Boost Problem? hmmm...

[84GNwith87eng]

Ok, driving down the highway cruising at 65-75, only around 5-10psi when I hear a pop or something under the hood. Car is driving like normal, but when I build boost, it stops around 3-5psi and stumbles.

With no boost, it runs fine. Figured I knocked off an intercooler pipe, nope, all secure. Thought then that the turbocharger went, but I can't see oil in the MAF pipe/up-pipe/intercooler that would signify the seal going. So I let the car rest for an hour, go out and fire it up. I can hear a slight ticking from the pass. side valve cover. If something is hitting in the head, would that cause me not to build boost?

If the turbo is indeed bad, which I was almost sure, wouldn't I see oil all inside the piping? What should I do next?

 

[T4Texas]

Cutting out under acceleration could be a lot of things... vacuum leak, coil pack, plugs, plug wires, ignition module, crank sensor, cam sensor, maf sensor, etc. Based on the pop you heard I would look for a vaccum hose loose somewhere (most likely between the WG actuator and WG solenoid, or maybe the one on the FP regulator).

When my turbo died it was siezed up completely. If you really think you have a turbo problem I would take off the MAF duct/pipe to the turbo inlet and see if the turbine will move by hand.

The ticking could be an exhaust leak at the turbo or header, or a weak lifter, or a busted valve spring, etc.

If you have a scan tool one of the gurus here should be able to give you more detailed help. Those are just some things I would check based on my experiences.

HTH
Dave

 

[84GNwith87eng]

I gotta double-check all vacuum hoses on my lunch break, that is probably it, but I didn't notice it when I was looking, we'll see....thanks!

 

[84GNwith87eng]

Big problem, started the car up today. When the scanmaster came on, I see 13.4deg knock, then 9, then 7, then 3, then it went away. This was in park.

My 02's are idle at 941 in park and are not cycling, car is idling at 2000rpms...sheesh...what could this be?

 

[TurboDave]

Big problem, started the car up today. When the scanmaster came on, I see 13.4deg knock, then 9, then 7, then 3, then it went away. This was in park.

My 02's are idle at 941 in park and are not cycling, car is idling at 2000rpms...sheesh...what could this be?

Huge vacuum leak, or hose between turbo and intake loose.

 

[84GNwith87eng]

i checked all intercooler connections/hoses, everything is rock-solid, all of my vacuum lines have ties on the ends and are secure, including hoses on fuel pressure regulator...


would a vacuum leak cause knock on startup????

Good oil pressure, turbo blades sping freely, no leaks....drives really crappy and feels like a vac leak, but i'm not sure :frown:

 

[T4Texas]

Did the "pop" you first heard sound more like a hose popping off, or a more like a backfire? I was guessing one of the boost lines between the turbo and WG solenoid because of the "pop".

It could also be one of the other things I mentioned before. If all the hoses and lines are definitely connected I would probably start with the coil pack/ignition module. The best way to check them is to swap them for known good units if you know someone near you that will help you out. Casper's has a tool to check them too, but it isn't cheap. You might try the troubleshooting tips on Steve Wood's site http://www.vortexbuicks-etc.com/
Lot's of good info there, including a bit about the coil pack. If it isn't a vacuum problem you are probably looking at spending a few hours cussing with a multi-meter while you try to figure out which electronic gizmo isn't working right.

I use turbolink so I'm not familiar with scanmaster, but I'm pretty sure it will tell you what your MAF is flowing, which can help eliminate that possibility. You also need to check your BLMs, which are probably high. If you do a search there is lots of info about chasing down the causes of that.

Was the tapping sound near the passenger side head there before this problem started? Maybe the crank sensor is making contact with the reluctor, which could cause the same problems you are having, but the sound wouldn't seem to be coming from the head. I've heard a lot about cam sensors tapping also but that would be on the driver's side.

Could also be something mechanical. How many miles on the motor? Is it even a remote possiblity that your timing chain jumped a tooth or two?

Hopefully it's something simple. At least it doesn't seem to be your turbo, that's an expensive widget.

 

[84GNwith87eng]

No lines came off, so I'm not sure. I know the turbo is smoking REALLY bad at idle, so it is probably going...I'm sure now it was a backfire. Getting a new turbo next week

Also, the tps was at .55 key on engine off, so that was off too...explains the high idle...