4AGE Bigport idling problem - sometimes

**Dimmy** · 30-04-2007, 07:32 PM

Hey guys, i've tried searching for an answer and have also tried finding the cause on the car but still unsure of what can be causing it

Basically, the car heats up and idles normally ~900rpm although sometimes after some driving and coming to a stop, the revs would drop off and it would idle at ~600 and i'd have to keep the revs up to stop the shakes. Also, if im coming to a stop and go from a gear into neutral, the revs drop below 500rpm and it stalls

So far i've cleaned my spark plugs, air filter, raised the idle a little ~100rpm, and checked the alternator which puts out 14.18V.

I've noticed it mainly happens after sitting in traffic and the car heats up just over 1/2 way, and ANOTHER thing which may help is that the revs drop & cluster dims when i press the brake which make me think it can be a earthing issue

Any other ideas???

Any help would be much appreciated

**TooF** · 30-04-2007, 07:55 PM

most probaly ISCV.
http://toymods.net/forums/showthread...ght=clean+ISCV

**Talasas** · 30-04-2007, 07:57 PM

Hmm, I've got this same problem at the moment after a fresh rebuild on my smallport. I notice if I ease the revs up to about 1000 it'll idle okay after that until next lights.

The cluster dimming just happens from the revs dropping a little low and the alt not outputting enough current at that point, my ammeter dips a little when this happens too.

My temp gauge also shows temps up near the 1/2 way point, I've take off one of the cooling fans and a turbo is sitting there so I figured that would have been the main reason.

I have an exhaust leak and have been stuffing about with the ECU lately so I figured it was just needing to settle again. I went over and checked all the sensors and some voltages and everything is set up beautifully.

Would be good to know what this is as a mate had this issue with his SR20 and it still isn't fixed as far as I know. :S

I should add this was just the 30kms the car had done without any boost.

And actually one thing does come to mind, I had had the throttle cable bracket installed because I couldn't find it so the only thing holding my throttle cable in place was some Cable Tie Performance. I've since found it and adjusted it, haven't been out for a drive to check if that was it though.

**Dimmy** · 30-04-2007, 08:30 PM

mine is also freshly rebuilt, turned 5500km today

Thanks toof i'll look into that

**oldeskewltoy** · 01-05-2007, 01:44 AM

I've had similar problems with AFM TVIS type engines. I've fixed this by cleaning the idle circuit in the throttle body. I also keep a spare complete throttle body - including the TPS and swap them out when the problem begins.... once swapped I do a complete throttle body service, then I keep the cleaned one for the next time the problem occurs.

Another issues I've encountered is the idle usually needs adjust 2-3 times a year. these adjustments usually are required when the tempurature change occurs. This doesn't sound like your issue since you say the engine frequnetly idles correctly

**lunar_c** · 01-05-2007, 03:29 PM

I have been having the exact same problem with my 1986 Twin Cam 16 / early Big Port 4AGE.
I just did a full service and while I was at it I pulled the throttle body off and cleaned it up with solvent and blew out all of the air passages for the idle bypass / ISCV with compressed air.
Resealed it with a home made gasket and the problem has gone away.
Also check simple things like air filter / fuel filter /fuel pressure but since it's a newly rebuilt engine I'd say it's just crud in your throttle body.

Edit : the 1G ISCV in that thread looks nothing like the one on the 4AGE big port .. so I'll try and help as best I can ..
Mark the hoses so you know which one goes where when it comes to putting it back together. Then pull it off the manifold and take a look ..
The ISCV is the round tube on the lower portion of the throttle body ... it also has the coolant hoses running to it .. there's a wax plug in there that expands when hot so when cold the idle is higher cos the bypass is open .. and when hot it closes letting less air through lowering the idle (from my rough guestimates from looking at it) .. blow a whole lot of carby cleaner through the ports in the throttle body and scrub everywhere you can see crap and wipe it dry then blow out the passages with compressed air.
If you can be bothered .. open it up and clean it properly but this method worked fine on mine!
Good luck
Regards,
Ben