High idle car jerking

[Ike66]

Well just recently my car started idleing high when warm. Normally it is idling at about 800 rpm but now when i first start it cold it idles at about 1100rpm then when it warms up it jumps from 1300 to 1500 constantly. The CEL has been on ever since i got it for EGR insufficient flow but its been throwing that code off and on for about 5 months and has been running fine until now. How would i go about checking the EGR valve and solenoid to make sure they are functioning properly? Also if it needs a new valve i may just consider blocking off the egr system completely but is there any kind of guide that would show me how. I tried searching and fond some help but most of it i couldn't understand. Also when i let off the gas the car jerks back and forth.....its worse at higher rpm but sometimes still noticeable at lower rpm. Could this have something to do with the EGR valve also?
Thanks for any help.

 

[Locke]

For the car jerking when letting off the throttle, I would check the VSS (if the speedo is erratic), the TPS, and your roll stoppers.

If you block off your EGR, you will likely forever have a CEL.

For the car idling higher when warm, check the ECT.

 

[Ike66]

The Speedo and tach dont do anything when the car jerks back and forth they just start dropping from slowing down.....And for the other stuff to check where would it all be located on my car? My haynes manual is junk for finding sensors. I wish there was a virtual engine bay tour of the 420a.

 

[Locke]

ECT is on your thermostat housing, TPS is on your throttle body, roll stoppers are the mounts nearest the front and rear of the car, on the crossmember.

 

[4UH8ERS]

High idle is normally from a vacuum leak, commonly around the throttle body.

Give a better explanation of the car jerking when you let of the gas please.

 

[Ike66]

When i let off the gas the car kind of throws you back and forth in the seat a bit. If i push in the clutch and let off the gas all the way its fine. The rps/speedo do not change when the car jerks.

Also would a vacuum leak be causing the idle to be high and surge up and down? Another thing is my cruise control doesn't work it only keeps the speed constant going down hills...on flat it just drops speed and wont speed the car back up.

 

[4UH8ERS]

When i let off the gas the car kind of throws you back and forth in the seat a bit. If i push in the clutch and let off the gas all the way its fine. The rps/speedo do not change when the car jerks.

Also would a vacuum leak be causing the idle to be high and surge up and down? Another thing is my cruise control doesn't work it only keeps the speed constant going down hills...on flat it just drops speed and wont speed the car back up.

Just so you know the 420a has been notorious for the "bucking bronco" effect .

You know when you cruise around in 2nd gear from like 1k to 4k then let off the gas and just let it idle itself forward it will sometimes buck thats nothing out of the ordinary.

 

[Ike66]

Ok it had gotten really bad sometimes with the high idle. But i had some plugs and wires here for it i never got to put in so i did that today. And it was weird after i pput them in for the first start it started up fine normally then when it warmed up it idled high and surged from like 1300rpm to 1500 rpm....then i drove it for like 10 minuets to go play hockey and when i started it like 2 hours later it started then stalled out. So i waited about a minute and started it again and it started and warmed up fine and stopped surging but its still idling at about 1200-1300 rpm and when i put the ac on high it went down to about 800. Does this soud normal?

 

[Ike66]

well i just went out and started the car up again and the idle is still not consistent when it warms up. It jumps from like 1100 to like 1300 and drops back down again repeatedly.But if i turn the fan on high with the ac it idles at like 800 rpm constant.

 

[4UH8ERS]

Because of your success for a short period of time when the plugs where changed, you might be fouling them out with a bad upstream o2 sensor. I remember when my upstream o2 sensor was taking a dump on me it threw no codes, but my rpms were jumpy at idle and when my car was cold it would buck pretty bad under mild acceleration.

edit: Running rich would usually cause the idle to bog down then surge up, it would not cause a steady high idle.

The reason the car idles at a lower rpm when the A/C is on is because it puts load on the engine from the compressor pulley.

 

[Ike66]

Hmm ill have to see if i can check the o2 sensor....i pulled the plugs though and they didn't look bad and the old ones were nice and tan like they were burning normally. But what should my idle be at regularly like 1100 rpm?

Also when i first put the plugs in and started the car cold there was a little water coming from the exhaust and i put my hand over the exhaust a few seconds and it didn't smell at all...then i tried it again after the surging started up again and my hand smelled a little like gas so I'm guessing that would mean I'm running rich.

 

[4UH8ERS]

normal idle is around 900.

 

[Ike66]

ok i disconnected the o2 sensor and drover the car for a day back and forth to work and what not and it stopped surging at idle and just started to idle steadily at around 2000rpm. So im guessing this would mean my sensor is bad or could it possibly just be dirty and able to be cleaned?

Edit: how hard is it to wire up a new o2 sensor with no harness to the old connector?

 

[Locke]

You cannot clean an o2 sensor. New o2 sensors come with a pigtail.

 

[snowboard1]

Hey i have the same problem with my car especially when cold. Just turn your BISS screw in on your throttle body this will turn your idle down!

 

[Locke]

Just turn your BISS screw in on your throttle body this will turn your idle down!

In case you didn't notice, this is the 420a Bolt-On Section. The 420a does not have a BISS.

 

[Ike66]

ok well now im not so sure its the o2 sensor i went outside today and let it warm up and when i first started it cold it seemed to be idling fine at like 1200 then i shut it off and opened the hood and looked at a few things. It was about 1/4 on the temp guage warm. Anyway i got in and started it back up again and it went to 3500 rpm then back down to 2500 and stayed steady idling there. Also the if you listen to the exhaust you can hear it making popping noises every couple seconds. And if i rev the engine when i let off the tach goes down to like 1500 and immediatly revs back up to 2500.

 

[Locke]

Have you inspected for vacuum leaks?

 

[Ike66]

yea ive checked all the hoses and they seem to be good....although my cruise control dosent work so i dont know if that could be the problem...but my cruise hasnt ever worked so i cant see that doing anything. The CEL was on for EGR insufficent flow but then it went out adn it been randomly on and off.

 

[Ike66]

Ok so over the past couple days i removed the throttle body,cleaned it throughly with carb cleaner, removed the egr valve and egr tube and cleaned with carb cleaner, tested egr valve it works as stated in manual, also replaced all vacuum lines that go to EGR system, Checked all other vacuum hoses, replaced throttle body gasket, and i tested the IAC valve and the TPS both were within specs in my haynes book. The only wired thing is when i removed my IAC the little thing came out of it so i cleaned it off and threaded it back in...but does that mean it is broken? Also i was looking at the car with my dad today and we tried covering the hole in the throttle body for the IAC while it was connected figuring if the IAC was bad covering that hole would make the cars idle go down or make the car stall but the idle did not change. My idle is now at 2000-2500 when warm and cool....also the engine seems to be running very rough. Any more ideas of what could be causing this would be greatly appreciated.

 

[4UH8ERS]

There is really not too many things that could cause your car to idle that high. I mean you can follow the throttle cable and make sure it is not hung up on anything, you can check for vacuum leaks, and you can check the MAP sensor. I really can't think of anything else that could possibly cause that.

 

[Ike66]

well i think its a vacuum leak somewhere but its defiantly not in the hoses, but i took the intake off last nigh and covered the whole throttle body with my hand until it suctioned to it ...i figure it should stall the engine but all that happened was the idle got a little lower and the car kept running.....theres really nowhere else air should be getting through to the engine except through the throttle body correct? Thanks for all the help

 

[Ike66]

Well i plugged all the vacuum hose ports on the intake manifold and started the car and it was idling high then i covered the throttle body to see if it would stop. The idle just went from like 2000 to 1500 and i could hear a hissing sound coming from somewhere on the passenger side of the engine. So i went ahead and ordered an intake manifold gasket set because i didn't know what else can be leaking....i couldn't feel a leak anywhere but if thats not it where else could it be leaking? Also if im sitting at idle at 2000 rpm and then rev the engine up to like 3000 and let back off the throttle the rpms drop down to like 1500 real fast then jump right back up to 2000 and stay there.....does this sound like it could all be from a vacuum leak?

 

[4UH8ERS]

Well i plugged all the vacuum hose ports on the intake manifold and started the car and it was idling high then i covered the throttle body to see if it would stop. The idle just went from like 2000 to 1500 and i could hear a hissing sound coming from somewhere on the passenger side of the engine. So i went ahead and ordered an intake manifold gasket set because i didn't know what else can be leaking....i couldn't feel a leak anywhere but if thats not it where else could it be leaking? Also if im sitting at idle at 2000 rpm and then rev the engine up to like 3000 and let back off the throttle the rpms drop down to like 1500 real fast then jump right back up to 2000 and stay there.....does this sound like it could all be from a vacuum leak?

Definately a vacuum leak. Change the intake manifold gaskets and if you have cruise control, then make sure you chack that vacuum box because it will be right there when you take the manifold off.

 

[Ike66]

i got the gaskets now ....first time around they gave me a transmission pan gasket which was a little off . Im gunna throw some new injector seals on while im at it. Also i got my boss to use his laptop data logger he has for his evo and it was throwing a code for TPS voltage too high...with the car off the this was reading 11volts or11%or something like that so i ordered a new one of those too(85 bucks for a sensor was kind of crazy but it does have a 5 year warranty). Its also throwing a cylinder 1 misfire code so i guess the plugs are fouling out from it running rich at idle. So guess im getting some new plugs soon too . Ill let you all know if its running good after i get all this stuff on. Also thanks for all the help.