(Junior Member)
09/09/20 10:37 PM
Idle Woes / New ECU not working

Just want to run this past anyone for some feedback. *BACKSTORY* so since I've bought my car I've always had a bad idle, over time it's gotten worse so I finally went to tackle it myself since no local shops wanted to help. So far I have done the following:
- Replace ISC
- Have had TB rebuilt / Blocked off FIAV
- New Biss o-ring
Since doing this the car actually now fluctuates just a little bit (no more 200-1000). I am still getting some fluctuations from smaller increments (900-1000). I haven't set the idle yet properly since I ran out of daylight so will pick up tomorrow. Something else to add is that when I give it a little gas the RPMs dip a little before ramping. Would my final issue be now the EGR valve perhaps? A check engine light goes on but I haven't been able to test a working scanner to see what it is.

NOW on to the 2nd issue
I just got back an ECMLink'd ECU and when I plug it in the car starts but dies after a second. This ECU isn't the original one but off another VR4. However when I plug back in my original ECU the car starts and is able to run. Any idea why this might be?

(poop load of room)
09/10/20 07:47 AM
Re: Idle Woes / New ECU not working

Boost leak test will locate the source of your idle surge. That or your TPS/Idle switch isn't set up right. Old injector seals love to leak.

Did you do the initial start up checks in ECMLink? Could be an A/F thing. Check injector scaling/deadtimes as well as the MAF being used.

(Nope still sticky fingers)
09/10/20 04:36 PM
Re: Idle Woes / New ECU not working

Check the wiring harness/plug for the isc make sure that it is working correctly, maybe try deleting isc with a blockoff plate and see if that helps

Have you checked to make sure the isc is working properly “stepping” when connected and removed from TB

I’m currently about to delete my fiav/isc in hopes of curing my idle surge

(Junior Member)
09/10/20 07:37 PM
Re: Idle Woes / New ECU not working

I tested the car without the ISC plugged in and it was the same result idling at where it was plugged. I also tested the voltage and its making 25v (currently having an electrical issue I just found right now). So my next idea is maybe to test for vacuum leaks (this is all on the og ECU)

When I plugged in the ECMlinked ECU everything was appropriate with the settings. Only thing I could find was the TPS was at 0% and after messing with the settings enough I got it to almost keep going, it ran twice through before dying instead of just once. Idk just a little frustrated today alot of this stuff is pretty new to me and a lot of the places around here haven't been willing to help me.

(Senior Member)
09/15/20 08:34 PM
Re: Idle Woes / New ECU not working

You never mentioned setting the biss screw or adjusting the idle switch.

(Junior Member)
09/16/20 12:29 AM
Re: Idle Woes / New ECU not working

tektic: I set the BISS but going through the car/referencing my manual I found the Idle Position Switch to be completely broken off the top and the green wire that plugs into it hanging off the back of the manifold. I also see the the TB isn't grounded at all.

I've ordered a new switch and will ground the TB. I'm hoping this should be the final hurdle and the reason why the chipped ECU wasn't able to run the car. Could it be the older ECU has learned to run constantly adjusting for the missing switch?

Whoever had this car before me has a lot of odd things broken, and a lot of DIY hardware in place for no good reason.

09/16/20 01:57 PM
Re: Idle Woes / New ECU not working

The idle switch isn't necessary, and you can simulate it in ECMLink. When I say it's not necessary, the car will idle without it, but not as well as with it.

Any way you can post of log of when it's running?

(Junior Member)
09/19/20 06:21 PM
Re: Idle Woes / New ECU not working

Sorry it took awhile, started a new job this week so finally had time to work a little more on the car today. Here is screens of the log:

(Junior Member)
09/25/20 10:49 AM
Re: Idle Woes / New ECU not working

Would anyone have a readout for a healthy running car to compare?

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