guytranspo

I posted earlier that, occasionally, I am having an issue with a rough idle and white smoke at start up.
The car also died while driving at one point.
Other than that, the car runs great.

I've checked just about everything, but nothing seems to help.

Yesterday, however, a strange thing happened that might give a clue that someone might recognize.
The car started with the rough idle. I let it go and opened the hood. I remember reading somewhere that a voltage or pressure issue at the injectors could be a problem. With this in mind, I unplugged the #1 injector plug, and the car smoothed out. Of course, it wasn't perfect, as it was running on 3 cylinders, but there was a noticeable change in the idle. I plugged in the injector, and the idle was normal.
Does this make any sense to anyone?

By the way, the car started normally today and drove great on a 20 minute ride.

This issue is driving me nuts.

Thanks

T&T Racing

All 4 injectors plus simultaneously eventhough the electrical schematic would try to convince otherwise. By disconnecting 1 injector, the electric current draw was reduced allowing the remaining 3 injectors to pulse at their proper duration. I do not remember if you sent the injectors for cleaning and testing to an injector service such as SouthBay.

V2Rocket

pulse duration is controlled by the DME, not by circuit overall current.
the way these injectors work is a big surge of current to open the "valve" and then it drops off to a lower amount to hold it open as long as needed.

whats your idle speed set at?
how old is the O2 sensor?

max_boost951

Still have the original injector harness? They get brittle and Broken wiring under the boot may have been the issue and moving it around caused a better connection on injector one

guytranspo

Thanks for the input. The crazy thing is that it doesn't act like this regularly. It's very intermittent. I guess it could be a faulty, and not failed, injector.
I have not sent my injectors in. That will, likely, be my next move.

guytranspo

Thanks for the response.
The idle, after warm, is around 900.
The O2 sensor is about 5 years old.

guytranspo

Thanks for the response.
It is the original harness.
I guess the harness could be brittle. The curious thing is that the idle got better when #1 was disconnected. Maybe a short could cause this.
I will definitely check it out.

87944turbo

Is your coolant level dropping? Sounds like classic head gasket issue.

T&T Racing

The pulse duration is controlled by the DME but if there is increase in electrical resistance in the fuel injector wiring, the voltage drops at the injector coil solenoids and the internal valves does not open fully, ie less fuel injected. Sorry for not being clearer.

guytranspo

Thanks for the explanation.

guytranspo

Would the resistance in the wiring be caused by a faulty injector, or defect in the wiring itself?

Thanks

T&T Racing

Good question. To verify, check the resistance of each injector, if all the same, then proceed with the wiring.

guytranspo

The injectors resistance is right at 2.8 ohms each.
I'm not sure what the resistance of the wiring should be.

Also, not sure if you have any knowledge of this, but I rechecked for vacuum leaks today and found that there is a bit of a leak at the throttle body shaft. There is also a leak from the plug on the idle control valve. Is this something that I should be worried about?

I drove the car again today. It started right up, idled fine, and ran perfectly.

It's really starting to drive me crazy.

Thanks again for your input.

T&T Racing

Ohm reading for injectors is spot on. In my situation with no start and then OK start, the bottom line was the injectors fired OK and then did not fire OK. I had the injectors cleaned and flow tested. Test before and after showed lower flow rate before cleaning and flow rate at spec after cleaning. Southbay Fuel Injector Service did the cleaning and testing