psychoideas

to my 'no spark' problem?

Car always ran a bit rough and sluggish. I unplugged the oxygen sensor and it ran better, although a bit rich.
I plugged the sensor back in and the problem remained until on one trip I lost all power. It didn't stall but there was no throttle response off idle. I unplugged the oxygen sensor and the car could rev again.

I limped home and parked it up and ordered a new oxygen sensor.
Fast forward to today and it won't start. Battery very strong and it cranks fine but no fire.
I pulled a plug and found no spark while cranking. So,

Is this related to the oxygen sensor?
Is there another problem that stops it from powering the spark plugs?

I have wired in the new sensor but have not yet screwed it into the exhaust pipe.

Any ideas?

Van

If there's no spark, then it's probably the speed or reference sensor.

psychoideas

Thank you so much!
I'll investigate this after work.

Humboldtgrin

Speed/ref sensor is the first suspect. Second is the coil or power to it. Third is plugs, cap, rotor (spinning due to backed out screw), plug wires that may be arcing out. But most likely the shielding on one of your sensors has seperated and is not sending signal to the DME. I've had this problem this last May on the highway. Car started to hesitate then just died while driving down the HWY. I replaced the speed/ref sensors and it was fine.

odonnell

Surprised nobody has mentioned the ignition switch yet, it supplies +12v right to the coil. But if your DME is getting power, and consequently the injectors, it's not the issue.

Tom M'Guinn

Always worth checking the DME relay as well.

How did you check for spark? Be sure to use a know good wire from the coil output to a solid ground. Otherwise, what seems to be no spark could be a bad wire (or if you try at the end of a spark plug lead, then a bad cap/rotor, etc.)

Does your tach bounce when you crank it? If not, that points to speed/ref sensors.

When was the last time you changed your cap, rotor and plug wires? DME relays and (to a slightly lesser extent) speed and ref sensors tend to be yes/no parts, so if the car started running worse and worse until it stopped altogether, then that would make me lean toward things that wear out or otherwise get worse over time, like arcing rotors, bad wires, etc.

Does not sound related to the O2 sensor per se. By pulling the sensor you were changing the air fuel ratio and probably helping mask whatever was going on.

Sounds like a little more digging is in order...

mytrplseven

Then again there might be an issue with your speed sensor clearance to the flywheel....

Tom M'Guinn

Fair enough!!

psychoideas

Ok Guys!
First off I'd like to thanks you for all the suggestions.
I haven't driven the car much but when I got it I changed pretty much all the serviceable items except for the timing belts.

As it turns out when I was playing with the oxygen sensor I've unplugged the lower of the two plugs near it. Either the speed or reference.
The plug is very brittle and most of it is long gone. But I did plug the two ends back together and she fired right up.

Once again thanks for the help and remember if any of you get down here to NE Victoria you can come stay with us.

Tom M'Guinn

Ah, well, those connectors are notorious for getting brittle and fraying wires inside. New sensors come with new connectors, and for the connector on the other side, you can either just replace the connector itself or get a harness patch that comes with new connectors. 944online.com (for example) has all that.

Humboldtgrin

Good lord replace your sensors! When the words brittle and broken are used to describe the connections then that's the sign.