Sr20det high unstable idle and trouble boosting

[RHSIL80]

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Hello first time posting. I've came on here a lot after my Google searches bring me here, but first time making an account and actually posting. I can really use some help I've tried searching but can't find someone with the same issue as me, I have and s13 with a full silvia front clip(redtop*sr20det, rhd, silvia front end,etc) my car started running really rough recently idling high at around 1200rpms and falling on its face when starting to boost but can still rev up all the way in neutral or even in gear if you baby the throttle. it does it at all times hot, cold, dry, raing, day or night. I've already adjusted tps to .46v and checked power ground and signal to maf, also checked continuity from ecu to maf and found no fault. I also removed valve cover and checked timing a d it is good. I'm running stock t25 turbo, stock intake manifold, Meagan headers, turbo elbow, and 3 in straight pipe*exhaust*with apexi tip and skinny type 02 sensor. I have a cx racing front mount intercooler and running stock*sr20det*maf and stock purple injectors. i also have a 255 walbro fuel pump and sard adjustable fuel pressure regulator with gauge and can see i have good fuel pressue and I have a Mines ecu and have also already tried swapping with my stock ecu without a change. I'm thinking maf but when I unplug maf car runs exactly the same way, most times I've seen maf fail it runs better or worse with it unplugged. I'm wondering if you guys have seen mafs fail this way before and/or maybe send me in the right direction. keep in mind this car ran perfectly with this setup for over 3 years and only recently starting doing this, it's not a fresh swap being started for the first time

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[nisileighty]

Sounds like a boost/vacuum leak to me. Check torn couplers, vacuum lines, etc.


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[RHSIL80]

thanks for the reply, how much in hg should I have at idle, I'm thinking 18-20 but not sure. I recently saw a few posts sending me toward boost leak but haven't been able to check cause I removed my valve cover and bought the wrong gasket so I'm waiting for the new one to reinstall valve cover and check boost but can't remember where it at off the top of my head. I did check all coupler and tried following vacuum lines. I'm going to try to bring my vacuum pump from work. maybe even my bov is leaking, I have a greddy bov venting to atmosphere

[RHSIL80]

also will a vacuum leak cause rich idle? my car is blowing a bunch of smoke at idle the way it running right now?

[nisileighty]

No, a vacuum leak will cause lean idle. It is possible to blow smoke when running lean, what color is it?

Your vacuum should be between 16-20inHg at idle. Try a compression test.

Also, while the car is running, unplug 1 injector at a time. If the motor changes behavior/stumbles/dies, that injector is firing. If it doesn’t do anything, the injector is either stuck open or not firing.


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[RHSIL80]

like regular gray smoke, I don't think it's compression. and I haven't tried to unplug the injectors one by one but I swapped all injectors when it first starting running rough and I was out of ideas and it didn't make a difference. but that's a good shout I'll try that as well

[jedi03]

check for torn couplers...sounds like boost leak or bad injector/coil/spark plug

[RHSIL80]

thanks guys I think I need to move away from maf and look into vacuum leaks and coils, injectors and spark plugs were both replaced neither made a difference. I'll give you guys some feedback as soon as I het a chance to try this stuff out

[RHSIL80]

ok guys so quick update my valve cover gasket finally came in. I unplugged all injectors and spark plugs one by one and they're all firing. I'm pretty sure it's an air leak, I only have 12-13in hg at idle and I think it's from under the intake manifold somewhere cause that's where the idle changed with brake clean. I have new intake manifold gaskets coming in so I'll be removing it this weekend.

[nisileighty]

When you remove it, it may be a a good idea to remove all the coolant lines to the throttle body and IACV as I’ve found they’re unnecessary unless you live in the extreme cold. Please don’t forget to cap them off.

It may be a good idea to replace all the vacuum lines for peace of mind. $10-$15 at any auto store will get you a good amount of vacuum hose.


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[RHSIL80]

yea I might do that I hate those coolant hoses, I think that's why I have the vacuum leak in the first place because I had to removed that manifold to replace the hose on the side of the freeway once in the dark to get home and i just reused the gaskets and who know maybe even damaged a vacuum hose or something working in the dark. also I think I might have an exhaust leak either at the gasket or on the exhaust manifold itself days I small line of smoke come out of the bottom of the manifold so I will be removing that too. thanks for the help