Diagnostic box questions and running issues.

[cWs306]

Hello, okay well i have an issue that seems like a vacuum leak, the car idles and runs like crap and eventually dies out but i cannot find any vacuum leaks or anything leaking. but heres the weird part. if i shut the car off, jump the diagnostic box ten to ground and start the car. it runs perfectly fine, like no issues what so ever.
so what do you think my issue is here?
what exactly does the diagnostic box do when i jump it from ten to ground? im so confused because it was running fine like 3 days ago.

[mikeinaus]

as far as i know the car goes into diagnostic mode. from what i understand of that timing is changed, it affects idle and i think it runs on a minimum of sensor inputs. are you getting any codes? normally our cars run worse in diagnostic mode, its funny your having the opposite effect. but if i am correct in thinking it runs on a basic set of inputs from certain sensors it would make sense that one of your sensors is malfunctioning.

[cWs306]

ohhhhhh okaay, that makes sense. and yah thats what i was thinking too. it runs like a top when its in diagnostic mode. i wonder what sensor would cause this problem to happen. because it runs and boggs and struggles to stay running then just dies out. way it dies is it seems something gets cut off. i dont know, theres no weird noises or anything and theres no check engine light at all. ive wiggled every hose and listened for any type of hissing sound. everything seems to be there visually.

[crazycanadian]

ohhhhhh okaay, that makes sense. and yah thats what i was thinking too. it runs like a top when its in diagnostic mode. i wonder what sensor would cause this problem to happen. because it runs and boggs and struggles to stay running then just dies out. way it dies is it seems something gets cut off. i dont know, theres no weird noises or anything and theres no check engine light at all. ive wiggled every hose and listened for any type of hissing sound. everything seems to be there visually.

I would possibly think AFM, coolant temp, TPS, could be the area of problem..

[cWs306]

Would a KL02 maf run better with a kl36 ecu? or should i stay with the JE50?

[RX8SE3P]

No, the KLZE ecu's will need JE50. If you use a KL02 it will idle like garbage and stall a lot.

[cWs306]

ohhh okaay. yah im having that exact issue right now. thought maybe i was backwards haha. trying to figure out my problem.

[cWs306]

Would my idle screw being bottomed out give you guys any ideas on whats wrong? i was thinkin about it and that doesnt seem right to me.

[RX8SE3P]

Put it in diagnostics mode, then undo the idle screw. Should idle at around 550-700. Idle should not change massively once your finished in diagnostics mode.

It definitely should not be bottomed out... you mean closed all the way?

[cWs306]

yah, for me to have my idle at 550-750 its 99.99% closed. other then that anything else itll be 900+.

[cWs306]

Can i drive my car while its in diagnostic mode?

[mikeinaus]

High idle suggest a vacuum leak. Its also possible the idle stop screw needs to be adjusted. Have you taken your intake off and looked At the butterfly valve in the throttle body? Its possible its being obstructed by buildup stopping it from closing. In diagnostic mode ID expect the car to run rich and have poor performance but I don't see it causing any problems.

[cWs306]

okaaay, well i replaced all my vacuum hoses and couplers on my intake so there cant be a leak there. intake gaskets and tb gasket r brand new. and honestly, i think my CEL is burnt out.. because im sure it would be going off right now..but it isnt lol.

[mikeinaus]

does the light come on with the key on but car off? if not your bulb is burnt like you said and should be replaced.

[cWs306]

yah, no theres no light what so ever.