Idle, Put in the new ECU. Help!

[joeym4130]

Well, been working on this idle thing since i bought the car about a month ago... Quick review: Got the car, idle surged from about 1000-1500. put MAF back to stock, had a bad ISC coil so I bought new ISC, didnt fix it, or change it, but noticed the new "good" ISC was twitching like an electrical problem. So figured (guessed) the culprit was the ECU, not controlling the ISC motor correctly. Found an ECU on the trader and here I am today. Been thru the faqs a hundred times for the surging...
I swapped the ECU out this morning, and fired her up. So she starts up, and goes into warmup mode, idles raise to about 2500-3000, wait a few minutes for it to come down, doesnt. She sits now and idles at about 2700 steady no surging..... in constant warm up maybe? the ISC moves correctly now so i guess that is ok..but new problems obviously have emerged. can u imagine the launch i'd have everytime i'd try to pull out in that high RPMs ahahahaha, in a parking lot or something! What could cause my idle to stay so high??? I am going to have to put the old broken ECU back in and deal with the surge cause i have to drive the car in a day or two...
I checked the TPS, i am getting about 12% reading at idle thru logger is this ok? In the book it says with key on, the TPS should read 1100-5600 ohms when moving throttle..mine is a bit below, like 800-4500ohms..would this be it?? I have no throttle issues, no bucking or anything though.
Or maybe the closed throttle position switch? (The rubber boot sensor thing on top of the TB). Its supposed to have continuity when throttle closed, mine does, but the wire going to the boot looks to be sort of damaged the insulation is off, im gonna re-solder a new wire in to replace it just in case. would this cause the high idle, for the car doesnt know that the throttle is closed?
My o2 not sure about but i think a bad 02 would be surge more then just high idling.. i get the voltage from the o2 kind of around .3 and jumping to .5-.6 sometimes at idle, not sure if thats bad... probably haha
So hopefully i will be an idle expert after all of this..if its ever sorted out...haha..any ideas of more things to check???

 

[joeym4130]

Ok, another update. Me and my friend tried to mess w/ the timing to effect idle, and we could still only get it down to 2000.... any help guys, plz!

 

[mitsutuner]

Data-log & check all your sensor functions, temp sensors functions esp.
If you can't data-log, rig up the tester described in the 1000 FAQ & check for ECU error codes.

 

[mitsutuner]

Seems like your BISS could be out of adjustment or deteriorated O-ring, easy to check & rule out. Next, Data-log & check all your sensor functions, temp sensors functions esp.
If you can't data-log, rig up the tester described in the 1000 FAQ & check for ECU error codes.

 

[joeym4130]

ok...i'll have to go log temp and all those tonight..didnt think of that, thanks! What kind of sensor failure could cause this? like T-stat or something?

I had to drive it today, with the high idle ECU in. She drives a lot better with the new ECU, i used to have a buck when i let off the throttle and that is gone, and feels different all together, like new. Now the idle is my obstacle haha...

Yesterday I did check my ECU for codes..DUH! It had a 36, Ignition Timing, but that could be from me and my friend adjusting the timing couldnt it? or this something different altogether?

 

[mitsutuner]

I'm not real strong on this topic, if somebody wants to elaboarate please do so.
I think what you want to do is first check for error codes & then check ALL sensor functions to be sure you don't have a condition that may have contributed to your previous ECU failure & probably not a good thing for your new ECU. This may or may not lead you to your fast idle diagnosis, not sure, I was guessing that a temp sensor failure someplace might be telling your ECU to stay in cold-start mode & hence the high RPMs.
I had my ECU reman. by a shop that somehow tests inputs & outputs and based on what they find wrong with your old ECU, can advise you if you have such a contributing problem. They even go so far as to state that their warranty is void if you do not correct the problem when you re-install the good ECU. I know for sure, the last thing on your wish list is another ECU.

 

[mad_mike]

The ECU uses 2 inputs to bring the idle down to open loop, which is the CTS (coolant temp) and the 02. The O2 has to come up to temperature in order for the ECU to even look at it. I have a non-dsm so im not sure where the O2's are and how many there are, but it could also be something as simple as the thermistat. I hope this helps u find the prob. it would also help if u had a wiring diagram to maybe troubleshoot and trace back those 2 circuits to find something that might potentially be wrong.

-Mike

 

[joeym4130]

ok thanks for the helpful info mike! thats something i was looking for, what changed the ECU's modes.
yeah on the 1g, i have i o2 sensor... maybe the sensor needs replaced, or i think i have heard of the o2 heater going bad too... I'll have to check it out..might as well...
I think my coolant temp is ok, the radiator fans come on, so that means its working doesnt it?
thanks guys

 

[mitsutuner]

It seems like you're on the right path, just a few more pointers.
There is a wiring diagram in the chilton manual, and sometimes you can find the problem using traditional resistance & voltage checks, but keep in mind these are static checks and may not reveal a dynamic "loaded circuit" failure. Using a data-logger to check sensor function is more definitive & much easier, once you get it set up & going & a wise investment if you're planning to keep the car & work on it yourself. Even a homemade error code reader might find your problem, 1000faq will link you page that tells how to make & use it--simple really.
At any rate, you want to find out if you have an ECU error code not only to help you find the cause of your problem, but also to make sure nothing is messing with your expensive ECU.
Google search "OBDI dsm" or links from the 1000faq to get info on datalogging.
Another thing, just because you're cooling fan comes on doesn't for sure mean your temp sensor is working because there are multiple temp sensors on the dsm, 3 are on my AWD turbo thermostat housing alonel

 

[joeym4130]

well i had posted it earlier but in case u missed it:

"It had a 36, Ignition Timing"

I didnt know what to do with this, I checked my timing, and its set correctly. This code came up when we were messing with the timing trying to idle her.
I have to wait til tomorrow to log her again, i had a big dilemma tonight to attend to, instead of the dilemma with this car haha...

I'll do a log at idle i guess? I'll monitor my o2, coolant, airT... there is a whole screen on MMCD where i dont know what they mean.. FTRL,FTO2, ACLE...but i'll log what i know. I still cannot find what my o2 should be reading anywhere..but dunno if that would be helpful anyway, since it would be reading o2v at 3000rpms instead of a good idle...

oh ok, i wasnt sure about the fan, thanks! haha.