Need help troubleshooting

[AKlowriderZ71]

In the last week or so my truck has been acting differently. I'll do my best to explain. This started after temperatures here got into the 20's and lower, but that may be coincidence.

Normally when I'm driving 65-70 mph on the highway, I will see 2-3 psi on my CTS. And if I come to a hill and/or ease into the throttle, boost will increase in a somewhat linear manner according to my throttle input.

Now, intermittently, I'll see 0 psi as high as 85 mph (haven't tried faster). When doing this, I have several times eased into the throttle and still see 0 psi, then a few seconds later BAM, I have 14+ psi. When the truck acts up, this is repeatable 3 or 4 times. If I romp on it, I see 21 or 22 psi, which is the max reading for the CTS as far as I know.

My thoughts are that my MAP sensor is crapping out, or my wastegate is sticking. I'm not sure how to test for these, because when datalogging the MAP, it should show zero psi if the WG is stuck, right?

Or maybe I'm completely missing something else. I don't know what's common that might cause this issue, so thanks in advance for your help.

 

[Kappa9012]

could be a stuck wastegate, any smoke when it happens? Do you hear the turbo at all when the gauge is showing zero psi?

 

[bevi]

X2 can you here the turbo or do you think the guage is not working properly

 

[AKlowriderZ71]

It's been dark out when I'm driving to/from work, so I don't know about the smoke. I have some time off now, so I'll check for smoke if/when it happens during the daytime.

As for hearing the turbo, I'm running the stock airbox & intake tube. I can't really hear the turbo ever, at lower boost pressures. But I'll try to listen closer next time.

I'm trying to determine if I have boost but the MAP sensor is dropping out, or if the wastegate is sticking & I actually do not have boost. Do wastegates stick often? Do MAP sensors fail often? Is there something else I should be checking instead?

 

[Kappa9012]

you can pull the c clip on the wastegate linkage and disconnect the rod, then move the wastegate by hand. See if it feels like it's sticking. Also if you have an air compressor, set your regulator to 20psi and put an air gun to the blue line going into the waste gate and watch the rod move. Do it repeatedly and see if it ever hangs up.

 

[AKlowriderZ71]

you can pull the c clip on the wastegate linkage and disconnect the rod, then move the wastegate by hand. See if it feels like it's sticking. Also if you have an air compressor, set your regulator to 20psi and put an air gun to the blue line going into the waste gate and watch the rod move. Do it repeatedly and see if it ever hangs up.

I do have a compressor, just no garage to work in. Maybe we'll get a nice sunny warm day soon.

Thanks for the info, that's what I needed to know. Does anybody have a pic of the wastegate linkage they could post up for me? Save me a few minutes of poking around.

 

[Kappa9012]

http://www.mazdaspeedforums.org/forum/f11/turbos-begginers-guide-18309/

Here's a thread on some mazda forum, scroll down and there's a few good shots of a turbo and the guts.

 

[AKlowriderZ71]

Thank you. I'm familiar with the basics of a turbo & its components. I guess I was really looking for a pic of the wastegate linkage as it looks when it's installed in the truck. With all of the typical harnesses, hoses, covers, etc that are always in the way.

 

[AKlowriderZ71]

Bump!

 

[AKlowriderZ71]

Not much of an update here. It has not acted up at all since I started this thread, and it's been well below zero so I haven't even popped the hood.