i'm really glad someone has done this crap already and weeded these problems out. thanks thook!

 

Haha......so am I! There's been many people before me, too.

 

There should be a cleaned up sticky of this info describing this problem and how to fix fix it. I know lots of people are having these same issues, more and more everyday I bet. Anyone notice if it's more mileage related or age?

Mine is a '91 with 176K. Its first started showing symptoms about 2 years ago, but it would come and go and was not very bad. It only got bad this year, and its really gotten bad in the past month.

 

The resistive strip wears from repeated throttle movement, so I'd say mileage related. You could let the vehicle sit for ten years, and even though many other things would foul up, the TPS would pretty much remain the way it was if the terminals didn't corrode or something.

Seems anywhere around 150k (+/-) is when they wear out.

BTW, 4Crawler's Cheaptricks website covers TPS symptoms and resolution pretty well. Plus, there's info all over the web. I guess the mod's don't see it's really necessary for a sticky considering this. As well, 4Crawler's a member here, and his site is kind of a sticky all on it's own....

 

i just checked my tps by unplugging it, and the idle jumped and smoothed out real nice! looks like i'm replacing that damn thing

 

Man thats great! I havent checked mine yet because it was running ok today.

Now you know the TPS is causing the bad idle, but it doesnt mean the TPS is bad....right? Can it just mean that its not adjusted properly?

 

Right......the IDL circuit may just need readjusting. However, if the VTA circuit is bad, no adjusting will remedy it. The VTA circuit is for throttle angle = how far the throttle is open past idle. Disconnecting the sensor is mainly just a good way to pinpoint. Then, you should test it and see what's definitely going on.

One way you can run a quick check on the IDL circuit is to adjust the sensor with the motor running. With the sensor connected, start the motor and let it warm up. Then, loosen the screws and pivot the sensor forward and backward until you find the point at which the IDL rpm changes. On one side of this point, the IDL will be high. You want to set the sensor on the low side. This is when the ECU is reading the circuit. However, if you can't get it adjusted to have a good idle, then the circuit is just bad.

 

My started running horrible again today. I disconnected the TPS and nothing happened. Looks like I need to test the AFM. It's running like an outboard runs when the fuel has water in it. Hit and miss but wont just completely die.

I changed the fuel filter recently so its not that, thats the first thing I thought when it started acting like it is.

 

I did the static test on the AFM according to 4crawler.com

I got big fat zero on the E2 - Vc, the specs on 4crawler call for 100-300 ohms. The other tests were all within specs.

I didnt do the dynamic tests including the sweep test because failed on the static test. Is there any reason to test further or is it a sure thing that the AFM is trash?

Wait.....I just noticed that the terminals are labled different according to the FSM, infact they are labled different on page EG2-233 than they are on EG2-234

 

Whuh????? I'll get back with you later or tomorrow.

 

i got home from school and mine started running terrible, loping while idle. real low idle, like 250

 

Unplug your EGR valve vacuum line & see if that clears the loping. If so, that's your problem.

Some other things to consider are:

1. Worn distributor. Can cause the problems you're talking about & be intermittent.
2. Wiring harness shorts. These are gettting OLD now and excess heat from the engine causes the harness to get brittle.

Good luck; it's a bear trying to track down this stuff on an older vehicle. Ask me how I know~

 

Is the diagram you're looking at on 4crawler's page for the 22re or 3vze?

Which manual are you looking at? In this manual?......

http://personal.utulsa.edu/~nathan-b...92volumeai.pdf

The pins are labeled the same/correctly. Note that on pg. 233 that the pins are labeled like this....

FC E1 (skip) VC E2 VS THA

On pg.234, they're labeled like this.....

FC E1 E2 (skip) (skip) VS (skip)

It all lines up the same, just take note of where the relevant pins are labeled and where irrelevant ones are not [= (skip)] on each page.

 

i murdered my egr in the parking lot of my school last night. i was taking it off to check the system, and it broke off at the lower threaded section of pipe! so i ripped the whole thing out, blocked off my ports with a few beer cans and some rtv, and limped it home, so now i can address the problem of extremely low idle (250-500rpm) that only shows up when the truck is up to temp. I've heard that could be the afm wearing out, along with a severely misadjusted idle screw and a misadjusted tps. any imput?

 

http://personal.utulsa.edu/~nathan-b...63troubles.pdf

I guess you didn't let that RTV cure before you fired it up and drove it, huh? Might need to that redo that.

 

I'm going to test my AFM again using the method in the 93fsm that has been linked to. Will the coolant temp sensor cause these same kinds of problems? Rough/low idle, surging while driving, ect.? Can the coolant temp sensor be unplugged while running like the TPS can to see if it helps?

When I unplug my TPS it makes no difference in idle. It still cycles between 850 and 500. It runs at 850 for around 20 seconds then down to 500 for about the same time, then back up and so on, back and forth, back and forth.

 

i actually let it dry out for three hours yesterday before i took it home. i had five hours between classes, i'm going to make a plate out of some stainless i have sitting at the house and gut my cat too( if i can).

 

Nope. You can't disconnect the coolant sensor and even halfway expect the engine to run. It'll fall flat on it's face. It's much like the AFM, in that respect. Very critical component.

The coolant sensor can definitely cause a rough idle, hard to start, but not so much "surging". I guess that depends on what you mean by surging, though. Aside from the AFM and coolant sensor, and since it is "surging", the fuel pressure regulator is another possibility. Fortunately, that's much easier to test.

Locate the vacuum line that actuates the regulator. With the engine running, clamp the line off with a pair of pliers and disconnect it from the regulator. Be careful not to tear it, though. In fact, clamp it off and use your other hand to pull it off. Anyway, take note of what effect this has. The idle RPM should rise rather noticeably since pressure has risen going to maximum. If nothing changes, the regulator is bad. This would indicate it's stuck and not responding to vacuum. Of course, the internal diaphragm could've also ruptured, creating low pressure and no vac response, but then you'd also see fuel in the vac line.

To test the coolant sensor, read this....
http://personal.utulsa.edu/~nathan-b...98engineco.pdf

Resistance should be high when the motor is cold, and low when it is hot. You can test it on the vehicle, but I think ideally you should test it in a pot of water and watch the meter as the sensor heats up. This way you can see if the sensor reponds smoothly to temp variation.

BTW, I got your PM. I'll have to look at the vid in the morning, though. I need some rest.

 

Not sure if gutting the cat's a good idea (performance wise), but heavier block off plates definitely is.

 

I just did that test. No change at all....nothing. I tried leaving the port on the fuel regulator open and closed off with my finger....nothing at all changed. No fuel was present in the hose. Does it make a difference that the truck was not at temp? It was a little warm from my morning drive but the engine was still at the high idle, not dropping to the low rough idle yet.

Most of the little hoses around the engine bay look bad. Some of them are cracking, some of them have spots that will mush with very little pressure. I probably need to change every hose under the hood.

But the fuel regulator hose looked like it was ok.




Update.....

The idle does raise when I disconnect the fuel regulator vacuum hose now that the engine is at temp.

I also decided to disconnect the TPS and go drive it around a bit. Well guess what.....the truck hasnt ran that well in a year! It accelerates smoothly, the idle is too high but its smooth, plus I even have some power when I push the pedal. It smells like its running a bit rich but it actually smells like the fuel is burning. Before it smelled like unburned fuel.

I'm sold...I'm going to buy a new TPS.