Wierd idle

[eksz]

Just put my 94 GS back on the road after an engine swap. It's got a stock Galant DOHC engine in it and everything else is completely stock. When the engine is first started (cold) it really does not want to idle. When cold I have to blip the gas constantly to keep her going and give her extra gas to make her move. I set the idle high (1000-1200 rpm) by adjusting the throttle cable to pull some extra pressure on the throttle assembly to compensate for the reluctance to idle. Once it is warmed up it idles fine but I noticed it seems to to have a cyclic increase in the rpms. Over the course of say 10-15 seconds the rpms start to increase and then drop back down. The range of the climb is only 100+ rpms (1000 to 1100-1200 or so) but it is noticable because it does this over and over. I am thinking I should adjust the throttle cable so it is not pulling any pressure on the throttle assembly but am unsure what to do to check or adjust so it will idle without the extra pressure the cable is putting on the throttle. Suggestions?

[mko]

Throttle cable shouldnt be under pressure, just loosen it enough to have just a bit slack (very little)

Now, this is a typical FIAV probelm. The lower part of the TB has two parts. One is the idle control that lets or stops air. The ECU regulates the idle motor so the engine keeps steady RPMs ( usually same as the base idle setting when engine is warm). The second part of the lower TB is the FIAV or choke. Theres water/coolant circulating around it and when its cold it raises the RPMs (usually in the morning), when the coolant gets warm the valve closes and the idle control takes over. When that valve gets dirty from residue in coolant system, bypass air from the valve cover that goes straight to the intake, contamination from the EGR...you name it...the valve gets stuck and usually lets some amount of air thru. Now why the idle is looping. Assuming that the closed throttle position switch is adjusted correctly( its built in the TPS). When that switch is closed it signals the ECu and the ECu cuts fuel to the injectors. With this said by factory setting with throttle switch closed the ECu hits fuel cut at 1200 rpms. So you have more air coming into the intake manifold the ECu sees it and tries to add more fuel, but it also sees that the throttle is closed and when it reaches 1200 rpms it hits fuel cut. The fuel is now less the rpms go down, the idle control catches it and then stabilizes it, but there FIAV valve is still leaking air that is registered by the ECU, it adds fuel the rpms go up, it hits fuel cut again and so on and so on........it loops all the time.

How to fix it. i personally used ful FIAV and ISC block off plate. Its a pain in the ass in the morning but I got used to it. There are also partial block off plates that eliminate the FIAV only - they are better for cold mornings. or you can try fixing it by cleaning inside the FIAV where the spring is or get a newer TB from 97 Hyundai Sonata. Most of the time they are in excellent shape, they are still 60mm and they are p'n'p

[eksz]

I live in Montana and winters can be extremely cold so I wanted a working fast idle air valve (FIAV). I replaced the throttle body (TB) and FIAV with a spare and got a rock steady idle speed of around 800 rpm so the FIAV was the most likely problem (thanks MKO),

Now I have a new idle problem.
On the test drive after replacing the TB the rpm was erratic at anything above idle. With cruise control set at 1500 rpm the car surges to 2000 and then drops back to 1500. Above 2000 rpm throttle response and rpm were mostly steady until 3000 rpm then it the surging reoccured. Engine rpm was very sensitive and erratic to any change in pressure on the gas pedal. I’m sure the throttle position sensor (TBS) is working as regardless where the TPS is adjusted there is a gradual and smooth decrease in ohms as the throttle plate is opened. I probably just need to adjust the TBS position on the TB. Testing the TPS with ohm meter across terminals 3 and 4 produced the following readings depending on the TPS's position in relation to the TB.

TBS Ohm readings with the throttle plate fully closed/fully open
With the TPS turned fully clockwise ................3.68/0.04 ohms
With the TPS turned fully counter clockwise ....4.55/0.50 ohms
With the TPS turned to midpoint…..................4.36/0.46 ohms

The test drive was done with the TPS twisted completely counter clockwise (i.e., mounting screws at extreme right of TPS mounting openings) . Because of the erratic idle at anything above idle I will adjust the TPS to the mid point of it’s mounting bracket and see what happens tomorrow.

Anyone know the proper ohm settings for the TPS or how to correctly adjust the TPS?

[eksz]

Twisting the Throttle Position Sensor (TPS) so the mounting bolts are about in the middle of the mounting opening on the TPS made huge improvement. No erratic idle, good power.

Anyone know the proper ohm settings for the TPS or how to correctly adjust the TPS?

[mko]

its not by ohm, theres closed throttle position switch inside the TPS and its a major PITA. So between pins 3 and 4 you put an ohmmeter and turn the TPS slowly until you have 0 ohms. It will snap to zero very quickly,its not like gradually decreasing. This is in case the TPS works.

Heres the whole procedure

http://www.4shared.com/photo/TM6N8wB...djustment.html

[eksz]

MKO,
Quick question before confirming the proceedure; The TPS sits on its side when in place on the TB. I didn't see anything indicating whether terminal #1 or #4 was closest to engine but assumed #4 was towards the engine and #1 towards the hood?

Proceedure to adjust the TPS: loosen the mounting bolts and with the accelerator fully released, rotate the TPS slowly until the ohms reading between terminal #3 and #4 goes to zero.

[mko]

on the picture: you have to look at the notch. When the notch is on top pins 3 and 4 are on the right. Either way, chose a pair of pins - left or right side - only one pair will make the ohmmeter snap quickly.On my TPS the pins were actually numbered

EDIT: i just looked at the wiring diagram and pin 3 is yellow/red in color and pin 4 is black.

I hope this helps

[mko]

I did this cuz i was tired of adjusting the damn thing. I got external closed throttle position switch of 1g eclipse, it bolts right up. You out it in adjust the thread so it makes contact right before the throttle is completely closed (around 2-3%), cut the wire of the stock TPS harness, and hook it up to the external switch. then look at the output voltage, it should be 0.5-0.6 V at closed throttle



This is what youre looking for, yes?