Help With R33 Fuel Cut

[1kr33steven]

Hi,

Im new to the forums and hope someone here can help ive been playing with cars for over 20 years now usually non turbo ect picked up a r33 for next to nothing with only some small cancer issues and needing a water pump so now that's all been done did pulleys timing belt spark plugs oil filters ect while I was in there.

Car spec 1997 gtst auto rb25-det

Now my issue is the car is what appears to be dead stock bar 3.5inch hks system from turbo back and a greedy hide away front mount kit and apexi s-avcr the guy I bought it of told me the avcr didn't work so I thought nothing of it when I took it for test run (have own chassis dyno) under no conditions or any gears did the boost go past 3.5 on the factory Nissan boost gauge.

I have since disconnected the avcr completely and connected the actuator back with no boost controller at all still runs 3.5 on the Nissan gauge so I fitted an aftermarket gauge and it read 4psi under full load at the highest point ever no surge or anything.

fitted adjustable boost controller and wound her up thinking buety this will get me some more boost (yes I checked turbo condition ect very little shaft play and relatively oil free) I can wind it up and run 5psi all the time very linear with no surge at all the issue is anything more and at about 4-5k rpm she start sounding like its hitting the fuel cut as if it was running 10-15psi as I have seen other do.

Car is run on united 100ron and I have dumped that and tried shell 98 couldn't notice any difference other than slight dyno figures but ambient temp ect would have more bearing as it was done on different days.

My thoughts

Air flow meter shagged or maxing at 5v for some reason

maybe crank angle sensor as I just pulled complete cover of when timing belt was done and havnt checked this since (did same when I drove it home from pick up prior to me touching it)

Map sensor f**ked ?

Any ideas ?

And if you have ideas link to how to check im pretty handy soldered tacho and got it working so simple volt checks on components ect are easy enough want to get everything right before I treat this thing how it was intended.

[Blackkers]

Since you haven't mentioned it, I'd be changing the fuel pump. 20 year old fuel pumps don't like to be pushed hard. A walbro GSS341 is about $100 and even if your pump turns out to be fine its a good thing to do for piece of mind.

Also, Superben will have something to say about searching the forum and someone will also state how they can't believe how many people buy cars that already have problems just because they're cheap.

other than that welcome to SAU, perhaps some of us can borrow your dyno some time

edit: did you change the fuel filter yet? Also pressure test the intake. you could have a massive leak which could cause this

Edited March 17, 2014 by Blackkers

[nicksamaniac]

Also, Superben will have something to say about searching the forum and someone will also state how they can't believe how many people buy cars that already have problems just because they're cheap.

I had a chuckle at this ^

I Like how you know who the haters are, and can predict the responses!

[zebra]

Please search for missfire at 4000rpm

has been covered more times than you can possibly imagine

[Ben C34]

Also, Superben will have something to say about searching the forum and someone will also state how they can't believe how many people buy cars that already have problems just because they're cheap.

I had a chuckle at this ^

I Like how you know who the haters are, and can predict the responses!

Haha, I'm certainly not a hater, but trust me you will get sick of the same questions over and over again.

In this case though he has taken the time and written a decent post to explain the problem.

So back to the topic, as you have a chassis dyno it will make things heaps easier for you.

As blackers said fuel pump and filter, along with new plugs and checking the timing, (search the correct way of doing it) and definitely check for boost leaks with a pressure test! ( I think blackers is on the money there)

Welcome and good luck with it.

Just curious why do you have the dyno?

[Blackkers]

I would also like to know how someone just happens to have their own dyno

[Badgaz]

^^ me too lucky bastard!

[1kr33steven]

Hi,

Thanks for the replies i will have a better search, No i didnt do a fuel pressure check or replace fuel filter out of sigt out of mind >< did all the engine filters spark plugs ect.

I do agree about the buying chep thing however im an ex mechanic (been out of it for 10 years) so when he said it had a blown head gasket i asked if i could test it when it tested fine and was 1k how could u not buy it turned out to be a split oil cooler letting oil in the water hence the guy thinking it was head gasket so i still feel it was a score as im half way thru modifying a Z32 computer to upgrade the af meter i figured get it all right prior to fidling with it.

How do i have a dyno is easy because me and my old man bought it but on a more serious note we race off road buggies and dad is an ex fitter and turner and motor mechanic teacher so we have such an extensive workshop you would think im talking shit, It may sound impressive but the dyno is a fairly old unit can only handle 300kw and we dont have a heap of the accesories that go with it basicaly we have the dyno an old vane diagnostics (fairly usless as its still dwell angle ect) and a new o2 meter for it we dont chase power figures its about torque spread ect for the buggy engine as we run in a class called sportsman so the capacity is up to 1330cc

Im located in melb SE suburbs and if your genuine and know your stuff i may be convinced to let you use the dyno PM and we can discuss but im an older fella and im not into wankers who want big read outs ect just genuine people who maybe i can learn something of so its mutualy advantageous

Thanks again for the replies and sorry for the repost but i am new and not overly tech savy when it comes to forums ect i spend most my time in the shed

[scotty nm35]

More likely the boost gauge is shagged from the factory if it's a cheapie, I bought one that read 4psi lower than actual.

Have you done a pressure test on the intake? I live local if you want to borrow my 3 inch intake plug, and simply cram 20psi into the rubber intake. If there is a leak the AFM won't know about it.

[Dose Pipe Sutututu]

too bad you've got a R33 Auto, I've got a Toshi remapped R33 S2 Manual ECU that would fix all your issues

[1kr33steven]

How much John as i do have a manual there just waiting to find pedal box ect for the right price and it says the same on the factory boost gauge and the aftermarket one i even tried a autometer and my usual saas one to be sure all came up with same reading.

I did not entertain the fact it may be boost leak bung blow of valve or anything like that whats local scotty as i might take you up on that offer is it just like one of those plumbers expandable rings ?

[Plattsy]

hey steven, def go see scotty. man has forgotten more than i know.

id also be checking the coil packs mate, 4-5k is classic coil pack break down. if youve plugged the original boost solenoid back in, this is when it switches to 7psi, and the coil packs arc out thru tiny cracks to create a fuel cut like break down.

if your afm is shagged you normally cant run past 2k rpm...

i say normally because with most 20 year old engines, you will fix one gremlin and another will pop up.

let me know if you cant fix it or scotty is busy, im in cranbourne mate, and had a 33 auto just like your self.... they have all the standard 33 issues, plus some added ones on top!

[Dose Pipe Sutututu]

factory boost gauge is NOT in PSI or kPa.. it's in a different measurement so when it registers 0.7, that's actually 1 bar

I can't remember how much I paid for it, but $300 is what I would want

[1kr33steven]

Hey Paulie,

Ive done a very crude check on the coil packs and they run ok while jumping a 20mm gap not sure if that means shit or not It isnt at a certain RPM its kind of hard to explain like i can fine tune my boost with the adjustable to 5psi and she will rev thru to redline in each gear well to third but then as soon as i go even 2 clicks to high on the adjuster then it sounds exactly like my mates used to when he tried to wind 14psi into at 13 his would run sweet but yea im pritty certain it sounds like the fuel cut kicking in for $200 i can get fuel cut defender and all but figure get it sorted stock before i worry about those kinds of things.

Ill wait for this scotty guy to come back and pressure test the inlet get me a new fuel pump and filter as ill need one for down the track anyway.

[Ben C34]

What are the afrs when the issue occurs?

That should give you some insight into what is happening.

1000 bucks is cheap, sounds like you should be able to sort out relatively easy.

Don't mess around with a fuel cut defender,waste of time.

[Plattsy]

Hey Paulie,

Ive done a very crude check on the coil packs and they run ok while jumping a 20mm gap not sure if that means shit or not It isnt at a certain RPM its kind of hard to explain like i can fine tune my boost with the adjustable to 5psi and she will rev thru to redline in each gear well to third but then as soon as i go even 2 clicks to high on the adjuster then it sounds exactly like my mates used to when he tried to wind 14psi into at 13 his would run sweet but yea im pritty certain it sounds like the fuel cut kicking in for $200 i can get fuel cut defender and all but figure get it sorted stock before i worry about those kinds of things.

Ill wait for this scotty guy to come back and pressure test the inlet get me a new fuel pump and filter as ill need one for down the track anyway.

thats the coils mate... gap your plugs down to 0.8mm might help a little.

put your going above 5 psi the coilpacks go into heavy usage and arc out..... you can try wrapping the shizza out of them in silicone tape... it might get you buy for now.

[Ben C34]

And testing the coils like that is meaningless,as it is easy to ignite the mixture at idle,much harder when under full boost which is when coil related misfires occur the worst.

[Plattsy]

superben is right.....

there is no way of testing the coilpacks under "high" boost.

you can swap one and try it, keep going until you find it. but more than likely, a few of them have deteriorated.

[1kr33steven]

I have not put the oz meter on it yet superben so cant tell i was sort of starting at basics KISS principle has saved me alot of hours over the years popping over to Scotts tonight after work to borrow his blanking bung test the manifold fuel pump ect then worry after that if problem persists.

[Plattsy]

scotty might have some spare coil packs too steven.... worth a quick swap to check.