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misfire on cold starts

Help, Advice, Owners' Discussion and DIY Tutorials devoted to the second generation C70, S40 and V50 Volvos -- awkwardly model year 2004 ½ onwards -- plus where to go for advice and discussion on Volvo's sporty C30 Coupe powered by Volvo's ubiquitous inline 5-cylinder power plant.
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mhamiton
Posts: 2
Joined: Thu Jul 13, 2017 6:54 am
Year and Model: 2006 C70
Location: Raleigh, NC
United States of America

misfire on cold starts

Post by mhamiton » Thu Jul 13, 2017 1:26 pm

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

RickHaleParker
Posts: 35
Joined: Mon May 25, 2015 2:30 pm
Year and Model: 1998 C70 Coupe
Location: Kansas
United States of America

Re: misfire on cold starts

Post by RickHaleParker » Fri Jul 14, 2017 2:23 am

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.
1997 S90, B6304S, AW30-42
1998 C70, B5234T3, AW50-42

begovic
Posts: 100
Joined: Tue Oct 27, 2009 2:19 pm
Year and Model: 855 turbo 1994
Location: Grand Rapids MI

Re: misfire on cold starts

Post by begovic » Mon Jul 17, 2017 5:12 am

Are you loosing coolant? Fuel injector leak?

mhamiton
Posts: 2
Joined: Thu Jul 13, 2017 6:54 am
Year and Model: 2006 C70
Location: Raleigh, NC
United States of America

Re: misfire on cold starts

Post by mhamiton » Mon Jul 17, 2017 7:17 am

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
Posts: 100
Joined: Tue Oct 27, 2009 2:19 pm
Year and Model: 855 turbo 1994
Location: Grand Rapids MI

Re: misfire on cold starts

Post by begovic » Mon Jul 17, 2017 3:49 pm

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.

RickHaleParker
Posts: 35
Joined: Mon May 25, 2015 2:30 pm
Year and Model: 1998 C70 Coupe
Location: Kansas
United States of America

Re: misfire on cold starts

Post by RickHaleParker » Sun Jul 23, 2017 9:48 pm

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.
1997 S90, B6304S, AW30-42
1998 C70, B5234T3, AW50-42

RickHaleParker
Posts: 35
Joined: Mon May 25, 2015 2:30 pm
Year and Model: 1998 C70 Coupe
Location: Kansas
United States of America

Re: misfire on cold starts

Post by RickHaleParker » Sun Jul 23, 2017 10:16 pm

mhamiton wrote:
Mon Jul 17, 2017 7:17 am
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.
1997 S90, B6304S, AW30-42
1998 C70, B5234T3, AW50-42

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