I have a 94 6-speed that I was having an intermittent miss and power loss with. Not knowing how old the Opti was and not really trusting it since I have 135k, I replaced it, plugs and wires. I still have the same problem now and am looking elsewhere. Could this be the coil and if so is it possible to check it? I will be checking fuel pressure tomorrow on the drive in to work to see if it's a failing pump. The car starts fine and doesn't starve for fuel at high rpms though so I'm leaning toward the coil. The car just hiccups once in a while and feels weak for short periods of time. Any help would be appreciated.

 

Hows your timing?If your not running enough octane your car could sputter as it goes into knock retard.Then it will feel weak until it resets.

 

I'm running 91 which is the best available to me here in Colorado.

 

The timing is all controlled through the computer I thought. The only way to change it would be to modify the program. Could it be a bad knock sensor retarding the timing?

 

Have you pulled the codes? Is your SES light on your DIC on?

 

I do not have any idiot lights on but I have not pulled codes yet either. I found the post with instructions for that so I will check that tonight too along with the fuel pressure.

 

my 93 had a slight miss when I bought it, now after replacing opti,wires, plugs, fuel filter, air filter , oil, tranny fluid and half a dozen sensors(not really, just coolant and O2), new u-joints, shocks and wheels!!!! I still have a slight miss, from everything I heard about 1st gen LT1's is that they will almost always have a slight miss....

 

I'm not to the acceptance point yet. I still think it's the coil or the fuel pump. I just want to do some more testing before I give up.

 

Don't automatically condem the opti. Check for stored codes first. If your miss is felt when the engine is under load, it may very well be the coil. That is a classic symptom of a coil on its way out.

 

It could be the coil as you stated. It could also be a bad O2 sensor. Just a couple of things I have seen. As others have stated pull codes and see what the ECM has to say. Good Luck.

 

There was a discussion like this on another forum... it's more then likely a burnt valve... Just a little "piff" every so often.

Don't worry about it.

 

I have a 94 A4 and I went thru HELL....trying to
correct the same issue that you have!!! here is what was wrong with
my vette.......1) burnt wire in harness ....cause lean condition with O2
sensor ( right ) replace three before mechanic solve
problem
2) O2 sensor went bad in three month ( lasy )..could
not believe it...but I change it again problem solve
3) ONE YEAR LATER MAY 16th..." service engine soon"
light .....check code 64 on forum ....lean rigth 02
well I already knew what to do ..I replace 02 sensor
and found out something interesting...the connects was not making good contact and the
readings were not matching the other 02 mechanic
straighten that out and " BAM " No miss she runs like
you will not believe.......Hope this help!!!
P.S. MY vette has 130,000miles and I relaced opti 15,000 miles ago

 

A burnt valve isn't serious?

 

My '95 has always had a slight roving (random out of either pipe) "pffft" at idle but only at idle, immediately off idle it is smooth.

 

not really... it's simply age. The engine won't run right, sure, but it will continue to run.

It's much like artheritis(sp). Sure, you don't run right, but what can you do? It's annoying, yes, but I would not stop and rebuild the motor tomorrow because of it.

It will get worse, yes, but it will take a long time for it to be a problem.

 

Is there a way to check the oxygen sensor if the wiring is good? I have no idea how old the sensors are so I guess it wouldn't be a bad idea to replace them, but I don't want to throw money away either. The coil is cheap too, but I would like to check it if it's possible. Is the 3rd sensor behind the cat on the passenger side the dummy one?

 

I have a slight miss at idle also. Replaced opti (but I knew it was bad), coil, wires, and plugs. Now the miss is intermittent. I think this is really weird; I’m at one stop light and it runs like a clock the next it has the same miss it always had. Could this still be a burnt valve? Ignition module?

I wouldn't drop the money into the opti unless that is definitely the problem. Those things are expensive.

 

My 95 had the opti, water pump, plugs, wires, coil, intake gasket, all replaced @ 27,500 miles (approx). The car was under GMPP ext warranty and I had taken it in for the idle "pfftt" miss, even though it was not real noticable. Dealership then replaced all that under the warranty. Thing is, it never showed symptoms of bad opti such as the higher rpm miss, etc. But who was I to turn down getting all that work done for a $50 deductible out of my wallet? After it came out fo the shop from all that: same idle "pfftt". Tech eventually proclaimed it to be "nc" on a later receipt, for "Normal Condition-- explained to customer". They had scoped it, found nothing out of spec.

Car has about 40,000 miles now and the roving "pfft" in the idle exhaust note is still there. Somethings's causing it because you can watch the engine slightly shake momentarily when it does it. But only at idle.

Search F-body forums and Impala SS forums (the real SS's, the mid 90's models that had LT1's) for "idle miss" and you'll quickly see that it seems to be a "characteristic" of a lot of LT1's.

I've since (the 27,000 dealer re-do) went to after market spiral core plug wires and AC Rapidfire plugs several thousand miles ago, and it made no difference.

I've checked for vacuum lines leaking until blue in the face and everything is in good shape. I've thoroughly cleaned the EGR valve, no help. I didn't block off the EGR port while I had the valve off cleaning it, to check, but the valve closes all the way every time anyhow.

Replaced oxygen sensors last fall, no help.

What I'm getting at is I don't think the "problem" is worth chasing, unless it begins to migrate up the rpm band and you start getting hesitation or stumble.

 

I actually don't have a problem at idle, it's random during acceleration like a hiccup, and sometimes it feels like I'm losing power and then it comes back on top of the hiccups.

 

Fuel filter?
Sticky injector?