•seeking help identifying cold start misfire• Coils and plugs replaced.

[Iroll_]

Good afternoon everyone,

Coils and plugs have been replaced and I am still getting a p303 cold start misfire and or after the car has been sitting for more than an hour.

Seems to be worse with the cold weather... Also, have an over-boost code. I plan on replacing the TCV valve but need assistance with my cold start misfire.
I’ve noticed the car will misfire after start but won’t set a code until I try to accelerate ( ie load).

I am thinking of replacing the number 3 injector and orings...Any ideas?

Car has not other problems/leaks or ailments.

Thanks in advance.

[pbierre]

Is your misfire code identifying Cylinder 3? Is it always that same cylinder misfiring? If so, it would be worth taking out the #3 spark plug, and doing a compression test. How does the plug look -- is it fouled? Gapped correctly?

[Rabid Koala]

This is generic, but if you experience a misfire when starting, do a cold start and immediately shut the engine off. Pull each spark plug out and check for signs of coolant. It may be a head gasket, or as was the case with a 1982 DL that I had, a crack in the cylinder head.

[Astro14]

Coils and plugs replaced - what brand? Misfire is nearly always the coil. Injectors fail, but coils are more common.

Start by swapping the coil and plug from cylinder 3 to cylinder 2. If the misfire moves with it: it's a coil. Get a new coil. Bosch or Volvo only. Everything else is junk.

IF the misfire stays on 3, then it's your injector.

For injectors, I would send all 5 out to this guy: http://www.hurstinjectorservice.com/

He's awesome. Did the injectors on the XC and it runs like new. Under $100, including shipping. A bargain. He's also done the injectors on a 1975 Mercedes 450 SL that I'm working on. Best way to go. New injectors will cost you more than twice what he does.

[Iroll_]

Thank you kindly for the replies, everyone. I sincerely appreciate it.
Plugs are OEM Volvo and coils are Bosch/ Hella with the little lightning bolt on the tops.

I will try moving the number 3 coil and plug to a different cylinder and see if the misfire changes location and or persists in the number 3 cylinder. Should the misfire persist in the number 3 cylinder...I will replace the injector.


Per the shop that replaced the timing belt, front crank, oil pan seal, cam seal and VVTI a few weeks ago....the engine's compression checked out as okay and the car has not been losing/consuming coolant.

Could a faulty MAF or throttle plate cause the misfire problem/failure mode I am experiencing?

Cheers everyone!

[ssicarman]

Move the coil to a different cylinder and move the plug to a different cylinder than the coil.
IE coil to cylinder four and plug to cylinder two.

[Charle]

I would check the wiring harness for the coils as well especially if the harness is solid dry.

[Iroll_]

I just replaced the fuel filter in anticipation of needing to replace my injectors...Surprisingly the cold start problem appears to have gone away.
I have a set of injectors of stand by should I need to replace them...For the time being...It appears replacing the fuel filter has fixed my problem.

[Xfingers]

Do you know how many miles were on the old fuel filter?

[Iroll_]

Do you know how many miles were on the old fuel filter?

I do! I replaced the filter at 182k in 2015. Many winter and even mild dessert adventures on Filter(Hengst)...surprisingly the housing was showing signs of surface rust. Sort of odd as the Seattle area does not use salt.

Plot twist: After I replaced the fuel filter the cold start misfire returned and I ended up replacing all of the injectors with refurbed units from a reputable seller on ebay.
Special note: I've already replaced the coils and sparkplugs.
Will update if anything changes...240k on the original injectors and yes I did run the car low on gas several times.