Jump to content

iac


bodes1320

Recommended Posts

This is his son, Rich. My dads a bit of a noob at this web forum stuff I think, so excuse his lack of detail hehe.

The car is a 1993 Cutlass International with the 3.4 DOHC. Forgot the mileage, but I think it might have around 50-60k, not sure. The other day it developed a high idle that would stay until the car warmed up, when it would drop down to normal. I believe he told me the SES light is on, but due to his work schedule I dont think he has had the time to check the code yet. Should be able to get around to that today though after I get home from work.

I'm thinking his IAC could possibly be stuck open, acting like a stuck choke that wont let the idle down. Hes thinking maybe his TPS could be reading wrong, but due to the fact the idle settles down after warm up I cant see that being the culprit. Anyone else have any ideas for us to check out?

Link to comment
Share on other sites

Easy fix, for someone who can handle tools without a problem. Common problem with these engines, lower intake manifold gasket. It leaks at start up, because the metal is cold, and then as the engine heats up and warms, the metal expands just enough to seal the leak. Usually its just a vac leak, sometimes it can be more. Start with checking the sensors, but more than likely it is the gasket.

Link to comment
Share on other sites

Lower intake gasket is shot and needs to be replaced.

 

When it heats up it expands to fill the gaps. What happens is the car is sucking air and hitting the rev limiter. While your down there I suggest replacing the oil pump drive seal because that can save you 5+ hours of labour down the road like what I should have done.

Link to comment
Share on other sites

Thanks guys. The car is going in tomorrow morning to a local dealer where a friend of ours works, and hes going to scan it and see if he can find the problem. Hes thinking maybe the EGR valve is the culprit, we'll see.

Link to comment
Share on other sites

Thanks guys. The car is going in tomorrow morning to a local dealer where a friend of ours works, and hes going to scan it and see if he can find the problem. Hes thinking maybe the EGR valve is the culprit, we'll see.

 

i hope you have DEEP pockets.

i cant remember the last time i went to a dealership and spent less then $600 for ANYTHING.

 

btw. the intake gaskets for a dealership to do is ruffly $650. all you need is a $20 gasket set the rest is labor. do it yourself in 3 hours for a first try. but you can do it yourself with the right tools in under 45mins.

 

EGR simple place 3 bolts a simple wire harness and its out.

Link to comment
Share on other sites

how would a EGR cause a high idle? I think it is the Lower Intake Gasket

 

Agreed!! 100%

 

the leaky intakes will cause your 02 sensor to screw up. your egr to screw up, MAF, and verious sensors to give bad readings.

 

its like my fuel pump problem. My fuel preasure got low and it threw codes. MAF sensor, O2sensor were going nuts. but it was the low fuel preasure causing all the trouble. Not once did a mechanic say fuel pump. I found that out on my own from testing the actual fuel preasure.

 

computers are dumb and contain only eyeline logic which is genaric at best.

Link to comment
Share on other sites

Well its a friend that works at a dealership so hes going to do it all for either free or charge my dad maybe 50 bucks at the most to scan the car. Hes not getting work done, hes just having the car scanned and looked at a little more deeply to see if they can find the problem. Our mechanic friend from the dealer came over yesterday to look at the car in our driveway and used a piece of rubber tubing to try and listen for a vacuum leak around the lower intake gasket and heard nothing. Which is why he doesnt think its that. The fact that it was replaced last year with a brand new gasket is another reason he doesnt think its that.

how would a EGR cause a high idle? I think it is the Lower Intake Gasket

If the EGR gets stuck open at startup, its providing another source of unmetered air for the motor to suck in, basically acting like a vacuum leak. Remember, the EGR isnt supposed to open until operating temp is reached.

Link to comment
Share on other sites

Well its a friend that works at a dealership so hes going to do it all for either free or charge my dad maybe 50 bucks at the most to scan the car. Hes not getting work done, hes just having the car scanned and looked at a little more deeply to see if they can find the problem. Our mechanic friend from the dealer came over yesterday to look at the car in our driveway and used a piece of rubber tubing to try and listen for a vacuum leak around the lower intake gasket and heard nothing. Which is why he doesnt think its that. The fact that it was replaced last year with a brand new gasket is another reason he doesnt think its that.
how would a EGR cause a high idle? I think it is the Lower Intake Gasket

If the EGR gets stuck open at startup, its providing another source of unmetered air for the motor to suck in, basically acting like a vacuum leak. Remember, the EGR isnt supposed to open until operating temp is reached.

 

he was only able to listen to the front lower intake gasket. so he didnt do a full diagnosis on the possibility of the lower intake leak. i believe this to be the prob as well.

a new EGR is $300. if for some reason you believe it is the culprit, try cleaning yours out first. i know someone made step by step instructions on how to do this a long time ago.

oh yeah, if you are throwin code 32 (egr code) dont be surprised that by changing it out or rebuilding it doesnt stop the code from coming up. the unit itself doesnt always make that code go, i learned this the hard way, $300 later... though i never did figure that prob out on my ole z. :oops:

i would listen to the masses here bud. i think almost everyone here who has owned/owns a 3.4 has done the lower intake gaskets at least once.

Link to comment
Share on other sites

yes the EGR stuck open can create a form of "vacuum leak" but within a short amount of time the engine is going to run rough and want to stall due to the buildup of exhaust gases. This is exactly what happened with my old engine, and the code I always got was for the IAC.

Link to comment
Share on other sites

Well after bringing it up to the dealer it appears that its possibly on of the gaskets between the heads and intake, or it still could be the LIM gasket. Atleast thats what I think he said. Im not sure what hes gonna do about it though.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...