Intermittent rough cold start 04 XC70

[abscate]

Take a good look at all your vacuum lines and induction hoses. They all need to be tight and clamped

On a rough running car, all those codes are meaningless chatter turbo valve has nothing to do with idle , so that’s not the cold start fault.

You will need tools and dirty gloves to inspect vacuum/induction lines. You can’t just “ look”

Example here.

viewtopic.php?t=79114&hilit=vacuum&start=10

Check this out on my T5….wierd cold start ftom a broken hose

viewtopic.php?f=1&t=84552

[P2metoo]

Update. Check engine light resolved 1 week ago and car has continued to have a slight rough cold start but otherwise smooth operation and good power. This morning had a recurrence of the bumpy rough cold start and check engine light came on. Had low power accelerating so felt like underboosted turbo. Haven't checked the codes yet, but expect the same P0299 and P0300-305.
My new TCV arrives tomorrow so hope it will resolve the issue. My theory is carbon build up over time on MAF sensor and in the TCV with 8-10 years of wear.

[P2metoo]

A 3 week trip kept me away from this issue. I got a new Pierburg BCS/TCV installed. After 5 days the issue persists. At this point I am going to take it into a mechanic and pay for a couple hours of troubleshooting. I'll see what they find.

[P2metoo]

Take a good look at all your vacuum lines and induction hoses. They all need to be tight and clamped

On a rough running car, all those codes are meaningless chatter turbo valve has nothing to do with idle , so that’s not the cold start fault.

You will need tools and dirty gloves to inspect vacuum/induction lines. You can’t just “ look”


Example here.

viewtopic.php?t=79114&hilit=vacuum&start=10

Check this out on my T5….wierd cold start ftom a broken hose

viewtopic.php?f=1&t=84552

@abscate I'm sorry I overlooked your post. This is probably the issue as those posts seem identical to my issue. I'll have the repair shop check for me. Unfortunately with some work trips and needing to tackle my jungle of a yard, I am out of tinkering time for the next couple months.

[P2metoo]

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.

Well, time has passed and I tried this test again after some bubbling in the coolant reservoir. The test showed positive for exhaust gasses. I will have a head gasket job in my future.

[awizarddresden]

If you vape or smoke there's a free way to test at least the intake vacuum lines. Pop the line off of the intake nipple. Take a big puff and blow it down that line. Do it a bunch of times and eventually you'll have enough smoke in there for it to be coming out of any holes in the lines.

Thats how I found my Compressor Bypass Valve was bad. It was giving a rough cold start for the first one of the day. IF the engine was warmed up it would start fine.

Replaced that and it starts right up now.

[jonesg]

the block tester fluid is quite definitive for gasket failure.
Not as serious as belt failure that crashes the valves.