I have a 91n/a i've had a hunting idle for a while....i resently checked the leading coil plugwire with a timing light to check to see how they are firing....but the flashes aren't consistant....sometimes stops flashing for a sec or two then starts again and its seems rythmic to my hunting idle too....so i went and checked the trailing coil plugwire but it doesn't skip flashes at all, like the leading does.....Has anyone out there had this problem???????????

 

It's normal.


-Ted

 

how is that normal???? It seems that when there is no flash the engine misses and sputters????

 

Does anyone know what r the symptoms of a coil going bad or not working properly????

 

One of the coils fires all the time, the other fires like three times per rotation of the ecentric shaft. I believe the leading coil is the one that fires off and on, trailing constant.

Why are you checking the timing, what exactly is the problem with the vehicle?

 

Someone datalogged the output from the coil and found it it misfired every 4th or 5th spark.
I dunno if that thread was still around, but it was a few years ago.
This is probably due to the wastespark'd function, cause it's firing into two mismatched chambers - one is in full compression and fuel, while the other is decrease pressure and exhaust gases.
It's easier to fire a spark in the latter than the former.


-Ted

 

the main problem is i have a cycling idle under a load and someone suggested to check the coils.....iv'e replaced the bac....have no vacuum leaks....don't know what to do next????

 

and of course adjusted tps with the two leds

 

the idle cycles about 400 to 800 at idle with headlights on and brake pressed

 

could a coil do that????

 

I've got the same gremlin ... added fuel at idle on safc.. smoothed out,,, on ported motor tho

 

hmmm....where do u adjust that???

 

[QUOTE=joel91]the idle cycles about 400 to 800 at idle with headlights on and brake pressed[/QUOte

Ah. A clue. The first thing that came to mind is .......the idle on your car is set wrong. What is happening in my opinion, is that when you put the headlights on and step on the brakes, you put a load on the engine and the BAC is trying to makeup for the extra load by raising it's duty cycle and it can't make up the difference because it;s being stressed out. If the real idle was set to 750 (set with the bac out of the picture), then the bac wouldn't be so stressed out trying to keep a 750 idle.

Try this to disprove me. Warm the engine up and pull the bac's plug off. If the idle dropped to nothing then I"m right. If the idle more or less stayed within approx fifty rpm of the idle before pulling the plug off...then I'm wrong.

If it keeps cycling with the bac disconnected, then look for a vac leak or two vac hose being crossed with each other.

If that does not work....try one of the other answers that are sure to follow this one.

YOu might also tell us how low your voltage reading falls when the lights are on and the brake pedal is applied. This could be a voltage problem also. I noticed some time ago that low voltage , really low voltage plays havoc with the ECU somethiymes.

About your timing light issue. If your using a inductive clamp around one of the wires and only see the light flicker for a while then go blank, then flicker some more.........reverse the clamp on the plug wire and I'm fairly sure you'll now see a steady light. That's for lead coil wires. There is/was a factory service bulletin addressing the flickering timing lights. The factory service bulletins are online at ALLDATA.COM....for a small fee.

If you don't like that tack, let the car idle. Slowly and steadily pull one of the wires out of the lead coil bore. Notice how it arcs steadily and not like your light did?? Now you realize it's your timing light NOT the ignition that comes and goes.

 

ok cool ill check those...let ya know soon

 

ive had the alt off and had it checked its good when the idle cycles the amp gauge still says a round 14vs and the battery i had checked is good too...when i pulled the bac plug off the idle stays the same and it seems when i try to adjust the set screw for the idle on top of the throttle body it doesn't seem to raise the rpm any....i can lower it but not raise it past like 700....but ill check again for vacuum leaks....thanks again

 

Just Wondering Does A 91n/a Have An Egr Valve???

 

Please stop posting every few minutes. Either edit your previous post, or save up all your thoughts and post them at once.

The behaviour you observed for the leading is normal. Also, timing lights are not a reliable way to check for spark.

89+ cars don't have an EGR valve.

Your hunting idle is likely caused by a vacuum leak, TPS adjustment (use the resistance method, not the lights) or a bad BAC valve. In that order.

 

ok sorry....ill try that