Surging Idle

[Dave Ingraham]

I guess I'll see it saturday when Justin puts in the bung in your exhaust.    Its not making sense to me. 

[BrandonDouglas]

I guess I'll see it saturday when Justin puts in the bung in your exhaust.    Its not making sense to me. 

Yeah sounds good, I'll explain to you what I've checked!

[John Hartman]

if the pcv(port nearest the intake manifold, facing the firewall) valve port is open to the air, this is not good.  It needs to be able to have engine vacuum on it.

this on its own won't make it wonky like you are describing, but if the large vacuum nipple on the intake manifold is not plugged off, it will. That is a huge vacuum/boost leak and if your car is still equipped with a mass airflow sensor, it will have hella issues like this.  you will also loose lots of boost and make the car slow and sluggish.

[andrew volcz]

its running a 4pin 2g tps

pvc intake port is plugged.  where the pvc would thread into the valve cover, a vent tube leads to the ground

and he is running on map now

[Brett Haviland]

you can do all the things you want in the world....  but if you dont make sure the idle switch in your 4 pin 2g TPS isnt set correctly then ur going to be chasing it around forever, yes it is possible your IAC is fucked, or maybe the FAIV is screwed too... but checking your stock switch only requires getting a feeler gauge and removing the TPS connector to test/set the TPS/idle switch

And no, you dont use a logger to set the idle switch on a 2G.  You use a DVOM and feeler gauge.

heres a quote from dsm forums

2G's critical adjustment is the Idle Position Switch that's part of the TPS.
The manual has you place a 0.0177" (0.45mm) feeler guage between the stop screw and the throttle pulley to open the butterfly and then adjust the TPS right to where the IPS (pins 3 and 4) switches from closed to open. Then they have you verify that the TPS (pin 2 and 4) reads between .4 and 1V while the feeler guage is still in place.
Anything in that range is ok as long as the IPS is adjusted correctly.
There is no way to adjust the TPS voltage independantly of the IPS on a 2G that I can see.

[BrandonDouglas]

I noticed today on the way to school it was just idling high, not surging anymore, possibly because the BISS is fully screwed in now.

I'll have to find someone to give me a hand this weekend as I don't have a feeler gauge nor a multimeter ha.

[BrandonDouglas]

To update this thread, the other night I gapped the plugs, checked/torqued head studs, tightened any and all vacuum lines and brought the idle up a bit.
It has been idling pretty rock solid the last few days at 900 so I think it was a small vacuum leak possibly, unless my problem is just hiding.


I also had my O2 sensor welded in, but I am still getting P0300 code.
Any ideas on what that could be guys? I spent about a half hour reading through DSM threads on other forums.

[Brett Haviland]

If you have a greentop cas on a 6 bolt swapped 2g then it can throw that code.   Its a random missfire.

I believe you can switch to a blacktop CAS (94 1G, and early evos, maybe GVR4 too??)

I believe dsm link or maybe the reflash ecu for 98+ ecus might be able to use a greentop cas without the random missfiring

[andrew volcz]

the 6bolt swap IS using a green top cas... im surprised this misfire wasnt apparent during the breaking/dyno tune.  worth a shot swapping out

i dont recall if anyone reported this same issue on the Ceddy thread on DSM Tuners

[BrandonDouglas]

Will a blacktop be a plug and play type deal?

[Brett Haviland]

yes,  the plug and wiring is all the same.  its just the insides (and well the outside too) that is different.  I belive it generates a bit different signal then the greentop CAS.

[BrandonDouglas]

yes,  the plug and wiring is all the same.  its just the insides (and well the outside too) that is different.  I belive it generates a bit different signal then the greentop CAS.

Cool ok.
Now should I use a 90-92 CAS since that was 6 bolt or are all 90-94's blacktop CAS' the same?

[Dave Ingraham]

Some stuff on a 90 car is different.    The 90 CAS wouldn't work on your car, wrong connector.   

[Jason Harwood]

Throttle position sensor?

Is this my old car?

[Brett Haviland]

THe blacktop cas was only availible on a 94 1G car specifically... but it also was used on the evo I-III and maybe the GVR4 as well.