Vague Idle Issue

[Entaran]

Ok, new random issue. It's not really a problem as it doesn't affect the car at all, just I don't get the lumpy idle I was looking for!

I -think- my TPS is out of adjustment but without a datalogger I can't be 100% sure and the scantool didn't show the TPS position (might have to goto Mitsubishi dealership? Do theirs work on Aspec vr4's?)

Issue:
When you turn the car on, it idles BEAUTIFULLY at 1200rpm (cold) and lowers to about 800 rpm (rumpity rump 272's).

As soon as you have driven the car or touched the throttle, when you back off, it will come back down to and sit at 1600rpm. If you give the throttle a really fast stab, it will go up and then drop to like 700rpm, then do the ISC-Failing-Revs from 600 -> 1600 thing slowly. Like much slower than when an ISC fails (my ISC is brand new genuine item was installed like 5 weeks ago).

Thoughts?

I haven't got an intake leak that I'm aware of/can hear, but I haven't pressurised the system yet either.

As I said, I'm not stressed about it as it's not affecting the car, but I'd like it to idle where it should if possible.

 

[brisvr4]

Is it the stock tb Lorrie? Or did you get it from throttlebodies.com?
I got mine from them and it tends to be a little sticky, I also have to give the throttle a light tap to get the idle down to 850 where it should be.

 

[SIVART]

you can check your TPS with a multimetre, Im not sure of the measurement should be but its usally around 0.51Volts

also check your condition for CAS and TPS plugs as they tend to be in bad condition,

and change your harmonic balancer, mine was reving the same as your till my balancer broke in half, I changed it and the revs go straight down, there is no hold at all now

 

[Entaran]

I don't have a harmonic balancer. It has an anodized alloy crankshaft pulley from beyond the limit. There's no balancer on it anymore.

Stock TB Tim, no mods that I've noticed. Am tempted to get one of those bigger ones tho, or send one to FFWD to get ported/cleaned up.

CAS plugs I know are pretty average, not sure what to do about it though. Can you buy just the plug trav and then rewire it? Weirdly enough, 20 minutes ago it decided to idle perfectly for about 6 sets of lights and some random parked-on-side-of-road-on-phone time then started doing it again :/

TPS plug I haven't looked at closely but at a glance is clean and fitted correctly. Will yank it and hit it with contact cleaner. Not even sure where to put the multimeter to check the TPS to be honest.

 

[bazeng]

Give the t/b a clean (carby clean)
Check your base timing and set your base idle again.
Then do as Trav said, check your tps voltages. I'm not sure what the max / min values are for the stock ecu or if the stock ecu can calibrate itself (I doubt it.. but who knows??)
But what you can do is try and find what the ecu looks for in voltage ie, closed = 0.3 volts / open = 4.9 volts... then try and rotate your tps to get those values.

Apart from that, check that your biss is sealing and that you haven't got a leak. You can do this by screwing the biss all the way in, with your timing wire grounded which should stall your engine (based on your throttle stop adjustment being correct also).

It should stall, if not, something is leaking.

Also the FIAV is know to go bad, so check that too!!

Also check that the tb closed sensor is activating (sometimes they go off adjustment).

The bloody stock idle control is terrible on our cars..

 

[boostboy76]

You're probably already aware of the Vfaq DSM Troubleshooting guide:

http://www.vfaq.com/index-main.html

The "Intake" section has a bunch of usefull info on adjusting the BISS Screw, Troubleshooting and resetting the TPS, and a few other interesting "how to's".

Don't know if this helps, but thought I'd suggest it.

 

[Entaran]

Ok, let's go through the list.

The TB is spotless. So clean that you could eat off it, or do your hair from the mirror polished reflection.

The BISS screw stalls the engine.

Base timing was set the day the wheel fell off (about 45 minutes beforehand) and is exactly -5 BTDC, although the car does have 272's I still believe that's the correct place to set it. It has since been checked (earlier today) and is still -5 BTDC.

I have no idea how to check the voltage on the TPS. Where do you stick the multimeter, someone got a photo that they can circle the pins on for me?

Where's the TB closed sensor? This may be the issue

 

[boostboy76]

There's a "how to" that shows checking the TPS using a voltmeter (with pics) in the Vfaq:

http://www.plymouthlaser.com/tps.htm

It may be different for an Aus-spec 4G63 though? Don't know.

 

[Entaran]

thanks mate

 

[Entaran]

*sigh* getting really sick of pulling the throttlebody out!

 

[boostboy76]

Just out of curiosity, were new TB Shaft Seals fitted as part of the new TB going in?

I also know with older Mitsu engines that any change to the intake side of things generally required the TPS to be reset.

Don't know if that is the case with 4G engines though.

 

[Entaran]

It doesn't have a new TB, it's got a new Idle stepper. Genuine, all the bits included.

The tb's spotless because I polished the fucker. Took HOURS.

 

[boostboy76]

Jesus, that must have cost a fortune from Mistubishi!

 

[Entaran]

Not too bad. Couple hundred I think, got it from trav. He'd know more than me.

... *checks receipt* $310. I think. That's what it says under "List Prc."

Wherever possible I use genuine parts on my car. I've done the aftermarket parts thing on previous vr4's and ended up changing the same part 3 times over after the cheaper options fail in 6 months.

 

[D3bb4]

I got a genuine one for a bit over 100 from supercheap

didn't know it was gonna be genuine until ordered and recieved it. came in mitsubishi genuine spares box

 

[blackvr]

Re: the TPS setting... From memory the signal wire to measure TPS voltage is the green/white wire. Will check on my ASpec tomorrow morning and advise if its different. The voltage should be between 0.45v - 0.65v, with 0.5 being most desirable. In practice, any where between those two voltages is fine. Just make sure thers a good electrical connection from the TPS plug... otherwise cut one off a late model magna and solder it in ( or Petroject offer new connector kit I think).

Definitely check that the single wire idle position switch is operating/set correctly.

I use Evoscan and its USB serial converter cable for my data logging with great results. Might be worthwhile investing in one to eliminate guess work and put yourself back in control !

Mike

 

[Entaran]

ECMlink has been ordered so I'll have full scale logging when it gets here. Not sure when it'll arrive though. No point getting a datalogger if that's coming.

 

[BMGTZ]

the ecmlink will definitely be able to let you know if the throttle body is sticking......it will tell you from a data log both the TPS volts and throttle position in percentage

 

[SIVART]

Im pretty sure you can see on the top of the TPS plug, that it says + & -

it might be good to try a stock H/balancer just to see

 

[bazeng]

US and AU tb are the same..

to check the tps, you will need to tap into the sig wire ... 1 of the 3...
1 should be 5v, 1 should be gnd, the 3rd sig.

make sure you use the tps gnd as gnding offsets may cause the sig to show a diff voltage to what it actually gets..