Hi.

I've been looking for a solution to my rough idle problem. I checked out my TPS and it did not meet the specs in the manual. So I went to wreckers and after a lot of hunting around through 20+ Magna's I found one that was ok. So I put it in and adjusted it as per the manual then let the car idle for 10 mins. This seemed to improve the idle a bit, but it is still rough.

How much resistance should there be between pins 1 and 2 when the throttle is closed. I get around 30 ohms. Is this too high? My thinking is that since it is a switch it should be very close to zero. What would it be on a new switch?

RTFB.
Gerry

mmm . . . I wonder what "RTFB" means? I do know what "RTFM" means. lol

The TPS has little to do with idle quality. On the second gen it is a closed switch with throttle off, and a rheostat with rising resistance as the throttle is pressed. Hence the name, "throttle position sensor" - it tells the rest of the electronics how much throttle is being applied. Affects things like gearbox shift speed and shift quality.
Anyhow, you need to look up which pins out of the four are the on/off switch, and which are the rheostat.

(I'm assuming the TPS does the same on the third gen as on the second gen. Flame me if I'm wrong, I've been known to be wrong before. lol)

Have you touched the ISC at all? ISC is more likely to be busted then the TPS.

Rough idle? Does it idle too low (= ISC) or does it fluctuate? Vibration at idle can be busted engine mounts.

Just being sarcastic. B is the same as M. I.e look in the book.
There used to be a link in the forums for the 3rd gen workshop manual, but I gave up in disgust after the third abortive search with the poxy internal search function.
However in the manual there is clear faultfinding info to check the TPS.
I would love to put the relevant pages in as a PDF but this stupid website does not allow this either.

However going back to rough idle.
Have you tried disconnecting the battery. Do it when the engine is cold. Leave disconnected for a minute or so.
Then reconnect. Start the engine and allow to idle for 10 minutes until up to operating temperature. Then if you have an auto so do a series of PNRND lever movements whilst stationary. Then on a flattish road gently accelerate to 60KPH, make sure that you get to top gear. Gently brake to a stop. Repeat a couple of times.

Sorry about the rants above but this website does not really allow one to be fully helpfull. 1) link to the electronic manual is not easy to find. 2) I have a local copy of the manual so I tried to post a small PDF of the section that you need to read. There does not appear to be a simple way to do this.

Gerry

J
There used to be a link in the forums for the 3rd gen workshop manual, but I gave up in disgust after the third abortive search with the poxy internal search function.
Sorry about the rants above but this website does not really allow one to be fully helpfull. 1) link to the electronic manual is not easy to find. 2) I have a local copy of the manual so I tried to post a small PDF of the section that you need to read. There does not appear to be a simple way to do this.

Gerry

I was about to post the link to the free manual at Lisho but the link no longer exists...searching further I found this reference to Lisho:
All site content will be removed in the next 7 days and will not return.

So looks like the end of that!....

How much resistance should there be between pins 1 and 2 when the throttle is closed. I get around 30 ohms. Is this too high? My thinking is that since it is a switch it should be very close to zero. What would it be on a new switch?

Its not a switch as such, but a variable resistor (known to some as a rheostat). The ECU uses the variable resistance to evaluate throttle position.

I do have a copy of the manual and the idle is around 700-800rpm according to the tacho. Before I left it to idle for 10 mins I disconnected the battery to reset the ECU.

Sometimes the idle can be really smooth, other times its quite lumpy. I'm thinking I should go through the procedure to check the ISC motor.

I presume you've done all the other checks, plugs, leads, rotor cap and button, vacuum leads etc. ISC should not cause a lumpy idle AFAIK.

the book is wrong when it states what pins to check, infact, the online manual, and the haynes books are both wrong. to check for adjustment, you need to put the miltimeter on pin 3 and 4, 4 being earth, then you turn the tps till you just start registering oHms. to check if the tps works, i think its pin 1 and 4 and it should register oHms, not too sure what the resistance is though

The bottom pin is the ground and the one above it is the switch. I have continuity between them when the throttle is closed. I check the pins that register in ohms depending on throttle postion and they are within spec.
The engine seems to have a slight miss at idle. Might try shorting out pins 1+2 just to make sure it is not the switch in the TPS.

I presume you've done all the other checks, plugs, leads, rotor cap and button, vacuum leaks etc. ISC should not cause a lumpy idle AFAIK.

Good advice. TPS is not related to idle quality. (Switch should be closed at idle, and open just off idle - its the only adjustment you can do.)

Check also (once you are convinced the TPS is not at fault lol):
MAF plug and socket for corrosion.
Cylinder compression.
Ignition coil.
Clean out the throttle body.
Check ISC for correct operation.
Clean out/check PCV valve, hoses.