Misfire at idle, occasionally low speeds. Lots of details

drmegadan · Post by **drmegadan** » 04 Feb 2020, 07:39

I purchased an '06 V70 on Halloween of last year for a grand (yay). 132k miles but with a pretty clean interior and exterior. It needed the normal V70/2.5T work: complete front suspension rebuild, plugs (NGK BKR6EIX), trans flush (drain and fill), brakes, timing belt/water pump, and motor mounts. The car drives great and feels brand new aside from a slight flex pipe exhaust leak. Except one small problem: a prominent miss once the car is warmed up. I've been troubleshooting and test driving over the last week or so and couple hundred miles and I'm stumped. I also have a 2005 2.5T V70, so fortunately I have a spare of each component I can swap.

The miss is most prominent when in gear but at a stop, as when it misses it seems to bog the car down, and the vibrations seem to be emphasized by transmission as its in gear. Lights dim slightly. When in park the same happens but its more of a blip, than a bog, if that makes sense. Same symptoms, but much less duration. Also, forgot to add. This car has yet to throw a CEL.

I swapped coils from the good car.
I verified torque on the spark plugs.
I removed and cleaned the throttle body
I verified I have no air leaks (pluging MAF and blowing compressed air into brass intake nipple).
No visible coolant loss after 150 miles or so of driving. I do get the slightest wiff of coolant in the cabin under the first full throttle run, but the overflow tank hasn't dropped.

What else should I look at? What else can I check? I tried using Torque last night to log the OBDII data stream, but all I got was speed and accelerometer data. I was watching specific values during my drive and attempted to differentiate symptoms from causes. I'm not sure I was successful but I'll do another actual log as soon as I find software capable of this. I don't have access to VIDA yet, but with two Volvos I might look into it.

Post by **abscate** » 05 Feb 2020, 10:00

Try another set of new plugs. While swapping, take a compression test to rule out valve issues, no additional labor

I’ve read of new plugs failing shortly after install for many decades, and had it happen to me last fall.

$3000 is a great PRICE for a stage 0 P2. ( you just haven’t spent the extra 2k yet,j

Post by **- Pete -** » 05 Feb 2020, 23:28

How far west into WI are you? I’m south of the cities & could bring ViDA with me next time we go to the cabin in W. WI.

Maybe I skipped over it, but does the “skip” dissipate at greater RPMS?

Like Abscate said, I’d re-check the plugs & rule out bad coils. I think I saw Iridium plugs in there somewhere - I personally have had the best luck with plain old copper Volvo plugs, not cheap, but buy from FCP, pay once & change regularly. I think you’ll read that most people reporting issues with plugs are using something other than the plain Cu ones.

I’ve run Iridium plugs in several other turbo vehicles that called for them & had no issues, but Volvo’s are picky.

Nice score on the $1k 06. My best so far was a $1k 01 XC 131k miles that had a brand new bevel gear, new rear driveshaft, new timing belt et.al + water pump, 4 new Conti tires, like $8,100 in dealer receipts the 4K miles prior to me buying it off the poor guy who ran into a bad ignition coil & threw his hands up. An additional ~$1k into it in parts & the rest in my free labor & it’s sweet. Make a good spare 2.4 + new BG down the road for me.

Post by **oragex** » 06 Feb 2020, 11:29

I would also search about FPS and PEM.

drmegadan · Post by **drmegadan** » 14 Feb 2020, 10:11

Thank you all for the input. Shortly after posting this, my wife gave birth to our first child, so I've been a bit distracted and haven't had a chance to do any more work on the Volvo.

I finally managed to get a log file from torque, but I don't see a smoking gun. Idle is pretty rock steady at 700RPM, and will only drop to about 630 or so for a half second and bounce back. Fuel pressure is steady at 300 ±5kpa (43.5psi) also.

abscate wrote: ↑05 Feb 2020, 10:00 Try another set of new plugs. While swapping, take a compression test to rule out valve issues, no additional labor

I’ve read of new plugs failing shortly after install for many decades, and had it happen to me last fall.

I plan on swapping the brand new plugs in the misfiring Volvo with the 'old' plugs in the Volvo that is currently running well. I'll do a compression check at the same time. Thanks for the tip.

- Pete - wrote: ↑05 Feb 2020, 23:28 How far west into WI are you? I’m south of the cities & could bring ViDA with me next time we go to the cabin in W. WI.

Maybe I skipped over it, but does the “skip” dissipate at greater RPMS?

Like Abscate said, I’d re-check the plugs & rule out bad coils. I think I saw Iridium plugs in there somewhere - I personally have had the best luck with plain old copper Volvo plugs, not cheap, but buy from FCP, pay once & change regularly. I think you’ll read that most people reporting issues with plugs are using something other than the plain Cu ones.

I’ve run Iridium plugs in several other turbo vehicles that called for them & had no issues, but Volvo’s are picky.

Nice score on the $1k 06. My best so far was a $1k 01 XC 131k miles that had a brand new bevel gear, new rear driveshaft, new timing belt et.al + water pump, 4 new Conti tires, like $8,100 in dealer receipts the 4K miles prior to me buying it off the poor guy who ran into a bad ignition coil & threw his hands up. An additional ~$1k into it in parts & the rest in my free labor & it’s sweet. Make a good spare 2.4 + new BG down the road for me.

Unfortunately I'm east Wisconsin, suburbs of Milwaukee. I appreciate the offer but maybe a personal ViDA will be in my future.

As far as I can tell, the skip only happens at idle or at very low speeds when decelerating for a sharp turn. At least its only noticeable at these times. Under full throttle the car feels great.

Based on checks I've already done, I think bad coils is lowest on the totem pole. Bad plugs, maybe; but if I had a nickel for every forum that said "these cars prefer OEM plugs" I'd have a lot of nickels. I've had great luck with the NGK's across my fleet. I'll swap them with known good plugs and see what shakes out. Based on how everything feels, I'd wager all my nickels on it NOT being plugs. I've had bad/failing plugs often enough before and I don't get any sense of problems under load.

So far I'm happy with the purchase, even with the misfire issue. There are some other minor issues relating to a weak blower and sticky radio buttons; but on the whole its a solid car for what I paid for it. After the suspension refresh its even fun to drive. Now that we have a child I'm daydreaming about a V8 XC90.

oragex wrote: ↑06 Feb 2020, 11:29 I would also search about FPS and PEM.

I've had FPS issues in our other Volvo and the problems were at speed and threw a CEL. Maybe it's not the case all the time, but I'm really struggling with the fact that it has no pending or historic faults when reviewed through Torque.

Post by **abscate** » 15 Feb 2020, 02:04

That 43.5 psi fuel pressure is a no go. If you believe your gauge?

Spec is 52 psi and it needs to be there. Get that fixed first. On P2s, that is usually a known corrosion problem in the Pump Electronic module or PEM

Whenever I catch myself using my “ experience” as a diagnostic tool, I remind myself how sparse the data is, unless you are a “ jimmy” and look at 10 different cars per day.

drmegadan · Post by **drmegadan** » 17 Feb 2020, 07:03

abscate wrote: ↑15 Feb 2020, 02:04 That 43.5 psi fuel pressure is a no go. If you believe your gauge?

Spec is 52 psi and it needs to be there. Get that fixed first. On P2s, that is usually a known corrosion problem in the Pump Electronic module or PEM

Thanks for the response, but I haven't found anything to support 52psi at idle. I don't blindly trust the gage, but the sensor appears to be functioning correctly. At this point it's pretty far down the totem pole of concerns.

Similar threads on MVS search.php?keywords=psi&t=73999&sf=msgonly indicate that 3bar (300kpa/43.5psi) at idle is normal for fuel pressure. I've been looking for actual technical documentation but haven't found anything yet. Would you happen to have a scan from VIDA or a Volvo service manual?

abscate wrote: ↑15 Feb 2020, 02:04 Whenever I catch myself using my “ experience” as a diagnostic tool, I remind myself how sparse the data is, unless you are a “ jimmy” and look at 10 different cars per day.

I'm not sure I follow.

Post by **abscate** » 17 Feb 2020, 18:27

If you go the link in my sig for the maintenance thread, then look for Catherine, my 2005 Volvo, I believe the exact pressure spec is on page 2 of that thread

43 psi is way too low.

Post by **chrism** » 18 Feb 2020, 06:42

Congratulations on BOTH new babies!
I would try swapping in the fuel pressure sensor from the other car. We had a failing FPS in our 2.5T that caused missing problems like yours but it took FOR EVER to finally get a CEL. If that doesn’t help then I’d steal $10 from the diaper fund and go pick up a set of BKR6ES (NGK 6364).

drmegadan · Post by **drmegadan** » 18 Feb 2020, 11:58

abscate wrote: ↑17 Feb 2020, 18:27 If you go the link in my sig for the maintenance thread, then look for Catherine, my 2005 Volvo, I believe the exact pressure spec is on page 2 of that thread

43 psi is way too low.

Excellent, thank you!

chrism wrote: ↑18 Feb 2020, 06:42 Congratulations on BOTH new babies!
I would try swapping in the fuel pressure sensor from the other car. We had a failing FPS in our 2.5T that caused missing problems like yours but it took FOR EVER to finally get a CEL. If that doesn’t help then I’d steal $10 from the diaper fund and go pick up a set of BKR6ES (NGK 6364).

Thanks!! Swapping the fuel pressure sensor was on my list of potential to-do's also. I didn't jump on it immediately because its just a little messy. The new baby has taken priority over the older baby so diagnostic work has been tabled short term.