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Discussion Starter · #1 ·
The # 4 cylinder on my 78 is not firing at idle. I have checked the plugs, wires, changed the injector, checked the valve lash, and the electrinic fuel injector connector and everything checks out fine. I changed the fuel injector plugs about a month ago and was running great until 3 days ago. would it make a differance if the wires were crossed on the injector plugs? I do have lower compression in that cylinder, but the miss came rather suddenly. Once the car gaines momentum it seems to run o.k.
 

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Can you isolate if your problem is due to fuel or spark?
You can check spark at the wire by taking it out of the plug (with the engine off, of course) putting a phillips screwdriver in and putting the screwdriver near (1/8 to 1/2) a good ground (I use one of the 3 strut bolt nuts)start the engine and look for sparks jumping from the screwdriver to the nut. If so, you have spark, if not... let's check injector pulse.
Buy an injector test light (it is really cheap, less than $10)and put it in the injector connector of the #4 cyl, again start the engine and look for pulsed light, if not, you have poblems with the wiring harness to the particular injector.
Did you say that other than idling the car runs fine?

let us know
CarlosZXT

> The # 4 cylinder on my 78 is not firing at
> idle. I have checked the plugs, wires,
> changed the injector, checked the valve
> lash, and the electrinic fuel injector
> connector and everything checks out fine. I
> changed the fuel injector plugs about a
> month ago and was running great until 3 days
> ago. would it make a differance if the wires
> were crossed on the injector plugs? I do
> have lower compression in that cylinder, but
> the miss came rather suddenly. Once the car
> gaines momentum it seems to run o.k.
 

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Registered
Joined
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107,695 Posts
Discussion Starter · #3 ·
> Can you isolate if your problem is due to
> fuel or spark?
> You can check spark at the wire by taking it
> out of the plug (with the engine off, of
> course) putting a phillips screwdriver in
> and putting the screwdriver near (1/8
> to 1/2) a good ground (I use one of
> the 3 strut bolt nuts)start the engine and
> look for sparks jumping from the screwdriver
> to the nut. If so, you have spark, if not...
> let's check injector pulse.
> Buy an injector test light (it is really
> cheap, less than $10)and put it in the
> injector connector of the #4 cyl, again
> start the engine and look for pulsed light,
> if not, you have poblems with the wiring
> harness to the particular injector.
> Did you say that other than idling the car
> runs fine?

> let us know
> CarlosZXT
With the engine running I can pull the # 4 plug wire off and it doesn't make a lot of differance in the way it idles , but it is getting spark, same with the injector plug wire. Can the control module be acting up? I checked the voltage on the control module plug according to the manual and that checked out o.k. I feel itis something in this area. Can a bad dist. cause a problem with just the one cylinder? Thanks for your reply, I'll keep you posted.
 

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Discussion Starter · #4 ·
> Can you isolate if your problem is due to
> fuel or spark?
> You can check spark at the wire by taking it
> out of the plug (with the engine off, of
> course) putting a phillips screwdriver in
> and putting the screwdriver near (1/8
> to 1/2) a good ground (I use one of
> the 3 strut bolt nuts)start the engine and
> look for sparks jumping from the screwdriver
> to the nut. If so, you have spark, if not...
> let's check injector pulse.
> Buy an injector test light (it is really
> cheap, less than $10)and put it in the
> injector connector of the #4 cyl, again
> start the engine and look for pulsed light,
> if not, you have poblems with the wiring
> harness to the particular injector.
> Did you say that other than idling the car
> runs fine?

> let us know
> CarlosZXT
With the engine running I can pull the # 4 plug wire off and it doesn't make a lot of differance in the way it idles , but it is getting spark, same with the injector plug wire. Can the control module be acting up? I checked the voltage on the control module plug according to the manual and that checked out o.k. I feel it is something in this area. Can a bad dist. cause a problem with just the one cylinder? It runs alot better when your driving but not exactly right. A little rough, but not real bad. Thanks for your reply, I'll keep you posted.
 
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