1990 Eclipse GST Weird Idle

[vietfoo300zx]

hi, my name is mike, this is my first dsm. its a 1990 Eclipse GST 5 speed. since i got the car i put a EGR block off plate to cure the idle surge but it still sounds weird at idle. when the car is above 3200 rpms it starts to sound normal, but below 3200 rpms it just sounds......odd..... i was told by the previous owner that his mechanic "said" that it could be a slightly bent intake valve in cylinder 1. I've had many of my friends look at it and they all say it could be a turbo mani leak to timing belt, which i think it needs changing, to a bad cam positioning sensor. but i just don't know what to tackle first. the valve cover on it now is cracked after i put a new pcv valve, fuel pressure regulator, and the egr block off plate. so theres a lot of pressure in the cylinder head i know that much. i was given a what looks to be in good condition cylinder head with out cams and an uncracked valve cover. but because of the excess pressure i dont want to put the new valve cover on just yet. Here's a youtube clip of my car, its best to hear it on HD. thank you for any help you guys can provide.

oo btw dont mine the excess sound when i'm on engine, i'm in my garage and recording through my HTC EVO.
my boost gauge is reading 30 cmHg or 11.8 inHg at idle.

YouTube - 1990 Mitsubishi Eclipse weird idle


-Mike

 

[sexystover]

oo btw dont mine the excess sound when i'm on engine, i'm in my garage and recording through my HTC EVO.
my boost gauge is reading 30 cmHg or 11.8 inHg at idle.

-Mike

first your idle is to high if thats the car fully warmed up, so you probably have a vacum leak or your idle is set wrong, also please fix that exhaust leak because it will greatly alter the oxygen sensors reading and cause the engine to run very poorly

you should read 18-21inhg at idle unless there is somethign wrong, possible vacum leak or maybe it really does have a bent valve, if you have the tools i would do a compression test and also a boost leak test and look for vacuum leaks.

 

[doubleclutch99]

def. do a boost leak test, compression test. and as already pointed out find the exhaust leak and fix it . you will be surprised how much that stuff affects everything on the engine. if you can post up the comp test results.

 

[vietfoo300zx]

first your idle is to high if thats the car fully warmed up, so you probably have a vacum leak or your idle is set wrong, also please fix that exhaust leak because it will greatly alter the oxygen sensors reading and cause the engine to run very poorly

you should read 18-21inhg at idle unless there is somethign wrong, possible vacum leak or maybe it really does have a bent valve, if you have the tools i would do a compression test and also a boost leak test and look for vacuum leaks.

I just took the car out to warm it up but normally it idles nice at 900-1000 rpms but vacuum stays at 11.8 InHg. yea my 01 A4 is normally at 19-20 InHg here in northern nevada. its odd, i drive around and when i'm in gear and i let go of the accelerator Vacuum reads as 20InHg, there something odd about that but can't put my finger on it.... So if it does sound like an exhaust leak then its probably coming from the turbo manifold. i can't feel air top side but i haven't check underneath the manifold yet. Theres no CEL but i'm gonna get for codes. is this still accurate to use

ECU Code Checking

or is there an eaiser way to check for codes?

 

[invictus]

11hg does seem a bit low vac leak like what saying maybe the cause, but as far as the let off the gas and it diving in the vacuum thats normal on a manual trans car.Also if the leak is coming from the where the manifold meets the head get an mls exhaust mani gasket theyre awesome for not leaking and you can use it over and over again.

 

[sexystover]

is that a hole in the top of your exhaust manifold? looks like it was tapped for an EGT if it is

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge) There you go this should help.

 

[vietfoo300zx]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge) There you go this should help.

thanks for the faq, but i dont have idle surge anymore cause i put in a EGR block off plate but when i say weird idle i mean the engine sounds weird at idle.

is that a hole in the top of your exhaust manifold? looks like it was tapped for an EGT if it is

it wasn't taped for an egt but its a slight crack cause it looks a little split but not enough for any air to escape. its probably an 1/4 inch crack with white residue around it.

 

[vietfoo300zx]

Anybody else want to chime in?

 

[Lofty]

Maybe a loose auto tensioner for the timing belt.
Maybe a bad balance shaft bearing.

Boost leak test it. I had a BAD intake manifold gasket and it made my car seem funny and sound funny.