Nowadays, it is quickly assumed that most engine problems are more electrical than mechanical, especially when the malfunction indicator light on the dashboard is activated.
The following example revolves around a Seat Ibiza with a three-cylinder engine with twelve valves. A diagnosis was performed and the following Diagnostic Trouble Codes (DTC) appeared:
- (P0106) – Manifold Absolute Pressure/Barometric Pressure Circuit Range/Performance Problem
- (P0301) – Cylinder 1 Misfire Detected
- (P0303) – Cylinder 3 Misfire Detected
- (P0300) – Random/Multiple Cylinder Misfire Detected
Accordingly, a simple misfire or an air leak is obvious. In fact, a quick check of the vacuum hoses revealed a crack in the brake booster hose. After replacing the hose, the fault codes disappeared. In the field test, however, the vehicle did not deliver its full engine power and the engine often stopped completely while halting at intersections. Further troubleshooting was therefore necessary.
Real-Time Measurement
Further troubleshooting revealed that a misfire, as indicated by the error codes, could be ruled out. With the help of a diagnostic tool and real-time measurements of the intake manifold pressure sensor at idling speed, values of around 360 mbar could be determined in the warm state. As soon as the engine speed was increased and the throttle was opened, the vacuum dropped as expected. When the engine was returned to idle, however, there was the risk of the engine stalling: this is why the engine management system became active and opened the throttle valve in order to briefly increase the injection time before reaching idle.
Is this now a problem with the engine management or is it a mechanical problem where the error codes incorrectly indicated an engine management problem?
Checking the Static Ignition Timing Setting
The next item on the checklist was the static ignition timing setting which can be checked with relative ease in this engine. The air filter housing was removed followed by the spark plugs from cylinder no. 1. Thereafter, the two camshaft covers, which are located at the end of the cylinder head and are fastened with 10 mm screws, were also removed.
The engine was turned by hand until piston no. 1 reached its Top Dead Center (TDC). Since there are no time markings, this could be checked by inserting the appropriate rod into the spark plug opening to ensure that the piston had reached its highest possible position.
With the correct time setting, the offset grooves of the camshafts must be aligned with the cylinder head housing. If the alignment is not correct, the ignition timing will be inaccurate and the camshafts will not be in the correct position.
Upon closer inspection, one could immediately see that the timing chain had jumped. The position of the exhaust camshaft (Fig. 1) visibly no longer matched the position of the intake camshaft in the horizontal cylinder (Fig. 2).
The performance losses and stalling were due to the asynchronous running of the camshafts. This caused a divergent timing of the valve openings.
Note: If it is clearly visible that the valve has come into contact with the piston, the damaged components must be replaced as recommended by the vehicle manufacturer.
Checking the Timing Chain
For this engine, it is essential to use the correct adjustment tools to ensure correct ignition timing and tuning of crankshafts and camshafts. The sprockets on the camshaft and the crankshaft pulley do not have keyways or adjustment marks.
The engine oil has been drained; in addition, all belts, pulleys, engine mounting, piping, wiring harnesses, timing chain cover, engine oil pan, and oil pump chain have been dismantled in accordance with the manufacturer’s recommendations to get to the timing chain for inspection.
The crankshaft adjustment tool has been fitted. However, because the camshafts were misaligned, the camshaft adjustment tools could not be fitted. This normally would happen at the beginning if the chain did not jump.
After dismantling the timing chain, the inspection revealed that the timing chain, sprockets, and guides were worn. This caused the timing chain to slip, which in turn caused the outlet camshaft to be displaced by two teeth, resulting in out-of-round engine running. A new timing chain kit was required (Fig. 3).
Installation of a New Timing Chain Kit
Since the introduction of this engine, an improved timing chain kit has been introduced to the market to reduce the risk of such incidents. It has been shown that this engine is a common problem in many Volkswagen, Seat, and Škoda models.
The new timing chain set (febi no. 30607) includes sprockets for the camshaft and crankshaft, new bolts, a new chain, a new pulley bolt for the crankshaft, an improved hydraulic tensioner, and longer, modified guides to prevent the chain from jumping in the future (Fig. 4).
Before replacing components, clean all fitting surfaces of the engine oil pan, the timing chain cover, and the engine. After this has been completed, install the new timing chain kit according to the manufacturer’s instructions and reinstall the oil pump chain, sprocket, and tensioner; tighten the sprocket screw. Finally, replace the oil pump chain cover.
Replace the crankshaft seal (febi No. 32471) and attach the silicone seal to the timing chain cover and engine oil pan mating surfaces before attaching these components to the engine. Replace the crankshaft and tighten the new screw.
Replace the alternator, water pump pulley, auxiliary belt guide, belt tensioner, belt, engine mounting, and coolant expansion tank.
It is advisable to carry out an oil change, replace the oil filter, and apply fresh oil to the filter housing during engine repairs of any kind so that hydraulic pressure is present during the first start.
Replace the air filter housing and other parts that have been removed during the work.
If the engine is running smoothly after the start, test the vehicle at idle on the lift and make sure that no oil is leaking. Stop the engine, check the engine oil level, and top up if necessary. If needed, check and delete old fault codes. Extensive testing should then be carried out.
