Head Tap & Screwy Idle

[Mischief7m]

hey guys, so i have a few minor problems i was hoping to get a little help with.

first, when the car is idleing or revving below 1300 RPM, i get a slight tapping. I uploaded a video of it, and if you listen very closely, you can hear it.
I know its coming from the head, but have not had time yet to pull out the stethascope and start poking around. it also sounds like its coming from closer to the firewall. making me lean towards a sticky injector. but i'm just not sure.

second problem, if its very cold out, or raining, my car will either idle at like 200-350 RPM, or just stall out. then, if i shut it off and start it back up again, it idles fine...then i put the engine under load again, and its right back to the screwy idle. i have checked all the connections to the Idle air control valve, intake temp sensor, and map sensor.


i have no codes (other than 42 no speed input to the ECU...so that should not have anything to do with a bad idle.)

if you guys have anything, i'm all ears

thanks,
-Trevor

 

[suprahero]

Does the tapping stop at any point or does it do it all the time? If it's tapping, it could be a very loose shim. Have you checked the valve clearance? You can take the valve covers off and check them with a feeler guage. You want to have .008-.012 on the exhaust side and .006-.010 on the intake side. I adjusted mine to .010 and .008.

When your car warms up and runs good, does it idle properly? Does it only idle bad when it's raining? Do you have a wideband hooked up? Mine idles a little rougher when it's cold out. I haven't had anyone fix my stinger perfectly. I've done the best I could with it with my limited knowledge.

 

[tsuper92]

my stock injector's on my 1j were nice and loud,compared to the top feed precision's i used later on.how good is the fuel pump?

 

[Mischief7m]

the tapping does not stop at any point, but it does get more quiet as the car warms up. i have not had the time to pull the covers, but probably will over thanksgiving break.

I do have a wideband, and the idle is not dependent on temp of engine. It starts fine (when it is very cold starts at about 1400 RPM, then slowly backing down as it warms up to a normal 7-800 RPM)

Usually it will idle normal even after driving, every once and a while (Usually in wet, or very cold outdoor temps...but not always) i will get the very low idle. and there are no misfires, and it does not struggle to run. everything is normal except for the RPM

there is no signs at startup that the idle will be wrong, but after driving, and coming to a stop the idle will either fall to 2-300 RPM or just stall.

if i start it after a stall, or shut off and re-start it...the idle will be normal again....then after more driving, it will return.

Keith-
I am running USDM 550's, but planning on putting the 370's back on.

If it is the injectors, then they aren't all loud, just the rear most one or two.

and as far as i know, my fuel pump is good. I have a walbro on it. I have the also seemingly good stock MA70 pump that i could put back on to try.

And come to think of it, I believe the noise did get louder when i upped the fuel pressure from 32 PSI to 42 PSI....and the idle problem also...
but what injector problem would cause a low idle only 50% of the time, and would not throw strange AFR's?


I think you may have nailed another one on the head haha.


Edit: Also, I don't have my SAFC dialed in Perfectly, but its pretty close...just figured that could be relevant.