Recently Ive been experiencing a weird issue and cannot seem to figure out whats going on. It seems that whenever I go WOT the car pulls really nicely up untill about 4k. At that point theres some hesitation and a noticeable tone difference in the exhaust and it just doesnt seem to be making any real power past the 4k mark. Definately not like it used to. It used to just continously pull harder and harder untill 7k. Now if I give it partial throttle and take it up to 7k I dont experience the power loss so much, its just mainly when I floor it and go WOT.
Ive replaced the Z32 MAF, changed the plugs, cleaned the TB and EGR tube and swapped out the coils with another set I have, cleaned the filter, and checked my belt to see if it was loose which it wasnt and still have the issue.
My vac. readings are normal and so is my fuel pressure.
My only thought at this point is maybe a bad injector however the car runs fine and idles smoothly under normal driving. No CEL so Im kind of stumped. Any suggestions?

 

Are you still making boost normally? Do you have a Cat convertor?

 

At first thought, i would assume that your MEVI isn't opening, but you did state that it feels normal at part throttle. If you haven't ruled it out yet, i'd say tie it open and take it up to 7k.

If you're still feeling the power drop off, I'd say that you have some sort of vacum leak that is related to load and boost. But then again, you mentioned that your vac. readings look good.

Does the hesitation feel like a 4th gen USIM? And if i'm not mistaken, you have 370cc injectors correct?

 

Belt slipping? Are you still getting the same boost pressure you used to get?

 

Test pipe with electric cutout. Even with the cutout open it does this. Im making the same boost that Ive always have, just doesnt feel like it.

 

Hmmm, I thought that too but I floored it with the car in my diveway in neutral and could see the acutautor move and stay open untill i released the throttle. Yes, Im running 370cc's.
I thought it may be a vac. leak also but I checked and replaced all my vac lines going to the FMU, MEVI, BOV,and boost gauge and also changed up all there sources so that Im only running two items per vac. source.
The only thing I havent done and is now making me curious is check all my piping and there couplers for a leak. Maybe a have a slight leak somewhere and its not really noticeable untill I go WOT.

 

I checked the belt, and its tight and Im still seeing 13lbs at 7k but it sure doesnt feel like it.

 

Just throwing it out there. I know you said you changed the plugs, but could you be experiencing spark-blowout? Im not sure how much of a possibility this could be, given that I ASSume you ran the same gap before and after changing, so IMO something else would be to blame.

 

I kind of thought that too but i dropped the gap a bit and Im also running a BAS.


I also want to say thanks to all who have responded so far, I appreciate the info and suggestions.

 

What about fuel pressure? More importantly, are you monitoring your A/F ratio? Its not uncommon for fuel pumps to weaken (OEM or Walbro). I have had a Walbro go out on me before. In my case, it was fine for regular driving, but once boost kicked it, it just would not provide the fuel that it used to. Got a new pump and the problem was solved.

 

Fuel pressure seems to be the same. Im not monitoring the AFRs yet. i have a WB im going to try and install this sat. and hopefully that should help with some trouble shooting.

 

it could still be the mevi. My mevi would open and close fine when the car was in neutral but when the car was under a load the mevi would not say open. I 1st noticed it during a dyno run it would open at 5k then slowly close. I made a tester with a wot switch and attached it to the mevi arm and a light thur the hood to see what the mevi was doing. The problem was loose fitting on my vac/boost gauge.

 

I know someone said it already but i would check the plus and coil pack it almost sounds like its breaking up up top. No spark no power.

 

I think so too. Im going to pull the plugs today and drop down the gap and see what happens. Im also going to pull out the BAS and see if it makes any difference without it.
Havent had a chance to get the WB in yet but its going in for sure this week.

 

You also dropped your heat range on the plugs right? Its like every 50hp over stock you go colder 1 step.

 

Yes, Im running NGK coppers, one step colder.

 

Well got it all situated for now.
I dropped the gap on the plugs down to .030 and went for a spin, still did the hesitation in the upper RPMS but not nearly as bad. I then figured I would take out the BAS and see if it would run better or worse without it. After I took it out the car began pulling like normal, all the way up to 7k. No more hesitation.
Nice to have that power back in the upper rpms.
So now I need to contact Kenne Bell and see if they can fix this BAS if not I may just have to purchase another one.

 

Glad to hear that you have fixed your issues. Its interesting that your BAS failed on you. I had never heard any BAS failing. Now you got me worried that my BAS (which I am using as a BAP) is going to fail on me : (

 

Well it always had issues. I bought it off Stephen Max and from the begining it always blew fuses if it was turned up all the way so that tells me it didnt operate right from the get go. It worked ok for me for a while, and then this began to happen.

 

I'm glad you figured it out Flava. What was your spark plug gap before you dropped them down to .030? You can probably put your gap back to where they were before you dropped them since the BAS was failing you. You want your gap to be as big as possible before blowout/driveability issues occur.

 

You said your car had no issues
Just get an M5...

 

.034
I had this gap when I first went boosted with the 3.0 pulley. When I dropped down to the 2.87 I began to feel a little loss in power at about 6500-7000. Nothing major like what I just went through, just not a smooth pull. I dropped my gap to .032 and that helped. So I then put the BAS in and put my gap back to .034 and was running strong untill just recently.

 

Trust me, everyday I think about it more and more.
Maybe next year.