thook

BTW, the TPS is merely a switch. Where the IDL circuit is concerned, it is just like a light switch. With a light switch, you have wires to the switch, then the switch, then the wires to the light fixture. If you're light bulb is flickering, you have to track down the problem within the circuit. Check the power supply. Say it's fine. You're getting 120v's from the breaker. Then, test the wires coming from the breaker where they connect to the switch terminals. Let's say all good. You're getting 120v's at the hot terminal. Now, test the output side of the switch. That would be the terminals where the wires going to the fixture would connected. Oops.....you're only getting 4v's intermittently. Somethings wrong with the switch. So, you're light's flickering. Something making poor contact.

Okay. With your sensor the IDL circuit is this switch. You can test for voltage, but the amount of resistance will suffice because it will tell you if the supplied voltage will even pass through the circuit properly.

With the light switch example, resistance should be zero as you don't want anything to compromise or impede the 120v's you need to be getting. The zero would indicate a closed circuit, meaning voltage can pass through. The light will turn on. If it read infinite, it would mean the circuit is broken, no contact between wiring and/or terminals is being made and voltage cannot pass. The light switch being turned off is a prime example. Contacts/circuit is broken. Light is off. Any amount of resistance value other than zero or infinite would mean there's damage to the wiring or terminal and the amount of voltage will be less than what's needed.

So back to the sensor, when the IDL switch is "on", or in range for a voltage signal to be relayed back to the ECU, it should read within the proper resistance indicating that the circuit is complete and the amount of voltage being relayed will also fall within spec/what the ECU is needing. Once the throttle plate opens, the IDL circuit/contact should break and indicate infinite. No voltage can pass. This means, to the ECU, the light is "off". Or, idle is off and throttle is open........which is where your VTA (throttle valve angle) becomes relevant.

So, when adjusting/setting the TPS, the resistance needs to be below 2.3k so that the ECU will receive a static reading of voltage (no more or less than what is needs....and, I forget how much it does need) indicating the engine/throttle is at idle. If the voltage is steady, the idle should be steady.........of course, provided nothing is wrong with anything else on the engine.

Anyway, hope that clarifies the subject for you a bit. If not, sorry. But, I try... If you have anymore questions, ask.

DupermanDave

I know how it is to adjust the TPS just a hair. I actually tightened the TPS screws so they were firm and just tapped it with my wrench to sort of knock it very slowly in the right direction. It's just a hair under the open/inifinite, but I don't remember the exact number. I think that because it's just under open/infinite by just a hair, it might have gotten nudged back or heat or warpage might have affected its position.

I'm going to make a few gaskets out of some cheeze-it boxes and work on the TPS some more. I'll need a few gaskets because who knows how many times I'll have to take the throttle body off.

thook

If you're sure that the values for all the other sensor circuits, aside from IDL, are within range, then you can always try adjusting it by hand with the engine running without using the meter and without pulling the TB, again. It's stinkin' easy. Just run the engine until it's warm, loosen the screws a bit, pivot the sensor back and forth until you find the point the idle changes from to high to low. Set the sensor when it drops to the low side. You're done adjusting. If it still won't idle correctly, you need to test the wires. If you get the same values at the connector that you did for the sensor/at the sensor, then the sensor's bad. Done. Buy a new one.

DupermanDave

I think I'll try adjusting it after work. I won't be able to get to the lower screw because of the kind I used, but maybe I can rotate it by just getting to the top screw.

thook

If the bottom screw is tight, that'll be a no go. Sensor won't move. Ever seen those very short, stubby phillips head drivers? They're only about an inch long, if that. Those work well. I have one. Fly me there for a week vacation and I'll let you have it.

thook

And, I'll set your sensor for you.....double

DupermanDave

I lowered the idle air screw a bit because the idle seemed too high and now it's idling fine with no surging, but just in case I made a few replacement gaskets in case I had to reset the sensor.

I just thought of one thing that may be affecting how I'm setting the TPS. The instructions call for something like a .57 feeler guage, and I only have like a .55 and a .028, so I was combining the two to make roughly .57. Is it good to go over or better to go under the size?

thook

Close enough, if the reading you get's in range. So, what was the reading?

DupermanDave

Took a sick day today because I think I have pink eye. Went to go work on the truck and got some readings and found out something else.

The readings with no feeler gauge is 141.1 to 115.4 ohms. With the .85 mm feeler it fluctuated from 212, to 217, then to 202. It kept bouncing around.

I found something else out too. I had a few really really thing feeler gauges stuck together, to my initial adjustment may not have been accurate. However, I just tested it and adjusted it with the proper gauges and it tests the exact same.

-edit-
went out to do some minor second adjustments.

Here's the new numbers on IDL and E2

With no feeler gauge at all, it jumps from 260 to 280 ohms

With the .559 (as close as .57 as I can get with one gauge) it's 250 ohms.

With the .559 and .305 (.864) gauges, it sits at open/infinite.

I tightened up the screws and checked again and they are about the same readings. How do they look? Is it good enough to button everything up and start the engine?

thook

What setting was your meter on, Dave?

DupermanDave

It's an auto ranging meter, so it will automatically decide on the ohm reading. I haven't figured out how to specify otherwise. These were below the thousands range because if I turned the TPS clockwise it would go to the K and then M range.

I need to figure out all the settings on this meter. My old one wasnt accurate enough and this one is too fancy.

-edit-

With the other non-auto ranging meter I have, I put it on the 200k setting and the test read 0.05k Ohms.

I put everything back together but havent started it up. I dont want to annoy the neighbors with an erratic idle on saturday morning.

thook

I don't know what to tell you on the auto meter. I don't have one, never used one, and I'm not an electrician or engineer. What I can tell you from using mine is that you won't get an accurate reading if the setting on the meter is too low or too high. The meter setting has to be on atleast and no more than 10k or 20k to measure the sensor right. Otherwise, I'm not sure how to interpret what readings you got on either meter.

Can you get a pic of your meter or find an image on google of it?

DupermanDave

Here is a picture I found of the non-auto ranging meter:

and this one is the craftsman pocket multimeter I have that does the auto ranging:

DupermanDave

Well, I think I've had my fill with this truck. It's still idling all floppy. I've replaced the throttle body gasket twice now, I've adjusted the TPS three times, and I have set the idle air screw back to where it was before all of this happened, and it still has a floppy idle.

Yet again, unplugging the TPS makes the flop go away, but plugging it in brings it right back. When I adjust the idle air screw to make it idle at 800 RPM (where it should be) I test drive it around and after giving it some gas it wants to idle back at 1100 RPM. So I lower the idle some more, and drive it around and suddenly it's idling at 500 RPM and wants to die.

I think I'm going to put the truck up for sale. I wanted a project truck to work on, but so far most of the crap I've replaced is to fix fluctuating idles (I've been dealing with this exact issue a year ago. Spent about $100 in parts fixing it.)

I'm quite cranky right now because my throat hurts from sitting out there breathing in these awful fumes trying to get the thing adjusted properly. I need a hazmat suit just to work on the dang thing.

thook

Dave, I don't know what to tell you on the meter. Sorry. But, going by what I understand from your symptoms, it's either the sensor or the wiring. More likely the sensor, though.

Suggestion......try PM'ing Roger Brown (4Crawler) or InternetRoadkill on the meter. Either of those guys will know what to tell you about the meter.

DupermanDave

I don't think the meter reading is wrong. It just seems like it's a frustrating combination of setting the timing, getting the TPS adjusted right and getting the idle air screw set right.

-edit-

I'll just work it one problem at a time. Im going to get my timing light from my parent's and I'll reset the timing. Then I'll see if the tps needs adjusted again.

I checked the wiring and as the engine was running I was able to check the readings with a multimeter. They seemed okay and as I checked a few terminals I could hear the idle drop down.

DupermanDave

I got it times and it seems to be a lot better. Idles fine, but I'll only be able to tell on the drive to work tomorrow.

I have a quick question on timing. Does it need to be set at 5 degrees BTDC? My haynes manual says 1 to 0 degrees.

DupermanDave

I'm still not sure what's going on. I reset the timing 5 degrees BTDC. Now in the mornings the idle is different than in the afternoon. I adjusted the idle air screw so it idles at about 750 RPM this morning. This afternoon it idles at 900 and if I hold the brakes the idle slowly climbs to about 1150 RPM. It takes about 30 seconds for it to climb. I know if I set the idle down to 800 now, in the morning it will idle really rough. I've been playing this game all week so far.

What's going on?

HighLux

Did you ever take off and clean the iac properly?

DupermanDave

Yes, I did that last summer when I was had the first idle issue. The IACV wasn fine and not corroded or gummed up. I've also changed the coolant twice since then.