Car Wars – The Emissions Light Strikes Back

If you’ve read about last year’s family holiday then you will have read some things about the ongoing problems I’ve been having with my car. To give you a bit of background I bought the Golf (Mk4) back in 2004 when it just had 23,000 miles on the clock. It ran like a dream, at least for the first year until it had its first MOT. From that moment on I was plagued by random appearances of the dreaded emissions workshop light, which in honesty is about as much use as an ashtray on a pushbike as it tells you NOTHING about what the hell the is up with the car!

I’ve had several mechanics look at the car and all of them have said that there was nothing in the way of a physical fault as when the error codes have been cleared the car runs normally. Anyway fast forward some 12 years and 71,000 miles later and the problems started getting worse…

Back in July 2016 we were just about to set off on our holiday when the emissions workshop light kept coming back even faster than usual which indicated the problem was getting much worse. My diagnostics checker was bringing up a 16555 error code as well as a 16687 Cylinder 3 misfire detected.

On a second inspection I noticed that there was a split in the breather pipe, when I looked at removing the pipe it looked like it had been sheared right through. I figured that this was one of the reasons why it was drawing in too much air so ordered a replacement part from eBay as it was cheaper than the dealers.

After replacing the pipe and cleaning the engine throttle body with carb cleaner I tried the car again, unfortunately the problem remained. Using my “Google-Fu” I started looking at the various diagnostic steps and proceeded to go through them. With the help of my brother (an “old school” mechanic) we went through swapping the spark plugs from cylinders 3 & 4, swapping the injectors between the same cylinders all with no change. Next we checked the ignition leads, specifically that on cylinder 3 and confirmed that there was a spark present. We also removed the Mass Airflow Sensor and gave it a clean with some carburettor cleaner. With the problem still present I had to rush out and pick up a spare set of ignition leads and a spare coil pack. Surprisingly after swapping the HT leads the misfiring disappeared.

While on holiday the dreaded emissions light came on several times, I quickly dismissed the code and we carried on with out holiday. When we got back the problems started to become worse, with multiple random misfires and one cylinder failing to fire again I thought I was going to be off the road yet again…

Shortly after we got back it was MOT test time again and I had missed being able to get the car into the local council test centre so took it to my local garage down the road. I then found out that the car had failed and the person testing it had given my wife a handwritten list of things that needed doing that weren’t on the failure certificate. It suspiciously looked like they were “fishing” for work so I booked another test at the nearby Kwik Fit (and you know how much I love them!), and guess what it failed again! This time with additional things the first garage hadn’t picked up on. Still the main reason for failing the test was being unable to complete the emissions test.

This time we ended up changing the coil pack and as a precaution we removed the EGR valve which was a royal PITA and gave it a blast of carb cleaner. I was surprised that it was not jammed open or covered in carbon deposits, at least it was another of the diagnostic steps checked off the list.

While removing the EGR valve we spotted another problem which had gone unnoticed… there were splits in the vacuum hose nearby. I had checked the hoses above the engine block by spraying them with carb cleaner but didn’t notice any change in the engine speed. These hoses were made from a hard plastic so they would not collapse under pressure. However, they had a reputation for becoming brittle over time. It’s probably another one of the VW designers ideas to sell expensive parts via  the dealers. Apparently there was a recall issued for VW models manufactured before 2000 for this issue. Sadly my car (2002) missed out on the recall but suffers from the same problem. We tried removing one of the pipes and after sawing off the split end soaking the pipe in a jug of boiling water to see if it would soften up enough that it could slide over the tapered hose barb to no avail.


After some more “Google-Fu” I learned that the supposed “fix” that VW had been doing was nothing more than replacing the damaged ends with a rubber pipe and clamping them. Why they didn’t to this in the first place I don’t know as it would have provided some isolation form the vibration that happens under the hood. So with that in mind I tracked down 16mm internal diameter reinforced fuel pipe and some jubilee clips and set to work replacing the defective joins.

With the joins repaired we were still getting the engine lean codes. This time I decided it was time we took a more serious look at where the leak may be coming from. Using an old metal paint tin, a Schrader valve from a bike inner tube and a length of plastic tubing I made a smoke machine. I connected the flexible tubing to one end of the intake hose which I had disconnected from the air filter and used an old rag to seal up the pipe as best I could. Next I found another old rag and put it inside the paint tin and set it alight, once the rag was burning I put it put and fixed the lid back on. The other end was connected to a bike pump and once we started pumping and confirmed that there was a jet of smoke coming out of the tubing we set about trying to locate any more potential leaks.

We didn’t have to wait too long as I saw a thin plume of smoke coming from the engine block near the dipstick. It looked like another pipe had perished and needed replacing so off to eBay it was again. With that pipe replaced we gave the engine another smoke test and couldn’t see anymore smoke. I thought we finally had the problem licked…

A few weeks later my wife was using the car and had to slam on the brakes when some idiot pulled out in front of her without looking. She called me afterwards and said that the light had come back on again… Like I said, just when you think you have things sorted out it decides to rear its ugly head again.

While trying out the brake I noticed that I could hear a “hissing” sound every time I pressed the pedal, the brakes were working but it felt like you hard to press a lot harder (and sooner sometimes) to get the same effect. So it was time to check all the recent repairs I had made to the vacuum pipes and I found yet another split pipe right near the brake booster cylinder. Talk about it being in an awkward place! It took much swearing and cursing the gods before I could clean up the split end and make good the repair.

The last thing I noticed was that one of the pipes from the air filter had come loose. Turned out that the retaining clip had broken so I had to make a quick bodge repair with some cable ties to hold the pipe in place.

So how has the car been since..? Well it did pass its MOT on the 3rd attempt, although I’ll have to admit that I’m not driving the car as much now as I just don’t trust it like I used to.

Still when you think that we’ve had the car for around 12 years and clocked up some 50,000 miles on it in that time and have only spent something like £1000 in garage bills we’ve had our money’s worth out of the car.