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Author Topic: Boost seems to have dropped off significantly  (Read 644 times)


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    • 1991 XR2
Boost seems to have dropped off significantly
« on: October 04, 2021, 02:50:39 PM »

Hey ya'll! New to the forum, excited to be here. Bought my '91 XR2 about 6 months ago in Seattle for a move down to LA. A small, sporty, red convertible with boost seemed like a good car for the Los Angeles area :-)

And although it was boosting great the first couple months I've owned it, I noticed a significant drop off on my commute home recently. The boost gauge will still move - but only a little bit - it doesn't ever make it much past 5. Also, the boost used to kick in with a small push of the gas pedal. Now is only seems to engage when I have my foot to the floor and high RPMs. Basically, it feels like the boost is about 20% of what it was when I bought the car. No smoke, no noises, just a smaller amount of boost.

I've owned SAABs in the past, and it was often the case that a simple vacuum hose popped off and killed the boost. It was an easy fix to re-secure it and things were back to boosty goodness. Was hoping I might have the same luck with the XR2, but neither I nor a mechanic (who only took a cursory look) saw anything out of the ordinary.

Has anyone had this issue in the past? Are there any "known" things I should investigate?

Thanks in advance for any thoughts!


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    • 91 BPT AWD Capri & 1991 XR2
Re: Boost seems to have dropped off significantly
« Reply #1 on: October 04, 2021, 11:21:44 PM »

Welcome to TeamCapri! Congrats on your new ownership.

Lack of boost is not really a common problem with the XR2, but not unheard of on a turbo car.
One thing to check is the wastegate actuator - it may be stuck open, allowing exhaust to constantly bypass the turbine and thus not building proper boost.
It's a bit of a chore to inspect - it's buried under the exhaust manifold, on the back side of the turbo stuffed up against the engine block.
A cheap USB endoscope/inspection camera might do the trick of getting in there.
You can apply air pressure to it from a compressor to check its movement - do note that it must be regulated way down else you risk damaging it, I would not surpass 20psi

Other areas to check might be the turbo itself (check for shaft play, easy check) catalytic converter may be clogged or physically damaged, boost gauge line might be compromised showing low boost, etc

The power the XR2 provides does vary fairly drastically depending on ambient temps, it will feel much peppier on a cool day. If you've been running it in nothing but hot weather it may feel down on power

But yes, normal behavior should have it go past 5psi regularly and with ease
Report back with your findings!
1.8L Turbo All Wheel Drive Capri... the "GTXR2"

Aus Capri

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    • 1989 Capri Turbo
Re: Boost seems to have dropped off significantly
« Reply #2 on: October 05, 2021, 08:30:21 AM »

I'd be looking at the actuator like rocket said, ive had one stick wide open before and struggled to make any boost. Also if you don't have a compressor you can check it with a bike pump, but like rocket said just give it little puffs with the pump as too puch pressure on the diaphragm of the actuator will damage it.  Does the engine seem to operate normally othar than the loss of boost?


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    • 1991 Capri XR2, 1991 Capri XR2 Rusted out Shell
Re: Boost seems to have dropped off significantly
« Reply #3 on: October 05, 2021, 06:56:02 PM »

I used a cooling system pressure tester to test my wastegate actuator. If you (or your mechanic) have access to one, it's perfect for it. Little hand pump and a pressure gauge. Just need to rig up a fitting.

If you don't see/hear an obvious boost leak, I'd put money on that actuator being stuck. Don't forget to look down into the front bumper, in front of the radiator. The intercooler is tucked down in there. It's a bit hard to see, but if you have someone give it some gas while you watch it, you'll probably be able to see and hear signs if it is leaking.