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2.8 cylinder not firing by Jecklen16
Started on: 11-30-2013 09:51 AM
Replies: 14 (234 views)
Last post by: Neils88 on 12-01-2013 06:15 PM
Jecklen16
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Report this Post11-30-2013 09:51 AM Click Here to See the Profile for Jecklen16Click Here to Email Jecklen16Send a Private Message to Jecklen16Edit/Delete MessageReply w/QuoteDirect Link to This Post
I started my 85 fiero gt 2.8 today for the second time after fixing the coolant temp sensor, and while waiting for the engine to warm up all of a sudden the rpm dropped a little and my engine started sounding like a chopper... It sounds like a cylinder isn't firing to me and I made all the checks as far as spark plug cables, distributor and coil and all look fine. Any ideas of what it could be and how to fix it?
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84fiero123
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Report this Post11-30-2013 10:23 AM Click Here to See the Profile for 84fiero123Click Here to Email 84fiero123Send a Private Message to 84fiero123Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Jecklen16:

I started my 85 fiero gt 2.8 today for the second time after fixing the coolant temp sensor, and while waiting for the engine to warm up all of a sudden the rpm dropped a little and my engine started sounding like a chopper... It sounds like a cylinder isn't firing to me and I made all the checks as far as spark plug cables, distributor and coil and all look fine. Any ideas of what it could be and how to fix it?


Could be any number of things, cracked plug, plug wire, or what I had once, a bad pickup coil, the wrap around it had all but disappeared and it had started to rust. just take the cap off the distributer and look at it, you will see it right away if that is the problem, the white coating will be missing and the wires themselves will have started to rust.

hope that helps, and I also hope that's not your problem because it is a pain to replace in that you have to pull the distributer.

Steve

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Technology is great when it works,
and one big pain in the ass when it doesn't



Detroit iron rules all the rest are just toys.

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Gall757
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Report this Post11-30-2013 10:53 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Swing down the fuse box and look at the INJ1 and INJ2 fuses......
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Jecklen16
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Report this Post11-30-2013 02:59 PM Click Here to See the Profile for Jecklen16Click Here to Email Jecklen16Send a Private Message to Jecklen16Edit/Delete MessageReply w/QuoteDirect Link to This Post
Okay so I started with the simple fixes, I checked all the fuses (all new by the way) and all passed my test light. I then removed the dizzy cap and rotor and used a wire brush to clean the rust off of the dizzy that connects to the rotor put dielectric grease on everything reassembled. Hooked up new spark plug wires but left the old spark plugs in and now all cylinders fire... that being done I know I still need to replace the old spark plugs, just dreading it as I heard it can be a PITA. Would spark plugs cause the engine to bog down when I floor it? Or is that most likely fuel pressure/fuel filter?
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Old Lar
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Report this Post11-30-2013 03:47 PM Click Here to See the Profile for Old LarSend a Private Message to Old LarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just use PB blaster or other penetrating oil on the plugs. The front plugs are usually the PITA ones. Mostly done by feel and whatever don't force them out as they could break off. When replacing them use anti seize grease on the threads.
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Fishogs 84
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Report this Post11-30-2013 09:59 PM Click Here to See the Profile for Fishogs 84Click Here to Email Fishogs 84Send a Private Message to Fishogs 84Edit/Delete MessageReply w/QuoteDirect Link to This Post
First, find which cylinder is dead. It will save you a lot of work later.
To do this, get a 20 oz Dr P bottle and fill with water. Put lid on & drill an 1/8 hole in lid.
As the engine warms up, dribble water on the exhaust manifold over each cylinder. Do not flood with water, a dribble will do.
If the cylinder is firing, the water will boil off, the dead cylinder won't boil, it will roll off.
Then you can check plug(s), wire, cylinder pressure, etc.

Saves a lot of work and heartache, if you know where to begin!
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Patrick
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Report this Post11-30-2013 10:05 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post

Fishogs, that's pretty clever. I've been working on cars for 40 years and had never heard of that trick before. Cool!
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Jecklen16
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Report this Post11-30-2013 10:07 PM Click Here to See the Profile for Jecklen16Click Here to Email Jecklen16Send a Private Message to Jecklen16Edit/Delete MessageReply w/QuoteDirect Link to This Post
Wow great info thanks!
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n7vrz
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Report this Post11-30-2013 10:20 PM Click Here to See the Profile for n7vrzClick Here to Email n7vrzSend a Private Message to n7vrzEdit/Delete MessageReply w/QuoteDirect Link to This Post
Another thing to do before you remove those front plugs. Shoot a blast of air around the plugs to dislodge any crud that might be down that hole with the plug. If you don't, the crud could easily fall into the cylinder or get between the threads of the head and plug when installing the new one.
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Neils88
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Report this Post11-30-2013 10:21 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Fishogs 84:

First, find which cylinder is dead. It will save you a lot of work later.
To do this, get a 20 oz Dr P bottle and fill with water. Put lid on & drill an 1/8 hole in lid.
As the engine warms up, dribble water on the exhaust manifold over each cylinder. Do not flood with water, a dribble will do.
If the cylinder is firing, the water will boil off, the dead cylinder won't boil, it will roll off.



Wouldn't pulling each plug wire off one at a time give the same result (no change in sound means it wasn't firing)...unless you're thirsty and need an excuse to down a bottle of Dr P....

[This message has been edited by Neils88 (edited 12-01-2013).]

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Patrick
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Report this Post11-30-2013 10:33 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Neils88:

Wouldn't pulling each plug wire off one at a time give the same result (no change in sound means it wasn't firing)...


One problem with that method, is that unless you take the extra step of grounding each plug wire as you take them off, you're risking damage to the coil.
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Slowbuild
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Report this Post12-01-2013 12:30 AM Click Here to See the Profile for SlowbuildSend a Private Message to SlowbuildEdit/Delete MessageReply w/QuoteDirect Link to This Post
Yes, pulling one at a time will do the same thing.

Also, instead of the water you can use an IR temp gun close up so as to be selective. I picked this up from working on diesels...no wires to pull ha ha. You use it to check the injectors etc.
Chay
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Gall757
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Report this Post12-01-2013 11:32 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Patrick:

One problem with that method, is that unless you take the extra step of grounding each plug wire as you take them off, you're risking damage to the coil.


Also risking damage to the ICM. Fiero ignition systems do not like this treatment.
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phonedawgz
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Report this Post12-01-2013 12:28 PM Click Here to See the Profile for phonedawgzClick Here to visit phonedawgz's HomePageClick Here to Email phonedawgzSend a Private Message to phonedawgzEdit/Delete MessageReply w/QuoteDirect Link to This Post
+1 it can damage the coil
+1 it can damage the ICM

Plus it can damage the coil such that the bad coil will cause repeated ICM failures.
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Neils88
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Report this Post12-01-2013 06:15 PM Click Here to See the Profile for Neils88Click Here to Email Neils88Send a Private Message to Neils88Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by phonedawgz:

+1 it can damage the coil
+1 it can damage the ICM

Plus it can damage the coil such that the bad coil will cause repeated ICM failures.


Good to know. I'll take that step off my old-school troubleshooting list...
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