Low Idle Speed 4g63 - sometimes its good..

[lars y]

Hello!
Fellow DSM`ers

I have a 97 gsx, the problem started a couple of months ago, when my idle speed dropped to about 4-500rpm on idle speed some seldom times. But this occured more and more often. Now its more like it idles fine on 1100rpm for about 10-20 seconds then it just drops down.

What is alarming now is when the engine is warm and the idle drops, the oil lamp starts to light!

I have changed the oil, but the lamp still lights.

Please help! Answers and ideas will be much appreciated!

Thanks
Best regards. Lars Y

 

[VETTE_50_TH]

Check your oil pressure sending unit. # 7 & 8

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James

 

[lars y]

Oh, but can the oil pressure sending unit have any influence on the idle speed?

-thanks for the quick answer

 

[VETTE_50_TH]

First, check for vacuum leaks. Easiest way to do that if you dont have a vacuum tester and a bike pump, is to spray starter fluid at all the places metered air could leak. EGR valve, ISC, your bov, all the intercooler piping from the turbo to the intake manifold. After that, test the ISC, those go bad and cause the motor inside to fail, letting air pass which shouldn't. Update your profile please. To answer your question it doesnt. But, check that anyway to make sure the light goes away because that is what controls it.

James

 

[lars y]

Ok, i have pressure tested the pipings from the turbo to the Intake Manifold, it was ok.
Uhm, whats an ISC?

If i rev the engine when its on low idle and the oil lamp lights, it stop lighting when im about 800rpm, so the oil pressure sensor must be working right?

thanks
-Lars Y

 

[VETTE_50_TH]

Your IDC= idle speed control, look up on how to test them, but basically its on the side of the intake manifold right behind where the throttle body is. Test each node...

1-2 2-3 3-4 4-5 5-6
inside the isc for a resistance on 28-33 ohms. Also check to make sure it has a good seal.

The sender is probably not bad. You might have to port the oil relief hole to allow more oil to flow at low rpms. Check your oil pump immediately. It could be clogged. If it has buildup, you turbo and engine internals might be starved for oil and its not getting any.

James

 

[res7bequ]

Just check for vacuum leaks like VETTE said and fix them. Whenever your RPMs are that low for that long your oil pressure drops alot causing the oil light to turn on. Fix the low idle(probably a vacuum leak) which will fix the oil pressure and call it a day.

 

[lars y]

The sender is probably not bad. You might have to port the oil relief hole to allow more oil to flow at low rpms. Check your oil pump immediately. It could be clogged. If it has buildup, you turbo and engine internals might be starved for oil and its not getting any.

James

So what youre saying is that even tho im at that low rpm my oil light shouldnt be on?

EDIT: in the manual it says that my car is supposed to be idling at 1150rpm

 

[lars y]

:\
Well, now i have witness the effects of a low idle. The engine got "rod knock" (sounds like someone is banging the engine with a hammer, that follows the rpm)
Its probably because of the low idle that have resulted in a low oil pressure (the oil lamp lighting when the idle drops)
So now i have to replace the rod bearings, just hope the crank is still ok.
The turbo is also "squeeling" when the car is cold, suffered some problems because the low oil pressure too?

VETTE_50_TH:
"First, check for vacuum leaks. Easiest way to do that if you dont have a vacuum tester and a bike pump, is to spray starter fluid at all the places metered air could leak"

Hmm how do i see where the leak is then? does something happen to the starter fluid? Should i drive the car a bit around?

 

[delta448]

If there's a leak the starter fluid will raise the idle speed.

Your oil pressure problem is caused by the low rpm idle, the oil pump is driven at engine speed. You should check for vacuum leaks after the engine is warm, or if you have a high idle speed. If you are getting low idle speed you should check/clean your throttle body and all of its little components like the FIAV, ISC and the BISS adjustment.

 

[alreadytooken]

hey man im sorry to say but you have symtoms of crankwalk. something that happens on 30% of 4g63 motors on 2g cars. i have the same problem on my car. chances are that your oil pump has lost pressure and now your crank bearings aren't getting the oil they need. so now your thrust bearing is lost and thats were that clicking noise is coming from. this is something that needs to be addressed now.
there is a good article on the website Magnus Motorsports were they probably fiqured out why this happens on 2g motors. im going to have my machinist do what they did. sorry bout the news

 

[lars y]

ah man, crankwalk is what i have feared the most..

Ill check it closer when im done replacing the engine on my other car..
Ive been considering buying a built engine from slowboyracing, so if it is crankwalk ill probably buy the stage II 2.3L longblock ...(can anyone recommend that one?)

Thanks tho, sorry for your problems too "alreadytooken" crankwalk sucks...

 

[ian_jl]

I have a similar problem I just did a 4g63 swap into my 1990 eagle talon TSI and im having a idle problem right from start up and when I try to push down on the gas pedal it starts to miss and then when i let off it stalls out, I can pull off the TPS sensor wire and idle sensor wire and it does nothing please help thanks

 

[dannyd97gst]

I believe that only 7 bolt 4g63's were prone to crank walk? The low oil/knock is not why the vehicle idles too low but rather the knock could be contributed to the low idle/low oil pressure. My 97gst idles around 400-500 when hot too but the oil light never came on and right now is not causing any problems. Sorry for your luck lars y but every dark cloud has a silver lining...time for a rebuild. I wish my motor would blow up so I had an excuse for a rebuild!

 

[I-DSM]

share ## pain built my 91gsx and idle problems since begining. bought a 2g throtle body complete installing today see if it gets fixed.

 

[lars y]

hell of a bump I-DSM
yea im not completely sure but i think the low idle was the root of all the problems (like many of the people in this thread told me). i took the turbo of the engine and looked inside and theres some serious shaft play >< so i think the whole engine was a bit starved of oil, probably a combination of a low idle and an old oilpump and maby some oil clogging in the engine canals.

but anyway, i bought a built longblock from slowboyracing with all the mods supporting a gt3076r im also going to use a 75mm accufab throttlebody so i wont have to worry about the ISC. if i get a low idle ill just adjust the idle set screw

 

[sugarfree]

Is there seriously not any proffesional mechanics on this site? Your oil light is coming on because the idle is not high enough to give sufficient oil pressure which is also why your engine is "knocking" I would suggest checking for vacumm leaks after the throttle body like intake mani gasket, injector o-rings, tb gaskets, iacv, egr, throttle body o-rings, and possibly the biss screw. It might help if you have link or something you can see a log with. Do not get carried away and assume you have crankwalk, that has literally NOTHING to do with idle Unfortunately there are a lot of different things that can affect idle speed but a repair manual can help you with diagnostics if you want to tackle it yourself. good luck

 

[lars y]

thank you sugarfree!
yeah i agree, as i said in my last post i think the root to the problem was that i had a low idle wich was causing a low oil pressure.

but that engine is now out of the car and im working on putting together a completely new one, and i will be replacing all those things you mentioned (plus alot more)

so im just excited to get this new engine in the car now =)

 

[TheRealMRDyno]

1) The oil light is probably on just because the engine RPM is so low.

2) The RPM being low when warmed up but not when cold probably means:
a) Vacuum leak, tolerable when cold due to richer mixture, or
b) IAC/ISM driver failing, semi-failed electronics will work when cold, but when they warm up they stop working.

Joe