Saab 1.9 Diesel Engine and Diesel Particle Filter (DPF ). An interesting set of faults.

Beware of aftermarket DPFs and other parts!

Aftermarket DPF removed from car.

We have just finally got to the bottom of a set of interesting problems with a 2005 Saab 9-3 Z19DT (8 valve).

 The History.

The car was brought to us with the customer complaining of heavy smoking whilst driving. On speaking to the customer a rather sad, and for him, expensive story emerged.

When the problem started he took it to a garage who immediately diagnosed a blown turbo, even though the smoking was intermittant ! A new turbo was fitted at enormous cost, 30 miles later the smoking reappeared, the car was returned, the turbo checked, diagnosed as faulty and replaced under warranty. Guess what. 30 miles later the smoking returned !

In frustration, and somewhat poorer, the customer took the car to another garage. Here a faulty DPF ( Diesel Particle Filter ) was  blamed and a new one fitted, along with a new EGR valve. More expense ! And …… You guessed it, 30 miles later the smoking was back ! The car was returned to the garage and the problem was re-diagnosed as faulty injectors, these were duly replaced, not a cheap job.  No luck, the smoking returned. At this point we were contacted and the car was brought in.

 The Investigation.

On arrival, and, whilst the customer was with us, we checked the car with Tech2 and found the DPF to be blocked, so first line of attack was to carry out a forced regeneration. As always prior to doing this it is prudent to check coolant and oil levels. The coolant was ok, however the oil level was a good two inches above the max level on the dipstick ! On sucking out 2 litres of excess oil we gave it a quick smell check and could smell diesel suggesting an injector fault.We then arranged to keep the car for further investigation.

The following morning we were able to devote some time to the car .On cold startup  a misfire was immediately obvious during warm up. By unplugging the injectors one by one we found that the fault lay with ( the new ) No2 injector.

This identified issue had to be resolved before we could go any further.

The Diagnosis and Repair.

The injector, being under warranty, was sent back to the garage who fitted it, it was duly replaced with another ( aftermarket ) new one and programmed in, the contaminated oil and filter were replaced and the misfire was cured. The next step was to regenerate the filter. We had difficulty in doing this as the system struggled to get the temperatures up to the required level, this was accompanied by lots of smoking and eventually Tech2 timed out the forced regeneration programme.

After a bit of head scratching a phonecall was made to the customer to find out more about the DPF replacement, it transpired that it was an aftermarket unit. We speculated that the flow rate was too great through the filter dissipating the heat, thus throwing out the parameters for automatic regeneration. A good secondhand unit was fitted and immediately a forced regeneration was possible without any problems, the next step was a good road test. All worked perfectly, however it was noticed that the engine took a long time to reach normal temperature, and once on an open road the gauge dropped towards low. This would also contribute to the car not being able to regenerate itself since as the temperature criteria for automatic regeneration would not be reached, a new thermostat resolved the issue and all was well. Best of all no smoking !

The moral of the story.

Don’t allow a garage to jump to snap decisions without proper investigation of a problem. It can get VERY expensive. In this instance the customer has paid out in excess of £2300 in parts that weren’t required, and in excess of £900 in labour to have the work done.

1. If aftermarket parts are to be fitted, make sure they are of a good brand name and quality. There are some very cheap replacement parts out there and the old adage still holds good “ you get what you pay for”!
2. Modern cars have got more and more complex with interactive electronics and systems. Specialist equipment is required to interrogate and draw live data from the cars. Make sure that your garage has the facility to do this.
3. If in doubt. Seek a second opinion.

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