trouble with idle

[doom26464]

ok latly the car seems to have a problem with ideling. But this is only in between warming up. The car idels fine when it is first started for awhile and when it is perfectly warmed up But inbetween this when it is warming up it idels like crap. Revs bounce around 700 too almost stalling at 200. It almost stalls the check engine and battery light turn on but then it regans revs again to 700 and then slowly bounce back down. Does anyone know what conrtols the idel or where to start with this problem???

 

[aye mate]

Check the codes. Sounds like a bad AFM.

 

[doom26464]

Check the codes. Sounds like a bad AFM.

i have no codes to check though.

 

[aye mate]

i have no codes to check though.

Meaning you already jumpered the T and E1 terminals in the diagnostic box, turned the key to the "on" postition and the Check Engine Light was blinking steadily?

 

[Justin727]

Vacuum Leaks. Did U Check Yet?

 

[tonysupra]

I had rough idle after I did my head gasket replacement. It only happens after a warm start. . . (like if i drive for awhile and turn off the engine and then i try to start it up, the idle will go up and down). . .it doesn't do it as much anymore since I did the stock AFM mod. I put the screw in the afm all the way out and it idles good now. But i'd check the afm.

 

[SupraDreamPDR]

my idle was jacked up when i first bought my Supra... i went through and replaced all my vaccum lines and any other hoses i could get my hands on. it idles fine now.

 

[Bishop92t]

The Check Engine Light (CEL) only comes on with a very few select codes that Toyota deemed bad. Most codes the car gets won't even throw the CEL, you have to actually check the codes to find out what's wrong. Could be bad AFM, TPS, ISC, maybe even O2 sensor, that's why you need to check your codes to find out more info.

 

[doom26464]

The Check Engine Light (CEL) only comes on with a very few select codes that Toyota deemed bad. Most codes the car gets won't even throw the CEL, you have to actually check the codes to find out what's wrong. Could be bad AFM, TPS, ISC, maybe even O2 sensor, that's why you need to check your codes to find out more info.

I know how to check codes im not a newbie to the supra world. But my check engine light doesn't come on, it blinks on for only a short second but its the same as if u stall the car the check engine light comes on right? so its doing the exact same thing. mabye it is giving me a code but I will give it a try and c what it reads if not i dunno what else to do.....

 

[lagged]

erm whenever the cel is illuminated a code is thrown. just because it dosnt stay on dosnt mean there is no code.

 

[doom26464]

well i checkecd codes and they where codes 25(Air-Fuel Ratio Lean Malfunction) and code 26(Air-Fuel Ratio Rich Malfunction). I tried switching out the afm from a 88 turbo but it still ran the same so the afm is not the problem. I bought some throttle body cleaner and some fuel injector cleaner and hope it might help if that does nothing then im stuck.

 

[jetjock]

Those codes signify your 02 sensor is out of range for longer than the ecu allows.

 

[Nick M]

I think you should look at the engine coolant temp sensor. You can still "ohm out" correctly, and have a bad sensor.

The sensor uses high resistance when cold, and low when warm. You might have an inbetween problem. I know the resistance is backwards from what you think, but that is the way the sensor is designed.

 

[doom26464]

so what your saying is I should get my oxygen sensor or my temp sensor replaced???

 

[doom26464]

any other suggestions guys?? I did order a new set of vaccum lines from suprasport but if that doesn't fix it i dunno what will:aigo: :1zhelp:

 

[NashMan]

to cheak isc just unplug it

 

[jetjock]

You shouldn't just throw parts at the car, especially since it's telling you what the problem is.

Measure the O2 sensor signal at 1500-2000 rpm when the engine is hot. The codes you have indicate it's stuck at either at full lean or full rich. Find out which it is and go from there.

If it's stuck rich (around 800 mv) pull a vac line or the brake booster line and see if it swings lean. If it's stuck lean (around 100 mv) inject propane or squirt some carb cleaner into the brake booster line. See if the sensor swings rich.

The sensor could be bad or it could simply be doing it's job by responding to a lean or rich condition caused by some other problem in the engine. Doing this test tells which it is. It you can make it swing rich and lean the sensor is good and the engine itself is the problem If you can't make the sensor swing the sensor is the problem. Pull it out and test it further with a propane torch.

If it's swinging between rich and lean at least 8 times in 10 seconds with 450 mv as the center point everying is OK. Course, if it were doing that you wouldn't be getting codes 25 and 26 in the first place.

Since your complaining about a bad idle I suspect your sensor is good and your engine is bad. I say that because a bad O2 sensor won't effect idle. After all, everytime you start the car the O2 sensor isn't involved until it warms up. You have other problems but fix the code related ones first. Is gas mileage poor? I'm guessing it is.

 

[doom26464]

You shouldn't just throw parts at the car, especially since it's telling you what the problem is.

Measure the O2 sensor signal at 1500-2000 rpm when the engine is hot. The codes you have indicate it's stuck at either at full lean or full rich. Find out which it is and go from there.

If it's stuck rich (around 800 mv) pull a vac line or the brake booster line and see if it swings lean. If it's stuck lean (around 100 mv) inject propane or squirt some carb cleaner into the brake booster line. See if the sensor swings rich.

The sensor could be bad or it could simply be doing it's job by responding to a lean or rich condition caused by some other problem in the engine. Doing this test tells which it is. It you can make it swing rich and lean the sensor is good and the engine itself is the problem If you can't make the sensor swing the sensor is the problem. Pull it out and test it further with a propane torch.

If it's swinging between rich and lean at least 8 times in 10 seconds with 450 mv as the center point everying is OK. Course, if it were doing that you wouldn't be getting codes 25 and 26 in the first place.

Since your complaining about a bad idle I suspect your sensor is good and your engine is bad. I say that because a bad O2 sensor won't effect idle. After all, everytime you start the car the O2 sensor isn't involved until it warms up. You have other problems but fix the code related ones first. Is gas mileage poor? I'm guessing it is.

hmm how do I go about measuring the o2 sensor??? my gas mileage isn't exactly poor and the engine did have the entire tope end rebuilt less then 10,000 km ago. I will try unpluging the isc sensor and c what that does.

 

[jetjock]

There is no ISC "sensor" You mean the ISC valve? All that'll do is freeze the idle speed at whatever it was when you unplugged it. If the engine still hunts you have other problems.

Measure the O2 signal in the diag block, there's a terminal there just for that. Look at your TSRM for info. It means squat your top end was rebuilt because you have an EFI mixture control problem. Your lambda (mixture trim control) loop isn't working.

Fix that first and deal with idle after. Course, both may be related. If the sensor is stuck lean you could have a vac leak for example. That'd give you codes and a high idle. Shouldn't make it surge though.

 

[isnms]

that broken bvsv is a big leak
oh, wait, never mind. he said it was connected directly to the charcoal canister.