hey guys, a while back ago I posted a thread saying that I had low idle when I stopped at red lights or so sighs I would do anywhere from 500rpm to almost 0. I did a compression test and in cyl 1, i have 170 psi and on the rest I have +/- 150 psi. I have about 155xxx miles on the engine. the test was a dry run. what do you guys think? I know the minimum it's 140 psi for it to run like ****.

 

Is it a GSR ? so you have 170-150 1-4cyl 25 being the max variance in cylinder compression you're kind of "walking a line". While 140 may be service limit most ppl will tell you under 180 and you'll start to feel the car being slower then it should if it's not a gsR(b18c1/c5) then you may be fine. you could do a leakdown test if you want to see where you're loosing compression but those number wouldn't start messing with your idle.

 

it's a ls, forgot to post it in there. and my friend said it could be piston rings. but I'm not too certain.

 

if it is rings, the numbers would go up after adding a tablespoon or so of oil.

 

so adding oil and doing it again I should see number change if the rings are the problem?

 

yes, a little oil will make the numbers go up. the numbers REALLY go up if the rings are shot.

also, are you using one of those adapter tubes? if so they lower the psi numbers. it's more accurate to screw the hose straight into the spark plug hole.

also only do a compression test when the engine is at operating temp. never cold

 

ok, when I tested it out want completely cold, but it wasn't at normal temp either

 

engine should be warm and throttle all the way open.

 

ok I'll do that I've I get the chance again and I'll repost it on here.

 

hey guys I did the test again, I changed my oil, ran it for about an hour while I had to go do some things. have it a test, the engine was normal temp, and I opened the throttle. cyl1 is 170+, and the rest are between 150-153.

 

you did this screwing the hose directly into the hole not using an adapter tube? if you did those numbers are extremely low. the average gsr is 210-220lbs of compression

your gauge is suspect if the numbers are the same cold as they are hot

 

it's not a GSR, it's a LS. and we used both a rubber hose and a metal tube. but they showed around the same numbers +/-. but nothing over or under 10 psi. the engine was at normal operating temp and the throttle was fully opened too.

 

how were you cranking the car over? did you use the ignition switch or a test button on the starter? if you used the ignition did you make sure to unplug your injectors and distributor?


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also, when was the last time you did a valve adjustment? the numbers arent great, but they dont indicate anything except the engine needs a valve adjustment, or is just very tired. your issue sounds more like a problem with your iacv or something of that nature


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I used my ignition, and yes we unplugged the fuse for injectors. but not the distributor. and I haven't had them adjusted in a while. when I took it to a mechanic to fix the shitty job a previous mechanic did with the timing belt he said he fixed everything but idk if he did the valves. and I've cleaned the iacv, but couldit just be bad?

 

Should always unplug the distributed, you say it won't start now again right ?

 

wonder how many coils autozone sells because of this?

 

my car started, it starts. my only problem is low idle to stall when I put it in gear or stop at lights. let's stay on topic lol.

 

whats your fuel pressure look like?


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haven't tested the fuel pressure.

 

if those numbers are accurate that engine is extremely worn

which could be part of the idle problem, the other is obviously junk in the IACV and or the timing belt jumped a tooth {which also could lower your compression to those very low numbers}

i had a type r with a broken ringland on a piston that had 170psi in a cylinder, just to give you a comparison.

you don't have a healthy engine if those numbers are accurate

 

I've always gone by anything under 200 and you'll "feel it" some say different but from the factory rated they sit at 270psi 1-4 so 200+ is where you want to be imo. have heard of 94 engines with 300,000K+ miles and no rebuilds still pushing 230 psi 1-4( H-T user: patrick94gsr)

 

totally. with the stock b18c in either flavor compression under 200-210 minimum indicates a problem somewhere

 

so it could be as simple as the iacv, or timing?

 

bud, if your compression is that low the engine is done and either needs to be swapped out or rebuilt.

would imagine it uses a good deal of oil too