But just to confirm: There is no adjustment for the fast idle speed?
Regards
Bernt
I thought we covered that before? You can adjust idle speed with the idle speed screw. Screw it in and the idle speed may not be as fast. In fact engine should stall if it is warmed up. Screw it out and idle speed should go up. If idle screw does not have much of an effect, then you are leaking air in. Then you "adjust" high cold idle speed by finding where air is leaking into intake manifold:
- through AAV that is not fully closed or
- through several hoses that could be disconnected or
- Connections between upper/lower 1/2 of intake manifold (harder to detect) and
- make sure throttle plate is fully closed at idle. If someone messed with linkages to throttle plate thinking that was how idle was adjusted, that could leave throttle plate slightly open. That could also mean that the TPS is not signalling to the ECU that car is at idle, which would affect idle mixture. (As Trog suggested)
Read everything in the section in EGV107 on Djets. It has a section on rebuilding a TPS. It explains how to adjust TPS. May not be your problem. It also has an original Bosch trouble shooting guide for EFI that includes explanations of how some things work.
Get your car running "like a sewing machine" again at 800rpm.
Disconnect the linkage to the throttle plate and see if rpms change. They should not if throttle plate was closed.
With engine idling, screw the idle screw all the way - engine should stall. If it does not, air is leaking in.
Try squeezing the inlet or outlet hose from the AAV so as to prevent any air flow through AAV. If rpms drop, then AAV is not closed fully.
Check for disconnected vacuum hoses at back of engine (to locking system and transmission) as well as one that starts at throttle body and goes to distributor via a switchover valve. Also check the hose that goes from back of engine to MPS.
Read everything you can on Djets! Lots of stuff on net. Acronyms are described somewhere in EGV107, but here are some:
AAV - Auxiliary Air Valve
TPS - Throttle position switch
MPS - Manifold pressure sensor
ECU - Electronic Control Unit? (The computer!)
Surging also known as sawing occurs when rpms go above about 1500rpm at idle. ECU then cuts off fuel through injectors until rpms are below about 1000rpm, then switches fuel back on and keeps repeating this, but only at idle. If you don't see this, as Trog suggested, linkages and TPS may have been messed with and TPS is not signalling to ECU that engine is at idle.
Get back to us once you have done some testing along the above lines.