Jeep Cherokee: 2.8 CRD inlet manifold sooting and EGR coking

Like most common-rail diesels of its era, the 2.8 CRD recirculates exhaust gas and crankcase fumes back into the inlet, and the combination bakes into a thick oily tar that progressively blocks the inlet manifold and EGR passages. Short trips and town use accelerate it badly. The result is gradual power loss, poor economy and smoke, and because it comes on slowly many owners never notice how much performance has been lost. Cleaning is labour-intensive rather than expensive in parts. This engine also drives its camshafts by belt and is an interference design, so timing belt history is worth establishing at the same time — a snapped belt destroys the engine.

• Gradual loss of power, particularly noticeable uphill or when loaded
• Black smoke under acceleration
• Worse fuel economy than expected
• Engine warning light with EGR or airflow codes, or intermittent limp mode

1. 1

   On the test drive, find a hill or load the car up and accelerate through the mid range — a healthy 2.8 CRD pulls strongly, and a doughy engine that runs out of breath is the main symptom.

2. 2

   Have a helper follow or watch your mirrors for black smoke under hard acceleration.

3. 3

   Ask the owner what fuel economy they actually get and what sort of driving the car does; a diesel used only for short town trips is the worst case for this.

4. 4

   Check the dash for an engine light and ask whether it has ever gone into limp mode.

5. 5

   Look at the engine bay for oily residue around inlet joints.

6. 6

   Ask directly when the timing belt was last done and for the invoice, since this is an interference engine.

7. 7

   If a workshop inspection is possible: have the inlet and EGR inspected with a borescope and the fault memory read for EGR flow and airflow deviation codes.

Parts involved: Intake manifold, EGR valve.

$600 to $2,500 at New Zealand independent workshop rates. That is for this job on its own, not for the car.

An estimate, in NZD, for the repair as normally carried out. What a specific car costs depends on which part has failed and what it damaged on the way — treat this as the floor for a negotiation, not a quote.

• “When was the timing belt last replaced, and do you have the invoice?”
• “Has the inlet manifold or EGR ever been cleaned or replaced?”
• “What sort of driving does the car mostly do, and what economy do you get?”

The failure described above is documented in published sources — owner forums, technical service bulletins, recall notices and workshop write-ups — held in our fault database. The inspection instructions and the cost estimate are KickTyres’ own interpretation of them, and it is a starting point for an inspection rather than a manufacturer statement.