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Old 08-17-2006, 08:03 AM   #1
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Default Supercharger gauge not showing full boost.

Can't figure this one out. Hoping you guys might have a good idea. My */C gauge never goes over the center zero mark. usually very slightly under. When I had the */C off when I rebulit my engine, it seemed to be fine. All internals spin well. It takes of quite well from 3/4 throttle, but not at full thottle. Seems to bog down. It has been running about 90-100 degrees everyday so that may have something to do with it, but the */C gauge is always constant. Never over that mark. Has anyone else had this type of problem?
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Old 08-17-2006, 08:09 AM   #2
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Sounds like you are dumping boost as soon as you make it. Check to make sure your BCA (boost control actuator) is working properly. Look at it as the engine is running. It is a little canister on the front of the SC. there is a little plunger going to the SC with a lever, it should be in the up position, and move down when you rev it. Here is a pic to show you what it looks like -

What is circled should be sticking straight up, and moving back down onto the stop when revving the car, if not, the BCA is leaky, or you have a faulty vacuum hose, or even a bad BCS (boost control solenoid).
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Old 08-17-2006, 08:45 AM   #3
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have you checked Fuel Pressure??

and inspected your Exhaust Manifolds for cracks?
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Old 08-17-2006, 08:47 AM   #4
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Originally Posted by 1993 SLE
have you checked Fuel Pressure??

and inspected your Exhaust Manifolds for cracks?
Mmm that would be more KR than low boost. In this case I'd start with vacuum hose checking and then move to the FP and EM'*.

(Morning buddy)
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Old 08-17-2006, 11:48 PM   #5
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Bump for this one... Ever figure it out?
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Old 08-20-2006, 12:59 AM   #6
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I would check into the BCA. These things are old (if original) and are in extreme environments. And move a lot (if you are heavy footed). Mine was leaking at the seal of the chome shaft and giving little to any boost.
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Old 08-21-2006, 11:26 PM   #7
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Sorry, I have been away from my comperter for a little bit. I checked the BCA. It seems to be working properly. It moves with the accelerator. It seems to open all the way up. I put a piece of foil over the screw adjustment and it crushed it all the way down to the nut. I have not yet checked the fuel pressue, but that is I feel suspect because it actually has better acceleration just a little less than full throttle. The gauge is consitent though.
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Old 08-22-2006, 12:05 AM   #8
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What about the MAP sensor? Maybe it'* getting lazy or the hose going to it is cracked...
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Old 08-22-2006, 12:57 AM   #9
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I'm wondering about your fuel pump/pressure.
If you're getting up high in mileage and with the temps this time of year fuel pumps are very prone to failing. If it'* weak that would explain the power the drops at full throttle (when it exceeds it current capacity).
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Old 08-22-2006, 07:33 AM   #10
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The pump I am not too worried about. I put a Walbro fuel pump on earlier this summer so I am pretty certain that it is still working correctly. I had this problem before the pump change and it did not affect it. Mileage I am not too worried about either as the engine itself only has about 5,000 mi. I have wonder about the MAF sensor as it was not replaced when the enige was rebuilt. Is there any way to test it? My second theory is that it may be related to having the original injectors. I am running a performance cam, ported heads and a CAI. I wonder if I am not getting enough fuel thru the injectors to match the air coming in, thus bogging down at full throttle. One other reason I think this may be an issue is that my car has a slight heat issue. I am running a 160 degree thermostat but the car will not run below 200, even cruising down the highway. I am attributing this either to a lean fuel issue or too restrictive of an exhaust since it is still the stock exhaust system. In any event, I plan to test my fuel pressue shortly to see if that may be an issue.
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