Idle issues - don't know what else to test

[7M-GTEric]

Alright guys, I set out today to try and find the root of a few problems I thought might be related; after a day of work, I'm more confused than before, and I'm out a $50 accordian hose till Tuesday :3d_frown:

So here's the problem; I had to replace my battery recently after the car sat without being driven more than once every 2 weeks or so for 4 months. Ever since then, I've had idle issues. It doesn't want to idle at 650; it usually starts to lope and sometimes even dies, so I set it higher to around 1k and that worked alright temporarily. To make this even worse, the A/C idle-up isn't working (also recent), so if I don't set it to 1k, it usually bogs down @ idle w/the A/C on.

Here's what I've tested thus far (as per TSRM)

Diagnostic check turned up a code 51;
checked TB for sludge; normal PCV blow-by
checked TPS sensor (w/o removing, checked resistance)
checked TPS signals @ ECU (w/o car running)
checked clutch start switch
checked A/C switch
checked A/C signal @ ECU
checked ISC (w/o removing, checked resistance)
checked VSV for heater core (had intermittent heat when A/C on)
checked VSV for FPR
checked every vacuum hose I could get my hands on
checked IC piping (ruined accordion hose while I was at it :icon_evil)
replaced PCV hoses, a couple other bigger vacuum hoses
replaced coupling btw. 3000 pipe and throttle body

Everything I tested turned up OK according to TSRM values. I didn't remove the TPS or ISC b/c they've never been tampered w/and I figure if they cleared the resistance tests, they're working fine? I did discover the EGR system seems to be clogged up; I guess I'll have time to clean that up, now I tore the accordion hose right @ the turbo inlet meaning I have to order another from Toyota and it won't be here till Tuesday. I haven't gotten to start the car so I don't know if anything I did worked, but I'm kinda doubtful.

Anyone have any suggestions? I'm kinda at a loss if it's not fixed...I'm hoping it was just a vacuum leak...:1zhelp:

 

[jetjock]

A good place to start would be the code 51. Assuming it's from the TPS (it usually is) as long as it's there the idle speed control system will be disabled.

 

[YotaRob]

Mine did the same thing when the iac went out. resistance will be fine but its stuck and messing with the idle skrew makes things funny thats why it was later removed from the TB.

 

[7M-GTEric]

Mine did the same thing when the iac went out. resistance will be fine but its stuck and messing with the idle skrew makes things funny thats why it was later removed from the TB.

Hmm...so were you able to fix it? I'd imagine all the blow-by over the years might be the culprit...

 

[jdub]

I'd like to know how you "set it higher to around 1k"?

 

[JDMMA70]

^
Im guessing he advanced the timing

TPS would be a great place to start

I got my car to idle and not die but it was still slightly rough, came to find out i didnt have the check valve inside the ISC

 

[jdub]

Either that or he messed with the "idle" screw some early TB's have...that is not good :3d_frown:

The code 51 has to be fixed 1st or the ECU doesn't go into idle speed control like JJ said.

 

[ForcedTorque]

You also didn't mention timing it with a light in your list. Fix the 51, and then recheck that timing.

 

[7M-GTEric]

I'd like to know how you "set it higher to around 1k"?

I set it higher by adjusting the screw on the throttle body; I had to do something to remedy it temporarily, as this is my DD.

I didn't check the timing; I'll have to do that once I get it running again, but last I checked it was dead-on. That was a while ago though...

Everything I've done already was either in response to the code 51 or some other problem I thought I'd check out while I was "in there"; code 51 calls for no IDL signal (TPS), no NSW (clutch start in my case) signal or no A/C signal (which I figure is why the idle-up doesn't work). Regardless, even if my TPS tested alright according to the TSRM, you guys still think that might be my problem? How would I go about diagnosing it aside from testing the resistance?

 

[jdub]

Well, as you found out, that idle screw doesn't do squat for you...the ECU will just signal the ISCV to change your idle. It is set from the factory and should not be adjusted.

This is how you set the TPS:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

A gumby method is to jump the diag block and turn the TPS until the code 51 goes away.

If the AC switch is depressed or you press the gas pedal, you will always get a code 51.

You cannot correctly set timing with a code 51 present.

 

[7M-GTEric]

Well, as you found out, that idle screw doesn't do squat for you...the ECU will just signal the ISCV to change your idle. It is set from the factory and should not be adjusted.

This is how you set the TPS:
http://www.cygnusx1.net/supra/Library/TSRM/MK3/manual.aspx?S=FI&P=101

A gumby method is to jump the diag block and turn the TPS until the code 51 goes away.

If the AC switch is depressed or you press the gas pedal, you will always get a code 51.

You cannot correctly set timing with a code 51 present.

Ah, gotcha on the ECU changing the idle; I'm obviously still learning about the electronics. I wish I'd never changed the screw on the TB now...

As for setting the TPS, it's still got the factory yellow paint on the screws; I don't see how toying with it will help anything, as it's clearly where it's supposed to be. If the resistance test showed it was working, is there another way to test it? The TSRM would have me believe it works simply off resistance in accordance to the throttle position?

The codes should be cleared right now b/c I disconnected the ECU a few times today, so if I get it running tomorrow I'll check again, this time being sure of the A/C switch. Hopefully then I can check timing. I'm leaning towards the TPS more and more though...

 

[jetjock]

As for setting the TPS, it's still got the factory yellow paint on the screws; I don't see how toying with it will help anything, as it's clearly where it's supposed to be.

 

[7M-GTEric]

Well, I got it running again today. I ended up patching the accordion hose. I think it'll be fine until/if I decide to buy a new one.

Other than that, I went ahead and replaced my air filter and added a few hose clamps on critical items that had the stock ones and it would SEEM that I've got the idle problem fixed; it musta been an air leak. At this point, there's no more code 51 (can't imagine why, I didn't "fix" anything that pertained to it, unless the A/C was on when I tested it...), and after driving for 80 miles tonight, it only acted up a time or two. The idle's still a tad bit high, but I suppose I can live with that.

Thanks for your help guys-I'll check over everything again in a few days, but for now I'm just tired of workin on it and ready to drive it! haha