Closed Loop Absent

Started by JonB · Aug 24, 2010 · 11postsSMF 2010–26

JonBAug 24, 2010, 10:38 pm · #1

I don't have a closed loop at idle; Aren't I supposed to?

I have it at part throttle cruise though.

Here's the problem, It idles rich. It sorta progressed, where it would take a few seconds after I parked, then go to an acceptable A/F ratio, but now it's nuts(stays rich).

No problem codes on the ECU, says everything is OK.

Goes rich when I mash the throttle, cool. Goes lean when I decel, cool. When I cruise and it needs alittle throttle, closed loop, cool. When I'm not on the gas, not deceling, or idle; open loop, rich, not good.

When I check the two LEDs for mixture, when the ECU is not in diognostic, they don't flash at all, nothing. Is this because it's not in closed loop? Diognostic doesn't say the AirFlow is bad.

TPS is set correctly I believe. Circut closed at idle, open when I touch the gas.

Any ideas?

alundraAug 24, 2010, 11:12 pm · #2

Same problem.
I checked some parts despite the fact of not having the codes. I found that my idle valve air regulator doesn't have the continuity as mentioned on FSM. Check the resistance of your oxygen sensor to.

How do you know than you're rich? Because vacuum leaks decrease mileage.

JonBAug 25, 2010, 12:04 am · #3

alundraHow do you know than you're rich? Because vacuum leaks decrease mileage.

Air/fuel gauge, smell, and black soot in parking spot where tail pipe is.

JayAug 25, 2010, 12:13 am · #4

JonBAir/fuel gauge, smell, and black soot in parking spot where tail pipe is.

Stuck injector? Close loop is only active during warm up period, and hard acceleration.

Your gauge reading sounds normal to me...
Mashed = rich = good
Decel = lean = good
Idle = Should be bouncing slowly = not good
Cruising = Should be bouncing faster = not good
Slow accel = should be kind of irratic, but bouncing

Sounds like to me that it's during open loop (Cruise and idle) that it's not leaning out the mixture properly. indicative of a stuck injector, vacuum leak, or the computer not getting the signal and dumping. But seeing as the ECU isn't throwing an 02 code, I'm going to lean towards stuck injector.

Another thing to check is the cylinder head temp sensor... those things cause all sorts of janky problems while not throwing a code

JonBAug 25, 2010, 12:31 am · #5

I just checked the resistance of the water temp sensor, and the wires to and from the ECU; They were good.

Could be a stuck injector, how could I check that, and/or find which one. Am probably pushing the cycle of the injectors. Pull a plug and look for an extra special black one? Would it be able to manage the closed loop like it does at part throttle cruise with a stuck injector?

I'll check the idle valve tomarrow.

Wish I could just take it to someone; I'm lazy and tired, but no one will touch it. I'll just have to fight through it. It's a bunch of old, crapy, and delicate electrical components attached to a 25 yr old hunk of iron, coated in road grime; It's amazing it works at all sometimes.

Thanks guys.

JonBAug 25, 2010, 12:45 am · #6

I'm also going to spray everything with ignition sealer tomarrow to see if theirs a vaccume leak. Anyone ever try that?

When the boost is on vac, it's rock steady at 20in. I was sorta thinking that meant no vac leaks; that's not necessarily correct though huh?

Spraying ignition sealer sounds so easy.

JayAug 25, 2010, 1:05 am · #7

JonBI just checked the resistance of the water temp sensor, and the wires to and from the ECU; They were good.

Could be a stuck injector, how could I check that, and/or find which one. Am probably pushing the cycle of the injectors. Pull a plug and look for an extra special black one? Would it be able to manage the closed loop like it does at part throttle cruise with a stuck injector?

Not the temp sensor, the Cylinder head temp sensor. It's completely different, and frustratingly hidden. behind the timing belt...

Checking the injectors is simple. Grab a good long screwdriver, put the metal end on the injector, and put your ear to the plastic handle. You'll be able to hear clear as day one that isn't ticking, because it's usually the one you say "I dunno, I can't tell" too

Also, if one was stuck open, You could do it by pulling the connectors off. look for the one that doesn't change anything. But be careful with the old ass brittle connectors
Black spark plug works to

Part throttle isn't closed loop. Should be open loop and bouncing. Not rich

JonBAug 25, 2010, 1:21 am · #8

There's two temp sensors; One goes to the gauge, the other to the ECU. I checked the one to the ECU. There is no third, is there?

Closed loop is when it's bouncing; The ECU is reading the O2 and making adjustments so many times a second, which is why the gauge "bounces"?

Should be doing that at cruise speeds, and I think idle, but not mashin' the gas or on decel(where the gauge should read steady (rich on the gas, lean when off the throttle and using the motor to decel)because of open loop. Or do I have that wrong?

JonBAug 25, 2010, 1:21 am · #9

JayAug 25, 2010, 1:35 am · #10

JonBClosed loop is when it's bouncing; The ECU is reading the O2 and making adjustments so many times a second, which is why the gauge "bounces"?

Your raising a doubt on my knowledge about the temp sensors. On my 20e the CHTS was behind the timing belt, and that little guy made it impossible to start on cold morning because it dumped WAAAAY too much fuel in. I needed to use starting fluid every morning

Edit: WOW

I cannot believe I have gone this far without knowing something so simple as that........................................ .....................
Your right for the open and closed loop terminology.
We're talking about the same thing, but MY terminology was backwards....

alundraAug 25, 2010, 6:42 pm · #11

You can also clean some units screwed on intake manifold agf check EGR by finger, engine stopped, idle and slow accelaration -you need to be 2 to do this, besause you need to let a finger on it, diaphragm on the bottom.