fabric

While I was at SIH, I was noticing my car had sluggish performance off the line. With another owners generous help, I swapped in their 89 LH so that I could have Olson run the sharktuner on it and see what happens. It showed that at idle the TPS wasn't engaging. Fine at full throttle. I had previously checked via multimeter, and it passed the test - resistence was like .05 for both full throttle and no throttle, no resistence at any other position.

So now I'm confused. Car seems to idle as intended - right around 650 at idle, goes up to about 750 if I put it in neutral. There's sometimes a very slight variation in idle, but it never stalls out, and the idle isn't making gross changes.

I also checked the EZK via multimeter, it checks out fine as well. I did not swap in the later model EZK, I'm not sure if that would have any impact.

Other than sluggish off the line performance, it seems to run fine. I know that the TPS not working right at idle messes up the air/fuel mixture, which could explain that problem. Do the checkes with the multimeter show a different issue than what the sharktuner says?

RyanPerrella

i would suggest you index the TPS. Thats most likely the problem. They are adjustable and mine is fully at one end of the spectrum to work, so mounting it in the middle of the adjustments as many people do, will lead to the idle not working, because its simply not tripping the switch

VehiGAZ

What exactly is supposed to happen when your foot comes off the gas and the the TPS trips?

I'm guessing it tells the LH to control the engine in idle mode rather than how it would control the engine at low rpms, right? Wrong?

I'm trying to understand how all this is supposed to work so I can better diagnose my problems.

Note that there is a post in the "rock steady idle" thread about adjusting the throttle cables at the bracket to get the switch to trip properly.

Bill Ball

Can you hear the TPS click reliably just on and off-idle?

Bill Ball

Did you check the idle position switch signal at the EZK and LH plugs?

Pull off both the EZK and LH plugs.

On the EZK plug, connect an ohm meter across pins 8 and 18. With the throttle closed the reading should be less than 10 Ohms. Open the throttle slightly, and the reading should be infinite Ohms.

On the LH plug, connect an ohm meter across pins 2 and 17. With the throttle closed the reading should be less than 10 Ohms. Open the throttle slightly, and the reading should be infinite Ohms.

worf928

If I read your description correctly your switch did not pass the test. If you saw resistance on the same pin at both idle and full throttle then the switch is dead.

There are two separate circuits on the Idle/WOT switch. One for idle. One for WOT. There are two pins on each of the EZK and LH connectors that must be checked. Two for idle and two for WOT.

At idle, you should get continuity (very low - but not zero or infinite resistance) between pins 17 and 2 on the LH and between pins 18 and 8 on the EZK. Off idle, the resistance reading between these sets of pins should be infinite (no continuity.)

At full throttle you should get continuity between 17 and 3 on the LH and between 18 and 26 on the EZK. Off full throttle (and at idle) the resistance should be infinite.

worf928

Oops. BB beat me while I was looking up pin numbers.

John Speake

Do you mean "sluggish off the line" suddenly developed, ot it was always like this ?

A faulty WOT switch could be the problem, I assume you checked knock sensors and Hall sensor signal were OK with Andrew's diagnostic tester ?

fabric

Dave, Bill - I sort of glossed over these details - I got the results as you described dave - between 2/17 on the LH and 18 and 8 on the EZK I get very low continuity readings at idle, and no resistence of idle - and the same deal with the corresponding full throttle tests for those pins. I still get no resistence when at full throttle when testing the idle position. So this all checks out. I'm not sure I hear a "click" but the tests all look right, which is probably more reliable.

John - this is a somewhat recent occurence. I didn't swap in the EZK, so I wasn't able to get any info on hall or knock sensor faults accumulating. We were seeing knocks on the LH while the engine was running, which I'm guessing means at least one of the knock sensors is working?

What I'm *hoping* is that I can give myself enough excuses not to pull the intake. I have enough other things I need to look at. As a general diagnoses, the car seems to have plenty of power after about 3K rpm, I"m not sure that's indicative of any thing. Flappy works fine as well.

worf928

Oh well then. I'll go back to my rocking chair

By 'no resistance' you mean infinite resistance right? As in no connection.

EDIT: Another thing you can check is the pins in the ECU connectors themselves and to make sure that the pins on the ECUs are nice and clean (and not broken etc...)

fabric

Correct - infinite resistence. I'll double check the connections. When I did my initial testing when having idle issues, I had jammed the multimeter probes into the ECU connectors, and had some issues after doing that, so I'll double check those, that's a good suggestion, maybe the connection is causing issues with the LH or EZK getting the readings.

Of course, I only had time to look at this just before leaving on vacation, so I'll be picking this up next weekend. Any other suggestions are welcome, I'll report back on how things are then. Thanks as always for the quick response guys!

John Speake

Try and run another test with a diagnostic tester. I recommend doing a battery reset to eliminate spurious codes that can sometimes accumulate. Then do a hard test drive, and read out any resulting fault codes on knock or Hall sensors.

fabric

THis is definitely in the future, but I don't have easy access to a tuner.

I guess my concern is that, according to the test outlined in the WSM, my TPS is working fine. The sharktuner said it wasn't able to detect idle. Could the LH have an issue itself, that it's getting the signal but not engaging the idle program? The connection looks good between the harness and the LH, although it's hard to tell if they aren't interfacing well.

I'm really mainly concerned about the discrepancy between the two testing methods.

John Speake

The tester Andrew used is not a SharkTuner..... and a faulty throttle switch is not going to affect performance off the line.

You are correct that a faulty LH can receive a WOT switch or idle switch problem, but not respond as it should. This is often a early sign of impending LH failure.

Try and beg borrow or steal a diagnostic tester and run some tests before you tear anything apart.

fabric

I sure hope not - it was refurbished last year! I did try a different LH, and that didn't seem to really solve the issues - idle was around 1000.

ALthough I'm not sure when I"ll be able to run any diagnostics on this thing, I'm going to heed your advice and not tear anything apart, since I don't have a good idea what the problem is, and for the most part it seems to drive fine, and feels plenty quick- and didn't seem that bad the last time I drove it off the line even.