help 4age wont rev!?!?

[ep71]

trying to get an ae86 to run, the car will idle perfect but will not rev up. ive checked the timing with a timing light and it appears to be retarding the timing when i open the throttle rather than advancing. the car is after a full rebuild but the engine is untouched, any ideas?

[PatrickAE86]

car was fully rebuild but engine has not changed..

maybe bad ground cause of new paint?
old petrol in the gastank?
old / thik engine oil?
dirty aircleaner?

just a few things i made up..

[Ivan141]

Some wiring mistake perhaps... Did you get the sensors on the back of the head connected the right way round? [insult mode] Are your sparkplug cables attached in the correct order[/insult mode].
Just some thoughts.

[jondee86]

Are you sure your IDL switch is properly adjusted ?? When you short out
the diagnostic plug, does the idle drop and the timing drop back 5 or 6
deg ??

When you snap the throttle open quickly, does the ignition first retard
briefly, and then advance to a higher value ?? Or does it just retard, and
then come back to the starting value, without ever advancing ??

I have read about this problem in two other forums, but have never seen
any proper explanation for WHY... or HOW to fix it

Cheers... jondee86

[ep71]

by idl switch you mean throttle position sensor is it? ive tried at at different settings but it makes no difference. when i cross the connector between t1 and e1 it doesnt cut back the revs/timing at all
when i snap the throttle open it will rev up once ok but after that it will just retard and fail to rev up at all.
ive checked wiring on all sensors and its correct, plug leads are correct and new, ive tried different fuel pump, distributor, throttle position sensor and still it wont rev. ive ran diagnostics and get codes 7, 8 and 11

[Ivan141]

Checked all engine grounds? This is also a common source of weird problems.Especially the one on the inlet manifold gets overlooked often times.

[jondee86]

The IDL switch is part of the TPS. It goes open circuit when the throttle
butterfly is fully closed, and tells the ECU to change from the "run" fuel
map to the "idle" fuel map. It is one of the requirements that must be
met before the ECU will go into diagnostic mode. If you saw no change
when shorting the plug, then the ECU did not go into diagnostic mode.

You need to set the IDL switch with a feeler gauge as per the FSM. The
switch needs to change state as the throttle butterfly opens. If it does
not, strange things happen

Cheers... jondee86

[ep71]

how do you go about setting it? thanks for all the help also

[jondee86]

You have to take the TPS plug off, and monitor the two pins that carry
the IDL switch signal. The switch is open circuit when the throttle is fully
closed, and closes when the throttle is opened just a little bit. You adjust
it by turning the throttle stop screw with a feeler gauge between the
screw and the part of the throttle arm that comes to rest on the screw.

I don't have the actual figures with me, but it is something like the switch
is open with a 0.4mm blade, and closed with a 0.7mm blade. The actual
dimension is less important than the fact that the switch changes state
when the throttle is opened a fraction. You can check this with your multi-
meter while manipulating the throttle blade by hand (engine off).

This setting also affects the off throttle/on throttle transition while driving.
So it is a good idea to get it set correctly.

Cheers... jondee86

[ep71]

ok ive now set the tps perfectly, got the change in resistance when throttle goes from fully closed to slightly open, got timing set to around 10 degrees btdc, checked continuity between all tps wires and the ecu, cleared all fault codes and its now returning one flash every 3 seconds indicating that all is well but still she wont rev. its slightly better now and the timing retarding has stopped but still the engine will not rev up