I have an 86 740 gle with a miss. Cleaned all intake components. Replaced all bad vacuum lines. (before all this it had a bad idel and would shut off at stop lights.) Pretty much cleaned everything that had air running thru it. This miss is there under load too. Don't want to just throw parts at it. Idels at around 1k. Starts fine and doesn't have a miss for the first few seconds then the idle levels out and the miss starts. It does not have any issues with accelaration. You step on it she goes. Any thoughts on what to test and how?

 

Have you "tuned" it up? You don't say. Check plugs, wires, fuel filter, injectors, flow, etc. Missfire can be caused by any of these things and more.

 

^^^What he said plus I'd add check the d cap and rotor. They get overlooked w/ electronic ignition but do wear over time.

 

indeed, my 850turbo was stumbling at idle, and turned out to have serious trails on the distributor cap and rotor, at 120k miles.

 

Ok. Altenator doesn't work. Not charging bat. Auto store tested and said good but car dies after about 15 miles of driving. Put good battery in and runs for 15 more miles. Don't know if this would have anything to do with original problem. Getting new alt, wires, rotor, cap, plugs and will post when done with that. Thanks

 

I don't trust those auto store tests, frankly. Fully charge the car's battery with a battery charger, then let it sit a couple hours or overnight off the charger and you should read close to 13V across the battery.... start the car and the alternator should raise that to almost 14V when you raise the engine just above idle. if it doesn't, something is wrong.

Do you get the red 'charging' light when you turn on the ignition before you start the car, and does it go out after the car is started? (this should be yes,yes)

note that red 'charging' light on the instrument panel is a key part of the charging circuit, if for any reason (bad wire, bad bulb,etc) that's not connecting the D+ pin of the alternator through the bulb to the battery + via the 15R pin of the ignition switch, the alternator won't regulate properly.

 

I'll have to check that out. This is my first Volvo so learning.

 

Even if it is not charging the battery it should still run off the alt. Correct or does that dash light affect that too?

 

Put new altenator in. Light on dash works(battery symbol). Started car then disconected battery. It keeps running. Ground wire (attached to assembly thru bolt on alt and to bolt on intak plenum) gets hot. Should it get hot??? If I disconnect ground with bat disconnected it stops running, which I believe is correct.(started new post for this)

 

Waiting on tune up parts to come in. Wires, dist.

 

no, it shouldn't get that hot. probably should clean up the surfaces under the connection, maybe even replace that wire. it carries quite a lot of current when the battery is deeply discharged.

 

tune up part in. installed. rebuilt the distruputer houseing. Bad seals oil leaking in. God on form junk yard. pressed out seal and put in. Put all back to gether. Now no spark. ?????

 

had to clean out the distributor plate. Lots of oil getting in past bad o-ring. Replaced o-rings. cleaned. replaced. New plugs. new cap & rotor. Tried to start. No-spark. (could the hall sensor cause this?)
No-spark at plug. No spark at distributor wire to block. (well did get one week spark once when testing wire from coil.
I also removed wires from coil for some stupid reason.(was working) Is the pic showing correct connections?
Blue to -(1) whites to +(15) What is the black thing that has one of the white wires connecting to coil?
https://volvoforums.com/forum/member...no-spark-4378/

 

Ok. May have solved problem.
Run down.
1-car developed bad idel.
2-car would die at stops.
3-was running off battery.
4-new alternator and now ok for battery and runs off alt.
5-car still had miss.
6-bought tune up stuff (cap, rotor, plugs, wires).
7-during tune up removed dist. plate and made a mess of it. rebuilt with junk yard parts.
8-after tune up. NO-SPARK. (thought I screwed up Hall)
9-RPM gauge worked during cranking and could hear injectors.
10-used timing light to see I had a very bad something. would flash so randomly and not much at all.
11-completely lost at this point and was getting sick to the tummy over it.
12-for some unknown reason decided to disconnect a little black box that was connected to the coil strap from the coil (white wire).
13-turned key and timing light went like a wild pig. (as in good spark pattern)
14-removed timing light. hit key again and she fired right up and purrrrrrrred.
15-no miss and battery is charging and runs off alt when bat disconnected.
Hope my story helps others.
Great site. Glad I became a member. Thanks to all the helpers. Invaluable.