Hi everyone,
I have a 2007 Mazda3 MZR-CD 2.0L turbo diesel manual with 170,000km on the clock. 90% of the time the car drives perfectly – smooth idle, lots of power, responsive acceleration, etc. During longer highway trips (greater than 30 minutes cruising, up to several hours) the car will unexpectedly loose power. I’ll be cruising at 110km/hr on cruise control, and then when going up a small hill, the car will rapidly loose power (often dropping out of cruise control), down to around 70km/hr. Down shifting and flooring the accelerator has very little response. No warning lights are on. If I pull over at this point, the idle is rhythmically irregular - dropping low and almost stalling, then recovering, the engine bay smells like rotten eggs. Turning the car off and on again usually resolves the problem. If I don’t pull over, the car struggles along for around 10 minutes before rapidly returning to full power.
A mechanic suspected fuel issues and replaced the fuel filter (which was dirty), but the issue continues. I have since replaced the fuel filter again (which was fairly clean) with no resolution.
I then began to suspect the DPF. It seemed the symptoms may be correlated with the car attempting / performing a DPF regen (i.e. during highway cruising, sulphurous smell from engine, etc). The DPF light has illuminated (solid) on two occasions recently, not at the same time as the loss of power, but maybe 20-50km afterwards. The DPF light goes out after some more highway cruising (I guess this means the regen was successful).
So far, I have performed two forced DPF regens – the first time the car blew a lot of pale smoke and took the full 90 minutes (the longest cycle according to the engine manual). The second time, no smoke and only 60 minutes. I have also removed, cleaned and reinstalled the EGR valve. It was a bit sooty but not obstructed or stuck open or closed. There was a fair bit of soot/gunk at the intake manifold end of the EGR pipe, and some flaky black material in the turbo hose between the intercooler and the intake manifold. I cleaned this as best I could but plan to clean more thoroughly.
I’ve scanned for error codes – none. I’ve watched live-stream engine data whilst idling and driving – when the car is operating normally, everything seems to be within normal ranges and responding normally to driver input – i.e. when accelerating, MAF and MAP increase nicely, fuel rail pressure increases nicely, etc. When the car is doing its rhythmical irregular idle when pulled over after loosing power, the key differences in engine data (compared to idling normally) are:
- Low MAF (jumping around 1-3g/s compared to 5-6g/s when idling smoothly)
- Low TP% (jumping down to 0.something% momentarily at times, compared to steady 4.3% when idling smoothly)
o I think this is referring to what Mazda calls the Intake Shutter Valve (ISV) – i.e. diesel version of a throttle plate. I’ve physically inspected the throttle body and confirmed there is a butterfly valve present, unlike some diesels).
- These jumpy values correspond with revs dropping low (i.e. low MAF and low TP% = low revs)
- The CATEMP21 and CATEMP12 values are >400degrees C, compared to under 400degrees when running normally – perhaps indicating the car is/has recently attempted/performed a DPF regen – potentially correlating symptoms with DPF regens.
Unfortunately I don’t have any live data from when the power loss occurs when driving at speed.
I’m aware that a slight loss of power may occur during DPF regen, but wouldn’t expect to drop from 110km/hr to 70!
My plan is to remove + get the DPF professionally cleaned + reinstall, clean the intercooler + associated pipes, clean the intake manifold, clean the MAP sensor, replace the air filter (not dirty but why not) and then change oil + filter and reset DPF.
What do people think? Am I on the right track? Any ideas?
Thanks!
I have a 2007 Mazda3 MZR-CD 2.0L turbo diesel manual with 170,000km on the clock. 90% of the time the car drives perfectly – smooth idle, lots of power, responsive acceleration, etc. During longer highway trips (greater than 30 minutes cruising, up to several hours) the car will unexpectedly loose power. I’ll be cruising at 110km/hr on cruise control, and then when going up a small hill, the car will rapidly loose power (often dropping out of cruise control), down to around 70km/hr. Down shifting and flooring the accelerator has very little response. No warning lights are on. If I pull over at this point, the idle is rhythmically irregular - dropping low and almost stalling, then recovering, the engine bay smells like rotten eggs. Turning the car off and on again usually resolves the problem. If I don’t pull over, the car struggles along for around 10 minutes before rapidly returning to full power.
A mechanic suspected fuel issues and replaced the fuel filter (which was dirty), but the issue continues. I have since replaced the fuel filter again (which was fairly clean) with no resolution.
I then began to suspect the DPF. It seemed the symptoms may be correlated with the car attempting / performing a DPF regen (i.e. during highway cruising, sulphurous smell from engine, etc). The DPF light has illuminated (solid) on two occasions recently, not at the same time as the loss of power, but maybe 20-50km afterwards. The DPF light goes out after some more highway cruising (I guess this means the regen was successful).
So far, I have performed two forced DPF regens – the first time the car blew a lot of pale smoke and took the full 90 minutes (the longest cycle according to the engine manual). The second time, no smoke and only 60 minutes. I have also removed, cleaned and reinstalled the EGR valve. It was a bit sooty but not obstructed or stuck open or closed. There was a fair bit of soot/gunk at the intake manifold end of the EGR pipe, and some flaky black material in the turbo hose between the intercooler and the intake manifold. I cleaned this as best I could but plan to clean more thoroughly.
I’ve scanned for error codes – none. I’ve watched live-stream engine data whilst idling and driving – when the car is operating normally, everything seems to be within normal ranges and responding normally to driver input – i.e. when accelerating, MAF and MAP increase nicely, fuel rail pressure increases nicely, etc. When the car is doing its rhythmical irregular idle when pulled over after loosing power, the key differences in engine data (compared to idling normally) are:
- Low MAF (jumping around 1-3g/s compared to 5-6g/s when idling smoothly)
- Low TP% (jumping down to 0.something% momentarily at times, compared to steady 4.3% when idling smoothly)
o I think this is referring to what Mazda calls the Intake Shutter Valve (ISV) – i.e. diesel version of a throttle plate. I’ve physically inspected the throttle body and confirmed there is a butterfly valve present, unlike some diesels).
- These jumpy values correspond with revs dropping low (i.e. low MAF and low TP% = low revs)
- The CATEMP21 and CATEMP12 values are >400degrees C, compared to under 400degrees when running normally – perhaps indicating the car is/has recently attempted/performed a DPF regen – potentially correlating symptoms with DPF regens.
Unfortunately I don’t have any live data from when the power loss occurs when driving at speed.
I’m aware that a slight loss of power may occur during DPF regen, but wouldn’t expect to drop from 110km/hr to 70!
My plan is to remove + get the DPF professionally cleaned + reinstall, clean the intercooler + associated pipes, clean the intake manifold, clean the MAP sensor, replace the air filter (not dirty but why not) and then change oil + filter and reset DPF.
What do people think? Am I on the right track? Any ideas?
Thanks!
