Hello. I know there have been many posts about misifres before but mine is just slightly different so I thought I'd get some input.

98 s70 turbo 115k miles

when i bought the car the seller told me that the CEL had come on before but then went away and that the car never ran different. The car ran fine so I bought it anyways.

I got an obdII scanner and read the stored code of

p0305 Cylinder 5 misfire. (it has 2 of these same codes stored)

I cleared all codes.

a few days later after a good run on the freeway (really the only time I have driven more than 2 minutes in it) the car starts misifring. Not bad, but noticable. NO CEL was displayed.


where should I start?


also someone please tell me which cylinder is 5

 

Ok this goes in the s70 section not v70.

 

moved it for you.

 

SORRY V70 I got confused.myfirstnewvolvo sorry to everyone I offended


Spark plug wires look good and say 48 05, 49 05, and the coil wire says 50 05

Coil looks orig.

Oil is ugly dirty. What oil is best on this car

THANKS

 

Anyone please help

Tech? I know your just itching to help me.

Thanks!

 

Have you pulled the dist. cap and inspected?
Maybe a bad injector.
Try running a good fuel injector cleaner through the system.

Have you made sure the spark plug well isn't full of oil or water?

Oh and sorry #5 cylinder is on the back side of the engine L/s side of car.

All Volvo engines go from #1 by the timing belt to #5/6 at the back of the engine.

 

no fuel or oil in the spark plug wells. A little old crusty oil residue in each right around the spark plug seat but nothing obviously wrong.

Took out #5 spark plug: looks normal

What is a good fuel injector cleaner? Techron? Chemtool?

 

I always use Techron.

 

Ok I put in techron fuel injector cleaner. How many miles before I can say this techron has had a chance to do its job?

I changed oil

I checked cap, rotor, plugs, wires, wires harness to fuel injectors all look newish and good

ran the car today and it was fine at first, later the CEL came on: misfire #4 cyl. reset CEL and drove home gently with a nice misfire. the car has been in the garage fora few hours and now runs fine. I know if I dirve it about 20 mins the misfire will likely come back


first it was misfire #5, now its #4, where do go from here?

 

Are the wires OEM?
If so how old are they? They will have the date stamped on them.

 

Spark plug wires look good and all of them say either 48 05, 49 05, and the coil wire says 50 05

the wires are OEM. they look newish. I guess the above #s mean that the wires are from 05? is that really old enough to cause a prob? Can i check them for resistance to see if they are in spec or is it not that simple?

the coil looks orig. I saw a post on volvo-forums where the guy said he ended up changing the coil and plugs to solve this problem.

I dont mind replacing all these parts, but I would hate to just wildly throw money at the car since dealer parts are not cheap

So are these volvos just overly senstitve to wear on ign parts? I dont get it: on an old volvo 240 or say a chevy, the ign. parts could be 5X as old an worn and the thing would still run great.


Thanks TECH!!

 

You asked about the wires: I think the wires are by Bougicord and the plugs as well as the coil bosch.

I think these are the OEM brands right? sorry my first newer volvo.

Thanks.

 

All Ign parts are OEM/ bosch.

Coil looks orig, plug wires may be 2 years old.

engine is b5254t 20V 2.43L

Thanks

 

Yes they OEM parts.

Most aren't that sensitive.
I am starting to hear problems of coils coming up lately.

 

so do you reccomend spending the several hunderd $ trying new coil (maybe plugs cap, rotor, wires as well) or is there anything else that I should check on like checking compression or leak down?

I havent driven but 40 miles since the injector cleaner,im sure thats notenough time for it do its job (how long) should I run it for to give it a fiar try?


Thanks thanks thanks.

 

Ill probably just start with the coil but can you get me the book specs for resistance on the coil as well as the plug wires (98 v70 turbo)

thanks

 

1 and 15 on the wiring 0.5 Ohm +- 10% or 0.5-1.5 Ohm bepending the which engine (coil)

Wires
Cyl 1 4.2 cyl 2 4.0 cyl 3 3.3 cyl 4 2.9 Cyl 5 2.3

You could also do a compression test as well.

 

which pin is "15" on the coil.

on the coil there are the two screw post terminals directly on top of the actual coil (red and blue wire) and there are terminals 1-4 on the conntactor plug attached to the bracket.

 

Sorry not sure don't have the diagram at home.
Thats what my Cheater book said.

 

Ok I did a compression check with all the plugs out (thats the correct way, right?) and all cylinders read 180-190.

To recap I only have the misfire after the car has warmed up or driven to a certain point. When I first start the car it runs great (very powerful) until maybe 20 minutes of driving the missing will begin?

afte the missing starts if I shut the car off and start it back up right away it will still miss even in neutral at idle. If I wait 5-10 minutes before restarting the car, it will not miss at idle in neutral but wil miss at idle gear (load). If i really let the car sit for an hour or more the missing is gone until another 20 minutes of driving has been reached.

I usually dont get a CEL unless I have been driving at high speed/ high acceleration when the missing starts. The only codes have seen are misfire cyl 5 (twice ) and once it said misfire # 3

I would like to think that my decent, even compression #s mean that the enigine internals are fine.

Given that the misfire codes have not been just one cylinder, I want to assume that the bad part is something that deals with all cylinders (not just one bad plug wire or one bad plug)????

Should I do another compression test when the engine is missing?

Should I just buy a coil and try it?


>>>>>>>> Thanks for all your patience in helping me track down the real problem rather than throw money at the car.