Backfiring above 1 bar of boost - FPR?
 

I have been away for a week, and upon returning today, the car wouldn't start. It turned over fine, but it wouldn't fire up.

After cranking for about 10 seconds and giving up, the car backfired. This happened several times.

Anyway, I sprayed a load of WD40 around the coilpack and around various connections, and sprayed easystart onto the air filter. The car then started first time.

I let the car warm up, and drove off. When I accelerated, the car hesitated and started to backfire like crazy, the revs refusing to rise any further. This happens at around 1 bar of boost, in all gears. It does not happen when the car is stationary and I'm just reving the engine under no load. It also runs smoothly until 1 bar of boost.

The car has a Knock Link fitted, and this is not going off at all during the back firing.

I can hear the fuel pump priming ok.

I suspect the fueling system, possibly the fuel pressure regulator.

The car was running fine before, although it's always had a starting issue; it always stalls after first firing up from cold, unless I blip the throttle immediately after starting.

The fuel filter was changed in the last 2 years, and I always run it on V-Power.

I know it's impossible to diagnose problems over the internet, but has anyone had the same issue before, and if so, what was the cause? Apart from the FPR, I'm guessing a leaking / split vacuum hose could cause this problem.

Also, could anyone recommend a decent fuel pressure regulator? It would be nice to have one with a second gauge inside the car.

Relevant spec as follows (mods done by the previous owner):

1997 Turbo 2000
VF28 turbo
Walboro fuel pump
larger injectors
Link ECU (version 1)
Boost controller (can't remember make)
TSL turbo back exhaust system
K&N cone filter
Vent to atmosphere dump valve (not sure which make)

Apart from the starting issue, the car has had no major issues in the just under 3 years I've owned it.

As ever, any advice would be much appreciated.

Head gasket? Sound similar to what I had.

Start boosting and back firing and coughing a lot.

could be your coil pack and/or leads mate,i would check there first.

cold weather causing overboost and hitting fuel cut ???????? for the reg i would say sard or aeromotive,.

backfiring,id say your your plugs leads or if not then coilpack

Thanks for the ideas guys! The coil pack does make sense, especially after the cold / wet weather.

Addi, the maximum boost is around 1.3 bar, and it doesn't get this high before backfiring.

Mrchips, I hope it isn't the head gasket! I have a block test kit which should prove one way or the other. There's no white gunk under the oil cap, and the coolant temperature is normal.

classic misfire scenario... plugs blow out or fail to spark with the higher cylinder load from cold ambients.

i'd do a bit of maintenance and swap 'em out. when you do, i wouldn't be surprised to see worn/spread electrodes. cheaper than coil packs at least and the first place i'd start.

fwiw, i always use copper plugs, change 'em every year, and test compression while i do. from experience my gap goes up 1 thou every 2500 miles or so. once above 45 thous i get full load misfires.

hth
ken

For people's info:

The problem went away the day after without any intervention, no missfiring or starting issues.

I've decided to fit a new coilpack anyway as a precaution, as there is definitely an underlying reason why the car wouldn't start in the first place. I suspect moisture got in somewhere while it was sitting for a week, and the logical place would be the coilpack.

Ride, thanks for the advice. I will change the plugs too, they could well be a contributing factor as they've not been changed in the last 3 years at least.