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Misfire fun.. new plugs & coil now its worse - with more cylinders!

3K views 19 replies 9 participants last post by  muppetman342 
#1 · (Edited)
Well, i need to enlist the fine volvo minds here. Searched around but nothing conclusive. I usually try to figure out everything on my own.. but i guess time to post my first help thread.

So car is new to me, 153k, I put 3,000 mi in it so far. It had a misfire on cylinder 3 showing in live data not real severe​ but radomly counting up most id see is 40 on a test drive. Had a ocassional misfire on cylinder 2, the connector was broken and attaching it firmly cleared that up.

Got new bosch FR7MPP10 plugs and one airtex/wells coil to play with. I changed the plugs and #3 coil. Now its Misfiring even more, like crazy on cylinder three. Pulled the new coil out. Swapped the old #3 coil with #4 cylinder coil, still misses.. Now i notice 1&2 are starting to misfire slowly and 3 is still wack. Put one of the older plugs that wasnt misfiring back in #3 incase bad plug, still missing on 3 and 1&2.

Anyone have an idea what to look at next? Im bout to check the ground straps and wire harness, oh the brittleness... and god forbid a compression test if i dont make headway.

At any rate i gotta figure it out so when i do, hope it may help someone else in the future.
 
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#4 · (Edited)
Looking in with flashlight it just looks, just dry reddish color, fairly normal I'd say.

The problem is like i moved the wires and now i have issue. I was hoping not to but guess ill have to pull the wire covers off.

Do i need to hard reset the computer? I reset codes and had battery unplugged.
 
#6 ·
get OEM spark plugs make sure they are all evenly gapped to .027”-.028”

not sure when the coil packs were replaced but you might as well replace those with new Bosch ones and be good for a very long time.
 
#7 ·
If theres a wiring harness issue then most likely there would be an electrical type of fault code stored. Example.... If a injector or a coil wiring issue was present then you would have a code for a injector or coil faulty signal, Signal too low, Signal too high that type of thing. First thing with multiple misfire symptoms is to verify the mechanical integrity of the engine, Aka a compression test on both a warm and cold engine. If all is good then replace all plugs and coils with quality replacement parts.
 
#9 · (Edited)
No other codes showing up. Looking back a few months its been 3100 misfire multiple cylinders, and 3130 misfire cyl 3 mostly & 3110 cyl 1, maybe 2 thrown in along the way.. counters were low each time it really didnt run bad. All this was with autolites gapped at .042! The car seemed to run pretty good, i mean it doesn't feel shot. I only knew there were misfires by scanning it and when I saw it had autolite plugs in it, i got the bosch FR7MPP10.

The original issue i had that lead me to look into it was a slight pause at 3800 rpm and 5k, I've read others have had similar issues.. That has seemed to go away after the first time i pulled the ote pipe and checked the plugs found #2 connector broken and seated it tightly.. Now its evem better, the power is great.

On to your last point, mechanical integrity. Man i just got this car, lol, it runs good and pulls strong... Seriously, I had a compression set in my hands but couldn't go through with it yet.. it cant be..
 
#8 · (Edited)
Well my luck, I've got it running good right now. I did a few things not sure which was the cause or cure. Lol. I'm thinking the wiring, or i jumped the gun on calling misfires before the ecm adjusted.

I started it and was watching the misfires on a snap on scanner, took it to the engine compartment and messed with wires and the connectors. Saw the misfires level off and stop climbing. Cool... I put the bosch plug back in #3, i had already swapped 3&4 coils.. Cleaned and reseated connectors on 1&2.. Also did a hard reset with the battery cables... I know, lol.

Started off with no misfires at all. A test drive for about 5 -10 minutes and it was clear 0 misfires. Pulled back up and stopped it in park to open garage, by time i pulled in i had accumulated 5 misfires idling on cylinder 3, but stabilized for the most part Engine runs good with no evident misfire and its not climbing. Back to normal at least. Good for tonight.

So to recap I have new plugs and the original coils in.

I drove home about 15min and it ran really good best since I've owned it i think. Boost feels better & the rpms climb strong with no hesitation. Boost peaked higher than I've seen before on this run. Peaking at 1990 hpa, calculated 1 bar 14.9psi, the boost reference was 970hpa.

I'll see what happens tomorrow. I will be driving it 70 miles, then I'll review misfires and codes when I'm back.
.
 
#11 ·
Well she ran great, smooth running & powerful. I got too busy to rescan it. I suspect ill see a couple misfires logged, but theres nothing noticable driving. I suspect it mostly happens at idle. I'll update if I find the source of the problem.

On a side note; I did notice my timing belt is walking/wobbling a little on the cam sprocket. Will need to plan a timing kit sometime soon.
 
#12 ·
You should do the belt asap. I will say I seen mine walking a round and I lost the belt not long after. It shredded in half. Luckily I didn't lose the motor. It jumped 4-5 teeth intake side and 3-4 teeth exhaust side. I was really lucky. I'll find the pics.
 
#13 · (Edited)
Thanks for the advice, at 150k don't know when its been done - may be original, doesn't look new.

I've got video od it im watching - heres a screen shot i took. You can see the shine by the belt, thats how much it wobbles. About an 1/8" or so.



Watching it wobble is making me cringe..
 
#14 · (Edited)
If you plan on keeping the car awhile / doing it yourself. Definitely check out the fcp kits. Imho. Best deal. Lifetime warranty including wear parts is amazing.

Sent from my LG-H810 using Tapatalk
 
#15 ·
Oh yeah im keeping it, i just bought it, and I'm doing it myself.

Ill have a look toward fcp, will be getting 4c there soon.
 
#16 · (Edited)
The car has been running good. However did scan it after a couple days now over 100mi, and it is still showing misfires on 3 & 1. However it's not really noticeable, maybe at idle you can tell, but barely perceptible. At least it's not missing like right after I did the plugs.. I'm just back to the same as before. Drivability is OK.

This is what showing today.



At idle the misfires will start to notch up ocassionally, and if I rap the throttle I may get a misfire sometimes.

Since swapping coils and plugs made no difference. Theres a good chance I'm due for a harness. I see Dave Barton offers one. - http://www.davebarton.com/volvoharnesses-960.html

Damn I'm tempted to rewire the harness and plugs myself since im skilled in that area, but will have to evaluate the amount of work to do it. May not be worth saving $175.
.
 
#17 ·
Damn I'm tempted to rewire the harness and plugs myself since im skilled in that area, but will have to evaluate the amount of work to do it. May not be worth saving $175.
Depending on how bad your connectors are, I'd imagine you can get new connector ends and just re-pin them yourself. Or, if the wires around the plugs are good, just splice new wires in. Most of the cost is likely in the connectors, wire is cheap.
 
#19 ·
Cool, guys. Thanks.

The benefit of making my own is maybe I can use better or heavier gauge wire.

On a side note.. My jet turbine fan problem fixed itself. Don't know how, plugged it back in now that it's getting warm and it works. Maybe has to do with the season change, think the pressure sensor was sticking and now its working.

One less thing to look at right now... I can move on to the haldex.
 
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