lack of boost

[big61fourby]

I am a bit confused about what the ECM does when it senses IAT too high (BTW, what is the magic number that this happens at?). Does it first pull boost, then fuel, or just fuel? If it does, how long would it keep boost levels in check? Any SES light for any of this?

Just made a pull this afternoon, about 4K, 20 miles, ambient near 95*. When pulling onto the highway, boost gauge would randomly drop to 0, and couldn't hear the turbo anymore. Then it would randomly (after tranny shift?) spool back up, and I had boost again. Any ideas? Is this normal?

[big61fourby]

anybody?

[Barry Nave]

Pulls fuel and boost. IAT would not of been high enough to have pulled fuel towing 4K.
Search on Boost should lead you to many Opt. as to why this would happen. ? would think SES would of came on.
Had a vac. line once that had a small hole. Boost was normal, though on a hard pull the waste gate would not hold above 8lbs and the boost would drop untill I let off or rpm was lowered. Using less power. Still the ses would come on.
Trouble shooting from vac pump (should pull 20 in.) to waste gate(12-15 in.) and then even after Eng. is turned of should still hold Vac.
What boost are you running towing the 4k?

[ 09-27-2005, 02:35 AM: Message edited by: Bnave95 ]

[big61fourby]

I

[Barry Nave]

Turbo Master replaces the elect. control from he pcm. I ended up with this type of boost when I could not get the electrical system to work with the boost.Went through the whole system and failed to figure out why the boost would not work. Turbo Master gives me control of the boost and the elect. system and pump is no longer part of it.
When the elect.part of the Vac. system works then it is still better control of the boost.
You will need a vac. gauge.
Check at the plug (tubing) going to the wastegate solenoid (driver side,above vavle cover,little black box) Unplug and check to see if you pull 20in. from the vac. pump.
At the waste gate, do the same. Should see 15in.

[Scooby]

I'll second the TURBOMASTER. It is not that expensive,and just your time alone fooling with the factory system might be worth the cost. I hate vacuum lines !!