Dknebes

I have recently installed a new Tec3-r on my 89 Turbo and can not get rid of an oscilatting idle from 700 to 1600 rpm. I am running full sequential and with some initial dyno pulls get 580hp at the rear 15psi. I have put in new injectors and a new fuel system and still have the same problem. I had a tec1 with tec2 chip before and did not have this problem. Rechecked the wires and have good fuel pressure. This is odd, if I set the initial timing at 6deg adv it seems to get rid of it. but it will come back at times. I know the initial should be 11 or 12 deg that is where it was before. I have tried the blend no help, worked the hell out of the VE and timing, and tried there new filter setting for idle, everything possible. I am running a crank fire and a 993 turbo dist for the sequential. Myself and the Engine builder think it is the Tec3r and are going to get a Tec3 and try it. This is a tuff one, I hope someone can give me the answer.

David

Geoffrey

First, since you are using the 993tt distributor for your sync signal, did you weld the distributor advance to prevent it moving with RPM? If you do not, it will change your timing as you increase RPM.

Second, are you running an idle air control valve? If you are, plug it off and disconnect it. Work the main ignition and fuel tables to get a stable idle while warm. This should be about 900rpm. Once you have it idling warm, plug the IAC back in and tune the IAC.

Some points of advice. Forget the MAP blend, this is for vehicles with unstable MAP signals which tend to be N/A engines with agressive camshafts, and/or engines with individual throttle bodies. I have yet to see a turbo engine that cannot provide a good MAP reference. You should see somewhere between 50-60kPa while warm, and it should be stable. I have seen unstable MAP signals at medium RPM and have solved it by placing a .030" restrictor in the MAP line at the maifold. This dampens the MAP signal. You can also put 20-25 degrees of timing in at 500rpm and 0-5 degrees at 1000rpm to provide a more steady idle. I have also at times drilled a 1/4" hole in the throttle plate with cars that do not have an IAC which allows more air in and a more stable idle.

Hope this helps. If you want you can send me your map and I'll look at it.

Dknebes

Geoffrey,
The IAC is blocked off and the kpa with the sequential inj is about 56kpa. I will look into the distributor to see if that was done but the distributor is used for the sequential for trigering the injectors. The blend was only tried as a last resort and did not help at all. The funny thing is this did not happen when the Tec1 was in. The timing was checked and zeroed at idle. The map signal is stable. Could the distributor being mounted so close to the crank fire cause some electrical interference? Thank you for your input it is appreciated.

David

Geoffrey

Since you are using the hall sensor in the distributor for a sync signal, IT CANNOT MOVE!!! If it does, then your timing will change. The distributor advance mechanism must be locked down. I doubt there is electrical interference but you can take your scope and look at the sensors to be sure.

Dknebes

I will check it tomorrow.

David

PorschePhD

Geoffrey is right. Forget the blend. Keep the IAC blocked off and adjust the TB to the point the car will idle on its own from the air coming around the TB. Then look at your maps at the KPA you are at. Make sure your map is picking up the RPM and KPA below the idle mark. If not as the car dips it drops off the map and will cause the idle to hunt until it can stabilize. I would also make sure that the O2 circuit is functioning properly. If the O2 is showing full rich and leaning the car out at idle doesn't seem to swing the O2 much either the O2 is shot or something is astray with the 3r. Both which I have seen. I will try to get the car to idle with the O2 off. Once the car idles on its own with no correction and the IAC off then go back and reestablish the settings for these. The biggest complaint and hardest part of the electromotive is not WOT rather partial throttle and idle.

Dknebes

Stephen & Geoffrey
Thank both of you for the input. The O2 was not hooked up and will only be used for data logging. The Iac was blocked of with a plate and RPM and Map was normal. The engine builder who is very, very good at this has worked with the timing and boxed it at low rpm and found a possible loose connection in the map plug. The idle has become stable and he will tune for a 18psi pull. I will post the dyno runs and a video shortly. I am not in the big boy power but should be a hair over 600hp at the rear. Thank both of you for your input, this can get frustrating at times.

David