1HD-FTE cold start grey smoke + rough idle (428k km) – extensive diagnostics done, looking for experience

[Lars224]

Hi all,

I’m trying to track down a persistent cold-start behaviour on my 2006 HDJ100 (EU spec) with the 1HD-FTE and Denso EDC-V4 pump. I’ve done quite a bit of diagnostics already, but the root cause is still unclear, so I’m hoping someone here has seen something similar.

Vehicle:

• 2006 Land Cruiser HDJ100
• 1HD-FTE
• ~428,000 km
• Automatic
• Engine otherwise runs very well, strong power and good fuel economy.

---

Symptoms

When starting from cold (especially below ~5°C, worse at 0 to –10°C):

• noticeable grey smoke for up to ~1 minute
• smell is typical “cold diesel”, not sharp raw diesel
• rough / coarse idle during this period
• engine smooths out as temperature rises

Additional observations:

• If I start driving immediately, the engine smooths out under light load, but grey smoke continues until it warms up.
• When returning to idle during the warm-up phase, the roughness returns.
• Once warm, the engine runs perfectly smooth.

---

Other characteristic

At idle and light load the engine sounds a bit “hard” / sharp compared with other 1HD-FTE engines I’ve heard.
Under full load it sounds completely normal.

---

Things already checked / eliminated

• Injectors: professionally rebuilt
• Valve clearances: checked and adjusted ~40,000 km ago
• No measurable oil consumption
• EGR: physically disabled (vacuum lines removed, valve closed)
• Grid heater: confirmed working (~100 A current draw)
• Cranking speed: strong (dual new batteries)
• No air in fuel system
• Engine pulls very strong under load

---

Fuel pump related tests

TCV (Timing Control Valve)
Disconnected the electrical connector while idling:

• idle becomes noticeably softer / smoother
• pump noise decreases
• but more smoke and poor throttle response

Reconnecting the TCV:

• pump noise returns
• idle becomes sharper/harder again

This suggests timing is being actively controlled and the valve responds.

---

SCV (Suction Control Valve)

• coil resistance measured ~1.5 Ω
• disconnecting SCV causes engine to stall immediately
• engine cannot be started with SCV disconnected

So electrically and functionally it appears to respond normally.

---

Observed timing behaviour

Using Techstream:

• injection timing during cold start appears to rise stepwise approx. 8° → 16° → ~19° CA, then stabilizes.

---

Additional note

The vehicle has a Dimsport Rapid tuning module (fuel / boost / timing), but:

• the cold start smoke issue was already present before installation
• behaviour did not change after installation or dyno tuning.

---

Questions

Has anyone experienced similar symptoms on a 1HD-FTE with EDC-V4 pump?

Particularly interested in:

• cold grey smoke + rough idle that disappears warm
• relatively sharp idle sound
• timing seeming somewhat aggressive at idle

Possible suspects I’m considering:

• base pump timing slightly advanced
• advance piston / internal varnish in the pump
• SCV affecting transfer pressure despite appearing functional

Before I start moving pump timing, I’d be very interested to hear if others have seen similar behaviour or identified a specific cause.

Thanks in advance.