Help! -Loss Of Power And Engine Shut Down After Boosting Hard

[rondofj]

Hey guys,

Here's my problem, hoping some of yous can suggest good advice:

I just installed my new JJR dump/front and PEC Aust O2 sensor the day before yesterday. My friend just took it for a drive today and I came back very disappointed and frustrated. Firstly, there is significant loss of power when boosting, like it boosts ok all the way to redline, revs cleanly and boost holds 10-12psi, but that oooomph and kick in the seat is sooo gradual and not as hard as normal, its just so nothing special at all, even putting foot to floor, it dosent accelerate as quick as it used to before the O2 sensor and dump pipe install a couple of weeks ago. There is no missing, revs cleanly, boosts cleanly, boost holds, but there is NOT MUCH power, no wheelspin in first as normal.

I installed coilpacks a few weeks ago and it picked up considerable midrange snappiness and torque then. The other thing I noticed today is that after driving on a hot day, my intercooler pipes - the J pipe just before the throttle body, and the pipe just in front of my fan is HOT like I can only touch for a second. Is this normal? BUT the pipe JUST after the cooler (cold side outlet) is cool like room temp which is normal and cooler hot side pipe is hot, so the cooler is definitely doing its job. But the pipes behind the fan and over the engine and just into the intake is too hot to touch, is this normal, or is this what is causing my power loss?? The turbo is running the heat shield but the dump is not, is this causing the pipes to be hot, dont think so??

Lastly the most frustrating bit is the engine shuts down after very hard boosting on WOT, no stalling/sputtering, nothing, just a complete shut down and lights on in dash, generally I found after hard boosting, but also in normal driving stopping at lights etc. Is this O2 sensor related??? Because these probs werent there at all before. The O2 sensor is not that tight, just hand tight and half turn with a shifter that I managed to get in there. The dump to cat is tight (grunting when tightening) but you can see the gasket edges (see pics) as its not a clean fit - slightly mis aligned.. But no exhaust leaks judging from sounds...

My battery is fine - holds 13.8 volts consistently so thats not the reason for shutting down. And I have the factory plumb-back BOV.

Please help! Driving me real nuts.... thanks in advance :(

Edited January 7, 2012 by rondofj

[rondofj]

For list of mods, please see my signature - running gapped coppers at 0.8mm, nistune and yellow jackets.

In summary : The car does accelerate, but very slowly, not much torque and not instant and snappy at all like before, no wheelspin/torque/power like before, but revs and boosts cleanly..boost holds well too. Engine shuts down after WOT & hard boosting...aaarghh..

Worried also about my intake pipe to throttle body and pipe behind fan both of which are too hot to touch. But pipe just after cooler at the bottom is at room temp so sweet.

My battery is fine - holds 13.8 volts consistently so thats not the reason for shutting down. Running factory plumb-back BOV.

Edited January 7, 2012 by rondofj

[boostn0199]

Check that you dont have a exhuast leak at the dump to turbo and did you get a split one? There known to give sealing problems.

[rondofj]

no its a bellmouth, there shouldnt be a leak - judging from sounds - all 5 studs and bolts are tight, the 6th bolt (middle passenger side) is hand tight as its so hard to get a tool in there

[rondofj]

didnt use gasket goo, re-used old gaskets which are in very good condition

[rondofj]

Got this from

:http://electromotivetec.freeforums.org/engine-stalls-at-wot-on-boost-and-ecu-datalog-freeze-t467.html

f I accelerate at WOT, the engine *almost always* stalls once the boost has come on. On the datalog, when this occurs, ALL datalogged parameters freeze at their last value, and remain at those frozen values until I turn the ignition off and restart the engine. I mentioned that this occurs *almost always*...it doesn't ever seem to happen in first gear. I can run the engine all the way to redline in 1st gear without an issue, but in 2nd, 3rd, or 4th gear, the engine stalls out as described. .........

Well, the problem continued and battery voltage wasn't the issue. After about an hour of driving, tuning, driving, and tuning, I got the VE table close enough for my liking and decide to turn off the EGO correction...VOILA! No more stalling.

Whisky Tango Foxtrot!???

I previously set the EGO parameters to disable EGO correction above 3000rpm and 120 kPa...every time the engine stalls, it's above 3000rpm and above 120kPa when the EGO correction should not be active. It's also during the acceleration period when the EGO correction should not be active (previously, adjusting the variable time enrichment duration made no difference...e.g. after this duration, the EGO correction *could* turn back on and run the engine lean; but this never is observed on the datalog.)

So, let's recap: Activating EGO correction somehow causes my engine to stall, during RPM and boost where it should not be active to begin with. Disabling EGO correction is the magical solution.

Well how about that? Hey, maybe I can short the coolant sensor and magically activate AutoTune VE Actually,

Does it mean my new O2 sensor has f**ked up my tune and making it run rich and have these bizarre issues??? Havent heard anyone with these probs after O2 sensor and dump pipe install.

Edited January 7, 2012 by rondofj

[Moodles2]

Disconnect the O2 sensor plug, it will run rich but will confirm if the O2 sensor is the problem.

[rondofj]

I ran it for 5 mins boosting hard without O2 sensor fitted yesterday, there was a noticeable increased 'shove' than before and boost was quick, but after decelerating the car did the same thing as today- shut down and dash lights on. There was no power loss yesterday but actually a gain you could feel in terms of shove.

[rondofj]

Stupid car feel like burning it lol..

[paulr33]

whatever is wrong, is seriously wrong

id say your ecu is toast, or the loom is f**ked or something is seriously damaged

have you got another known working ecu you can try?

does the nistune have any working diags or display? have you got consult you can connect up (does it work with nistune, i assume it does)?

check the ecu and loom for a loose ecu loom connector

whatever is wrong, is seriously mangled

ie its not just a loose cooler pipe

not much would make the engine "stop" and all the dash lights come on

[rondofj]

Shit man ur giving me the shivers.. Hope thats not the case.. I noticed it goes off always after WOT when u decelerate rapidly or a few times when coming to a stop at the lights. I cleaned my aac a week before changing the dump and O2 sensor and adjusted the manual idle screw, all was gud then, can i rule this out?

I been reading on the net that theres a lot of pple having this symptoms with their cars, many have reported something to do with the car vacuuming too quick and stalling after releasing the accelerator, something to do with no air at that point and carbies in older cars, some have said its the fuel cut, something to do with the tune, the afrs, running rich at that point etc or the fuel pump earth needs to be better, yet for some pple it is the EGO gas correction mixtures/O2 sensor related? but why is this happening after i changed my dump and O2 sensor? IM really worried, no dont have a spare ecu and loom, how can my ecu be fried?

[blind_elk]

I have lost count of the number of times it has been stated that the ECU will ignore the O2 sensor during acceleration - it ONLY works on CRUISE!. So, the installation of a new O2 sensor should be coincidental to the problems experienced. Rarely does the O2 sensor play any part in idle as well. However, it might be set to operate from too low revs - try raising the lower threshold to say 2000rpm. (in my Wolf ECU, closed loop, ie "use O2 sensor", is set to operate between 1500 and 4500 rpm, and below 45% load (50% is where boost starts))

The new dump possibly improves the efficiency of the whole system, to a point where the ECU is unable to cope with the changes. In such a case, it would not be inadvisable to do a bit of fine tuning of the ECU.

The stalling coming back from WOT could be a due to not having "shut down injectors on overrun" working correctly. It could be due to turning the injectors back on after overrun too late.

Your intake pipe is hot because it is sitting in a hotbox (ie engine bay), and close to a hot engine and hot radiator.

[Hanaldo]

The Neo ECU's are a bit different though, they are flagged for O2 feedback across the entire fuel map, every cell has it enabled and it can't be switched off per se. So there is no lower threshold or higher threshold, and they can cause problems at idle and higher rpm if they aren't working properly. Mine was.

[OMGGTR]

how many wires does the old o2 sensor have compared to the new one?

not saying this has anything to do with ur problem but just going to basics eliminate 1 thing at a time go over everything you have touched and make sure each step is bullet proof...

if you are able to get a hold of a scan tool maby try chek for faults and chek actual data im pretty sure theres o2 voltage etc.. maby its faulty...

also try a compression test

[rondofj]

Ok guys so just disconnected the O2 sensor plug and went for a spirited run. Good and bad news. The power is back where it should be, boosts and holds hard all the way to 7k rpm, shove in seat is good, second-third gear is easily cop territory..

Bad news is the car shuts down after suddenly releasing throttle. As when boosting on WOT and then letting go throttle and decelerating.

[rondofj]

Shit didnt complete my post damn iphone. Engine also shuts down at super low speed when releasing throttle suddenly as when approaching driveway.

So O2 sensor not the culprit as its disconnected, WHAT could it be?? Battery is consistently holding 13.8V and idle is good at 900rpm after initial cold start 900rpm.

Do i need to get a mini laptop nissan consult cable and ecutalk to diagnose?? And maybe even buy the Nistune licence and learn my own tuning?? Getting expensive, just did my couipacks

[rondofj]

Now this- damn iphone again for posting incomplete posts

[rondofj]

V8tzr, new and old sensors both have two white wires each and one black wire each

[rondofj]

When engine shuts down, three lights come on in dash- battery light, engine light and teapot light (oil press?)

[rondofj]

It looks like a vacuum issue to me - suddenly release throttle then engine shuts down and these three lights come on.