 Missing Diagnostics, ... know what cylinder - did I miss anything? |
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| vesnyder |
 Aug 3 2006, 01:37 PM
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#1
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Senior Member  Group: Members Posts: 680 Joined: 14-April 05 From: Cleveland, OH Member No.: 3,933  |
I've been having a sporadic missing issue for about a week now and I cannot figure out what it is? I am cheap so I started with the things that were the cheapest to repair. Just ordered a new distributor cap and rotor, but here are the other items I've already checked.
- Checked the valves. I had just done my first valve adjustment and may had screwed it up - looked fine - Tested the injector and cleaned it out - appeared to work fine? - Replaced the spark plug. Solved the problem, but only momentarily. - Checked for signal to the spark plug by putting one of those lights in the spark plug circuit. Looked OK. Any chance the spark from the dizzy is not strong enough? Next solution is to install the new cap and rotor on the distributor. Did I miss anything? |
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| So.Cal.914 |
Aug 3 2006, 02:43 PM
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#2
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"...And it has a front trunk too." Group: Members Posts: 6,588 Joined: 15-February 04 From: Low Desert, CA./ Hills of N.J. Member No.: 1,658 Region Association: None |
QUOTE(vesnyder @ Aug 3 2006, 12:37 PM)  I've been having a sporadic missing issue for about a week now and I cannot figure out what it is? I am cheap so I started with the things that were the cheapest to repair. Just ordered a new distributor cap and rotor, but here are the other items I've already checked. - Checked the valves. I had just done my first valve adjustment and may had screwed it up - looked fine - Tested the injector and cleaned it out - appeared to work fine? - Replaced the spark plug. Solved the problem, but only momentarily. - Checked for signal to the spark plug by putting one of those lights in the spark plug circuit. Looked OK. Any chance the spark from the dizzy is not strong enough? Next solution is to install the new cap and rotor on the distributor. Did I miss anything? If you have points don't forget the condenser, A arching sparkplug wire can cause a miss. |
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| Bleyseng |
Aug 3 2006, 06:19 PM
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#3
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Aircooled Baby! Group: Members Posts: 13,034 Joined: 27-December 02 From: Seattle, Washington (for now) Member No.: 24 Region Association: Pacific Northwest |
Clean all your grounds...
under the relay board Tranny ground strap battery terminal and bolt to body |
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| drive-ability |
Aug 3 2006, 06:39 PM
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#4
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Senior Member Group: Members Posts: 1,169 Joined: 18-March 05 From: Orange County, California Member No.: 3,782 |
QUOTE(vesnyder @ Aug 3 2006, 12:37 PM) I've been having a sporadic missing issue for about a week now and I cannot figure out what it is? I am cheap so I started with the things that were the cheapest to repair. Just ordered a new distributor cap and rotor, but here are the other items I've already checked. - Checked the valves. I had just done my first valve adjustment and may had screwed it up - looked fine - Tested the injector and cleaned it out - appeared to work fine? - Replaced the spark plug. Solved the problem, but only momentarily. - Checked for signal to the spark plug by putting one of those lights in the spark plug circuit. Looked OK. Any chance the spark from the dizzy is not strong enough? Next solution is to install the new cap and rotor on the distributor. Did I miss anything? ***** Under what conditions does the problem accrue be specific please. (IMG:style_emoticons/default/clap56.gif) |
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| swl |
Aug 3 2006, 07:57 PM
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Senior Member Group: Members Posts: 1,409 Joined: 7-August 05 From: Kingston,On,Canada Member No.: 4,550 Region Association: Canada |
Vance it really sounds like you have a bad connector somewhere. Do you have enough slack with your spark plug wires to swap the one on the bad cylinder and see if the problem follows the wire? Jeff already mentioned the ground cluster. The other electrical I would be checking is the lead to the injector. This can be done by removing the connector to the ECU and putting an ohm meter across the appropriate connectors. Should be low resistance. Have a helper wiggle the wires and see if you get jumps on the meter.
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| vesnyder |
Aug 4 2006, 07:05 AM
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#6
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Senior Member Group: Members Posts: 680 Joined: 14-April 05 From: Cleveland, OH Member No.: 3,933 |
Thanks for the help. It does appear to be electrical and very random. It has been very hot around here and could be heat induced? Having recently pulled the motor I cleaned up all the grounds and they should be good! I will check the points and condensor - except would bad ones only affect one cylinder? Will alse check the injector wires, except that the fuel delivery seemed OK when I pulled the injector? Not sure about the slack in the wires - will check and see if I can swap wires or borrow one and test it? Thanks again?
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| swl |
Aug 4 2006, 07:17 AM
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#7
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Senior Member Group: Members Posts: 1,409 Joined: 7-August 05 From: Kingston,On,Canada Member No.: 4,550 Region Association: Canada |
I agree about the points and condensor - hard to imagine how they would effect one cylinder unless that cylinder was already marginal.
The randomness really makes me think it is a bad wire. As you troubleshoot you disturb the wire and fix/break it. |
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| lylegd |
Aug 5 2006, 02:13 PM
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Newbie Group: Members Posts: 49 Joined: 19-August 04 From: Fort Collins, CO Member No.: 2,574 |
Vance, the spark plug connectors have a resistor built into them. Use a VOM to measure all four connectors and see if the cylinder that is missfiring has a higher resistance then the other wires. You may have to do this twice, once with a cold engine and again when its hot.
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