Boost Issues - Searched!

[hoganalley]

Hey guys:

I've searched the forums and I have a grasp of what's going on, just not sure of the trouble shooting options.

I was boosting normally for a K04, between 22-25 psi up until about a month ago. I put in Shell 91 and all of the sudden I don't boost past 10! I figured it was the ECU compensating for the fuel, but when I put Sunoco 94 back in it didn't boost any higher. I searched and found out I can disconnect the wastegate and see what I boost. I just did that and I'm all the way up to 25psi.

So.....obviously the turbo's ok, but is it the wastegate or the N75 that is causing the problem? I don't want to have to pull the turbo, but I will if necessary......any thoughts?

[mike-2ptzero]

Did you reset the ecu(clear the DTC's and do a tb adapt) to see if the boost comes back? Sounds like you could be in a limp mode.

[hoganalley]

yeah, tried that right after I filled up. Left it off for 30 mins, checked codes, none - cleared it anyway, and then did the TBA. Still no boost. I'm going to do it again to see what I get.

Last night when I was driving home I floored it in 3rd and it went to 5psi...held there until 3000 and where I normally get the K04 spike to 22-25psi, it only jumps to 10. Feels like the same power, but the gauge just hits a wall at 10

[hoganalley]

ok.....reset ECU. Still nothing. I believe it's the wastegate, but how can I tell if it's the N75 or the wastegate?

[akielb]

Pull the N75 and get a MBC - just get a cheap one like this

CLICK HERE

[hoganalley]

thought about that, but the N75 should be fine with the K05 file, right?!! Didn't have any problems before......been running this for almost a year

[mike-2ptzero]

Might want to try putting in another N75 valve from a friend if possible. Dont think its your WG if you were able to hit 25psi with the vac line pulled from the wg.

[ILoveT]

Also check and make sure the two wires leading to the N75 aren't busted. I had to resolder mine back together. You just peel back the weather cover.

[CaddieManAudi]

Ive been Wanting to go for a MBC because with the n75 I can only get 12psi of boost. If I went MBC what would I have to do when removing the n75? (Not R and R of it but for the wires and ecu looking for an n75?)

[hoganalley]

So is the N75 a bad setup for a K04 chip? If I get another N75 I'm thinking of getting an H. I've heard good things about it and from what I understand it smooths out the boost a little bit.....may help the jumping boost I had previously.

I don't have a friend who has one, but I'll see if maybe I can buy one and try to return it.

[mike-2ptzero]

The N75 is what you want, MBC/EBC's dont work well with the K03/K04. They tend to give a on/off issue when at part throttle.

[hoganalley]

Ordered the N75H from 034.....they seemed to have the best price. I'll let you guys know what I find out.

[beejohn]

you really need an N75F, the stock upgraded replacement. not H.

[hoganalley]

well....considering mine is original, and probably a C, I know the F is the replacement for the C but I thought the H provided a smoother boost curve than the F?.......

[ShawFM]

Hey guys:

I've searched the forums and I have a grasp of what's going on, just not sure of the trouble shooting options.

I was boosting normally for a K04, between 22-25 psi up until about a month ago. I put in Shell 91 and all of the sudden I don't boost past 10! I figured it was the ECU compensating for the fuel, but when I put Sunoco 94 back in it didn't boost any higher. I searched and found out I can disconnect the wastegate and see what I boost. I just did that and I'm all the way up to 25psi.

So.....obviously the turbo's ok, but is it the wastegate or the N75 that is causing the problem? I don't want to have to pull the turbo, but I will if necessary......any thoughts?

The 22psi to 10psi happened to me last week. The vac line from the diverter valve to the manifold separated. No codes, drove fine but no boost. After a long search I found it. Reconnect it and full boost right away. Just a thought for a quick check.

[hoganalley]

Did a boost leak test and wasn't getting any leaks.....so I don't think it's that. It's a holiday here for us today so I'll double check everything just in case!

[hoganalley]

Alright! Updated......got my N75 on the weekend and swapped that out. While I was doing that, I found a HUGE tear in the nipple that holds the N75. Ran it out for a bit and it spikes to 20-22, and holds 18-20. Swapped out the TIP and it's a lot tighter and smoother now.

Looks like it was the N75!!

[Ayefore]

either way, I would also check your spark plugs to see if they are going or not. No one's mentioned that at all. Also what plugs are you running?

[hoganalley]

nope, not them. Changed those last oil change in May. Brand new. BKR7E's....I believe....gapped to .28.