Popping on decel, fuel pressure regulator? Options

[PDXMike]

Hey all,

My 75 1.8 L-jet has always popped on decel. I've looked for exhaust leaks, including dropping and reinstalling the entire exhaust and getting it smoke tested. My decel valve is working correctly. This thing makes a LOT of noise, even when just letting the engine spin down with the clutch in. It sounds like some crazy-tuned dirt track stock car or something. This is fun for the first 5 minutes or so, then anybody within 100 yards of me wants to run me off the road.

While testing my decel valve, I noticed that the same vacuum line that controls the decel valve also runs to the fuel pressure regulator. Is it supposed to cut the fuel supply off when vacuum pressure goes up? Could this have anything to do with my popping? If the injectors are still firing I'd be pumping gas right through into the exhaust, right?

I have a Monza muffler, which probably isn't helping.

Is this a crazy theory? What else can I try?

Thanks,

Mike

[porschetub]

[quote name='PDXMike' date='Sep 27 2015, 01:40 PM' post='2243633']
Hey all,

My 75 1.8 L-jet has always popped on decel. I've looked for exhaust leaks, including dropping and reinstalling the entire exhaust and getting it smoke tested. My decel valve is working correctly. This thing makes a LOT of noise, even when just letting the engine spin down with the clutch in. It sounds like some crazy-tuned dirt track stock car or something. This is fun for the first 5 minutes or so, then anybody within 100 yards of me wants to run me off the road.

While testing my decel valve, I noticed that the same vacuum line that controls the decel valve also runs to the fuel pressure regulator. Is it supposed to cut the fuel supply off when vacuum pressure goes up? Could this have anything to do with my popping? If the injectors are still firing I'd be pumping gas right through into the exhaust, right?

I have a Monza muffler, which probably isn't helping.

Is this a crazy theory? What else can I try?


Never dealt with these but have heard of issues,don't think your injectors will be firing fuel out the exhaust however ,your throttle is closed so that's covered by the AFM throttle positioner ,as mentioned I would look @ the exhaust unless you a lean condition on deceleration which is not that likely.
Has the exhaust blown its guts out like the old beetle glasspacks did ? don't know.
No the FPR cannot shut the fuel off.
How did you go with the timing ?that's a key issue if not right,check your advance plate on the dizzy they can stick up ,very common issue, good luck.