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?
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
------------------ Technology is great when it works, and one big pain in the ass when it doesn't
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?
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.
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!
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.
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).]
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.
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
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.