Well, I am getting a little stumble from time to time. I am not throwing any misfire codes, just P0400 for the EGR(heard it COULD cause a stumble). It can happen at any RPM, but usually when I am maintaining speed or slowly accelarating from a stop I notice it. I changed the engine oil, tranny fluid and rear diff fluid this week and didn't notice any chipped teeth on the gears or anything like that(all Mobil 1). I have a MSD coil I put on last summer and still have the original lying around, but I am wondering if that matters(might give it a shot, it was still good, I just changed it to change it). I am taking the car to Florida next week and I don't want it to die on the road somewhere.
Oh yeah, I did plugs and wires at the beginning of april when I did my headers. Oh yeah, when it stumbles, it's not really noticeable except to me and the tach needle doesn't fluctuate at all.
Any thoughts?
Mods below:
!CAGS, TB Bypass, Jet-Hot Long Tubes, Off road y-pipe, NGK TR55's, MSD SuperConductor wires, Russel OTVC Looms, Hooker Super Comp Catback, Air Foil, LT-4 KM, B&M Ripper Shifter, SLP Shift ****, MSD Blaster Coil, Hypertech 160°, Fan Switch, Holley Power Shot Air Filter, De-Screened & Ported MAF, De-Grilled Air Box, LT-1 Aluminum Pedals, WS-6 TB Plate

 

Okay, here goes, take notes please!

It's probably the Opti, and, it could be a few other things as well, so here goes.

I'm ASSUMING that it only happens when the engine is warm, correct? If this IS the case, then you could do a few things first, like:

New plugs &/or wires.
New O2 sensors.
Clean or replace the EGR valve.
check for vacuum hoses with tears, or replace all of them anyway, it wouldn't hurt, that's for sure! Some of the vacuum paths don't start working until the engine is warm anyway, so maaaaaaaybe. This may also tie in with the O2 sensors and EGR valve, so changing all of them wouldn't be a bad idea.

If it stammers when it's either cold OR warm, then:

Change the fuel filter...Have you changed it recently?
Fuel pump...How many times have you run out of gas in your car? Even if only once, running out of gas damages the fuel pump.

What's the odometer reading? Is it close to 100K? Do you have the factory cat? The dealer suggests that the factory cats last for approximately 50K, however lots of 4th-gen f-body owners have theirs for over 100K. A clogged cat does not make LT1 happy. You have an aftermarket cat, so this isn't the reason, nor is your MSD coil, those coils kick butt, especially over the factory coils. Don't go back to the factory coil.

After you figure out what to change, and you do change them, AND it is still trippin when it reaches normal operating temps? Then guess what???

It's the Opti.

Should you need to replace the Opti, DO NOT BUY USED OR TRY TO JUST REPLACE THE CAP & ROTOR, buy a new one, LT1's likey new ones. Get a new waterpump as well, you have to take the waterpump off anyway to replace the Opti, so WTF??? Might as well do it at the same time. Change the plugs too, wouldn't hurt!

I think that's about it. Good luck!

IMHO, if it only happens when your car is warm, then 20 bucks says it's the Opti.

 

Lets see, I have no cats(long tube headers with AIR and EGR), O2 sims in the rear, new front O2 senosors, new plugs/wires, Fuel pump was replaced in February and I know not to run out of gas with it. Fuel filter was changed a week later. The odometer reads 66,XXX. Guess I'll attack the EGR and vacuum hoses tomorrow.
Thanks

 

If it happens most in direct drive(4th) and at low RPM(-2000) when you aren't accelerating, it's completely normal. I've had that 'problem' since I got my Z years ago. Years later still nothing replaced except the EGR as part of normal tune-up and the 'problem' is still there. My car rolled over 142K this week and still on the first Opti. People tend to exagerate how bad the Opti is and replace it at a pin drop because it's such a bad design it must be what's wrong. 4th gen f-bodies run rough in comparison to a luxury sedan, 'butt to pavement' feeling and all.

If it's just a minor buck that doesn't even budge the tach, leave it alone. These are the sort of thing we manual peeps have to feel, while our automatic friends have it eaten by the converter.

If you feel you absolutely have to spend money to fix this... might I suggest a new cam? Make it nice and bucky everywhere That or you could get your hands on a MAF that still has its screen intact

 

Like they say, it could be the opti but....
first go back a double check your wires. I would suspect them first since your install with headers was in April. Maybe something moved and just now got hot/close enough to become a problem. Good luck.

 

Wouldn't have anything to do with my partially burnt through throttle cable? Maybe a 1/3 of it has burned though cause the cable ties broke and it was laying on the header. I put a header wrap on it for the time being and re cable tied it out of the way.
Oh yeah, checked the wires, they are fine. EGR tomorrow.

 

Hey man, my car is doing the same exact thing. I haven't been able to scan the code yet as it only seems to come on when it's not being scanned, just my luck. I was thinking egr as well. Please post after you change it. I'm praying that's all i need. Good luck!!!