misfire on cold starts

mhamiton · Post by **mhamiton** » 13 Jul 2017, 13:26

I'm trying to help my father with his 2006 C70. It's got 180k miles and just started popping a CEL. The codes are P0300-P0305 (random misfire, and misfire on each cylinder 1-5). He initially changed the plugs and coil packs with OE, although I advised against this. A misfire common to all the cylinders sounds to me like a mixture issue.

I looked at the freeze frame data, the misfires are occurring right at cold start (within 5 seconds of starting). All the data PIDs look reasonable except the MAF was reporting 19.1 g/s at 1423 rpm. After the initial misses the car runs and drives normally. MAF reports 6.5 g/s at 1600 rpm when I was viewing live data.

My questions:
1. Does the car even use the MAF on cold starts or does it default to a speed density fuel table?
2. Should I keep looking down the path of the MAF reading, or should I suspect an intake leak and have him get a smoke test. I know the turbo and all the intake plumbing is original.

Thanks for any suggestions,
-Michael

Post by **RickHaleParker** » 14 Jul 2017, 02:23

It could be a lot of things. Your need to do a process of elimination.

If you suspect the MAF sensor, get a can of MAF cleaner and clean the sensor wire or plate. Just make sure nothing other then the cleaner comes in contact with the sensor wire or plate, they are fragile

You can do an intake leak test by spraying ether around the intake. If there is a leak, the leak will suck in the ether and your hear the engine surge. Keep the ether on the intake side, do not spray it on the exhaust side.

begovic · Post by **begovic** » 17 Jul 2017, 05:12

Are you loosing coolant? Fuel injector leak?

mhamiton · Post by **mhamiton** » 17 Jul 2017, 07:17

No coolant loss, but I did consider that. Since it's missing on all 5 cylinders, a single injector or HG leak doesn't seem likely. Did try cleaning the MAF but made no difference. I suspected it might be an intake leak, especially since the turbo and plumbing are original and untouched at nearly 200k miles. It's difficult to determine what it's doing since once it runs a few minutes it's perfectly normal--fuel trims at 0% LT and ST, nothing showing anything out of the ordinary.

He even had it at the dealer for diagnosis and they told him "it has misfires." That irked me more than anything. I can't figure out why the first thing they didn't do was a smoke test, or a fuel injector leakdown test.

The other thing that makes me think it isn't a fuel injector or water in the cylinders is that it starts completely normally. No extended cranking or hard starting. If it wasn't for the CEL you'd never know it missed at all.

begovic · Post by **begovic** » 17 Jul 2017, 15:49

Test fuel pressure and fuel pressure sensor. Try to see pressure on the cold start when misfiring.
Fuel pressure sensor is known to go bad.

Post by **RickHaleParker** » 23 Jul 2017, 21:48

This does not happen often but is easy to check. A restricted air filter can cause the symptoms you have. Pull the air filter and see if it fires up without misfiring but do not drive it without a filter.

Did you check for small holes and loose connections in the air intake ductwork?
Is the ductwork clear?, sometimes the mechanic forgets to retrieve a shop rag.

Post by **RickHaleParker** » 23 Jul 2017, 22:16

mhamiton wrote: ↑17 Jul 2017, 07:17 He even had it at the dealer for diagnosis and they told him "it has misfires." That irked me more than anything. I can't figure out why the first thing they didn't do was a smoke test, or a fuel injector leakdown test.

Because they know there are a lot of things that can cause misfire on all five, diagnosis is a process of elimination they cannot tell you what the cause is until the process of elimination is done. On my S90, the misfire on all six was a clogged exhaust resonator. I tried a lot of other test before I found the cause.

mhamiton · Post by **mhamiton** » 04 Aug 2017, 11:11

Thank you all for the replies--sorry for the delay posting back.

The car has been back and forth to the Volvo dealer several times these past 2 weeks. First they told him there was nothing wrong and to "run a fresh tank of premium and see if it gets any better." He told them to take the car back and diagnose it correctly (even suggesting a smoke test after letting it sit overnight). They had it a few more days and said they couldn't find anything wrong. he complained to Volvo corporate, they took the car back, said the same, and now refuse to work on the vehicle (wtf--maybe I've been involved with Jaguar cars too long... my dealer would be thrilled to throw parts at the car until it was fixed).

Since the misfire on startup, it now also has a hesitation when cruising, like when you go up a slight incline on the highway.

The MAF was replaced with a new OEM part, no change. I told him to check the fuel pressure next, as begovic suggested. After that I'll look over the vacuum lines and air filter, but since the ST and LT fuel trims are at 0% when it's running I'm not suspecting a vac leak. I'll also suggest he do an exhaust backpressure test. RickHaleParker, did your clogged resonator show up as high backpressure or did you have a rattle?

Thanks,
-Michael

Post by **MadeInJapan** » 06 Aug 2017, 09:32

Which dealer in Raleigh? My brother-in-law is having his older model S40 (2002) towed down to me in Knoxville next month from there because wherever he was taking it said nothing could be done for it anymore, while I think the solution is one of the "typical" issues these cars have and I can fix it without to much $ or time. Anyway- the car has been sitting for a year now because it can't pass NC inspection unless the issue is fixed. We'll see, but I have lost faith in the place he swore was great when he first got the car (seemed really expensive to for routine work). Sometimes I think many Volvo dealers just don't want to hassle with what they consider are older cars.

mhamiton · Post by **mhamiton** » 10 Aug 2017, 10:48

MadeInJapan wrote: ↑06 Aug 2017, 09:32 Which dealer in Raleigh? My brother-in-law is having his older model S40 (2002) towed down to me in Knoxville next month from there because wherever he was taking it said nothing could be done for it anymore, while I think the solution is one of the "typical" issues these cars have and I can fix it without to much $ or time. Anyway- the car has been sitting for a year now because it can't pass NC inspection unless the issue is fixed. We'll see, but I have lost faith in the place he swore was great when he first got the car (seemed really expensive to for routine work). Sometimes I think many Volvo dealers just don't want to hassle with what they consider are older cars.

I believe he was taking it to Weaver Brothers Volvo. It certainly seems like they have no interest in servicing anything that isn't a current model. And this has to be something straightforward. If I had access to all the dealer diagnostic data points on this car I'd probably have been able to get it solved with no issue. But I'm trying to help from 60 miles away with a OBD2 tool that has limited PIDs.