Airflow Issues

 After 3 years my 1992 Mercedes SL500 has been repatriated back from Neil's Garage.

Gaskets have been replaced, it has two new fuel pumps, I've used up three Mass Airflow sensors and the rotors, HT cables and plugs have all been replaced - all to no avail in curing the misfire. Neil finally gave up and, for sporadic work over three years, storage and a wash, he charged me only £20 after I offered him £500 for his trouble. He was glad to see the back of it.

The symptoms are a misfire, but only once the engine warms up. The initial solution was to replace the MAF sensor with a 2nd hand unit from e-Bay. That didn't work, so that's when he tackled the gaskets and other associated peripherals at mates' rates, thinking that the warming up of the engine was causing a gap somewhere in the intake system or a fuel restriction on one side of the 5 litre V8.

All this had no success, so it must have been something to do with the MAF, as the car didn't misfire with the MAF sensor removed - albeit that it didn't pull at all. I thought I may have bought a duff MAF sensor and so purchased another one, but with again the same result.

I am now coming to the conclusion that I was unlucky enough to have bought two, consecutively duff MAF sensors and the only option now is to either clean the sensors with electrical contact cleaner, which has been known to work on other Merc SL500s, or dig deep and purchase a warrantied 2nd hand MAF sensor for about £450, which would have been cheaper in the first instance than all the other parts I spent money on. However, I couldn't find any that were warrantied, but I have now.

That's the problem with classic cars - you have to rely on 2nd hand parts, as new parts are no longer manufactured.

On the plus side, the car has doubled in value in the intervening 3 years and had no miles put on the clock. I purchased her for £5,500 and she's now worth £10-11,000 - providing I can get it running without a misfire. Mind you, the price of refuelling it has gone up dramatically too, although. Under the old rules, she's be road tax exempt next year, but that all changed in 2018 and she now has to be 40yrears old.

If I can eliminate the misfire I'm minded to sell it, as I really want to buy a Triumph GT6 project and £10k would go a long way to restoring one in reasonable condition. 

Watch this space.