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Help cheeky sort this idle !!!

cheekychimp

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Joined
Apr 19, 2004
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Location
East Sussex, U.K.
I know there is a whole load of information in the VFAQ on this. I've been through there once (can't say I understood it all though) and back through some of the threads in here and the archives trying to find stuff to attack next.

Cliff notes so far are that the car does not idle correctly. There is some idle surge, although to be honest it is minimal. The idle won't however remain steady and ends up far too high after cruising for a period of time. The biggest issue is that 'blipping' the throttle causes the engine to stall. This happens at junctions, but it also happens at very low loads i.e. slightly raising the RPMs just backing the car into a parking space.

A few issues to deal with. This is a 1990 JDM car, currently running a USDM 1G DSM ECU with the original 1990 harness.

Issues we have dealt with so far: -

(1) Swapped Pins 6 and 14 in the 1990 harness to match the current ECU;
(2) Removed DSMLink and replaced with a chip Jeff burnt me for my setup to eliminate any issues relating to my lack of tuning prowess;
(3) Installed an AFPR since I had previously been unable to install my fuel rail which has the AFPR integrated. Fuel pressure is currently set to 43.5 psi which corresponds to the settings in the chip that Jeff burnt for me;
(4) Reset BISS after grounding the connector at the firewall and connecting the DSMLink cable to the OBD1 connection port under the dash.

Given what I have read from the VFAQ and talking to a few guys, future things on the list to examine are: -

(A) Vacuum leaks (need to make up a tester and pressure test the intake)
(B) Get a logger and check TPS position
(C) Idle closed switch
(D) Re-circulate BOV (not convinced this is the issue at idle but it's an easy fix and needs to be done anyway!)

So my questions are

1. Apart from the obvious loose couplers, where might I find leaks? (BOV, throttle body ... any others?)
2. Can someone tell me step by step how to calibrate the TPS? Apparently the VFAQ is wrong.
3. How do I check the Idle closed switch? I also remember something about having to ground it properly?
4. What is it that I am grounding exactly when I reset the BISS? I have the connector at the firewall located but is plugging a logger cable or the DSMLink cable in at the OBD1 port necessary/sufficient?
5. Anything else I should check out?

Thanks to Yiuwa for his help so far.
 
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Muskrat

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Jun 13, 2004
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2,107
Location
Lexington, KY
A couple things I noticed right off that bat:

1) Before you switched pins 6 and 14, did you check continuity from the plug to the pin, to make sure you had to do that? Pin 6 should go to the MAF plug and pin 14 should go to the TPS. Reason I ask is I recall someone saying the JDM harness was the same as a 90, but don't quote me on that. It'd be good to double check anyway.

2) Definitely get a logger.

3) TPS should be set at 10% (per logger reading) when the throttle is closed. Adjust TPS before playing with the BISS.

4) Recirc your BOV if you're still running a MAF before it. This CAN be causing your issues.

5) Do you have access to a known good ECU you could swap in? I had idle issues for a long time, and it turned out it was the ECU.
 

Telecaster

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Feb 26, 2002
Messages
573
Location
San Jose, CA or Philippines
Are you using v3? If you are it will be easier since you can ground the connections via the check boxes "misc" tab. To set base timing, check "ground timing connector." To set the idle with the BISS: check both "ground timing connector" and "ground diagnostic pin." In case the idle switch isn't functioning, you can also simulate the switch based on the tps.
 

toybreaker

iconoclast
Joined
Apr 30, 2006
Messages
3,581
Quote:

1. Apart from the obvious loose couplers, where might I find leaks? (BOV, throttle body ... any others?)

The intercooler core is another likely place for pinholes

Quote:

2. Can someone tell me step by step how to calibrate the TPS? Apparently the VFAQ is wrong.

Set it for 10% against a closed throttle. You can also set it by voltage to .5 volt closed, and the verify it goes to 5 volts at wot.

Quote:

3. How do I check the Idle closed switch? I also remember something about having to ground it properly?

The closed throttle switch is grounded thru the throttle body. There's alittle ground tab that goes under one of the intake elbow mounting bolts and terminates at a 4mm screw on the top of the t-body. If that tab is missing, you can just run a jumper wire from the 4mm screw over to the intake mani ground over by the throttle cable. That ground belongs on the lower bolt, independant from the t-cable bracket, The cad plating or corrosion under the cable bracket may mess with the ground when the engine is hot.

Quote:

4. What is it that I am grounding exactly when I reset the BISS? I have the connector at the firewall located but is plugging a logger cable or the DSMLink cable in at the OBD1 port necessary/sufficient?



Without a logger, it would probably be best to do it the old school way. Just make a jumper wire and ground things as specified in the vfaq. That way, you can be assured the ecu is in the correct mode to adjust things. Might not be a bad idea to check the base timing whilst you're at it.


Quote:

D) Re-circulate BOV (not convinced this is the issue at idle but it's an easy fix and needs to be done anyway!)



^^^This

Quote:

5. Anything else I should check out?



Has the t-body been rebuilt?

Make sure the throttle plate isn't hanging up/sticking in the bore.

Checking the iac coils for resistance would help eliminate a bad/weak coil.
A test by substitution with a known good iac would also help narrow things down. I'm always a little leary of throwing a used one in there without checking it, because the possibility of damaging the iac drivers in the ecu with a bad iac is very real.

Has the ecu been re-capped, and was there any acid damage to the board?

When I'm dealing with an idle problem, one of the things I like to do is watch the iac count as I load the system down. Twisting the steering wheel back and forth at a warm idle should command a ~ten count increase in the iac count, (provided the load sensing wire is hooked to the power steering pump.) It should also never read "zero", there should always be a small count showing on the iac.
 
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Paul,
Try advancing the CAS to add a few degrees extra timing advance to see if that helps with the stalling. Just stay out of the boost. When you push in the clutch and get off the gas coming up to a stop, the rpm's and timing advance drop so quickly that the ECU often can't catch it. If that helps I can mail you another chip with more timing advance in the lower maps.
 

cheekychimp

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Joined
Apr 19, 2004
Messages
7,333
Location
East Sussex, U.K.
Right guys, bear with me on this. I'm really not that mechanically gifted!

Jeff, how much advance are we talking about here? You burnt me a second chip for the 98 RON fuel which I presume has more aggressive timing maps. Is it worth throwing that chip in or is the timing advance added only at higher RPMs/WOT? (i.e. do I need to increase BASE timing?)

Muskrat, I'm concerned about the pins issue too. I have no idea if ALL JDM cars are identical irrespective of year OR if 1990 VR4s are even identical to 1990 DSMs regarding ECU pinouts (I kind of doubt that). As far as the pin out diagrams we have seen, the 1990s and JDMs are identical except for pins 6 and 14 which are reversed. This is kind of critical since pin #6 in the 1990 was the Idle Closed Switch so could very possibly have a hand in the stalling issue. Pin #14 conversely was the MAF reset. I'm not sure what sort of issue this would cause. What's an easy way to check 'continuity'?

I will recirculate the BOV as stated. I'm not trying to give anyone a hard time over that one, I know it does cause stalling issues but people's mileage seems to vary on this one. When the car was stock I vented to atmosphere for two years and the car never stalled once. RPMs didn't even dip. I also thought that as this was the BOV the issue could only manifest itself coming off boost when the BOV opens. I can stall the car in off boost conditions at very low RPMs which confuses me. I'm interested to run with Jeff's idea and see if that turns up anything.

Telecaster, I have V2 but I'm increasingly thinking of throwing it all in the box and getting an upgrade in the 'downtime'. The check boxes thing sounds like it will make things a hell of a lot easier in the future but for now I want to stick with Jeff's experience on this and troubleshoot other issues. I think if I do this, swapping back to DSMLink or ECMLink in the future will be relatively stress free. Right now I'm stumbling about in the dark on the tuning front because I have no idea if there is anything else wrong or if the car won't idle because I have set dead time, maf compensation, VE for the 2.3 litre or anything else wrong.

John, the original idea was to keep stuff stock and swap new items in one at a time to help diagnose problems with new parts. I think that plan has backfired on us. All the new parts were designed to work together and not installing items has caused all sorts of headaches (the lack of the AFPR) mis matched piping and couplers which I am sure house a vacuum leak (I'll be amazed if they don't!). I'd kind of like to just throw on the Forrester Manifold and TB and eliminate the IAC, FIAV and all that other stuff just to see if it idles. I don't have the A/C running yet and the car won't cold start without a fight anyway as it stands. The only issue is that it uses a different TPS which I don't think we can get round without going back to DSMLink.

So for now. I'm assuming the logger only tells me TPS position, not set it? Is that correct? I have to fire up the logger, get the TPS reading and then manually adjust at the TB until the logger reads 10%, correct? Then I need to check the .5v to 5.0v thing with the throttle pedal full depressed/released? I'll check the ground on the throttle body, but how can I establish if the idle closed switch is actually 'functioning'? Will the logger tell me this?

ECU is good, and we've tried several all with the same problems so I'm leaning towards stuff in the engine bay being the culprit. IAC I couldn't agree more. I'll do the other stuff first and either swap in a new one or eliminate it all together.

GUYS!!! Thanks, and get back to me. Let me do this stuff and a vacuum leak test and we'll go from there.
 
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I believe all logger programs will show you the Idle Switch function. In MMcD it is not quite as intuitive: under "FLG2" you want to look at the "I" feature to see if it toggles when you tap the gas pedal.
The 98 octane maps only have extra timing on the higher maps, not the lower ones that might be causing your problem. That's why I recommended advancing the CAS.
 

cheekychimp

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Joined
Apr 19, 2004
Messages
7,333
Location
East Sussex, U.K.
Jeff,

Roger to that! That's what I needed to know. I'll bump base timing up a couple of degrees and see if that works!

Incidentally Jeff what's your experience with 1990 ECUs. The pinout diagram comparison chart that shows differences between the 91-92, JDM and 90 ECUs is what led us to assume we might need to change pins 6 and 14. You told me to check the colours of the wires at the Idle Closed Switch and stated

Quote:
Paul, the easist way to check your harness is to look at the Idle-closed switch on the throttlebody. I believe that wire is ALWAYS green, with no stripes. On the newer cars that wire needs to go to pin #14 of the harness, but your 1990 car probably has it going to pin #6. It should be relatively simple to connect an ohmmeter to pin #6, without the car turned on, and see if the wire gets shorted to ground, except when you tap on the gas pedal.



So assuming we were correct in swapping the pins, if we do that same test now with the Idle Closed Switch going to pin #14 we want to put an ohmmeter on pin #14 and see if it shorts to ground all the time we aren't standing on the throttle, correct?

I'm just confused now because I'm wondering if ALL JDM ECUs are identical 88 through 92 and if the differences in 1990 cars are only USDM DSM cars.

My vehicle was using the dual board non-Eprom ECU when it was stock. Did we do the right thing swapping the pins?
 
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The older dual-board ECU's (which we have never had) and what we call the "1990 ECU" boards both had the idle-closed switch on Pin #6. Here in the US they moved it to pin #14 in 1991 model year. The GVR-4 manual shows it as a solid green wire.
The crossover year may be different in Japan, but I'm fairly sure the same applies there. If you are running a 1991/92 USDM ECU you want that green wire going to pin #14, whereas the MAF RESET wire is a Green/Light Blue striped wire. So yes, you should be able to put an ohmmeter on pin #14 and see it short to ground when the throttle is closed.
 

Yiuwa

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Joined
Aug 10, 2003
Messages
641
Location
Pokfulam, Hong Kong
Hi Jeff & Paul,

I did the continuity test for Pin 6 & 14 from ECU harness to respective destinations in MAF and throttle body, and I am pretty confident that I made the swap correctly. Having said that it doesn't harm for Paul to double confirm that

Logger - I will lend you my spare unit when I come by next time. If you really need that urgently you may borrow the unit in Ken's car. I think setting the base timing, TPS and boost leak should be the definitely be done before we explore new stuff. Your IAC motor - I think I did that resistance test as per instruction from VFAQ, though you should try to do it again

Yiuwa
 
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cheekychimp

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Apr 19, 2004
Messages
7,333
Location
East Sussex, U.K.
Okay ... update.

Yiuwa swung by today for some more diagnostics followed by lunch. He brought a logger setup with him but we couldn't get it to communicate with the ECU. Swapped in three known working ECUs and couldn't communicate with any of them. Connected the logger to Yiuwa's car and got a connection straight away.

What was even more confusing was that we then went and got my spare ECU with the DSMLink chip in it, and tried to use the DSMLink software to connect to it. That wouldn't communicate either!!! The DSMLink setup was working fine before. So I don't know if we have an issue with the harness now /ubbthreads/images/graemlins/dunno.gif

Ken thinks we should swap in a known good harness the week after next when he's got some free time, and then really work on getting it running. So I guess we'll be going back to the shop. I feel good that we might get this sorted now but disappointed that we made no progress ourselves.
 

The communications connection to the ECU is rather simple, just pins 1 and 2 on the ECU harness. The problem is that the communications lines also connect to other things in the car, which could be causing the problem. If in doubt, just run 2 new wires and a new ground to the ALDL connector, with nothing else tied to them. You could just move the connector right to the ECU and tap it in too.
 

cheekychimp

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Apr 19, 2004
Messages
7,333
Location
East Sussex, U.K.
Jeff when you say Pins 1 & 2, are you referring to the connectors at the ECU or the diagnostic port? I presume from the way you worded it you mean the ECU harness in which case how can I tell which pins at the diagnostic port connector need to go to Pin 1, Pin 2 and Ground?
 

Pin #12 of the ALDL connector is supposed to be GROUND. You short pin #10 to pin #12 to put the ECU in diagnostic mode. That is pin #2 of the ECU, as you can see below. The data rides on pin #1 of the ALDL, which is connected to pin #1 of the ECU.

 

iceman69510

Turn Right Racing
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Gotta memorize that last post... /ubbthreads/images/graemlins/idea.gif
 
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