**MK4 GOLF 20V TURBO AUM ISSUES HELP**

[Mk4_AUM]

Hi everyone

I bought my mk4 last November and bought the car with a few misfiring issues which I have sorted now, recently the car has been getting some form off backfiring from the engine bay (not exhaust all stock) now first off all before I go any further the car is completely stock other than a forge DV and a custom stage 1 remap which punches out a tidy 230bhp but this remap has been designed to have specific mods done to the car first. Which is a oversized turbo intake pipe (TIP) and a 3"de-cat downpipe along with a performance exhaust.

I haven't yet upgraded these and still am in the process of doing so, back to my original problem the backfiring seems like there is engine compression getting into the coolant system, the pops I hear from the engine bay are coming from the header tank and any pipe to do with the coolant system. Also under boost the car surges almost... cant think off any other way to explain but when it surges and you let off the throttle the bang then happens?!?!?!

I've been told by the previous owner it could be the re map because the car hasn't got the correct equipment to punch out what it can and what its capable off.

Things I've replaced new:
4 BRAND NEW BOSCH COILS
NGK BK7RE PLUGS
BRAND NEW BOSCH BANK 1 LAMBDA (2ND IS DELETED)
NEW THERMOSTAT (WAS GETTING STUCK THOUGHT WAS BACKFIRE ISSUE)


My question is would the remap be my issue here if I upgrade the tip and exhaust I shouldn't get any more backfiring from my coolant system and the surging will be gone?

Thanks for taking the time to read I hope someone can help me 

[barrym381]

Get the car scanned for fault codes and I can't see the map being at fault though

[Mk4_AUM]

Ok will do, any insight on the backfiring and what that could be?

[Mr_Orange]

That sounds off... There should be nothing engine compression related anywhere near the coolant system. I hate to suggest it but I'd get the engine checked over for potential head gasket problems.

[Simeon]

I'd agree with Mr Orange

Surely if you want to rule out the map issue you can get someone to flash a stock map back onto it for not very much?

[Mk4_AUM]

Orange- I thought it was of as well never had anything like it before, there was no signs off head gasket going no overheating no gunk...

Simon- thatvis my next option if this cat doesn't work and also a sniff test.

After doing some research I think I've found a potential culprit, when I get the popping sound I then check it after and I'm getting a white powder almost like flour consistency over pipes/header tank and bonnet. From what I've read I think its catalyst which leads me to think my cat is the issue weather its blocking up under high boost I dont know...

I am tomorrow going to take it out and replace it with a 3"de cat and see if this resolves my issue will keep you all posted thanks

[davkav]

Did you get anywhere with this? From your description it sounds like your coolant reservoir tank is blowing off due to excess pressure.

This is going to be from cylinder compression entering the coolant system, so most likely head gasket failure.

[barrym381]

Did you get anywhere with this? From your description it sounds like your coolant reservoir tank is blowing off due to excess pressure.

This is going to be from cylinder compression entering the coolant system, so most likely head gasket failure.

Head gasket failure on a 1.8t   

[davkav]

Head gasket failure on a 1.8t   

huh?

[barrym381]

Head gasket failure on a 1.8t   

huh?

How many head gasket failures have you seen on a 1.8t as none of my 35 of them have ever failed