Contour Enthusiasts Group Archives Forums Modifications 3.0L Duratec 3.0L Drop in Surging problem

I am a newbie here so please forgive that. I have read some of the posts on the 3.0L performance and I didnt see any with the problem I am having. I have a 1995 Mystique, formerly A2Steve's, with a 3.0L conversion done. I believe it is running 19 lb injectors with the stock 2.5L ECU. The problem I am having is that it seems to be running very lean from idle to 3000 RPM and the car surges, the CEL is on for lean on bank 2. I would maybe like to put a differenct ECU in it but being a 95 pretty much every place I called to see if they can make a custom one for it said I am SOL because it is ODB-I not ODB-II. Are there any quick fixes, i.e. injectors or other bolt ons, that would remedy the situation?

Thanks for your time

Kurt Kiefer

Find out what is causing the problem rather than throwing random parts at it. That won't do anything but lighten you wallet.

Ditto! What he said.

Try looking for a vacuum lea first, or a bad O2 sensor on that bank second.

Alright, over the weekend, I removed the IAC, cleaned and lubed it, inspected all the intake manifold gaskets and retorqued it according to the rebuild instructions on the site here. The motor still seems to be running lean from idle to 3000 rpm. The O 2 sensors were mentioned in one post, is there any way to test to ensure proper working order of these? Any other ideas are welcome.

Thanks

Kurt Kiefer

You need an obd scan tool, most will support the late OBDI as well as OBDII. Then you can check out your O2 sensors to see if they are switching normally. If you are running lean on one bank and not the other then it is likely a vacuum leak from the lower intake on down, a bad O2 sensor on that bank, or one or multiple fuel injectors not firing.

Oh, and when I say a bad O2 sensor, that means its up you or whoever is doing the checks to check the plug for corrosion or the wires for missing insulation, etc. Not just say "oh its a bad O2 sensor". Troubleshoot that circuit for that bank on the car and make sure it is operating properly or at least in good condition. If the sensor is not switching very much or is swithing but the average voltage is low, you'll get a lean indication even though the air fuel may or may not be off by much.
If it were an injector, troubleshoot the wiring before replacing it.

I would like to thank warmonger and tourdeforce for all the advice, after thoroughly inspecting the vacuum system I found a crack on one ports leading from the intake manifold. A little plastic weld and voila no more surging. Thanks again

Kurt Kiefer