5000-6000rpm Flat Spot
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verified userMy car has been doing this for a while but it has the worst flat spot around 5-6 thousand rpm when pulling hard,after 6 it screams again to 7. And if I leave the car idle too long then hop in the turbo bogs hard,but if I shut the car off for 30-45 secs boost is back and pulls good again..... till 5000rpm anyways then as explained above. sitting at lights is enough to cause the bogging. I cant put my finger on the symptoms.1. if it was fuel it would only get worse... not pick up again after 6000! .... ithink
2. if it was air...again it would only get worse as the rpm rises!....ithink
3. spark... maybe inconsistent spark dont know how to check for sure but it did get better after plug change but only marginally and it only seemed to PUSH the rpm through the flat spot faster.
Thanx guys
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did you change your wires when you did your plugs?
what about an ECU issue?
does it happen in every gear?
what about injectors how are they flowing? if they are leaking it could explain the bogging down at idle...
thats all i can think of
1990 GTR32 Skyline
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Good call I just found a leaking injector but im not sure that its the entirety of the problem i only noticed the smell of fuel abut a week ago but the problem has been ongoing for about 6 months, the thing that gets me is when i shut it off and it "RESETS" it self? my mechanic doesnt think its an ecu problem but he hasn't actually looked into it, doesn't matter what gear its in its all in the motor.
and its not a bog at idle its more like it has a massive boost leak if it idles too long then shut it off for 45 secs and its all good again.
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again this is where a nissan consult cable and software could help. i'd pull the ecu codes, check the ground on the maf, try a different maf, or check the det sensor
It's seems you have a timing issue.. does the car pull between 5 and 6k? and rev slower or vice versa?
what are your AFR's or EGT's looking like st these RPM's?
These symptoms say to me a knock or knock sensor issue..
when the car idles for a while it might get hot and knock,, the ecu will retard the timing... when you shut it down and start it again the ECU might return all or most of the timing advance explaning why the motor will pull once more..
Mine isn't bigger than yours.. I just like to drive
how much is the consult and where do i get it?!! the fault codes show me nothing 5 and 5 !
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It's seems you have a timing issue.. does the car pull between 5 and 6k? and rev slower or vice versa?
what are your AFR's or EGT's looking like st these RPM's?
These symptoms say to me a knock or knock sensor issue..
when the car idles for a while it might get hot and knock,, the ecu will retard the timing... when you shut it down and start it again the ECU might return all or most of the timing advance explaning why the motor will pull once more..
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The flat spot occurs from 5200- 6000 then pulls hard again after all the way to 7500
I dont have anafr gauge and what is an egt? Exhaust temp?
may try swapping the ecu out of my other pulsar and see what happens.
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how much is the consult and where do i get it?!! the fault codes show me nothing 5 and 5 !
http://cgi.ebay.com/ebaymotors/_Automotive-Tools__NISSAN-ECU-CONSULT-OBD1-DATA-CABLE-300ZX-240SX-MAXIMA_W0QQitemZ200306472027QQa...
if you're not feeling cheap, here's one of the best ones you can buy. http://www.plmsdevelopments.com/consult_if.shtml
http://www.gtiroc.com/forums/showthread.php?t=27858&highlight=flat+spot this may help
try changing the fuel filter and some injector cleaner maybe?
Also u might wanna check ur maf and also ur intake for any leaks loos connections and what not.
Running Mohawk 94, I note the same and find it is a bit less flat around 5k with octane booster. So, as related before i lean towards a spark timing/detonation sensor effect partly due to fuel octane and maybe more.
Fwiw: an MSD detonation sensor I ran once in a dodge colt would false for any sound at 5000 hz. i.e. 'ping'
Typically it was mechanical noise (or sometimes ice/gravel bouncing off the oilpan etc) . The errant 'alarm' was adjusted with a sensivity control on the box, likely an inline variable resistor to cut voltage i guess.
If the detonation sensor is indeed 'falsing' at 5k because of 'noise' how best might the sensors trigger point/sensitivity be adjusted without harming the engine?
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Thanks Bill call me later and maybe we'll check some of this out over a beer or two!
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