Boost problem, cuts out under heavy load

WannaBREz · Post by **WannaBREz** » Tue Apr 07, 2009 7:10 am

If I accelerate normal it will run fine. Soon as I nail it, it gets into boost, car dies, tach goes to 0 for a second, and then it will come back to life, does it one more time, and then pull to red line like nothing happened. Is this a NIStune related problem, or a car problem? On a factory eccs with the z31 maf it never did this. Is there an ignition setting I am missing?

Bernardd · Post by **Bernardd** » Tue Apr 07, 2009 9:35 am

Can you datalog it? Post the datalog and the binfile.

WannaBREz · Post by **WannaBREz** » Wed Apr 08, 2009 7:26 am

Here is the link for 3 logs and the bin file. Looking at the timing and it just randomy falls off at points.

http://www.mediafire.com/?sharekey=d0ee ... 739011d398

WannaBREz · Post by **WannaBREz** » Sat Apr 11, 2009 7:16 am

No help available? I am wondering if it is because I am getting my MAF power from the coil. IF it is getting some kind of interruption.

WannaBREz · Post by **WannaBREz** » Sun Apr 12, 2009 4:25 pm

So after hours of reading this forum, I think I narrowed it down to an error in my math for the injector multiplier. I changed that and went for a drive around the block and it ran fine. Tested the load on boost and got it sideways no problem at 6 psi with not cut outs.

So I guess I will get it plated and see what some real world driving will do.

TM_S13 · Post by **TM_S13** » Sun Apr 12, 2009 10:01 pm

are you doing things with a wideband ?
anyway, that's good news you got that sorted

Matt · Post by **Matt** » Mon Apr 13, 2009 8:34 pm

sorry didnt get to download and go through your logs before easter break

i've never seen this issue before with the timing. its not based from any other loggable input

are you still getting the same dropouts with timing now with the change in K constant?

are you looking at your AFRs also? you need a wideband to correctly tune your vehicle

WannaBREz · Post by **WannaBREz** » Tue Apr 14, 2009 8:48 pm

No, after changing the multiplier it is running good with no timing issues. And yes, I need a wideband. Gonna get one soon. I dont know if it was related to mixture. I know sometimes it woud go into the "lean" area according to the narrow band, which really means little.. but i could feel the car loose some power randomly while driving, and sometimes it would just choke, timing falling off, and then come back.

I drove it all day Sunday at stock boost (6psi) and did fine. No issues. I was at 10psi before. Injectors are alright up to 12psi... any higher and your asking for problems.

But I do have a question the injector multiplier, Mine is in the hundreds, yet the tuning guide places it in the 10's of thousands... Can I move it up to the thousands without an issue, or are the hundreds where it is supposed to be?

I have stock 260cc (1981 280zxt) Nissan Z injectors with the z32 MAF.

Matt · Post by **Matt** » Tue Apr 14, 2009 9:37 pm

Different ECUs have different K constants... no two are the same

The early model ECUs (Z31) have a K constant in the hundreds so we always adjust K constant as a percentage of the original value

brett_32i · Post by **brett_32i** » Thu Jul 16, 2009 8:13 am

i had very similar symptoms with mine. would be driving fine then occasionally when you nail it, it reaches about 4000rpm full load, engine cuts and you roll to the side of the road.
last time this happened, the ecu had died and matt ended up replacing the rom??
since then i haven't had it happen.

brett_32i · Post by **brett_32i** » Mon Oct 05, 2009 7:57 am

i'm still getting this issue.

full load around 4000rpm occasionally it just cuts out. i need to grab the keys and turn off and back on. (the ecu doesn't just recover)

it is consistent only with what conditions it happens under (full load, ~4k rpm). however it doesn't do it every time, maybe 1 in 10?

due to that, i have ruled out wiring faults as i believe this would give me cutouts going over bumps or pushing around corners.

i need to have a better look next time it happens, and check what is on and what isn't (like fuel pump, tacho signal etc)

in the meantime, can any suggest any possible reasons for this?
what signals if lost by the ecu require a power off to reinitialize? (ie afm or dizzy)

Matt · Post by **Matt** » Mon Oct 05, 2009 3:54 pm

if the ECU is getting a dodgy voltage due to electrical noise at that load/rpm then it may be corrupting the ROM contents on the board

we have replaced the board, so the problem being isolated to a single board fault is removed. it makes me think either an ECU voltage regulation problem

does consult if you have it connected during a series of runs disconnect about this point or show any strange behavior if data logging all your possible parameters in stream mode?

definitely NVRAM corruption from what I can tell if you power off the ECU and then recover and the car runs again. That is why we have the burn feature so it only stores permanently once the user wants it to, otherwise in situations like this you would be stuck on the side of the road. However we need to find out why the SRAM in your board is receiving dodgy control signals cauisng the issue

If you remove the lid of your ECU and wiggle the 4 pin connector, does the vehicle drop out. Protect the knock sensor board from shorting if you attempt this test ( at idle is sufficient)

brett_32i · Post by **brett_32i** » Mon Oct 05, 2009 4:57 pm

i dont have the knock board.

i still cant run the consult with the engine running to get any data.

is the voltage problem internal? or supply?
could i improve it by adding a capacitor etc to the supply? (which didnt help the consult at all)

brett_32i · Post by **brett_32i** » Mon Oct 05, 2009 5:33 pm

so there is no 'protection mode' if the afm goes too high too quick or anything like that?

Matt · Post by **Matt** » Mon Oct 05, 2009 5:46 pm

so if you dont have the engine running then consult is fine, but as soon as you start/have engine running then it disconnects?

sounds like some serious electrical noise issues, especially if its disconnecting consult

type 2 boards only have the NVRAM chip and the logic chip. It has sufficient filtering caps already on it for both

perhaps the cap around the ignition system has problems? but usually its grounding. have you had a look at the latest 'installation and diagnostics' manual for resolving grounding issues?