Rapid Boost Gauge Fluctuation.

[Daniel Jost]

Hello,

I will start off saying that this problem kind of has me baffled... I have a friend's Turbo Buick that I have been working on for months now because he picked it up as a basket case of things that were done completely incorrectly and/or had very poor workmanship. After doing a bunch of work to get things back to the way that it should be or correcting other modifications I am fighting a weird problem with the boost gauge getting VERY unstable after about 16-17PSI (I could run 15PSI all day at part throttle and be stable), and the car runs terrible.

The boost/boost gauge flutters very rapidly between 20 and 25 PSI of boost. I have the vacuum line routed directly to the WG actuator, it is a 6776 turbo with a HD WG actuator. I have ported the DP puck (Used to build boost until you lifted the throttle) and have done this before so I am sure I have done it correctly, and the WG is set at the minimum boost level (Rod all the way out until it has a small amount of pre-load). I got this car not running because a roller rocker backed itself off and killed the engine, and when the car was running before that is was very poor, words can't explain how messed up this car was when I got it.....

It did not have a boost gauge, WB02, scanmaster, or any other tuning tools other than the MAFTPRO when the owner got it which really scares me looking at the mod list... I have the AFR at WOT around 10.6 right now with the alky on. Tried adding more and taking less, also timign from 17-21° of timing at WOT. I understand the IAT's are around 45-50°F and this may cause some bad running with alky, could being too cold with alky be my issue?

The car's mod's are as follows (That I know of);

-3.8 Displacement forged pistons and billet caps
-Billet roller rockers
-212/212 Flat tappet cam
-GN1 Alum 14 bolt heads (Only 8 bolts used)
-CNC machined intake
-Accufab intake with Powerplate and 70mm TB
-Precision 6776 Turbo
-Unkown stall (Seems like a 34-3600)
-83# Low-Z injectors and Driver'd ECM
-Sumped fuel tank and Fuelab Digital Prodigy pump, and supporting fuel lines
-Razor's Alky kit, dual nozzle kit, knob set on 5 (Tried varying alcohol amount to little change)
-Huge front mount IC
-MAFTPRO with a tune I have been trying to correct because it barely ran with the previous owners 63.5% fuel added... ugh..
-Aftermarket headers (Haven't found any leaks)
-3.5" internal WG down pipe and 3.5" cutout.
-Coil Hotwire
-Vacuum Brakes.


Any help would be appreciated, in the 10+ years I have been messing with these cars I have never been so confused on what is causing a problem... I'd say I'm pulling my hair out but it is already gone, maybe from the last 10 years?

Thanks, Dan

 

[earlbrown]

I've found when you're really stumped it's best to get back to basics.

I would hang a vacuum gauge in it and see how it acts at idle, and run a leakdown test. Need to eliminate mechanicals before trying to tune around them. I'd also stick a dial on all the pushrods and see if all 12 lobes are the same height.

 

[dsapper]

If its an autometer gauge they have a tendency to do that, so do some other brands. They sell pressure snubbers to correct it.

 

[lost2a6]

Possibly a wiped cam lobe.

 

[Daniel Jost]

Thanks guys cam lobes are my next thought.. I would probably cry if I have to swap a cam on this thing too now, my own buick is begging for some attention...

I'll check it out and let you guys know what I find.

,Dan

 

[turbo nasty]

If vac is stable at high idle....i would psi the intake tract and look for boost leak.

 

[Daniel Jost]

If vac is stable at high idle....i would psi the intake tract and look for boost leak.

This was my next train of thought, If I can't find anything I will have to build a pressure tester.

Thank You, Dan

 

[TurboBob]

ignition issues can be boost sensitive. I have had a flaky coilpack, as well as flaky wires give me grief above some level of boost.

If you need help setting up the Maft Pro, let me know.

Bob

 

[87chrisss]

I had a similar issue a boost controller took care of it. Try a boost controller and report back

 

[Daniel Jost]

ignition issues can be boost sensitive. I have had a flaky coilpack, as well as flaky wires give me grief above some level of boost.

If you need help setting up the Maft Pro, let me know.

Bob

Bob I might take you up on the MAFTPRO help, I have been wading through the waters of it so far and have a cable coming from full throttle to connect through laptop to make changes easier. Here I thought I would never be messing with anything but an MS3 on these cars ever again... As always new knowledge is good knowledge!

Thank You,Dan

 

[TurboBob]

with the Pro, verify the software version thats in the unit, make sure the chip is correct for the injectors, and double check the installation.

Then, if you reset the pro and go back thru the setup menu on the LCD, it should run and drive pretty well.

Let me know how it goes.

Bob

 

[Daniel Jost]

Hey Bob, How do I verify the chip? I think it is just a coded number on it now that specifies MAFPRO chip... Maybe have another burned? I would not be surprised to see it was the wrong one with this thing being the pile it was when I got it.... It is only a 4.4 version right now so I will need to get the software to update it since I understand there is a newer version now? Also I had to pull the original ECM when I got it because the power terminal to it was corroded completely off and every time you would hit the throttle the car would miss and pop and the CEL would flicker.... So I pulled it apart and desoldered the Low-Z drivers and put them in a spare 7148 ECM I had sitting around, fixed that! LOL

Thanks, Dan

 

[Daniel Jost]

Also I thought I would just let everyone know that I checked lift last night on the cam lobes.... I found Cyl #6 to only have 0.128 lift on the exhaust lobe... The rest were showing what looked like right around 0.282 (I could be off a bit but with alum heads and stainless exhaust it didn't give much to mount to so I had to get creative). With the lift being drastically so much less you could see it on the rocker movement, I pulled the lifter with a magnet and looking through the 3/8 hole it doesn't look real bad but I don't think the measurement or my eyes lie.... I think the owner is starting to think I am full of crap and I am about to give up on Buicks after this car... Ok... maybe that was an over reaction but seriously... I guess next is pulling the cam out...

P.S. I don't think it was much of a surprise the cam failed, since I asked the owner if the last guy ran ZDDP and he didn't know so I doubt it ever had it... Well a new one is on the way...

Thanks Again, Dan

 

[TurboBob]

post or pm me the chip number.


4.4 is ancient, the software definitely needs to be re-upped.


Sounds like you are making progress.

Bob

 

[Daniel Jost]

Pulled the cam last night. I got it out in under 2 hours from when I pulled it in the shop.... I must have done this too many times... I never checked bank 1 because I already found a problem on bank 2 so I never even wasted my time. Upon removing the cam I measured I was missing about 0.050 off of a lobe on Cyl #6 and about .040 off of Cyl#1. I also noted that there were several others showing early signs of failure, it was a good thing I just bit the bullet and went for the worst. I'll post pictures up soon.

,Dan