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[CapriManxr2]

Hey all, picked up a 91 xr2 a few months back and have been cleaning it up. Started with new springs and struts along with brakes. But when I did the cold air intake, I began to hear the turbo fluttering, like a stututu sound. I know that could be bad for the turbo and was looking at all the hoses that connect the BOV to the intake J pipe and the aluminium intake manifold pipe and they seemed tight. I tried looking inside the throttle body as well, it was pretty clean in there too. I also have an overboost issue where the PSI will go to roughly 13PSI and then the fuel cuts out or maybe spark? I'm quite new to Capri's but they're fun to work on and I just got stuck on these couple of problems. Any help would be appreciated.

[Rocketman]

Overboost can be caused by a few issues. Is your exhaust stock? (larger exhaust/open downpipe the stock wastegate can't keep up) If so you will want to check to make sure the wastegate is functioning. The little black line that tees off the aluminum crossover pipe is the boost source for the wastegate. You could try applying regulated air to it from a compressor (no more than 10psi) with a flashlight you should be able to look down between the turbo and the block and see the actuator rod moving. I recently heard from a friend who acquired a turbo where the actuator in the turbine housing was seized. (sounded like the turbo sat off the engine on a shelf or something)

Over ~11 psi the overboost switch is tripped, you will hear a buzzer and the ECU will cut the engine until the boost condition is cleared

Usually when going to a cold air intake with the stock bypass valve you will hear a "mooing" noise like a sick cow, particularly when letting off at part throttle. If you're having the compressor stall sounds you may want to look into replacing the bypass valve, there's a rubber diaphragm in the OEM piece that might have failed. Could also check the vacuum lines to the bypass valve to make sure they are routed properly

[CapriManxr2]

Thanks for the response, all the hoses that connect to the bypass valve are tight and seem to be going to the right place. I took out the bypass valve and looked into it and tried cleaning it, there were some black chunks that came out of the valve. Can I replace the bypass valve with a blow-off valve? Is that how that works? And the exhaust is loud, I resurfaced the resonator and got new bolts, along with a new gasket, which seemed to help but it is definitely louder than stock.

[CapriManxr2]

another thing is I don't hear a buzz when it overboosts. And could the faulty recirculator valve affect my speed? I swear my car was faster and then the flutter noise started to happen, maybe it messes with the air to fuel ratio? If the recirculator valve can't recirculate then maybe there is more fuel to air in the ratio?

[Rocketman]

Yes if the bypass valve has failed, it's not going to close and thus vent a significant portion of your precious boost back into the pre-turbo intake.
Black chunks are likely the deteriorated remains of the diaphragm inside the BPV. This would be the first case I've heard of one failing, and is noteworthy as these cars age.

It may also be contributing to your overboosting

You can replace the bypass valve, there are a few upgrade paths - searching the forum here should yield some results. You could also switch to a blowoff valve.

[CapriManxr2]

Thanks for help Rocketman, Found a forum on switching to the audi bosch diverter valves. One step closer to bringing the capri to it's former glory!

[owent616]

This does not have anything to do with the rest of the post, but what cold air intake did you use because I am interested in upgrading mine to a cold air intake as well. Thank You!

[CapriManxr2]

I used an off-brand cone filter from my local O'Reilly. You will need a bracket that fits right onto the MAF to slide a cone filter onto it. You might want to find a way to bolt the intake somewhere because for me it just sat there limp for some time until I bolted it down. This is the adapter that I used to put a cold air intake on it. https://www.ebay.com/itm/222230887314?hash=item33bdfe3b92:g:8rUAAOSwmf5hnVHY&amdata=enc%3AAQAHAAABAKEmPCFypRVUKjFop%2F8d0yq6k8IulerDjuUHC4EoExFefFgPsb1yazkDxQOQ0O4uYJqbBF42o4jLt3R6iakLrAW80SCRwF1KK2KAX7y8cStEN7gTjHpKw1diRhdhhWrIbXuZXRtTZOnB%2B0Y88%2FFmTy7jU3X9ji3X3wFE50zespbaL%2BpeODD4CFG0Xrgt3xfBUa4nAYybEdyH8PS5n8Nl2nJNznrLyVi8KUkvd3WUGg5Fsy1YBnf5AyAwQX0E2aNkPui3TZn%2BmWKfjqvrgWsWVLhwtiUdyo2P9GcH405Gk8rZbIquH%2FsNgjC08WeOFxoKBsWVkVvli46Vbq6b2asvc1U%3D%7Ctkp%3ABk9SR9KJ8avdYQ