View Full Version : Low Boost

03-05-2011, 10:55 AM
I have researched alot the past couple days, and here's what I have: 99.5 aeb 1.8t unitronic chipped, dp, forge dv, upgraded tip, running stock k03 thats new to the car, original turbo took a dump, I'm at 197,000 miles. I do own a Vag Com and have logged some stuff. Everything runs great, no misfires, CEL's, fuel trim looks good from what I gather from reading online (MB 032 on Vag). My car won't boost to 18 psi, I clearly remember it doing so after the chip. It will spike to 17 then fall to 15 or so. If I go WOT, let off and WOT again really quick it will go 18 17, then fall. Now here's the thing, after a spirited run, when I let off the gas and drop her in neautral and just coast the rpm's stay high and slowly fall to where they are supposed to be. From what I gather something could be wrong with my wastegate flapper, maybe an exhaust manifold leak (sometimes I think I smell exhaust but at this point I think all kinds of s**t) ???????? I have ordered a bunch of gaskets and plan on examining the turbo when I get it off. Could this be my problem, would either problem described above have these symptoms? So here I am asking for some insight, I'm all ears and will check back throughout the day. Thank you to those that respond in advance. On a side note if anybody lives in or around the Bel-Air, MD area and wants to log some stuff on the Vag, run your codes I'm down(free). I've had people do it for me, I guess it's time to return the favor. I only have the kII interface from ross tech, so I think I can only scan up to 2003or4, sorry. If needed email me at rob.mwpropane@yahoo.com

03-05-2011, 11:22 AM
Forgot to mention I know psi because I installed the vent gauge mod.

03-05-2011, 04:20 PM
Anybody? I did the research, I just want to know if I'm heading in the right direction. Any thoughts...

03-05-2011, 04:29 PM
Sounds like you might have issues with your MAF, sure you dont have any vac leaks?

03-05-2011, 06:41 PM
Maf reads 160g/s mb 003. I pressurized the system from the tip, I did have a problem with crankcase ventilation tube, it was cracked. Fixed it. Reset my fuel trims, so far they read .8% and 0%, mb 032. I have looked and looked. When I seafoamed the engine I saw smoke from manifold, but I just tightened, never retested. I will look again for vacuum leak. Thanks for the response. Does anybody else have any ideas? I can post logs of the maf, but from what I've read it seems OK...

03-06-2011, 08:26 AM
This might sound obvious, but have you rebuilt your DV? Thats usually the main culprit for boost drop off in my car. My Forge 007 needs a rebuild at least once a year.

03-06-2011, 09:01 AM
What tune do you have company?

03-06-2011, 09:14 AM
If by rebuild you mean take it apart and grease up the shaft I did that about 2 weeks ago. Thanks for the reply, and as for the tune it's unitronic stage 1+ which is just the tune they have for 93 octane. Thanks for the suggestions, every time I think I've found it, it's not it.

03-06-2011, 12:37 PM
From what I remember the MAF should read 250 g/s at idle. Does your boost gauge have a vacuum side to it? If so what is it reading? It should be around 20 in-hg.

03-06-2011, 02:34 PM
When you rebuilt the dv, did you test it for functionality? (pushing the piston up, capping the top hole with your finger, and letting the piston try to fall)?
The O rings in mine got flat spots and wouldn't hold vacuum a while ago.

03-06-2011, 04:40 PM
From what i have read maf readings should top out at 160g/s, I'll post them in a bit. Vac does go to 20 in hg. My dv did not have any o rings, just a metal cylinder. I was thinking forge but i believe it was made by samco. So I pulled the Turbo. I needed to replacelp gaskets any way. My exhaust housing has 3 small cracks in it although they don't go through to th.e other side, I'll post pictures in a bit. I didn't get to the manifold yet. I don't think it's totally shot(Turbo) but it's on its way out. To be honest though I don't know s*** about what I'm looking at. Thanks for the ideas.

03-06-2011, 04:46 PM
I did a really intense inspection on all the lines that I took off, no leaks. I also seafoamed today before I took it apart.

03-06-2011, 06:32 PM
Ok, so I tried uploading pictures it say they are to big, so I need to take smaller ones. I ran out of my 25 time trial period on MS Office Excel, so I can't copy and paste. I'm tired, but the pictures show 3 very small cracks on the exhaust housing on the inside of the turbo. They do not run all the way through to the outside. It's not ideal, but I don't think it was the cause of my problem. There is a crack I'm concerned about a little next to the wastegate. It's leading away from the wastegate, and I suppose caused by heat. The shaft on the compressor side moved in and out about 1/32 of an inch. Not ideal, but...As far as my MAF logs, thet start at like 2.67 and run all the way to 160. As far as I know this is right on. I'll have to check the dv monday to see if it works right. It's only about a year old. I'm still stumped, but I've been meaning to replace the gaskets for a while so it's not all a loss. I plan on taking the exhaust manifold and intake manifold off tommorow. I'll be able to get a better look under the intake manifold at all the lines.

03-07-2011, 04:18 AM
Here's my Monday morning bump/plea.....???

03-07-2011, 06:20 PM
Okay, here's an update. I pulled the turbo, exhaust manifold, intake manifold, and did an extremely intense search for any ripps or tears. I replaced all gaskets and cleaned her up as best I could. I stopped at a shop and they told me my turbo was fine even with the few minor internal cracks. Everything looks good. I pulled the dv apart and made sure it was good, hold vac and everything. She started up on the first go and I went for a run, and found the same problem that I had before I took it apart. The only other thing that I can possibly check is the n-75. I've read a couple posts on it, but if anyone know any tips I'd appreciate it. The damn thing still idles high as hell after a good run, and the boost only reaches 15 psi, and when coasting after a run rpms are like 1500??? Sometimes it feels great, but for the most part all she will do is 15 :( Any ideas anyone?

03-08-2011, 03:24 AM

03-08-2011, 01:11 PM
Anybody out there, can anybody hear me..... Pink Floyd, LOL, but seriously....

03-08-2011, 03:43 PM
So I'm brainstorming..... bad throttle body, bad n-75, bad Ecu????

03-09-2011, 07:05 AM