1500 rpm idle

[phill]

Ok I searched and didn't find anything about this. Maybe I searched the wrong thing who knows.

I recently had a new engine put in my 1998 RS and now sometimes when I'm coming to a light and I drop it in neutral the rpms drop to 1000 and then climb to 1500 to 1700 until I come to a complete stop. Then drop to about 800 rpms. however It doesn't happen every time

I remember reading something about air in my cooling system so I ran it without the cap on for awhile in hopes of getting all the air out. It worked but then a few lights down the road it started again.

I have OBX rad. hoses, a 180 degree thermostat, and a 16 psi rad. cap.
the cap is a few psi stronger than oem and I thought that might have something to do with it.

Can you guys tell me what you think?

 

[bradcapes]

check your idle screw, are you venting the bov, do you have the proper mods to vent, could still be air in the lines no cap wont always fix it you need a tool dont know what it is called but i had to do it to my car

 

[sparco431]

check your idle screw, are you venting the bov, do you have the proper mods to vent, could still be air in the lines no cap wont always fix it you need a tool dont know what it is called but i had to do it to my car

..........................................its a N/T

 

[phill]

Right, its the nonturbo 420a. I don't have a bov. has anybody else heard of this tool bradcapes is talking about?

 

[pj91gsx]

check->idle screw, ignition timing, vacuum leaks

 

[phill]

Timing is spot on and there are no vacuum leaks. If the idle screw is that little thing that you use to adjust what angle the plate in the throttle body sits at its good too.

 

[phill]

I want to say its part of the cooling system but I'm not 100% sure

 

[pj91gsx]

Timing is spot on and there are no vacuum leaks. If the idle screw is that little thing that you use to adjust what angle the plate in the throttle body sits at its good too.

you have to have the idle down to 750 for it to check if or else it will not read accurately. Im not sure how to do ignition timing with 2g motors, because there is no CAS.

 

[phill]

I was just at the Shop that swapped the engine yesterday for a 500 mile service and check up and they checked all of that stuff.

 

[pj91gsx]

I was just at the Shop that swapped the engine yesterday for a 500 mile service and check up and they checked all of that stuff.

ok. I read about ignition timing and it says you need a code reader to do it on a 2g. I don't trust all mechanics. Not all mechanics know about the newer car things.

 

[phill]

it's not timing. its perfect. Any other have any ideas?

 

[No_Skillz]

Pay attention to your coolant temps when this is happening. Any drop during cruise?

 

[ekanddsm]

check your nuetral switch on the trans. you coast up to a stop clutch in? shifter in gear? or out of gear?

 

[pj91gsx]

I want to say its part of the cooling system but I'm not 100% sure

There is a valve object that is on the theromstat that helps change idle by using a wax pellet with vaccum lines, to make the car idle higher in the cold to warm up quicker. The term is FIAV, i think.

 

[Eclipse37]

Ok I searched and didn't find anything about this. Maybe I searched the wrong thing who knows.

I recently had a new engine put in my 1998 RS and now sometimes when I'm coming to a light and I drop it in neutral the rpms drop to 1000 and then climb to 1500 to 1700 until I come to a complete stop. Then drop to about 800 rpms. however It doesn't happen every time

I remember reading something about air in my cooling system so I ran it without the cap on for awhile in hopes of getting all the air out. It worked but then a few lights down the road it started again.

I have OBX rad. hoses, a 180 degree thermostat, and a 16 psi rad. cap.
the cap is a few psi stronger than oem and I thought that might have something to do with it.

Can you guys tell me what you think?

Lol I have the same problem with my 1997 eclipse R/S but I ahve no idea what the problem is not to mention im getting a 1995 gst so I dun care .

 

[pj91gsx]

Lol I have the same problem with my 1997 eclipse R/S but I ahve no idea what the problem is not to mention im getting a 1995 gst so I dun care .

If the gs-t has idle issues, it has boost leak and ignition timing problems written all over it.

 

[rstchris]

I know exactly what you are talking about. The only thing that will cause an idle problem on a 420a is a vac. leak or a dirty iac. Two bolts, pull it out and clean the valve and the hole in the TB with carb clean on a rag wrapped around a small screwdriver or something to get the cheese out of the TB idle hole.

 

[phill]

I know what you're talking about too, I had a problem with my idle a few months back due to a 55mm throttle body upgrade. Its not the iac or tps I know that for a fact.

Coolant temps stay under half but over 1/3 after it warms up no matter what.

When I'm coasting to a stop the car is out of gear but I usually have the clutch in still. Where is this neutral switch?

 

[tattoochuck]

i have the same problem .... i tracked it down to an exhaust leak, small crack in the e manifold,, causing the tps to read wrong.... check for an exhaust leak.....

 

[cjridert1]

Do this - when your idle is high at a stop, get out and rotated the throttle plate closed with a bit of force. If this fixes it, your idle switch is sometimes working, sometimes not - indicative of a cable too tight or restriction there. The car will idle high unless the idle switch is sending a signal (log it if you want/can).

 

[phill]

I don't have a logger but I have been wanting to get one. What one can I use with the 420a? Maybe xmas?


The throttle plate closes fine, the cable is actually a bit loose.

Where typically does the manifold crack because I just looked at mine and couldn't find anything? I listened too but didn't hear anything

 

[tattoochuck]

it can crack any where.even a hair line crack will do it but it can be else where like the down pipe gasket even a small pin hole...only way i found mine is i heard it .did u take the heat shield off cause thats where i found mine.......listen for a whistle sound while driving if u hear that then u know its a leak or a vac leak...or pcv vaulve...

 

[phill]

Don't have a heatshield. I have a stainless steel header and downpipe.

it stops after a cooling cycle, like when the fan comes on. I think I'm just going to look for a weaker rad. cap and see if that fixes it.

 

[phill]

Ok so it still does this "coasting" idle problem.

I've cleaned the throttle body, checked for vacuum leaks, replaced the IAC, and put the weaker rad cap back on and nothing changed. I'm totally stumped.

I included a video to try and show what I am talking about. I'm driving at first in 4th gear i believe but then i throw it in neutral and coast and in the last two seconds or so is when I come to a complete stop.

 

[phill]

I apologize. I cannot get the video to work so disregard that. I'll keep trying to format it but I'm not all that knowledgeable with computers so bear with me