2006 Volvo V70 turbo

[KCMike]

Our V70 starts and runs fine until it gets well warmed--usually about 30 minutes, depending on whether driving city streets or highways. At that point it begins to choke, sputter, and eventually stop completely. It will restart immediately and run a short distance (usually no more than 1/2 mile) before beginning the process again. Once it cools completely the cycle starts again. The mass air flow sensor was replaced in 2022. Recently the fuel pump was replaced along with the fuel filter and fuel injection pressure sensor. The problem persisted. Diagnosis is particularly difficult because the car must be driven for a half hour or more for the problem to occur--and I don't know what sort of readings are being given once it is pulled into the shop after such a drive. Whatever they are/were, they have not been constructive in coming up with a solution so far.

[BlackBart]

I’ll be very interested to read the solution to this.

I’m no expert, but I might start by thinking through what changes as it heats up. It starts perfectly, everything is fine. The engine should be up to operating temp in 5 minutes or so. What changes after 30? The rest of the engine compartment can continue to heat up.

Aluminum and steel expand and move - is something loose enough to cause a vacuum leak? A split vac hose somewhere that opens up? Is a relay failing as it heats up and shorts out? Is an electrical connection loose and heat causes it to stop contacting? Is there a sensor or sender failing with heat and sending the wrong info to the computer? (I would think it would just fail, and the computer reverts to default).

[KCMike]

Thank you for the good questions and comments. I will run them by the current mechanic--the first, who are always quite good, gave up and sent us to a "Volvo Whisperer"--although he is still puzzled. What particularly doesn't make much sense is that once it stops, or we turn it off because it is bucking like a colt, it immediately starts back up and will drive for a while without incident. I would think once it gets hot enough for a leak, hose opening, short, etc. that it would stay that way for a bit and act up immediately on restart. But, again, thank you--I'm not a mechanic, so I'll pass these along.

[BlackBart]

Yes, that makes sense on hot re-start.

Hmm..