1988 turbo coupe looses power around 3,500 rpm.

[turborich]

i own a 1988 thunderbird turbo coupe. the car seems to loose power around 3,500 rpms or so. it seems like it flattens out. i have an adjustable boost valve on it and it runs a t 18 psi where i have it set at. ive installed new plugs, wires, cap, rotor, checked for vacuum leaks, checked fuel pressure, i'm not getting any engine codes, it's a 5 speed. anyone one have any ideas???

[thunderbird muscle]

Is the boost valve working properly?
It 3,500 should be around the begining of your real boost.

[g_lower]

try pulling your valve cover and checking your rocker arms and your cam lobes. my 83 had the same problems and it ended up being a flat cam. thanks Graham

[jlewis]

That's a hard one to diagnose exactly. I'd have to side with the cam idea too. You could have a damaged cam lobe that is not running enough lift and so it chokes at higher rpm. Also make sure the exhaust and intake(filter) are not stopped up. The converter's not stopped up is it? This would also make it choke at high rpm. And the last thing I can think of is that if your knock sensor is hooked up then it could be malfunctioning or something may be causing excessive knock in your engine(bad gas or wrong timing) and the sensor is pulling a lot of timing. This is actually really common on these, they'll run like a dog if the knock sensor pulls timing. You could try unhooking it but only if you know what knock sounds like. Then drive it and listen for pinging, knocking, whatever you call it. Then figure out what's causing that if you hear knock. If it doesn't knock and still runs bad with the knock sensor unhooked than look elsewhere. This is probably the easiest thing to check. I have the same car as you and I unhooked the knock sensor. I run premium(93), 11° BTDC, and 17 psi. Haven't heard any knock yet.