Boost Problem

JUGGERNAUT

New member
I was on my way to work this morning and my truck was driving fine. I gave it some throttle to pass someone and it fell on its face. It seems like it runs fine until I go into boost. The more throttle I give the more it slows down. Until I start to let off. Then it speeds up as I let off until its out of boost. It also wont shift while in boost. Any ideas what might cause this? The truck is all stock except for an adjustable fpr.
 

crazykaese

91ProtoTy/IndyPaceTribute & Sawzall Master
Re: Boost Problem

Your fuel pump is on it's way out - especially if it's still the stock pump. My Walbro did the same thing when it went bad.
 

JUGGERNAUT

New member
Re: Boost Problem

OK, I just ran datamaster on it. and Im throwing code 44. Lean 02. My FP guage also jumps rapidly back and forth between 35-45 psi. I would guess thats related?
 

JUGGERNAUT

New member
Re: Boost Problem

I replaced the fuel filter today. The gauge stopped jumping around but it didnt help at all with the problem. I bought the truck about a month ago and did a full tune up, except the filter which i did today. The previous owner also provided me with all the receipts for maintenance and the pump was done less than a year ago. I could really use some help here. Thanks
 

JUGGERNAUT

New member
Re: Boost Problem

I did a boost/vacuum leak test last night and found a small leak between the intercooler and throttle body. Could this be causing my problem?
 

Flyin Ryan

hated cuz he drives fords
Re: Boost Problem

JUGGERNAUT said:
I did a boost/vacuum leak test last night and found a small leak between the intercooler and throttle body. Could this be causing my problem?

I wouldn't think it would cause your truck to fall flate while in boost but vacuum leaks do cause tons of issues on turbo vehicles so fix it and go from there and also did your data log show any spark retard when the truck does what it's doing?
 

JUGGERNAUT

New member
Re: Boost Problem

It wont even go into boost anymore. Now it falls flat between 5-0 lbs of vacuum. Ill fix the leak tonight and Ill check my datalog for spark retard. Thanks
 

JUGGERNAUT

New member
Re: Boost Problem

I replaced the boot and the leak is gone. It didnt fix or change the problem at all. There is no spark retard at all on my datalog.
 
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Tooky

Serious about performance
Re: Boost Problem

Can you share your datalog with us? Or email it to me, my contact is on my website (see sig). I'll be able to gleam some info on how your engine is producing power, by the shape of the boost and RPM curves on the graph.
 
Re: Boost Problem

I had that. Try shooting compressed air into the vacuum hose that goes to the wastegate actuator. It worked for me. If you have a bad fuel pressure regulartor it messes with your fuel also. Let us know what fixes it.
 
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JUGGERNAUT

New member
Re: Boost Problem

Tooky, I emailed you the file. Thanks for taking the time to look at it. I have no problem posting it up here though too in case someone else wants to look, I just dont know how.
 

Tooky

Serious about performance
Re: Boost Problem

Ok, wow. I just got done looking at the file and it told a lot more than I thought it would.

dm_juggernaut_leanthrottle.png



3 words: LEAN LEAN LEAN! The higher the injector BPW (fuel demand) gets, the leaner the truck runs. Here it looks like you're gently leaving a 0 MPH stop to reach a 31 MPH cruise. The STerms (short term fuel trims) max out at FULL LEAN (see the blue line flatline when it Hits The Roof??) Look at your O2 mV (red line), they drop to basically zero (anything consistent below 100 is totally lean, nearly a total lack of fuel).

According to this run you never went over 31 MPH and never more than 1/3rd Throttle.. I thought the problem was under boost? Regardless it's obviously appearing to be a lean condition so I'd start by verifying the fuel pressure and make CERTAIN your AFPR is getting a solid vacuum signal, maybe check the spark plugs to make sure they haven't suffered damage, and then wondering about that fuel pump.

If you need further diagnosis do you have any Datamaster files with 100% WOT? (Not that I would go out making new WOT runs with it so lean at this point - I wouldn't go into boost at all until you get this fixed!)

It has a Code 44 O2 Lean like you said. The problem won't be solved until you find the cause of that code. The ECM is trying to tell you there's a problem, as loud as it possibly can. :D
 
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JUGGERNAUT

New member
Re: Boost Problem

Thanks again for looking at that Tooky. I get good vacuum and good fuel pressure at idle. When I give it some throttle the FP drops to 19lbs. I think Im going to put the stock FPR back on just to see if my new adjustable one is bad.
Also, about your question: When the problem started it would do it around 5 lbs of boost. Now I cant boost period.
 

JUGGERNAUT

New member
Re: Boost Problem

I put the stocker back on and still does the same thing. I guess its time for a new pump. Is walbro the perferred pump? I run one on my GN and one on my Impala SS and never had any issues...
 
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