5500 rpm fireworks...wtf??
 

So I changed out my valvecover today and now I have an issue. Everytime I get to 5500rpm under boost, I get BAD backfires/pops/flames out the muffler. I have not tried to go past 5500 and let off. The only think I can think of is the VVT solenoid, but I pulled it out and tested it.....and it works...well, it clicks and the actuator moves. I've checked the cam sensor to make sure it's hooked up and that the COPS are properly plugged in and all of those are fine. I even changed out the plug wires and got the same result. Obvously, the only things I had to move were the VVT, coils and the CAS...all of which I have gone back and checked.

Any ideas?

I suspect something with the VVT because IIRC it changes over at 5500rpm (I have the base VVT map that FM uses). It seems like something is causing TONS of fuel to go unburned...as I had a misfire problem before (too much gap) and once from water getting into the plug holes from washing the car and it feels similar....but far worse. All full throttle conditions from 2000rpm to just over 5000rpm are just fine. Going up to 7k in vacuum is fine too...but once I go into boost, I get sever breakup.




-update-ish

OK this morning I tried looking over some stuff. I took the VVT oil feed line off the soilenoid assembly to check the filter to see if there was any debris in it and it was nice and clean. Then I took the assembly off the valvecover and looked it over too...and it was also clean. Put that back together and started the car. When I did, it hesitated right after startup and then revvs went up and down quickly between 1500 and 2000...like a bad vacuum leak. Opened the hood and couldn't see/hear/find anything....by this time idle returned to normal. I backed the car out of the driveway and tried driving down the street but the car started bogging severely at ~2500rpm....no power. Got it back in the garage, hooked up the laptop and noticed my WB02 AFR rearing full lean (23.8). This lead me to unplug the WB02 which made the reading go to 14.7....but soon as I plugged it back in, AFRs climbed back up to 23.8. Applying throttle did not show and change in AFRs. So I put the Hydra settings to closed loop (no WB02 input). By this time, the car would rev normally again with no bog. Took it back out...everything seemed normal...until 5500rpm in boost. Back to square one.


W T F

VVT wouldn't cause backfiring. And it's continuously variable--there's no "switchover" anywhere.

do you have a rev limit set? are you overboosting? the hydra boost cuts 3 psi over your boost target.

hitting overboost protection...check your MAP signal lines too.

I kinda doubt it's overboost because i've been driving for the past week with no problems (1 week since I changed out the manifold). Not to mention the car was running just fine at all targets before the valvecover replacement and that WOT is just fine everywhere else (all gears and any rpm under 5500)...including going WOT in 6th gear from low rpms.

I didn't mess with any vacuum lines either. But, I can try to turn the boost down a hair and check over the vacuum lines. My big concern is why my ARFs are reading at max lean all of a sudden.

open your hydra map. LOOK at the boost setting.

checked boost target... 14.75...boost seen in gauge 14psi.


I've gotten breakup between 5500 and 6500 rpm...mostly closer to 5500 @WOT. I'm not thinking there is a exact change over for the VVT, i'm thinking that it's not doing what it used to at those RPMs and the targets are not being met. I mean, that's the ONLY thing I can think of. Unless one of the coils has gone bad. Could that be a possibility?

And what can I do to check the WB02? I had one go bad and it sat at 14.7...like when doing the Zero Grade Cal settings when calibrating. It's at least changing when I plug it in....albeit it runs fro mthe Zero Grade Cal up to all the way lean. Might this have anything to do with the sudden rich/ignition cut problem? Although my problem happened with both the WB02 reading and with it set to closed loop.

all i know is that any position the vvt could be in wouldn't cause what you describe. you'd notice a change in power output but that's it.

If one of the coils was bad it would run poorly all the time. Have you put your old valve cover back on? I'm trying to think of things that are related to the valve cover. Coils was a good idea, same with VVT. Could it be that some of the seals in the valve cover are shot, or the PCV is shot, and your pressuring the crankcase too much?

OK.... still no progress.

I took the coils off my GF's MSM (same as my car) and put them on my car.... no difference. Coils not bad.

I've notived that when I hit this ignition cut (what i'm going to call it for now), and back off the throttle, the tach needle jumps a bit..not fall...but a little shake. Also, If I hit the ignition cut, back off, go to the next gear and get back on WOT, it stumbles until I let completely off and then it's fine....until I get to 5500/6000 rpm...in which I get shut down again.

I did one run in 6th gear from 2500 to 4500 rom and there were no problems.
On my last drive, I did some data logs and i'll attach them.

Yes, I know the AFRs are reading full lean...I already addressed that I have seen this and have not been able to figure out why.

have you checked your plugs? cracked insulator?

Nah, it's not one bad plug..or even two... it's like the ignition is getting completely cut..followed by quite a bit of fuel igniting in the exhaust. Ever hear a car with launch control/two-step bouncing off the ignition cut when waiting to launch? Yeah... it sound like that and feels like i'm hitting redline...but at 5500-6000 rpms.

On my way to work today, I nailed it in 2nd gear..got all the way to 7000rpm and let off..and about 1 second after I lifted off, I got a massive loud crack of a backfire.. like when the ignition cut...but just after I let off. The next time I went into WOT boost, I noticed boost dropping and heard a boost leak. If I was getting a boost leak up that high, could that cause the ECU to cut ignition as a safety? When I was hitting this ignition cut, I wouldn't keep my foot in it..so I never watched to see if boost was staying up....i'm honestly too afraif to keep my foot in it.

It sounds like something the hydra is doing. is there some signal it isn't receiving that it needs? Could be as simple as a loose wire causing hydra to lose some signal at 5500rpm and go into a spark-cutting safe mode.

ps. I don't know anything about Hydra.

Called FM, they didn't have any breakthrough/concrete ideas.
Jeremy suggested that I run it in open loop (I think he meant closed?) to eliminate all WB02 input and see if that's tripping the ECU.

I grabbed some tools here at work and put the charge pipe back on the compressor and disconnected the VVT solenoid per Jeremy's suggestion and noticed an immediate stumble. So it seems that the VVT solenoid has quite the impact. I didn't even need to give much throttle or high revvs for it to stumble...just normal acceleration. Plugged it back in and things were normal again...until I went back into boost and popped the charge pipe back off lol

So i'll pick up another VVT solenoid from MM, replace it and disconnect the WB02 and see what happens.


I am currently in closed loop - no difference..even with a fresh old good map loaded.

No, he meant open. Closed uses feedback to "close the loop" between the input and the output (uses saved data and WB input to generate output) while open loop leaves a gap between the input and the output. (uses only saved data to generate the output)

yah, uncheck the "enable closed loop" box.

You sure you didn't get an injector wire caught/nicked somewhere by the valve cover, so when the RPMs get up (engine torquing or whatever), it momentarily grounds an injector dumping fuel?

Frank

Thank you for clarifying that..seriously. I know the difference, but I always get them confused :doh:

Well, made some recommended changes..but no difference.

-Made sure open loop was enabled (14.7 NB02 enabled and auto-tune off)
-disconnected WB02 to eliminate any possibility
-replaced VVT solenid (hey..gotta make sure)

Did another datalog and took video.

If anyone cares to analyze it.. you can see where I started in 2nd gear, went WOT, got ignition cut, shifted to 3rd, got a mild breakup, let off (tach needle bounces around a bit), get back on WOT and got ignition cut again. Sorry, i only had my cellphone to use...but you can tell those backfires are REALLY loud.

Video0012.flv video by teamFBG - Photobucket

If anyone wants to look at my map..let me know and i'll email it to you.

same kinda shit i was getting on MS where my spark was craping out and i was hitting boost cut cause of it to. Still havent fixed the boost cut issue but i can confirm that since scot fixed my spark outputs to put some more feed voltage to my coils the shit is running alot better. If your map sensor allows it turn off the boost cut function and see if this helps you. I would have done this but i only have a 2.5 bar map sensor so thats a nogo :(

Mine did the same exact thing that you are describing a few months back. It was my spark plugs the entire time. Once they were changed out it was fine.