thank you

 

There is a schrader valve on the end of the fuel rail. You can probably get a loaner fuel pressure gauge from at auto parts store. I believe pressure should be around 43 psi at idle, but do a search and double check that

 

Did Robert link you this video?

 

Thank you guys. I will check the fuel pressure off of the Schrader valve and go from there.

My dad told me that it might be the wires arching off of the head cover that is over the wires. Have any of you seen this happening? I wonder if the guy who replaced the wires didn't install everything properly and there is a missing plastic harness that holds the wires down at the driver's side of the motor.

Robert, thank you for sharing the video on here. I appreciate it. You were actually the one who told me to check the fuel pressure

 

I dont think it would arc to the plastic cover

 

It would be much more likely that the wires would arc to the head then to the plastic cover unless it's really oily/dirty or had a lot of moisture trapped under it.
You can always pull the plastic cover off and use a spray bottle to mist the wires with water and look for arching.

 

Well guys. Here is what has happened. I have since cleaned and replaced ground cables and that helped some. The last tank of gas I added injector cleaner and it is now running with no hickups since. I'm not sure if the combination of not being grounded (the ground wires were extremely tarnished and the one on the passenger side was ripped down to just a couple copper threads) and using the injector cleaner, but I'm pleased with how it is running.

Thank you all for your advice.