Intermittent rough cold start 04 XC70

[P2metoo]

Hey. My 04 Xc70 has a cold start issue about half of the time. The engine shakes and feels like it is going to jump out. It's worse in gear. The check engine light flashes and sometimes stays on. I get random misfire codes and sometimes a turbo fault code.
Once the engine warms up the car drives smoothly. The check engine light clears on its own. I've replaced air filter, Volvo spark plugs are 4 years old with 15K miles, got new Bosch coil packs on all cylinders, motor mounts are good, timing belt is in good conditionand isn't due for another 10K miles. Transmission fluid looks good, bevel gear seal weeps. My buddy hooked up his scanner and said the fuel air mix was good. Not sure what path to take next for troubleshooting.

[Vova585]

I would say that you did the basics. Without investing into ton of diagnostic equipment, it would be hard to pinpoint anything. I woukd suggest to send to dealer and pay 1-2 h diag fee. It could be variety of the issues: low fuel pressure d/t leaky injector or backflow valve, problems with engine compression, vacuum leak which stops after warming up, ecu internal fault....I would hope that dealer would perform in cylinder compression test or cylinder balance test(through transducer or via amp clamp), check for vaccuum leaks, check for stable fuel pressure, connect their diagnostics and check initial parameters(maf, coolant temp, air temp). Your O2 sensors are not playing a role upon start at all, so doubt the problem is there.

[yanga001]

Cold start only issue? Is it an issue after the engine has run a while and then been left off? I used to have this on a p80 v70 on one cylinder due to a slightly breached head gasket.

Random misfires are interesting (assuming you mean to all cylinders) as it would likely point to a fuel pressure issue, spark signal, or air metering.


Clean the maf with some maf cleaner and see if you can monitor the flow when you start it up.


What are the exact codes you get? It can help narrow it down.

[P2metoo]

I'll try cleaning the MAF. I get the P0300 - 305 codes. P0299 was the turbo code but has only come on twice. Changed all the coils 2 months ago when I discovered they were all from 2008. Not consistently the same code. Once it warms up it has no issues. End of June I drove 75 miles to the airport, parked outside for a week and drove back with no problems at start. Then yesterday I had the issue again. Hopefully it is just a dirty MAF sensor. Will update after I clean it.

[jonesg]

It does sound like coolant seeping into cyls after it cools down, rough start due to moisture , after it warms up the moisture clears out.
Same thing happened to my old volvo 740, the definitive test was block tester fluid to detect exh gas in the coolant.
I would do that first to eliminate the worse case scenario, then chase other possible causes.

Block test kit is $22.
https://www.amazon.com/Combustion-Leak- ... iewsAnchor

Go over the basics, the last thing disturbed was coils, check the wiring and ground bolts on each.
Leave the plastic coil cover off, when it starts acting up touch the coil connectors and wiring.
Also put your hands on the injector connectors.

[P2metoo]

After a little frustration with the tamperproof screws cleaned the MAF sensor. It still had a slight rough idle at cold start but it went away much faster and had no extreme vibration. I'll keep monitoring as it is hard to tell with these intermittent issues. Current Bosch sensor had an mfr date of 2014 so it caused an issue at some point 11 years ago. It might be time to replace again. I'll order that block test kit @jonesg recommended to rule that out. I do have a slow coolant leak where I am adding some a couple times a year but I can open the reservoir while the engine is running without anything bubbling out. Thank you!

[jonesg]

if you open the coolant bottle when the enginer is stone cold it should not be under pressure, if it releases pressure when opened cold thats a sign for leaky head gasket, not definitive but a red flag.

[P2metoo]

Phew. I passed the block test so head gasket is intact.
Performance is still significantly improved after cleaning the MAF sensor. With the P0299 turbo underboost code, I am thinking to change my TCV as it may be worn or clogged.
IPD TCV came installed on the car when I bought it 8 years/46K miles ago. Should I order a new IPD TCV or can I switch to the OES Pierburg without making adjustments ($30 less)? I try to stick with OES on these sensors/controllers, but IPD has worked so far. If spending the extra $30 means I can plug and play, I'm all for it. I'm ignorant on interchangeability between the IPD and OES TCV and they are visually different.

[jonesg]

mine has a pierburg.

[P2metoo]

Read some more. I'm going Pierburg.