Stuck on 7psi!!!!

[agent]

The car is a 95 gt legacy, for some reason it only wants to boost 7psi on both turbos ???

The ecu is throwing no codes, and when I reset the ecu the car will run normal boost for a while then it goes back to 7psi randomly and stays there.

I have recently replaced the AFM and Cam angle sensor, changing the plugs this weekend but Im at a loss as to what to check next. boost solenoid?? where and what is that, Im pretty amatuer when it comes to turbo systems but will learn fast.

appreciate any help, thanks

[Joker]

BBOD something is wrong with ECU/boost control - its rnning on wastgate pressure - sorr yI cant help other than tell you its borke!

[Guest the_return_of_the_jedi]

 JoKer said:

BBOD something is wrong with ECU/boost control - its rnning on wastgate pressure - sorr yI cant help other than tell you its borke!

as is your keyboard...

the issue here is the TT system...

[agent]

 the_return_of_the_jedi said:

the issue here is the TT system...

Yeah its starting to be such a hassle, is there some sort of a safe mode it gets stuck into if something else is not right? I guess if there was it would be throwing a code.... hmmm so lost

[THUNDA]

try plugging the green diagnostic plugs in then driving your car

my old legacy gt used to have a weird rev cut at 4500rpm, but if i just drove it when the green diagnostic plugs plugged in it would go away never spat a code though

[Guest boostin]

If it boosts fine and then drops back to 7psi then it is probably picking up a knock (detonation).

Are you running decent fuel??

[agent]

yeah knocking crossed my mind, is there any way to adjust base ignition timing?? I'm running BP98 octane as with all my cars I own, pulled one plug out after work today and its pretty shagged so hoping that is part of the problem, also I think the thermostat isn't quite opening fully as well so will be replacing that tomorrow also.

[Guest boostcut]

i have seen the fpr vacuum line come off the early tt engines and cause them to run bout 5psi. could be a vacuum leak anywhere tho....

[Guest]

 boostcut said:

i have seen the fpr vacuum line come off the early tt engines and cause them to run bout 5psi. could be a vacuum leak anywhere tho....

+1 I would follow the primary waste gate line and so on make sure everything is where its meant to be , any leaking there and the boost control solenoid would render useless,

also have a look at your intake air control solenoid valve relief valve, exhaust gas control solenoid valve

Differential pressure sensor is working normally. Things like that, there is a form here somewhere explains how to, well I think there is anyway have a search

i cant insert a pic so let me suss that out and yea get back to you

[Guest boostin]

A leak in a boost control line would result in overboost....

[Guest]

 boostin said:

A leak in a boost control line would result in overboost....

huh

I was talking about a vacuum line going to the boost control solenoid causing him to run wastgate pressure that would be around the 7 psi , was sourcing a pic of turbo inlet housing and the waste gate and turbo inlet pipe line running to the solenoid, was just a good idea to check everywhere well in my IMO

[Guest boostin]

 EGOREX']

[quote name='boostin said:

A leak in a boost control line would result in overboost....

/quote]huh

I was talking about a vacuum line going to the boost control solenoid causing him to run wastgate pressure that would be around the 7 psi , was sourcing a pic of turbo inlet housing and the waste gate and turbo inlet pipe line running to the solenoid, was just a good idea to check everywhere well in my IMO

I understand what you're trying to say, but its not a vac line. Its a boost line. And any leak from that line will make boost pressure higher as there will be less pressure to the wastegate diaphragm. Thats how the boost solenoid works. it bleeds pressure off the line and hence off the wastegate.

Have you made sure all your hose connections are tight? Like at the turbo outlets, throttle body etc??

[Guest]

oh compressor port linked up to the compressor side of the turbo via that line , and because that line has a leak or what ever, there is no limiting of boost pressure oh and there for that boost pressure isnt resticted by the set spring pressure and you get overboost, man i feel so dumbass today really i do

i knew that, because it just came to me then, i F8cken knew that..

that still dont sound rite, its rite but am i thinking of somthing els WTF beed time to many late nites

[agent]

The hoses seem to be alright, I'll have a real good look at them today, but I'm sure its an electrical problem because it runs normal after resetting the ECU then the problem returns randomly again.

[log1call]

Yup, that does make it sound like electrical. Since there are no codes you need to look for what isn't going to set a code.

In general it's the ecu being crook or having bad power or earths that wil give electrical problems that don't set codes.

Have you run the car in diagnostic mode and done all the checks?

[log1call]

"The ecu is throwing no codes, and when I reset the ecu the car will run normal boost for a while then it goes back to 7psi randomly and stays there"

Are you sure that it is truely random?

Do you think it could be that it takes two restarts before it does it.

The reason I ask is that some codes are only set after two trips have had an intermittent fault. So if it was two trips, or the very first occurance of the problem that caused it, it could point to something. The only trouble with this is that there should be codes if it's anything that causes it to go into failsafe.

And here's a bit of advice I've posted a number of times before on these forums....

If you are getting elusive, varying, intermittent codes, or no codes at all, and the car is a few years old....

Pull the ecu and have a look inside. Look for blown transistors(they can explode a piece out of the side of them), burnt resistors, cracked circuit boards, dry solder joints, leaking capacitors, water damage.

Use a magniying glass and inspect every component, circuit and joint.

It only takes a matter of minutes and given the number of things that can happen inside there, and the number of checks you could have to do to track it to there, it's best to do it earlier than later in the diagnostic process.

[Guest boostin]

I have seen cambelt tensioners bouncing and knocking on the tensioner plate. The knock sensor picks this up as detonation and retards ignition timing. A new tensioner normally fixes that.

The other I have seen is electrical interference on the knock sensor wire. We drove the car with the knock sensor removed (ie not bolted to the engine and physically unplugged) and there was still a voltage on the wire!! We had to run a new shielded wire from the knock sensor to the ECU to fix that one, and made sure the shield had its own earth at the ECU.

[agent]

Ive replaced all the spark plugs and runs alot better now, but it has a miss above 10psi... I may have gapped the plugs wrong, anyone know the gap spec?

[Guest boostin]

If you fitted the correct plugs they are pre-gapped to 0.8mm.

[THUNDA]

0.8mm g, cheapies spark plugs need gapping before you put them in, had the same problem on my old bc5