← Misfire / rough running on all engines

Symptoms · 6.7 Cummins 2007-2018

6.7 Cummins 2007-2018: misfire, rough idle, hesitation or surging

5 documented failures on this engine list this among their signs. They are ordered from the most widespread down. Each one shows the signs in its record's own words, how to tell it from the others, the usual fix and any recall or bulletin.

Holset VGT turbo sticking / actuator failure Very common · 40 complaints · 1 recall/bulletin
Lift pump / fuel delivery weakness Common · 32 complaints · 1 recall/bulletin
EGR valve sooting / failure Common · 16 complaints
Injector 'chuffing' / seal blow-by Common · 12 complaints · 4 recall/bulletins
Head gasket failure (tuned / overheated trucks) Rare · 3 complaints

Not sure which engine you have, or want the recalls for your exact truck? Check your VIN: it names the engine and lists the campaigns for that model year. Whether a recall is still open on your VIN: nhtsa.gov/recalls.

1 Holset VGT turbo sticking / actuator failure

verified How widespread: Very common 40 NHTSA owner complaints match it, out of 1,355 checked

How it shows up

excessive idle/lope or whistle change; failed regens because the turbo cannot build regen heat

Its other signs

loss of exhaust-brake function (the classic first sign - the VGT is the exhaust brake)
low power / boost DTCs (over/underboost), smoky acceleration
turbo actuator DTCs; 'Service Electronic Throttle'?

How to tell it apart

actuator/nozzle-position DTCs and live vane-position PID vs commanded - stuck or lagging vane position is the tell
test the exhaust brake at cold start: no RPM dip / braking effect = nozzle not closing
inspect vane motion with the actuator commanded (shop tool); look for soot coke in the turbine housing

Usual fix

replace the electronic actuator alone when vanes move freely but the actuator is dead (cheaper than a turbo)

Recalls and bulletins

TSB 11-001-08

Root cause, parts and sources →

2 Lift pump / fuel delivery weakness

verified How widespread: Common 32 NHTSA owner complaints match it, out of 1,355 checked

How it shows up

long cranks, hesitation, power loss when the tank is low
FCA (fuel control actuator) ticking / rough idle when failing

Its other signs

P0087 / low-rail-pressure DTCs, worse under load or with tuning
water-in-fuel warnings if filtration is neglected

How to tell it apart

measure supply/return fuel pressure under load (the decisive test) - spec per service data
scan rail-pressure actual vs desired under a load test; P0087 points delivery-side first
isolate FCA vs lift pump: FCA symptoms (ticking/rough idle) vs delivery starvation under load

Usual fix

replace the worn lift pump with a stock-type in-tank unit (stock trucks)

Recalls and bulletins

TSB 08-036

Root cause, parts and sources →

3 EGR valve sooting / failure

verified How widespread: Common 16 NHTSA owner complaints match it, out of 1,355 checked

How it shows up

rough idle, smoke, occasional power loss; failed regens

Its other signs

EGR flow DTCs (P0401/P0402/P0404-family), check-engine light
valve found coked with soot on inspection

How to tell it apart

read EGR DTCs and commanded-vs-actual valve position PID
remove and inspect for coke; clean vs replace decision follows condition
check the EGR cooler and CCV filter state at the same time - they share the soot/oil load

Usual fix

clean the valve (if pintle moves freely after cleaning, reinstall); replace when worn/stuck

Root cause, parts and sources →

4 Injector 'chuffing' / seal blow-by

verified How widespread: Common 12 NHTSA owner complaints match it, out of 1,355 checked

How it shows up

fuel smell, smoke, rough cylinder balance; balance-rate DTCs

Its other signs

audible 'chuff chuff' exhaust beat (compressed gas past an injector's copper seal)
fuel in the oil / rising oil level (pairs with the oil-dilution mode)

How to tell it apart

cylinder-balance / contribution test to locate the weak hole
listen at the exhaust for the chuff beat; check oil level trend for dilution
return-flow / leak-back test per injector where equipped

Usual fix

replace copper sealing washers (cheap) if the injector itself tests healthy

Recalls and bulletins

TSB 05175565A$TSB 18-002-14 REV. B TSB 18-002-14 REV. A TSB 18-002-14

Root cause, parts and sources →

5 Head gasket failure (tuned / overheated trucks)

verified How widespread: Rare 3 NHTSA owner complaints match it, out of 1,355 checked

How it shows up

misfire on startup after sitting (fluid into a cylinder)

Its other signs

coolant loss, combustion gas in the cooling system, pressurised degas bottle
white smoke, sweet smell; overheating events in history

How to tell it apart

block-test the coolant for combustion gas
monitor cooling-system pressure rise vs RPM (combustion leak signature)
compression / cylinder leak-down if a specific hole is suspected

Usual fix

fix the overheat cause first (fan clutch, coolant leak, DPF derate ignored) or the new gasket dies too

Root cause, parts and sources →

Other symptoms on the 6.7 Cummins 2007-2018

Hard start, long crank or no-start Loss of power, limp mode or derate White smoke from the exhaust Losing coolant Overheating or temperature creeping up Oil leak, oil consumption or rising oil level Ticking, knocking, rattle or whine DEF, DPF and regeneration warnings

Everything on the 6.7 Cummins 2007-2018 Its recalls and bulletins

Order: how widespread each failure is in its record (near-universal, very common, common, occasional, rare), then the number of NHTSA owner complaints that match its keywords. Complaint counts are keyword matches, not a manual review of each complaint. A symptom listed here means the failure is documented with that sign; it is not a diagnosis of your truck. Tiers: verified, aggregated, contested, data-gap. How we tier and source facts.