Rough & Infrequent start + Rough Idle & random misfires

[Adrew19]

So I've been having quite a frustrating time getting my 2001 XC70 (183k miles) to start consistently. When I turn the ignition it will crank for a while and only turns over 50% of the time, less when it's cold outside. Once it's accelerating or cruising there's no misfires. I've taken it to four different shops in my area with no conclusive diagnosis as to what's going on.

Currently getting code P1238 (turbo control valve) as well as P0300 (misfire)

The most recent shop I took it to noticed low fuel pressure & recommended a new pump.

Here's what I've done/replaced so far:
- New battery
- Factory Volvo spark plugs
- Bosch Coils (cleaned grounds as well)
- ETM (Xemodex), this was the first thing a Volvo shop recommended.
- TCV & vacuum lines
- Replaced induction tubing on both ends of charge pipe
- Camshaft position sensor (had a code stored for that)
- MAF sensor
- MAP sensor
- Fuel filter
- Fuel pump & relay (no PEM on this early p2 model)
- Cleaned injectors & replaced dampener
- Cylinder compression is good

*PCV service, cam seals, exhaust vvt seal, & spark well seals was done a few years back as well as the timing belt, alternator and water pump.

Any insights or ideas of what could be causing this issue would be appreciated!

[dikidera]

I am in a similar boat though with a NA engine. However I am arming myself with a pickup probe and will see exactly what my ignition waveform is like, and then maybe correlate that with crank and or cam on my oscilloscope.

Since you mention you had a cam code, could it be you have bad timing? I wouldn't rule out the alternator too or even an oscillating VVT, do check if you have mildly flickering interior lights and headlights.

Why did I mention VVT? Because I've noticed mine on idle will sometimes flicker between 0 and 1, and I've also seen it climb up to 3 degrees of advance especially when cold and if I blip the throttle it goes back down to 0.

Basically I think you need to find a technician that has invested in good expensive equipment like automotive oscilloscopes. For instance having an oscilloscope hooked up to cam, crank, ignition and oxygen sensor, on a very expensive oscilloscope with 12-bit ADC and boatload of memory, you can correlate not just which ignition event happened, but also what the oxygen sensor detected when that ignition event happened.

Because from your post it's fairly evident that throwing money at these cars is never going to solve the problems and while I am no expert, I am also kind of just tired and wish to drive a fully functioning non-misfiring car.

[lrock]

what's your pressure read on the schrader valve at the end of the fuel rail?
and what kind of gas do you use. brand and grade.

[jonesg]

what Irock says.
confirm fuel pressure at the rail now you have a new pump. buy your own gauge for $22.

https://www.amazon.com/BETOOLL-Fuel-Pre ... r=8-5&th=1

then move on to what dikidera says, sensors related to ignition timing.
if you used non OEM parts you probably threw good money away.

[vtl]

CPS (crankshaft position sensor) wires go too close to starter, their take interference up from it. ECM can't see crankshaft position and denies ignition. Cutting CPS wires and routing new ones away from the starter helps with that syndrome.

[Adrew19]

what's your pressure read on the schrader valve at the end of the fuel rail?
and what kind of gas do you use. brand and grade.

Premium gas usually from Shell or Chevron. New fuel pressure gauge on the way. Mine didn't have a schrader attachment that fit.

[Adrew19]

I am in a similar boat though with a NA engine. However I am arming myself with a pickup probe and will see exactly what my ignition waveform is like, and then maybe correlate that with crank and or cam on my oscilloscope.

Since you mention you had a cam code, could it be you have bad timing? I wouldn't rule out the alternator too or even an oscillating VVT, do check if you have mildly flickering interior lights and headlights.

Why did I mention VVT? Because I've noticed mine on idle will sometimes flicker between 0 and 1, and I've also seen it climb up to 3 degrees of advance especially when cold and if I blip the throttle it goes back down to 0.

Basically I think you need to find a technician that has invested in good expensive equipment like automotive oscilloscopes. For instance having an oscilloscope hooked up to cam, crank, ignition and oxygen sensor, on a very expensive oscilloscope with 12-bit ADC and boatload of memory, you can correlate not just which ignition event happened, but also what the oxygen sensor detected when that ignition event happened.

Because from your post it's fairly evident that throwing money at these cars is never going to solve the problems and while I am no expert, I am also kind of just tired and wish to drive a fully functioning non-misfiring car.

Yeah this has been something I've been wondering for a bit now. I'll call around and see if theres any technicians that have experience with this. Thanks!

[Adrew19]

CPS (crankshaft position sensor) wires go too close to starter, their take interference up from it. ECM can't see crankshaft position and denies ignition. Cutting CPS wires and routing new ones away from the starter helps with that syndrome.

Oh good point! I didn't think of this but have run into this issue on other cars in the past. I'll look into this before taking any bigger steps.

[Adrew19]

what Irock says.
confirm fuel pressure at the rail now you have a new pump. buy your own gauge for $22.

https://www.amazon.com/BETOOLL-Fuel-Pre ... r=8-5&th=1

then move on to what dikidera says, sensors related to ignition timing.
if you used non OEM parts you probably threw good money away.

Everything is OEM, the car had sat for 2 years with around 150k miles before I picked it up. Hoping to get it back to where it's reliable enough for some roadtrips and whatnot so most these things I've been fine replacing for peace of mind. Also done some suspension work on it as well.

[lrock]

what's your pressure read on the schrader valve at the end of the fuel rail?
and what kind of gas do you use. brand and grade.

Premium gas usually from Shell or Chevron. New fuel pressure gauge on the way. Mine didn't have a schrader attachment that fit.

I usually just grab a pencil gauge for $1-2; only use it for the fuel/EVAP system and toss it at the end of the day.

I use shell 93 and every time I fill I have to let it crank for longer than usual and open the throttle or it wants to shut off, idles super rough. Do you have a similar experience?

Do you have any way of pulling data, either vida or Bluetooth obd2 dongle?