1G idle is at 1500-2000 rpm???? what causes that?

[joshcasey]

Hey all i researched this and everything i found is nothing my car is doing, doesnt matter if its hot or cold out, when i start my car for one it barely starts sometimes and i have to keep my foot on the gas, when it starts it runs great but idles at 2000 rpm then when its warm it idles at 1500 ish rpm, if i start out too fast it boggs now like its getting too much fuel, a week or so ago my check enging light was on but since it started running like this my check engine light has been off, ive been fighting this for about a yr now and its quite frustrating...im very limited on my diagnostic equipment and refuse to take it to a shop ive been a mechanic for 6 yrs now and i have never seen this, any helpful suggestions???

 

[herms99gst]

have you checked your iac and for vaccum leaks?

 

[90_gsx_E]

my gsx did that, all of a sudden one day it would not run below 2k rpms, my problem was fixed after I replaced the ecu.

 

[joshcasey]

thats my next step is to check for vacuum leaks and ive replaced the iac before with a used one and that one idled at 3k so i put mine back on and it was fine for about 6 months then it started doing this
and it occasionally fluctuates from 1500 to 3k till i come to a stop this started happening tonight

 

[DSM1G90]

Did you reset the IAC, then do your BISS screw adustment ..along with checking if the IAC unit was good?

This could be ECU related though,esp with CEL light coming on.

 

[92AWDHX40]

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

sounds like a surge or similar idle issue, good reading here.

 

[jo_91gs]

Yep, those are the signs of a faulty ecu..caused by leaking caps. It usually starts happening at around 90k mileage (if its in original state)..,cheap components, with those symptoms, until your car just completely stops turning on one day. Its easy to find out if you open the ecu because the damage is usually visible on the circuit board. I payed around 100 for the rebuild..totally worth it.

 

[joshcasey]

car has 200k on it when it idles at 1500-2000 rpm there is no check engine light, today my idle went to normal when my check engine light came on, but if i shut the car off it barely if at all wants to start, ive had the ecu out before and everything looks great, i just replaced my alternator because it went out and since then its been idling normal then idling high then back to normal its odd, how do i reset the iac? when my car doesnt start after being on i can push it not even that fast and dump the clutch and it fires right up everytime, my brother is going to be sending me his iac that is known good and see if that helps but again ive hit a wall, i checked all my vacuum lines and there was one spot of concern that i replaced and it didnt change anything, and my biss screw is all the way in, it wasnt, so i screwed it in and it didnt change anything,

 

[Mt95tsi]

is your car idle surging? clean the tps then adjust your idle a bit

 

[LiquidX]

is your car idle surging? clean the tps then adjust your idle a bit

Care to explain cleaning the TPS? Do you know how the TPS is designed and works?

 

[joshcasey]

it idle surges randomly but hasnt for a few days, yeah and i dont think you can clean the tps ive cleaned the throttle body before but ive never heard of cleaning a tps on a 4g63. for the time being im due for new plugs and wires so im going to replace plugs wires fuel filter air filter the works to see if its a maintenance issue and then when i get my new iac i will post the results of replacing it.

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

sounds like a surge or similar idle issue, good reading here.

thank you very much that actually helps alot and almost solidifies my idea to replace the idle controller

 

[DSM1G90]

I still call it an ECU problem, esp with CEL light coming on.

True, you can crack the case open and everything looks good inside, but you could have a few sensor drivers that have opened up or shorted, caps that have dried out so it won't hold any more of a charge anymore and to filter current, or a ground trace that has minute cracks to prevent a good ground.

Best to have that unit checked before spending the money that isn't needed elsewhere..and with 200 K on the odo, no ECU can last that long without any problems.

 

[joshcasey]

ill have the ecu checked i guess but every one of the dsms in my family (which is 5) i do believe only one ecu has been replaced and that was due to water damage, other than that every one of our dsm have over 170k at least and have have ecu issues, so sorry if im very hesitant on getting my ecu checked, plus ive never seen an ecu cause these prolems, and still allow the engine to run, :-|

 

[bryanwheat]

ill have the ecu checked i guess but every one of the dsms in my family (which is 5) i do believe only one ecu has been replaced and that was due to water damage, other than that every one of our dsm have over 170k at least and have have ecu issues, so sorry if im very hesitant on getting my ecu checked, plus ive never seen an ecu cause these prolems, and still allow the engine to run, :-|

1g ecu's are notorious for problems. The idle control circuit is very common to have problems. Pull the ecu and check the board for damage.

 

[TrystanGST]

Vacuum leaks, TPS settings, BISS settings, throttle cable adjustment, stop screw adjustment. All of these have cause idle issues on my car at one point or another. The real kicker is that they're all related, so fixing one means going back over the others.

 

[joshcasey]

so went around checking everything no vacuum leaks or anything like that noticed the car has to be push started when its alittle chilly outside, it will crank fine but it acts like its getting too much fuel, pulled my o2 sensor out and saw that the tip is albino white, pretty sure its burnt out, gonna replace that and get my exhaust welded up so it doesnt leak and see where it goes from there, ill update again once ive done this

 

[miguelmcv]

Make sure you have no Leaks between the head and O2 sensor, If you do have a leak at that area, you will get high Idle.

Also, check your Temperature Sensor.

 

[jo_91gs]

What do you mean when you say, "it acts like its getting too much fuel"on post #16? I'm not sure if this will help but, I had another similar problem with my throttle cable causing idle problems. Make sure that your throttle cable doesnt have tension where its bolted to the intake manifold. Believe it or not this will cause high idle in hot weather. Make sure your cam sensor is aligned and installed properly, and adjusted to "0".

 

[obsidian]

throttle closed position switch. Make sure the wire is securely on the sensor. Play with it to see if anything happens. Make sure that one wire is completely intact.

It's the one wire on the back of the TB. That could be out of adjustment also.

 

[obsidian]

Any updates?

 

[DSMAvenger]

Add 1 vote for ECU


Chris

 

[spainobain1234]

WOW I have the same problem, nobody cared to answer it?
ANOTHER unsolved mystery?
Please help us
Taking it to the shop!

 

[WES_393]

High/Surging idle is usually cause by:

Misadjusted Throttle Cable
Dirty Throttle Plate
Faulty ISC
Faulty TPS
Vacuum Leak at/after Throttle Body (including BISS O-ring, injector seals, EGR valve, emissions lines, etc)
Exhaust leak before Front O2 sensor
Or any combination of those things.

 

[nicks1999spy]

i had a problem with that same thing was iac changed it with a used one ended up going bad not long after put a new one in there only 80 bucks been fine ever since also adjust ## set screw a little if needed

 

[DeNcHi]

I am having the same issue, i have an exhaust leak but its at the flex pipe, but idles random, usually high until you let out the clutch, took isc out and cleaned it, could someone point me in the direction of the biss set screw? sometimes it doesn't start after its warmed, but i do know for sure that my coolant temp sensor isn't working right, so that may be one issue, any ideas ?