1.6 FSI - High Lamba Reading + Misfire: Injector, Lambda Sensor, Timing Chain or Other?

[markmooch]

Hello all,


I have a VW Golf mk5, 1.6 FSI SE on a 54 plate with a high Lambda reading of 1.3 which has resulted in it failing the MOT test. The MOT tester said it needed a new Lambda sensor and that would sort the job (stop the misfire, turn off the misfire / emissions light), the mechanic said it would cost £120 to fix and the boss said that wouldn't necessarily fix it. They did not do any real diagnostics or fault finding and I don't fancy chucking money at it indefinitely until something sticks.


Recently I have had the car at an auto-electrician for some other electrical issues and they reported a misfire on cylinder 4 (fault code P0304) and random misfire (P030). They also checked the wiring and said that was not at fault, as the auto-electrician said, he would, 'bet his bottom dollar' that it is an injector.


I had told the auto-electrician that when the car was serviced 2.5 years ago that the spark-plugs were changed and the coils tested (although they had all been previously replaced by me at different times when they went). Also a compression test was carried out. This was because the misfire and misfire / emission light was present then too.


The car has also been looked over again today and I have talked to a few mechanics (with the car present) who all believe it is likely to be an injector, except of course for the MOT garage (lambda) and except. . .


. . . One mechanic whom had his suspicions aroused upon starting the car today and heard a fast loud engine rattle which I have heard many times in the 6 years I've owned the car, it has never caused me any problems. He however believes it to be a timing chain issue (this car is not a belt) but needs to look further on Monday and could be the cause of all my problems.


Lastly just incase, I have tried carburettor spray and injector cleaner in the past to no avail, the car is fairly low mileage 7.5k a year average (90k total) and an injector fault has never come up on any diagnostics in the past. The car has had the misfire for around 3 years but has never failed an MOT because of it.


I'm at a loss as where to put my money and time is also running out very fast (MOT already out, re-test weds, work to go to).


Has anyone experienced these symptoms before or would they have a possible solution?


Is timing chain tension a big job? Can that lead to misfire and therefore the engine running 'lean' and putting too many fumes out? Is there anyway I check the Lambda sensor myself?


Much appreciated.


Mark

[Crasher]

The compressions should be checked again before you do anything. FSI injectors do play up and are difficult to change so all four should be done, a special seal setting tool is required to put the Teflon seals onto the injector. Changing the timing chains is a big involved job, again requiring special tools for alignment. Both Lambda sensors can be checked in a diagnostic mode provided by the ECU and accessed using a diagnostic system such as VCDS BUT it often pronounces a sensor OK when it isn't. You should put your money into having the car properly diagnosed by someone who knows what they are doing, a VAG specialist or main dealer.