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1996 850 Base NA Severe Misfire after smooth running

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

zupta82
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1996 850 Base NA Severe Misfire after smooth running

Post by zupta82 » Sun Feb 24, 2019 6:50 pm

Hello everyone, I hope this is not a long and annoying explanation, I am absolutely lost and don't know what to do!!

I have a 1996 850 Base Model with a 2.4 liter. In the past two weeks I have been trying to chase down a severe misfire with no check engine light. I have replaced the plugs wires cap and rotor, checked compression (180psi all cylinders), checked fuel pressure(45 psi with relay terminal jumped I then pinched the return line and pressure wasn't building so I replaced pump). I also blew into the pressure regulator and no air was going thru. I manually checked the following sensors and power stage coil with a voltmeter according to the chilton manual (coolant,maf,iac,tps,crank).
I did however notice that when testing for the correct voltages on one of the "cam sensor" terminals harness it was reading battery voltage instead of 5V. At this point I was thinking it may be the ecm or the path within the harness to the cam sensor.

I also tried a good used ignition coil that I had laying around and both o2 sensors are only several months old. I also checked for grounds and B+ voltage at the ecm.

Lastly, I was going to check for a plugged converter with the use of a vacuum gauge but can't get even get it to idle and I noticed that the plugs are wet with gas

I would greatly appreciate some help!!



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Re: Severe Misfire

Post by abscate » Sun Feb 24, 2019 7:25 pm

Confirm plugwire order. Easy To mess up And some references have them wrong


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Re: Severe Misfire

Post by zupta82 » Sun Feb 24, 2019 7:32 pm

Oh by the way I forgot to mention when I checked for spark on some of the cylinders I couldn't hear the crackling sound when I lifted them off the boots.



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Re: Severe Misfire

Post by zupta82 » Sun Feb 24, 2019 7:37 pm

I will check the firing order of the wires, I did remember immediately after replacing the plugs, cap and wires the engine did seem to run smooth for about 3 minutes and then began to misfire again.



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Re: Severe Misfire

Post by erikv11 » Sun Feb 24, 2019 10:16 pm

Are you sure the cam seal is not blown out under the distributor cap, sending in moisture and oil?


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Re: Severe Misfire

Post by RickHaleParker » Sun Feb 24, 2019 10:58 pm

Turn off the lights and watch for arcing, specially around the coil. If your doing this outside wait until night fall. Sometimes a boot does not seal up correctly.


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Re: Severe Misfire

Post by zupta82 » Tue Feb 26, 2019 8:22 pm

Sorry everybody I haven't replied, I had to take a break because this is driving me crazy.

I went ahead and checked the plug wires for correct order and they are fine and I did not see any arcing in the dark.

Also, I was able to start the engine and take a vacuum reading and I am getting about 15 inches, I changed the cam sensor with a good used one. I did notice that the rpm's are not moving during the misfire and the lights are slightly dimming. Also, when disconnecting and connecting the negative battery in between testing I did notice that there were no sparks jumping from the battery to the cables



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Re: Severe Misfire

Post by abscate » Tue Feb 26, 2019 11:41 pm

Don’t disconnect the battery while running. This can cause a large range of expensive problems.

What kind of parts did you use for replacements? We recommend OEM only here


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Re: Severe Misfire

Post by zupta82 » Wed Feb 27, 2019 4:21 am

I did not disconnect battery while running. There was times when I had to disconnect the battery when testing some sensors and I had to remove the battery from the car to charge it. I also have been using oem parts from the junkyard



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Re: Severe Misfire

Post by abscate » Wed Feb 27, 2019 4:35 am

Hmmm...tough one. Can you pull out a plug, ground the thread part with wire to the block, Andy crank looking for a bright blue spark? That will tell you about the health of the ignition system.


1 SWMBO for 30 years
2 Volvos
3 VWs
4 Careers
5 cats/dogs/gears
6 Perfect Ladies in waiting
7 Drivers
8 Boats- with a big pointy metal thing on top

1999 V70 T5M 56 2005 V70 NA M56 VWs BMW

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