Rough Ideling

[nellys gto]

hi guys iam new to this forum i have a 1992 sc400 the motor hunts and races all started last week hit kick down and it took off then its like it had no power. when i shut it down left it for a minute fired up again all was well, it would only do this it you accelerate quicklly. then it would do this hunting. i was told to replace the afm which i did but made no difrence what so ever. when the car is hunting if i disconneted the afm it runs perfect. know it will not idle propply with the afm plugged in. ive done a check on the ecu arfter clearing the codes. and all it said is efi ng then 2 dashes no codes came up.

has anyone ever come across this before. any help would be greatlly appricated.

many thanks neil

[James Horning]

Check for any vacuum leaks AFTER the air flow meter, cracked hoses at the throttle body or the large hose at the throttle body .

With the engine hot and idling , gently wiggle the harness connector at the AFM and at least 14" from the connector end with your thumb and index finger,notice if the engine stability changes.

[Steve]

I would do what James suggests.. check engine mounts for wear as the engine can move about more which in turn will put streess on the hose after the air flow meter

[nellys gto]

thank you both very much ive checked for vacum leaks on the small line but to no avail ill check out the big pipe had a similar problem with my tiburon that turned out to be the big intake pipe. ill try and plug the afm back in and woble the wires and see if this makes any diffrence. again thank you both very much will keep you posted on how i get on.

regards neil

[UCF3]

Sorry, I haven't read through what you've done already. Is it possible you still have bad fuel in your tank? Have you tried using dry gas?

[nellys gto]

Sorry, I haven't read through what you've done already. Is it possible you still have bad fuel in your tank? Have you tried using dry gas?

hi mate ive tried diffrent gas and still the same problem this is what ive tryed if changed the tps still the same ive swapped the fuel pump ecu still no change ive tried another motor ecu still the same and ive changed the afm still the same, ive not checked the big intake pipe as of yet because when i get of work it is dark and at the moment the weather is very wet here. but will check the big air pipe over the weekend.

regards neil

[UCF3]

Sorry, I haven't read through what you've done already. Is it possible you still have bad fuel in your tank? Have you tried using dry gas?

hi mate ive tried diffrent gas and still the same problem this is what ive tryed if changed the tps still the same ive swapped the fuel pump ecu still no change ive tried another motor ecu still the same and ive changed the afm still the same, ive not checked the big intake pipe as of yet because when i get of work it is dark and at the moment the weather is very wet here. but will check the big air pipe over the weekend.

regards neil

How about the spark plugs. On my old 2JZ the valve cover gasket leaked water after I cleaned the engine bay. Had to remove all the oil and excess water and made this rattling noise.

Any chance you could record the sound on video?

[nellys gto]

Sorry, I haven't read through what you've done already. Is it possible you still have bad fuel in your tank? Have you tried using dry gas?

hi mate ive tried diffrent gas and still the same problem this is what ive tryed if changed the tps still the same ive swapped the fuel pump ecu still no change ive tried another motor ecu still the same and ive changed the afm still the same, ive not checked the big intake pipe as of yet because when i get of work it is dark and at the moment the weather is very wet here. but will check the big air pipe over the weekend.

regards neil

How about the spark plugs. On my old 2JZ the valve cover gasket leaked water after I cleaned the engine bay. Had to remove all the oil and excess water and made this rattling noise.

Any chance you could record the sound on video?

hi mate sorry unable to post the noise up throught you tube all i can say is the revs are up and down and some time will hols a rev at approx 1500 rpm then will drop it but while it is still huntingine check all the plugs there is big plastic covers on v8s so no water can ingress the ht leads/ spark plugs. just got off work right know will check what has been posted by other members and give them a go.

regards neil

[UCF3]

Oh, one more thing. See if you can find an idle control valve. That might be the cause.

I remember our friends at Planet Soarer once did a write-up on it.

http://www.planetsoarer.com/IAC/iac.htm

[nellys gto]

hi all problem solvedturned out to be the iacv. i changed that and a new temp switch and so is back to normal giong to drive her a bit gentlly for a while to let the egu learn its new operating setting. i appricate all of your responses. :)

many thanks neil