94 850 turbo Cyl 5 Misfire

[IG-88A]

Hello, all. I was out for a couple of hours today, and upon arriving home I checked for codes using the underhood OBD box. I do it everyday now, because my CEL bulb is burned out, and because of recent issues with EVAP and intermittent KS codes. Anyway, to my surprise, I got a code for misfire at least one cyl, and cyl 5 misfire 3 way cat damage. I never felt a stumble or loss of power today, and I've never had this code since purchasing the car back in May. I'll also note that just two weeks ago, I replaced the plugs (Volvo), wires (Bougicord), cap and rotor (Bosch). Odd that this would happen suddenly with brand new new parts. I'm waiting for the engine to cool down a tad to recheck my gaps, and perform a compression test, even though I've never done one before. I checked that all my wires to the plugs and distributor were secure, and they seemed to be.I just wanted to post here to see what other people have found in their personal experience, and see if anyone had any helpful tips or recommendations. This scenario makes me a bit nervous. Thanks.

[erikv11]

I don't have any good ideas for why the codes showed up but given you say the car seems to be running just fine, first order of business is to clear them and see if they come back.

[IG-88A]

Indeed, erik. I will do that. Thank you for the reply. Firstly, I checked my gaps. All at .28". Secondly, I think that I may have let the engine cool down a little much, because all my compression readings were low across the board. At least not within the 150-180 (I think) that is the optimal range. Instead mine were in the 120s, or slightly lower. Here are the readings I got. #1-119 #2-123 #3-122 #4-125 #5-115. I tested #5 first, and worked right to left because that was the bad seed. Could the engine cooling down further as I worked have dropped the other cylinders within that same range? Just asking because #5 still reads low compared to the others, and it was the cylinder in question. Should I try this again with a warmer engine? Or since these numbers are all close, should I be good with what I've found here? None seemed staggeringly low compared to the others, so I skipped the wet test. If I should have gone ahead with that, let me know. Also, how warm should the engine be? I've read, on here I think, that you only want to change spark plugs on an engine that's stone cold. So how is it okay to go through the same motions with a warm engine when testing compression? I think I let it cool down too much based on that. Sorry if my posts get wordy, but I want to cover all bases and give as much info as I can. I hope nobody is discouraged by long-winded posts. Thanks.

[IG-88A]

Okay. So I cleared the code, then went to leave to run some errands. Upon starting, the RPMs fluctuated between maybe 700-1000 repeatedly. With occasional jumps up to maybe 1200 or so.The idle was all over the place. The car felt like it was on the brink of dying, and you could definitely feel a shuddering. I went to the store real quick and it seemed like it was sluggish and just different. Even the brakes felt soft and weak, even though I'm sure that's just my mind overreacting and paranoia setting in. Upon arriving back home, the RPMs were stable during idle at 1000. I checked for codes, but there's nothing back yet. Suddenly, something isn't right though. I'm disconnecting the battery and trying a hard reset. We'll see if that improves things.

EDIT- Unhooked my negative cable for a hard reset, relearned the ECU, and the idle has stabilized somewhat. It's not as smooth as it seemed before all this, but its not as bad as it was on the initial startup. After giving it about ten minutes around town, the only code to return is my 315 EVAP. We'll see if more return tonight. I'm still going to try to find an 850 at a junkyard so I can try another injector in #5. Still open to ideas.

[erikv11]

Good info in your posts!

It is fine to change plugs on a warm or hot engine. I do remember that came up in this forum a while back but there is no merit to the stone-cold-only argument.

That said, I agree with your comments that the compression is probably fine. There is no harm in testing it again (I like to drive it for 15-20 minutes, pop the hood, then get to checking compression pretty soon after that), but I think you already have your answer: no major problems in 5 or any other cylinders. The numbers are low but that could be either the gauge or the temp or a combo; the grouping is good.

If the misfire-in-5 doesn't come back then i don't think I would mess with that injector.

Keep an eye out for nudged or otherwise amiss vacuum lines, that could help explain the behavior after you checked everything. If it acts up again I think I might try unhooking the MAF, see if that fixes any stumble/idle issues. Just because it is a super easy, free test.

[IG-88A]

Thanks again, erik. So, if I start getting that crazy, stumbly idle again, unhook the MAF, and notice an improvement, that would point to a faulty/dirty MAF, correct?

I did a quick once-over on the vacuum lines immediately following the drive after first experiencing the crazy idle. I was fresh out of anything aerosol that wouldn't leave a greasy mess, so I didn't try spraying around. I did listen, and also pulled a cap off the vacuum tree. Idle picked up when I did that. i didn't hear any hissing with the cap in place. Though, its hard to tell sometimes with the hissing noise either a pully or the serpentine belt makes, along with the hissing from the idle air control valve.

[Volvofan94]

Though, its hard to tell sometimes with the hissing noise either a pully or the serpentine belt makes, along with the hissing from the idle air control valve.

The hissing sound you mentioned here, makes me think it could be a torn intake manifold gasket on the cylinder 5 intake runner. Maybe check your intake gasket next. From reading the previous posts it sounds like your vacuum lines should be ok.


Last spring my 850 Turbo had the code for a misfire in cylinder 5 with the 3 way Cat damage code along with other strange codes. I think the knock sensor codes may have been in the mix too. The engine ran poorly and could barely hold an idle without some throttle. Shown below is how the old intake gasket looked like on my car when I removed it. After replacing the gasket with an OEM Volvo one the codes haven't returned and the engine runs smoothly.

Good luck!

Torn intake gasket on cylinder 5

[IG-88A]

Interesting. I'd actually read a thread earlier today discussing that possibility. Had you replaced your gasket before, or is that the one that was on the car when you got it? I wonder how it even splits clean through like that. I changed the pcv system out in May, so I installed a new intake gasket then. I was careful in trying not to disturb it too much while installing the manifold, but I may have accidentally done something while fighting with the EGR connection or that bracket that holds the dipstick tube. I have a spare gasket. They sent two with the kit for some reason. But if there's an issue with the average gaskets, I may have to pick up an OEM one. I was also planning to try the NA manifold as well. Maybe now is the time. I was hoping after buying suspension parts with the tax refund, that I'd have a solid stage zero to build on. But might as well tear into it and have a look. If the weather holds out. That'll have to wait til next weekend though.

So you're saying that you shouldn't be able to hear a slight hiss through the upper IAC hose? Or even in that general area? Maybe I did mess something up while reinstalling the manifold.

However, I have sprayed around under the hood with brake and carb cleaner before, to see if i could notice any idle fluctuations. even in that #5 area, and got nothing. I've always heard that sound though.

Thanks for the input.

[Volvofan94]

The intake manifold gasket wasn't original to the car as I replaced it when I put in a new PCV system around the May 2013 timeframe. I think mine became torn was some of the intake manifold bolts were loose on that side and the manifold jiggled around slightly and eventually tore through the gasket.

Normally a hissing sound shouldn't be heard from the IAC area. When the key is in position II (engine not running) the IAC valve should buzz, but shouldn't produce a hissing sound. With the engine running, does the hissing sound come from the top of your manifold by the IAC area or from somewhere down below?

The hissing sound on my car was coming from below the IAC area by cylinder 5. A new intake gasket was installed when I replaced PCV system as part of my Stage 0 plan. I thought maybe the hose that connects the oil trap to the PTC may have broken where the hose bends to go around the engine block. But while feeling around in the area I couldn't find an air leak. I did a tune up on the car, bought a new MAF sensor, and a installed a new fuel injection relay, but had similar results. At last the problem with the intake manifold gasket was identified. I found this out by one of the lower intake manifold bolts were loose by cylinder 5. After tightening up the bolt and checking the other intake manifold bolts the engine ran better but the damage was already done to the gasket. The next day I went to my Volvo dealership and bought an OEM one (I didn't want to wait for shipping ). With the new OEM gasket installed the hissing went away and my Volvo ran better than ever. Another interesting anomaly with this issue was the boost gauge needle didn't go most of the way down the vacuum (left) side when I coasted.

Here's a link to a thread about the boost gauge issue:
https://www.matthewsvolvosite.com/forums ... =1&t=62014

[IG-88A]

Thanks, Volvofan. When I first got the car, it only got driven for a couple of very short jaunts around the neighborhood, because of the serious smoking issue of the clogged PCV system. I actually had it towed from the previous owner's house, so as not to cause any leaky seals. The fact that I basically dug right in to the PCV issue, makes me now wonder if it always did the hissing from the IAC area before I serviced the PCV. I do remember being concerned enough about it to search, and remember seeing it posted a couple of places where a slight hiss from the upper hose area is normal while the engine is running. But maybe it isn't. Its awfully hard to tell if its in fact the IAC hissing or a leak from an intake runner, or somewhere else in that general area. Its just hard to pinpoint with all the noise from the injectors and everything else. It does buzz in position two though. Like I said, I have sprayed carb cleaner in that area before, and never got a response. I'll have to check my turbo needle. I think it basically sits halfway between far left and dead center when idling or coasting, but it may sit a bit higher. I've never really checked on it in those situations. I've never got those codes that you posted in your other thread.

I had to make a trip downtown last night. A total round trip of maybe thirty miles. Mostly highway. While on the highway, I decided to play with the throttle a bit, just to see how things felt. The engine and noise from the turbo seemed louder than normal, and it just didn't seem to have the same throttle response as I'm used to. It just felt like it was trying, and not quite getting there. Similar to when i had a tear in a turbo hose, but noisier. Not rattly or sputtery or anything. Just louder. The slight shudder under idle still remains, as well as a bit more vibration under load. There were no codes once I arrived at my destination, or back home. But it sure didn't feel like the same car. I guess the only thing to do now, is to start taking things apart.