Boost holds back after 8psi,,,need help

[djsan67n808]

i dont think i have any leaks.. i just changed the boost solenoid, full tank of gas, changed wastegate(dont know how good this one is). my trucks seems to not want to boost after 8psi. It doesnt boost spike but it seems to hold back then the boost would come out little by little. Did anyone every experience this problem before.. please help.

 

[Divergent Lightning]

Re: Boost holds back after 8psi,,,need help

Your stock ECM could be pulling the boost and timing because of knock. Or on the stock ECM it doesn't let you boost past 8 psi on the first attempt to get WOT. I would check on both of those first

 

[djsan67n808]

Re: Boost holds back after 8psi,,,need help

how do you check the ecm?

 

[Divergent Lightning]

Re: Boost holds back after 8psi,,,need help

That is a stock "feature" of the ECM. The only way to get past that is to get a chip, be it ultimate, dig chip or a custom burnt chip. The only way to check teh ECM is to replace it with a known good one and compare.

You might also want to replace your boost solenoid. They are about $20 so they are pretty cheap to replace.

 

[ghettosled]

Re: Boost holds back after 8psi,,,need help

if it wont make more then 8psi, then check the wg selenoid connection, and if it looks good pull the vacuum line going to the wg selenoid.. should spike the boost gauge.. if not, then check for loose IC piping, or a plugged exhaust.,

 

[djsan67n808]

Re: Boost holds back after 8psi,,,need help

thanks mike.. i just replaced the solenoid not to long ago.. would a plugged exhaust cause the boost to drop.. i kida hear a airl leak some where in my exhaust near the back of the cab..

 

[ghettosled]

Re: Boost holds back after 8psi,,,need help

i'm not sure if this is your problem, but yes a plugged exhaust will cause a severe drop in boost. Just had a customer bring in a ty complaining it wasnt making boost. Seemed to drive fine, but under a load it would bog down and not build any boost. You could hear a whistling noise (very high pitch like a bad wheel bearing or something coming from under the truck) At first it sounded like it was coming from the flexplate area, but once i got it on the lift i could see a large exhaust leak on the inlet side of the cat.. Basically it had clogged up so bad it was coming out through a slip joint in the exhaust.. Cut cat off and sure enough it was all broken up.. DIdnt help either the guy had a 2.5" exhaust installed on his ty with a flowmaster muffler (so we changed all that as well)

Granted there is not a substantial amount of detonation present, I'd check your compressor blades on the turbo, then pull the wg line and watch for an overboost. If it still wont make boost, then i think your exhaust is plugged.