unstable, jerky, 10 afr idle + stalling.

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Posts: 5
Joined: Wed Jan 13, 2016 8:51 pm

unstable, jerky, 10 afr idle + stalling.

Post by eddyk-fab » Tue Jan 19, 2016 4:43 am

hello fellow nissan enthusiasts.

any reply would be much appreciated .. but i would like to have the very experts to answer. those would be the ones who would read well what i have to say.

now for the problem i have, i have got a ca20det stroker for a great deal, started it for a month or so and drove around with no issues. until one night, while it was idling great, the idle jerked off, got unstable and the afr dropped to a 10/11 idle. then the car never idles more then a couple of seconds while jerking, then shuts down.

the engine's mods are the following :

ca18det block, ca20 stroker crankshaft, jun forged 85 mm pistons, race series bearings, ported and honed cylinder walls, block oil restrictor, JUN 272 high lift cams, with solid lifters and springs and ti retainer kit. overhauled oversized valves . JUN early style adjustable cam gear pulleys. metal HD.

fully lightweightened, counterweighted , and balanced internals with lightweight flywheel and twin plate clutch from os giken.
engine was obviously build in japan, with a CA - SR ecu extension harness to plug an SR20 kakimoto tuned ecu.

engine has nismo 550 cc injectors... split fire coil packs and split fire spark plugs, kakimoto top mount header, perkins tb25 turbo charger that was swapped in my country after they blew up the gtx28R ball bearing.

what i have done is fitted bench tested stock injectors, bcpr7es spark plugs because 2 of the split fires were missing .. and stock ecu to start and inspect everything on stock.

compression numbers are 140 across all 4.. more or less 2 to 3 psi.

what i have done first, was drive the car without external wastegate. it was jerking on the rev, but no bad idle at all. at least it was ilding ... then i fitted an external wastegate without vacum line to stay running a while on the turbos internal wastegate... then i encountered a boost creep and surge up and down as i discovered that the internal wastegate port was jammed and stuck in the middle, and that is what was causing jerking as well, so i loosened it up, closed it shut and tightened the adjustement screw from the internal wastegate actuator to shut it off, and routed a vacum line down to the external wastegate... drove the car with no issues at all for around a week as the external wastegate was working properly ... screamer sound was beginning to sound at around 0.3 bar, as i have boost set to 0.5.. to run as stock as possible until i was done with the inspection that i need to do before tuning the greddy ultimate .

mean while i had already done a custom made plug and play extension harness using the male ecu connetor that came with the engine, and wired up the greddy universal harness... set up the jumpers and started and drove the car with no issues on the greddy emu, exepct for the idle running high.. then after turning the car off, then on, it idles down low with no problem, i assume that was because the idle air control valve signal wire was not connected on the plug and play , its cut to short on the connector, and was hard for me to wire it up. so i left it.. how ever no problems so far..

until as i said earlier, one night as it was idling great, out of nowhere, it got jerky.

i have tried 4 different cas, 4 different mafs, 5 different aac valves, ficd valves, 4 differnet air regulators, 5 differnet TPS, 3 sets of injectors, even changed the stock FPR...ran compression tests every day,changed 3 water temperature sensors, i changed literally every single sensor on the engine. i have tones of ca parts, most are working parts taken of actual working engines.
i even tried 3 different ecu's .. ran self diagnoses mode 3... ran idle switch and start signal diagnoses mode 4 ,ran real-time diagnoses mode 5... no issues at alll,.. expect a few times got ignition code from mode 5 only when beer rev limiter was banging... and i always got maf codes from mode 5 every time the turbo flutters .

i have inspected resistence according to FSM resistance of coils, injectors, all is working properly, im curently following up diagnoses procedure from FSM to inspect the power supply routing on the hole efi harness, so far i have inspected the hole ignition system with no issues from ecu down to the coils themselves, water temp as well has power and ground, the unit intself has correct resistance on different heat ranges. maf wiring also has voltage and ground, cas aswell...

and i will continue tomrw if it stopped raining ...

what i havent inspected yet , is air flow meter according to fsm, cas rotation according to fsm, but i have changed 4 ,5 sets and problem remains with no change what so ever...

i am also facing alot of back fire through the exhaust... and as soon as i lay my foot on the throttle, and take it off flutter sound comes out of the turbo like crazy... i think thats due to how close the maf is to the turbo... knowing that thats not the problem as i have been driving the car for a month with the maf that close without isssues ...

i canot get the car to idle to set timing with timing light... and if i drive the car, everything beyond 25 percent throttle and the car responds good... abit rich but good.. idle is completely jerky and unstable to the point where it canot sustain it self and the engine dies... and if im driving around with 5 to 10 % throttle position, the afr jumps from 10 top 18 back and forth ( rich / lean / rich / lean ) and the engine missfires as the afr fluctuates , its like ur laying ur foot on and off throttle really quick trying to jerk the car on purpose... but having my foot constantly on 5 to 10 % and it does that jerk so hard, that means i cannot cruise at all... to have the car running well, i must always apply load to the engine... cruising mod with jerk the car off , either miss fires the ignition for some reason or leans and richen the mixture due to some problem with the fuel system ..

tomrw i will inspect fuel pump power supply routing, and inspect the actual fuel return line to make sure its not clogged and causing the extra pressurized fuel ...

if anyone has questions please ask, so i can make anything clear, although i have done my best to speak all thats in mind at the current time.
i will have my account only all the time, even if im working on the car... unless i am asleep.

ANY PROFFESION HELP,. would be much appreciated... and even if any noods or beginners have anything to say.. i would love to answer back.. i am down to earth , so NOOBS dont be afraid to ask ur questions..

thanks to all in advance , special thanks to matt.

best regards


Posts: 4
Joined: Mon Jan 11, 2016 9:52 pm

Re: unstable, jerky, 10 afr idle + stalling.

Post by Magic » Fri Jan 22, 2016 12:25 am

Hi Eddy,

I'm also a NOOB. You don't mention anything about what MAF you are running?

I had similar issues a while back,

One was related to a Faulty MAF plug- dodgy wires - poor earth
Two was the vacuum pipe from the Blow off valve (Too long and bent) and
Three was the AAC Valve screw that needs a turn or two inward or outward.

Have you tried those three?

Posts: 35
Joined: Fri Jan 01, 2016 10:56 pm

Re: unstable, jerky, 10 afr idle + stalling.

Post by mattlovo » Fri Jan 22, 2016 1:53 pm

Did you try to calibrate your TPS ?

Then follow the FSM to set your target idle by removing the plugs from your IAVC and FICD.

Last time I had that issue, it was due to the engine coolant temperature sensor. It was dead.
Results in the engine having no idea what setting to use and dump fuel in randomly. Get a new sensor, which is cheap and also similarly found in the SR20DET.
Check plug head to ensure you got voltage going through those wires.

Maf has to be as far away from your turbo as possible.

When in doubt, check the FSM steps for testing =)

Posts: 4
Joined: Mon Jan 11, 2016 9:52 pm

Re: unstable, jerky, 10 afr idle + stalling.

Post by Magic » Tue Mar 08, 2016 7:29 pm

Hi Mattlovo

This is good feedback.. I'm going to try perfect mine too with this method.

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