se7en_

Ok. Here's the details.

My car was fine, so naturally I had to 'Modify' it more than it already was.

old mod list:

550 densos
z32 maf
t517z turbo
freddy intake

I added:

apexi HG and arp studs
procams and BC head package(valves, springs, retainers, 5 angle valve grind)

Now it won't idle with the maf plugged in.

Things I've checked:

boost leaks - none. holds psi.
timing - 15 degrees
TPS - 0.46v at idle
Checked maf voltages - 1V key on engine off - 1.42v at idle with 5v ref wire disconnected so it'll idle
I also double checked both grounds on the maf and they are good as well.
12V wire on maf is good too.
It idles and starts perfect, but it won't idle with the maf plugged in.

I can get it to run with maf plugged in if I fuck with the throttle.

I should add. It ran fine with this setup before the head swap.

Anyone have anything else I can check?

ultimateirving

Procams? I heard some where these required solid lifters. Is that a non-truth?

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se7en_

There are two type of procams. Hydraulic and solid. I have hydraulic ones.

Kingtal0n

Does the engine die as if you cut the ignition suddenly? As if all the fuel is being pulled out at once?

Do you have a wideband?

Try making a boost leak on purpose to increase the maf voltage- see if that will get it to idle.

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se7en_

No. it seams to just trail off. and I can keep it running if I feather the throttle sometimes.

I don't have a wideband. Workin on it. I'll try the boost leak to increase the maf voltage and see if that helps...what would that tell me though?

se7en_

bumpski bump

steve shadows

What EMS are you running Power FC?

Either way I can probably help you figure this out via tech support sessions remotely. Sounds like a wiring issue on the MAF if it's not a problem with the ECU / EMS setup.

Just make sure to email me because I so busy with remote tunes for various builds and drifting teams that I am rarely on Zilvia haha - I try though

[email protected] or direct message me on my fb page: https://www.facebook.com/shadowerks

Thanks

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inopsey

what bullshit. if you know what the problem is why do you not post the answer here for everyone to see? why do you ALWAYS try to solicit business on this site when a member has a problem instead of sharing your knowledge which is sub standard in the first place? at least go back to pm the op instead of this bullshit. spammers like this is why this site has gone down hill so far in the last year.

to the op. have you tried a different maf or checked continuity of the wires to the maf? i see your in alberta i can recommend a shop in the north, central or southern part of the province depending on your location that you can take your car too if you feel the need to pay someone to fix this. they all have experience with sr20 engines.

se7en_

I have checked the maf wiring. Grounds are good, and shows 1v with engine off and 1.42v at idle. 12v was good too. Tried a different maf too. I'm running a stock ecu with daughter board. Tuned to z32 maf and 550cc.

Def

Did you just install the ROM tune, or were you running it before the cam install?

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se7en_

rom tune was run before. Ran great.

civicej8

I know you said you did a boost leak but what about your intake manifold gasket?

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se7en_

I'm checking that tonight with a smoke machine. I'll post what I find.

se7en_

Smoke machine found two tiny leaks after the throttle body, one at the brake booster vacuum port. Repairing both didn't fix the problem.

se7en_

I'm going to set the timing with the spark plug wire method. maybe my pigtail wire is acting up...

inopsey

provided everything else is right, (timing etc) when you changed your head gasket you maybe changed the cr of the engine by using a different thickness? maybe your ve has changed and you need a retune. the head work and cams would also changed the ve of the engine.

se7en_

I doubt it would change enough, and its not ve tuned, its maf tuned.....unless I'm wrong?

inopsey

do you get a stable maf voltage at idle or does it fluctuate?

ve refers to the efficiency of the cylinder; how much output (power) per volume written as a %. more/less efficient flow threw the engine will change the ve. if your tuning for power you always try to achieve max ve in every cell. maf or map doesent matter here. changing the compression (difference thickness headgasket) of the engine will change the ve at idle. anything that improves the air flow in the engine will theoretically change ve, whether its enough to put the tune off so it wont idle is a guess without a wideband. adding forced induction will change the ve when the turbo is forcing air into the engine with boost.

you tune ve at idle for afr (14.7-16afr) and timing to give a steady idle. ve of an engine changes from altering how air flows through the engine.

Nikzilla

I agree with inopsy.

Considering the changes you've done to your head, you've probably significantly altered the ve of your head, resulting in your tune being too harsh for the engine.

When you unplug the MAF, the ecu goes into safety mode, running a much more conservative tune. This would explain why you can idle without the MAF.

My suggestions are to try to retard the timing, or if you have an adjustable FPR, increase fuel pressure. See if it will idle with the MAF under those conditions.

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se7en_

I see what you are saying, but really, the head was decked about 0.007" and the head gasket is approx 0.015" thicker than stock...really not much difference. And the 5 angle valve grind shouldn't change anything(I'm and engine rebuilder, and I've done a few heads that didn't need a retune.

Regarding the cams, It still idles smooth with a steady maf signal. 1.42v at idle, which is what most people have when idling with a z32 maf. Maybe I'm wrong here?

Nikzilla

That means that you actually lowered your CR, hmm.

Can you describe exactly how it dies?

Also, a valve grind does affect VE since the gasses flow around them. It's a pretty subtle change though.

se7en_

I agree. When i start it, it idles up to approx 2200 rpm for about 3-5 seconds, then it stumbles for a second or two and then quits.

se7en_

I should add that it starts right up everytime.

Nikzilla

How certain are you that your mechanical timing is dead on? It's pretty easy to skip a link when reassembling the valvetrain.

Did you do a compression test to make sure your head is airtight?

Do you have a consult port?

Try to advance or retard the timing and see if you can get it to idle that way.

se7en_

I don't have a consult port on this car unfortunately. I am quite certain on the mechanical timing. I'll do a comp test tonight, but I wonder what it should be with my cams...I've seen as much as 50psi lost with cams.

I have messed with the timing to no avail...

Nikzilla

Count the links.



Also, are you trying to mess with the timing alone? Because the way I do it is, I have a friend start the car with my right hand on the CAS and my left on the light, and I rotate it as it starts dying to keep it alive. If you're just rotating it a bit and starting, you won't be able to keep it alive.

se7en_

i'll check the mechanical timing tonight as well.

se7en_

Oh boooooooo. I just happened to check the resistance of the coolant temp sensor tonight. No continuity. I guess I should fix that before attempting anything further!! On a side note, I sure wish my ecu still had a working led so I could check codes.

se7en_

Double post

Kingtal0n

changing around the compression with head gasket thickness and deck beef will not affect an engine to the point where it will no longer idle.

This is a far far overcomplication of this issue. The problem is much more subtle.

I asked you to create a boost leak and determine if the engine would idle. I assume you never tried that. I suppose you want reasons.

1. If the engine did idle with a boost leak it would tell us the maf output voltage is too low (engine starving for fuel)

2. if the engine did NOT idle with a boost leak increasing in size we would next test to determine that the maf voltage is too high (too much fuel)

MAf voltage is parabolic so this will not hold at any RPM above idle. Clearly if the engine is able to idle with no maf connected the problem is a communication issue involving the fuel/fuel map and associated variables (any sensor altering fuel)

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