Here are the pictures of my current set up. Witch runs good when cold but the miss still comes back when it comes up to running temp.
This is good troubleshooting info. Many times knowing all the ways that an engine will work correctly can help us eliminate some
of the possibilities of what is causing the engine to misbehave at specific times. By the way, I fully believe that an engine can
run well cold but misfire when up to temp. More on this in a minute.
But I do have a question for you. In your first reply (#4) you mentioned that you have a misfire "after installing the Autozone tune up parts".
The following makes a big difference in our troubleshooting. Which of the 2 categories below does your scenario fit into:
A) The engine was running fine prior to the parts swap, but started misfiring
after installing the Autozone parts?
-or-
B) The engine was misfiring prior to the parts swap, and after the Autozone parts were installed they didn't improve the misfire?
(Unfortunately, as many in here can attest both scenarios are quite possible these days.)
looks like I got 80K on the fuel filter, I have read somewhere that this may cause a random misfire so I will change that out next.
This is straight up a good preventive maintenance practice -- a win no matter if it fixes your random misfire or not.
I concur with changing that fuel filter asap.
New Dizzy and ICM, New Cap, New Rotor, New Wires, New plugs, New EGR valve, New IAC valve, it is not throwing any codes.
The only thing I have not replaced is the Coil but It did check out OK with an volt meter test. Are these coils noted for creating a miss when they warm up ?
Schurkey's guidance on the coil is spot on. Anything high-voltage (especially vintage high voltage) is pretty much guilty
until proven innocent. Conversely, it's never been easier to buy brand new, out of spec problematic parts that are not as good as the originals.
Check your coil carefully per Schurkey's recommendations, and IF you decide to change the coil do yourself a favor and don't buy the
stuff that's literally the 'too good to be true' price. (Especially if the ebay & Amazon parts also happen to be available on Alibaba. (!)
****
OK, now to further discuss the 'good cold, misfiring hot' thing.
IF the engine was running fine prior to swapping the Autozone parts in, then the highest probability is that
you received one of more parts that was bad out of the box. (Sometimes bad QA by the parts vendor, other times
a part is returned by a previous customer and they unknowingly wounded it, sometimes invisibly.)
EDIT: This has happened to me so often that I now take each part out of the box and look for 'witness marks'
showing evidence of previous installation? If I see these telltale marks, then I ask for a different one...especially
if the parts store is a long distance from home base.
But if your engine was running this way before the parts were changed and still no joy, then let's work through
what your engine uses cold, and what gets added to the mix once everything is up to temp.
Since your '94 is a TBI, with the exception of the EGR valve everything you have listed above is involved
and working as advertised when cold. Once the engine coolant temperature approaches normal operating
temps, the EGR valve will start operating under computer control. IF you have the
exact right EGR valve,
then adding this into the mix shouldn't adversely affect the driveability. But as with everything else, a lot
of incorrectly-spec'd parts are being sold these days. Be sure to verify that the vacuum opening in your
new EGR valve matches your old one. (There are 4 good photos shared by a forum member that really
clears this up.
EGR valves calibrated for smooth OEM-style transient operation.)
****
OK, if you are still reading this then I'm going to assume that you have verified that you have good fuel pressure
(post fuel filter change) a good coil, and have verified that your new EGR valve meets the OEM spec? Then
it's time to talk about Open Loop vs Closed Loop operation.
Open Loop is how the GMT400 engines run A) when the O2 sensor(s) is not up to temp, or B) during
WOT operation. IF the engine operates smoothly cold, and then after 2-3 minutes from a cold start
it's like somebody threw a switch and the rough running starts, then it could be that the O2 sensor
got switched in, and now instead of the fuel injector duty cycle being set by the factory tables, now
the fueling is being 'fine tuned' by the feedback being reported by the O2 sensor(s).
With a
healthy O2 sensor, going from Open Loop to Closed Loop operation is the equivalent of
going from fairly precise to really precise operation. Obviously, if your O2 sensor is old, tired, lazy, etc.,
this is where a marginal O2 sensor takes a smooth-running engine and messes up the drivability.
Garbage in from the O2 sensor = PCM (ECU) garbage fueling calculations.
Since they live/work in such a harsh environment, O2 sensors are just like tires & spark plugs -- they
are a wear item. NOTE: If your O2 sensors have been recently changed, verify that they are one
of the brands that plays nice with the TBI computers. Some do, many don't.
(And I mention the O2 sensor because it's not on your changed parts list.)
****
And IF your wires, coil, fuel filter, O2 sensor(s), etc., are all good and the driveability issue persists,
then here we have to stop and gird for battle.
Simply put, in order to fix from this point on we need the computer's perspective on what's going on.
Schurkey and others who've been around the block are going to be asking for live data, O2 crossover
counts, short and long term fuel trims, misfire counts by cylinder, etc. This *is* fixable, we just need
to be able for the computer to show us the data, and then we follow that data to guide us in the direction
of the highest probability fix.
One last thing. Even in the pre-computer, pre-feedback loop days, every once in a great while we'd
have to troubleshoot an engine that ran fine cold, but rough when fully up to temp. (Not nearly as often
as when the engine ran poorly cold, but fine when up to temp.)
If after ensuring that the spark & fuel systems are 100%, then we'd have no choice but to venture down
the path of a possible mechanical issue. (Think valves not always seating 100% of the time as they rotate
when opened and bad spots mesh, etc.)
But not to worry about that at this time. Please let us know if your problem commenced with the Autozone
parts installation, or was the problem already showing, and the Autozone parts just didn't make a difference?
Apologies for the length, but there's a lot of moving parts in this misfire scenario, so I thought a good
overview might be helpful.
Best of luck. Let us know what you find.