BPT bucking past 3000 RPM

Cpl_Bryant · Post by **Cpl_Bryant** » August 19th, 2005, 12:20 am

So finally I am attempting to drive the BPT with everything hooked up. Now I get a really bad bucking around 3000 RPM that repeats at even intervals as the RPMs climb toward redline. In other words, when accelerating (regardless of throttle position) it will be going fine, start spooling up and then dives forward like I slammed on the breaks. It does that for only a second then returns to accelerating like before, but only for another second. Then it dives again and back again at very consistent times (about 1 second each). It does not do this in neutral or in 1st gear. But from 2nd gear on, it bucks whiplash hard.

I messed with the vacuum lines. I gapped my plugs down to .30 inch. I am thinking the BOV may be a problem. I though I heard it make a fluttering noise one time. I did not upgrade the ignition either, I am thinking that could also be contributing to the problem. Everything is pretty much a stock GTX engine except for my Magnecor 8.5mm ignition wires. I am dying to get this fixed now that I have gotten a little taste of the boost. I've read a lot of other threads with similar problems, but couldn't find an answer that really suited the problem. Anyone have any thoughts on this issue?

BuGS · Post by **BuGS** » August 19th, 2005, 2:32 am

Well I couldn't see how a BOV would do that consistantly. Maybe your fuel map? What are you useing? I know when I would go lean it would be like someone put on the brake. And also, does this happen at WOT??

Cpl_Bryant · Post by **Cpl_Bryant** » August 19th, 2005, 12:32 pm

I am using the GTX ECU (BP26). The problem happens at wide open throttle and everywhere in between. Any kind of acceleration. I also noticed today that in neutral, if I rev it up around 5000 or 6000 RPM it will vibrate and shake and then the RPMs will drop down without me letting off the gas. I verified my TPS as well and it is in perfect adjustment. Still, every second it feels like I am mashing on the brakes. I tried running it without the air filter too, thinking it might be restricting the flow, but no difference. Need help bad.

Cpl_Bryant · Post by **Cpl_Bryant** » August 19th, 2005, 9:36 pm

Also noticed today that there is black smoke that comes from the exhaust each time the car bucks. So now I am thinking it gets too rich or something? Maybe not burning enough each time? Do I really need to upgrade the ignition to MSD or something?

Franko · Post by **Franko** » August 19th, 2005, 9:42 pm

do you have a boost gauge? It sounds like your hitting the stock boost cut. It has been described as 'feels like you hit a brick wall' What is your boost going to? Tell me everything you have on the car.. What kind of bov, what kind of intercooler.. how you have you piping ran. Tell me as much as possible so that I can diagnose this problem.
You do have the wiring done properly yes? From what I remember youre using the mx3 harness right? Converted like mine is..

Tell me everything.. I think I might be able to help you.

Cpl_Bryant · Post by **Cpl_Bryant** » August 20th, 2005, 11:25 am

No, no boost gauge yet. I've been trying to spend the bare minimum right now just to get it running. Stock BOV. Mitsubishi Lancer Evolution intercooler (big). Piping is ran around those tow hooks underneath and up to either the turbo or stock pipe that goes up to the throttle body. Using the 93 harness with the splices you told me to make for the TPS. Also using magnecor 8.5 mm wires with NGK plugs. I think that's all that would apply to this problem. But you think the black smoke would come out like it is if I was hitting the stock boost cut? Oh, and I also noticed a tiny bit of oil dripping from the turbo compressor outlet. The guys that machined my flange to bolt up to the turbo also managed to make the hole somewhat smaller than the original.

Also, after watching your video on your site, I was looking at your BOV. Where do you have that small hose going to? Take a look at my vac lines: http://www.mx-3.com/phpbb2/viewtopic.php?t=44073 Do you agree?

Franko · Post by **Franko** » August 20th, 2005, 2:43 pm

I think I can tell you whats happening here.. Youre overboosting.. since you dont have a boost gauge you cant tell its happening.

Do you have an aftermarket bov?

Also, Ill tell you what these hoses are for

"H" is for the idle air control valve. You hook this up to "K" on the intake pipe.
"I" is the vacum source for the bov which is in the bottom pic. If you decide to use that one it connects to "C".
Where you have "F" labeled, this part is used for the stock blow off valve.. Its actually a recirculating system.. So when you let off the gas and the valve lets all the air out you wont really hear a whoosh because it gets blown back into the intake before the turbo and after the maf. This is simply to prevent the car from running rich due to air being let escape that has been read by the maf but not burned in the engine. I have this hose taken off and blocked since I have an aftermarket bov. You wont even notice it being a little rich when it blows off.
Anyway, "F" connects to "A" on that valve.
"D" and "E" make things confusing. Both of these lines are going to your wastegate. You MUST simplify it down into one. There is a T located right where "D" and "E" meet. Remove this T along with the hose "E" and just put a straight connector in there. I just got one from canadian tire thats a straight through for it. Now when you have that done.. "D" HAS TO go to "J" This is where the boost source comes from to open the wastegate. IF YOU DO NOT HAVE THESE CONNECTED CORRECTLY YOUR WASTEGATE WILL NOT OPEN MAKING THE TURBO OVERBOOST!
I noticed the way Josh has told you to hook up the vacum lines is wrong... The car will NOT RUN if you hook it up like that.

I believe that "E" and "G" could have been used for a boost control solenoid. Since there needs to be a reference line and a boost line. You dont need either of these. Block "G" off.

You cannot see "H" or "K" but they are hooked togethor.

Also, where your maf connects to the intake pipe.. I never had that with my engine.. so I cut off part of the stock intake of the b6 and used that on the intake pipe... It worked PERFERCTLY.. its smooth inside and everything.

Now, you said you noticed oil.. It may be normal..

In this image you can see that there is a hose that goes from your valve cover to the rubber part that the maf conencts to.. Not "G" but the one thats hooked up and you dont have labeled. Whenever you are boosting, instead of oil going from your pcv valve directly into your intake manifold as it normally would, the pcv gets closed off to prevent the crankcase from being pressureized.. which is not good.. So the crankcase gasses gotta go somewhere.. so they put it to a place that dosent get boosted and your turbo sucks in the oil and puts it through your entire intercooler system and then into the intake.. I recomend removing this.. and putting a filter on your valve cover. I have this done with mine with no problems. If you have idle issues you can consider reconnecting it.. but I dont think you will and its not worth it.

If you need anymore help man.. Im here if you need me.

Cpl_Bryant · Post by **Cpl_Bryant** » August 20th, 2005, 5:01 pm

Wow my vac lines were all messed up (I had tried some other ways to try to fix this problem before you posted Franko). So now I have them all like you said, but the car is still bucking like before. Could the wastegate be stuck?

Franko · Post by **Franko** » August 20th, 2005, 7:42 pm

It is possible that your wastegate may be stuck but I doubt it.. did you mount that turbo to the manifold? or was it just on the engine?
I really think that this may be caused by too much boost. How loud does the turbo sound when it spools? If its really really loud then it might be overboosting. Did you hook that line up for the wastegate like I said? Its very important this line be hooked up without any leaks or kinks. If that line dosent hold 10 psi then the wastegate wont open and the turbo will overboost.

This bucking.. is it just one buck then you let off the gas? or many bucks?

Cpl_Bryant · Post by **Cpl_Bryant** » August 20th, 2005, 8:12 pm

Fixed it. The problem was the connecting hose on the intercooler inlet side. Air was escaping from it as I revved the engine. My friend saw some nearby grass get blown and I traced the air to that coupling. SON OF A %$#@&!!!!! The overboosting is probably what caused the bad seal there though. The engine runs fine now. I've got the lines just like you said Franko. By the way, you are the man. Seriously you have been my savior numerous times durring this swap and I really appreciate it. Hope you get your car back in shape soon. Seeing that video made me scared!! Thanks again.

Franko · Post by **Franko** » August 20th, 2005, 8:28 pm

Lovely! Your car WAS overboosting and thats what caused the bucking.. alot of air was flowing but not building any pressure because the leak. Thats why I asked all about your setup.. Great to hear man.. Im glad that I could be such a help to you... I couldent have you driving around with things hooked up in a way that might damage your engine.

Ohh and my car is fixed by the way.. I had it perfect again in less than a month.. check out my cardomain site on the last page.. You can see its better than before.. I got a better intercooler and the new bumper fits better.. so Im very pleased.

Anyhoo.. if you ever have any more trouble dude Ill gladly help you out..
Be careful with all that boost..