ISM weird spool

[Spiky75]

Something started today on my ism. If i floor it or will say 75% or more ioose all my boost to about 5-10 psi. To be able to reach gull boost ( 33-35psi), i need to be maximum half throttle..... what could cause that?

[tom chelbana]

As a 14 year ISM 500 engine you would need to have more then half throttle to get full boost. The engine would full throttle to get 33 psi.

[BonS]

I'd check your throttle position sensor. A scan tool is certainly the easiest way to do that. but a multimeter can do it also. Some have a single sensor (3 wire) while some have dual (6 wire) sensors.

[CountryB]

Do you have an exhaust brake?

[SargeW]

Turbo elbows and fittings need to be crazy tight to contain that amount of boost pressure created. If the running condition is different than it used to perform, then it could be a loose fitting or clamp. Start with the easy stuff first.

It could also be a sensor, or even a blown gasket in the turbo. But start with the easy stuff before starting with the more expensive stuff.

[CountryB]

If he can reach full boost at half throttle, then it sounds to me like the turbo (itself and gasket) is fine and the CAC and all the piping is fine. If any of those things were bad he would not be getting up to the 33 - 35 psi boost he reports.

I think it is going to be an electronics issue (if you have a computer controlled wastegate) or something like the exhaust brake partially closing or sticking.

[Spiky75]

I have put the reader on and i think i found the problem. Egr is sticking open. Im waiting to receive the new one and see. Hopefully it is just that.

[Wild Card]

while yor into the egr, clean and blow out the internal ports and you might want to replace the IMAP sensor. basically do a complete EGR system tune up.