Hi Guys, not the first time but it seems my idle is playing funny again!
I have recently cleaned the throttle bodies and removed and reinstalled the throttle cable and new throttle linkage. After that i found that the car will:
Rev keep climbing up and down from 1100rpm- 1700rpm even i m off throttle completely and this problem is intermittent. It seems this problem become more serious when the car is stuck in traffic and or in slow speed.
Could this be that i cleaned the throttle bodies too clean that when all dirt is removed then there is air leak from the butterfly?
Please kindly share your thought and I am planning to take off the TB and send to Titan for complete rebuild.
I would normally expect a leak or throttle butterfly gap to give a constant higher revs, how fast is the cycling? Do you still have an idle air control valve and did you fit an Emerald? If you have an emerald you can hook up a PC and it should give you some hints.
Spray something around the throttle bodies and see if the rpms change - if you use brake cleaner, be really careful how much you use, as it can get really exciting!!
Make sure that the idle throttle stop is what is actually stopping the butterflies - if it’s holding on the cable it goes back to different places each time, if the idle stop isn’t touching, the same result happens.
Make sure that they’re balanced as pairs. Same deal as carbs, they need to be open the same amount for each pair, or individually - but don’t think the Titans can be set individually. Ideally you want a proper balancer, but same result can be had from a bit of pipe if you have decent hearing.
As a base set up with the engine off, disconnect the cable so it’s free from the top mount, wind on a load of idle screw, then run a bit of something - 2mm welding wire used to a good start - between the throttle housing and the butterfly on one pair, then make sure it’s the same on the other side, and adjust to suit on the centre linkage. Then start and wind the idle speed back to something sensible. Don’t drop anything down the throttle bodies!!
If you have an Emerald, make sure that the throttle position is reset once you have done the above, then you may need to tweak the idle speed up or down, and repeat until your happy.
Then refit cable, with a small amount of slack, and adjust down stop at the pedal to make sure you’re not using the throttle bodies as your full throttle stop.
And if you’re really keen, get rid of the mess at the pedal and fit a late S2 type cable. So much better.
From memory you can delete the IACV from the system and from the Emerald software, then use the Emerald to adjust the idle speed with ignition timing. Depending on how (well) its been set up, it can make the idle speed jump all over the place.
But you may have upset the throttle settings, balance across the throttles, idle stop and the throttle position sensor. At a minimum you will need to recalibrate the tps as the idle position may have moved.
Generally for an engine to speed up and slow down it needs changing amounts of air, that is how throttled engines work. Changing the fuel and/or spark timing also has an effect but not that great. Looking for leaks with a spray is a good idea but I would not expect a leak to change cyclically and make the engine hunt.
Look at the emerald reading and see if it is trying to control the idle speed (in idle mode). Check the tps reading is steady (should not budge). If you look at the highlighted boxes on the fuel and ignition maps you will see it staying in the same load column/row but the rpm load/row will be changing as the engine hunts.
If you edit the column it is hunting in to have a constant fuel rate and spark advance you will confirm if the mapping is making it hunt or something else.