same problem with two 87 grandnationals

I have a question? I cannot get full boost on my girlfriends Grand National. My Grand National is suffering from the same problem, the engine in my grand national has been rebuilt, I thought that would fix it. No dice. So I was wondering if any of you have had the same problem? because two out of two doesn't seem like a coincedence? I kind of figured this problem is common and trial and error with replacing parts and sensors is becoming expensive! Could it be the fuel pump? it's not the turbo charger! because it's been machined, balanced, fitted with new bearings and seals ... flawless! What sensor informs the computer of the boost pressure? If I can't fix this my GF is going to think I'm a tool! because I feel like one! Help would be very muchly appreciated.

I have a question? I cannot get full boost on my girlfriends Grand National. My Grand National is suffering from the same problem, the engine in my grand national has been rebuilt, I thought that would fix it. No dice. So I was wondering if any of you have had the same problem? because two out of two doesn't seem like a coincedence? I kind of figured this problem is common and trial and error with replacing parts and sensors is becoming expensive! Could it be the fuel pump? it's not the turbo charger! because it's been machined, balanced, fitted with new bearings and seals ... flawless! What sensor informs the computer of the boost pressure? If I can't fix this my GF is going to think I'm a tool! because I feel like one! Help would be very muchly appreciated.


bad wastegates?? if you were real careful, repeat real careful, i think you could keep the wastegate closed and take a quick drive. check your boost gauge , not the factory junk lights, and give it quick throttle. moniter the boost gauge with the wastegates closed boost should jump right up. DO NOT stay in the throttle as all sorts of bad could happen.

leaks in intake tract? you are using good clamps on the up pipe right? you would probably hear some noise if it was leaking by the connections. what boost level are you trying to attain?

bad fuel pump will just make you go serious lean. the boost should still be whatever you set it for with your wastegate.

unless you have a 3 bar sensor installed (like for a scantool) the computer doesnt moniter boost level

I've tried the wastegate by disconnecting the electronic control valve connector on the passenger side valve cover the boost comes up to 15 then I let off.The boost is worthless because of knocking and loss of power.are you 100% about the comp not controlling this valve?the stock wastegate does not have a mechanical control and when I disconnect the wastegate control valve the comp tells me this with a stored code.Question would a bad fuel pump or lean condition cause a knock at higher boost levels making the knock sensor to limit timing and possibly boost if to say this was all connected and controlled by the comp?It's just that the wastegate actuator solenoid valve wiring goes directly to the comp?

It's only got 22 647 miles on it (the GFs car) and it was beat by an acura legend,oh the shame!!! The car is definetly broken but its not mechanical turbo bearings well within tolerances,cylinder compression is perfect valve springs are as good as the stocks can be,what gives?

I've tried the wastegate by disconnecting the electronic control valve connector on the passenger side valve cover the boost comes up to 15 then I let off.The boost is worthless because of knocking and loss of power.are you 100% about the comp not controlling this valve?the stock wastegate does not have a mechanical control and when I disconnect the wastegate control valve the comp tells me this with a stored code.Question would a bad fuel pump or lean condition cause a knock at higher boost levels making the knock sensor to limit timing and possibly boost if to say this was all connected and controlled by the comp?It's just that the wastegate actuator solenoid valve wiring goes directly to the comp?

computer does control the wastegate solenoid. my understanding is that it is controling it via load and other factors that are controlled by your chip. is the wastegate adjustable? meaning that you can shorten the rod for more boost or longer for less boost. the drive test that i suggested in 1st post would be done with the solenoid still hooked up but the end of the wastegate rod disconnected. the flapper would be wired shut. this will tell you if the turbo is building the boost. knock will definately get the computer to pull in the timing and maybe bleed off more boost if everything is connected and working. maybe try some potent race gas 116 and see if the knock is gone. this may however lead to a bad O2 sensor. if better gas doent help then maybe its a fuel problem. what is your base fuel pressure and do you have a way to moniter fuel pressure while driving? my car is set at 45 psi with the vacuum off and then under boost it climbs about 1 psi per lb of boost. say i'm set for 20 lbs of boost i should see 65 psi on the rail. if you are not getting this or you are loosing fuel pressure as you go then sounds like a fueling problem. do you have some way to moniter the O2 voltage? this would be another way to tell whats happing. if you start at say .820 and drop off below .750 ( i think thats as low as you want to go) then you are running out of fuel. ive had my car for ten years but am really still a novice when it comes to tuning. have you tried any sites like turbobuick.com, turbobuicks.com, t6p.com or any other place? there are some very very good tuners on these sites that could set you up better then me. i'm sure you know that you dont want to hear that knock as its bad news for the motors innards.

Thanks,I bought a fuel filter today and when I went to install it I couldn't. It seems the previous owner had had a cracked fuel line. he had cut off the fittings and replaced it with a filter for a carbureted system and rubber hose.Rubber hose?Thats gonna go tommorrow!I'll replace it with fuel lines with new fittings.A buddy of mine with a scan tool adjusted the throttle position sensor and I ended up regaining a pound and a half of boost.So things are comming along soon I should be at the 22psi my old chip runs!

I should be at the 22psi my old chip runs!


22 lbs of boost?? i'm hoping you are spraying alcohol at that boost level. if not then theres your knock. best i got without alky was 18 lbs on my boost guage before knock set in.

No alky, but the comp sets into a fuel enrichment program that seems to kill the knock quite well,so long as theres extra fuel to be had if not it limits the boost as soon as any knock is detected.I'm still considering alcohol, but first things first. Cool SR 71, fastest turbofan made to date and they were designed without computers, leak like a siv at room temp. but fast.

I have a question? I cannot get full boost on my girlfriends Grand National. My Grand National is suffering from the same problem, the engine in my grand national has been rebuilt, I thought that would fix it. No dice. So I was wondering if any of you have had the same problem? because two out of two doesn't seem like a coincedence? I kind of figured this problem is common and trial and error with replacing parts and sensors is becoming expensive! Could it be the fuel pump? it's not the turbo charger! because it's been machined, balanced, fitted with new bearings and seals ... flawless! What sensor informs the computer of the boost pressure? If I can't fix this my GF is going to think I'm a tool! because I feel like one! Help would be very muchly appreciated.

I'm think you reversed the hoses going to the turbo compressor housing and the wastegate and the orifice(spelling) is on the wrong side of the T. I have done this by mistake and the boost wouldn't go past 12 psi. Once I reversed the hoses, boost shot up to 23 psi. I run the RJC manual boost controller which is a much better setup because it doesn't start to bleed at 10 psi like the stock setup. The boost shoots to 20 psi real quick.

I'm currently waiting for a Grooms level 2 Shortblock so I can install the P&P heads/intake, PT61 and front mount I/C. It should run real well I hope. Alot of new parts to install so anything can go wrong.