newdude1

So I have this problem that I cant seem to kick. I have had the car about two years now and I have yet to drive it over a month. First Ill list the modes and then explain the problem.
-S14 sr20det
-Greddy front mount
-hks bov( in the process of trying to recirculate it now)
-z32 maf
-740cc injectors
-JWT ecu
-All gaskets replaced

So here is the problem. Im having low vacuum. its at 10 vac at idle. But I cant seem to find a leak anywhere. It occasionally will drop down to 5 or 0 and stall out. When reving the car, its sputters under 3k and then past it runs perfectly fine. Also at idle the wideband reads really lean, like all the way past what it can read and goes blank.

Im open to suggestions on what to look at next. Any help is would be greatly appreciated.

rc1honda

Well the obvious answers would be to grab a boost leak tester and search for it. Maybe a small hole in your front mount, or bad coupling. The problem may not be in the vac line.

Also a common place for a large boost leak is up near the fuel rail. Make sure you have those little spacers that goes on between the rail bolts and the mount. You could have a leak near the injectors that your missing.

Maybe check any kind of rotted line up near the brake booster too.

newdude1

Well I did that last sunday with a bike pump and no luck. So for shits and giggles I bought a small air compressor and going to give it a try again.

But are there any sensors that could cause a problem with this?

omar14

Well a boost leak on the hoses won't affect your vac. Problem it's somewhere in the intake,gaskets, hoses, brake booster or idle control valve or just Turing the lil plastic screw on the idle control valve will help your vac


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theboy

adjust your IACV until its idleing rite. If that doesnt work then find one and replace it. Thats only if your possitive you dont have a vaccuum leak. But from what it sounds like, its a vaccuum problem. Go back through and make sure all the gaskets you replaced are seated correctly. And every little vaccuum port has been connected or plugged off. Buy some sea foam and run it into a vaccuum line. Look for the smoke to come out of your leak. Fix issue. Pin holes are holes that will cause big head aches and you will miss them. Sea foam will find them.

LimeLite Racing

Usually the easy way for me to find a vacuum leak is to start disconnecting vacuum hoses, one at a time. It makes it especially easy that you are noticing a leak at idle. Good luck to you sir! If you can't find it, sell it. (Simple suggestion considering it's more than likely the easiest fix of your life.)

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newdude1

would a leak from the valve cover cause this? I hooked the tiny air compressor, which cant even move my boost gauge, and found a spot on the valve cover that was leaking air out.

Autobacs

Check your fuel injector seals also.

newdude1

Well its running a little better now that I sealed that one spot.

So I was letting it idle spraying around carb cleaner trying to find a leak. Found what I think was a small one in a coupler. Also check the fuel injector seals and they are fine.

But it still feels like it kind of missing up to 3k. Not as bad as berfore though. Then I checked the coils and they all are working. Any other ideas?

LimeLite Racing

If you are getting ANY sort of leakage coming from your valve cover, replace that gasket ASAP. Hook it up with some RTV at least for the time being and after the new gasket purchase.

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newdude1

On the valve cover gasket do you use rtv or is it fine with out it? Because I replaced that not too long ago but used rtv.

newdude1

I have been looking around on here and found something that might help me. What do you think about the knock sensor being bad?

Because I read that when they are bad or about to go out they can cause missing at low load but be fine at wot. Which is exactly my problem. Think that would mess with low vac?

But it would deffinatly explain the missing problem.

LimeLite Racing

It's possible, but from my experience not the most probable. I would rule out all of the other cheaper basic possibilities first. What color RTV are you using? Did you let it sit properly?

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newdude1

I used the red kind and yes I let it settle for 24 hours.

Tantwoforty

in my experiences ultra grey lasts longer

LimeLite Racing

Ultra grey is good, I always use red personally. Unbolt it, re-rtv it and torque it down in a criss-cross pattern.

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newdude1

On the rtv, do yall put it on the gasket or on the head? Im just going to order a new one this week.

Also is there a way to check to make sure the knock sensor is working right??

blksylv

id try checking for codes as far as a bad sensor

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honDan

^ this....

240zach

3k....mafs love to mess up around 3k...check that

newdude1

Well the problem with that is the car is only wired up for a consult and my ecu doesnt have the light to check it.

newdude1

And its not the maf. It revs above it just fine.

But Im reading the fsm and it says to only use rtv on the half moons. Should I do that or the whole gasket. I had to order a whole new one, old one was ripped somehow.

newdude1

Well if it was the maf it wouldnt rev past 3k.

So I ordered a new valve cover gasket but still have a question. Do I rtv just the half moons or the whole thing? The FSM says just the half moons but other places I read says differently.

newdude1

Anyone one know?

revolutionz_s13

camshaft timing...if you have too much (or too little, i cant remember) overlap, it can affect how much vacuum you pull, and would also affect power output/timing. just an idea.

newdude1

So I replaced the knock sensor and the valve cover gasket. And basically still the same thing going on. Its missing under 3k and sputtering trying to hold the throttle steady.

So decided to look at the cas. I took the cover off and found two cracks on both sides of where the plug goes in. I took some pictures. Would this cause problems?

nismolvr

Fix broken CAS plug.First off check your timing and if its off set it to 15 btdc.If thats ok, Do compression test , if you have low compression youll have low vacuum.
The vacuum gauge is a great diagnostic tool here is a link that will help.
Theres reference to Carburators , Still usefull for fuel injection tho. Engine Vacuum Gauge Diagnosis | MILEPOSTS Garage (Tech Tips) .

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newdude1

compression is good. 150 across the board. And the cracks are inside the CAS. Not on the plug or cover.

KiLLeR2001

Cracked CAS is definitely not going to help you in any way...

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newdude1

Well ended up replacing the cracked cas. And it is running better. But still a slight hesitation or missfire when holding partial throttle. Tps is .45 closed and 4.0 open. Any other ideas that I can check?