I apologize in advance for the novel I'm about to write, but I think it is relevant for the diagnosis...plus it will eliminate some possible solutions if I have already done something that could have fixed it.

Background info.:
I have a '93 T/A with about 115K miles approx. It has had MSD wires put on it, a Meziere electric water pump, and K&N filter before I bought it (related to engine that is). I put a 3" Dynomax cat-back system on the car. I just installed long tubes (LPP copies from Ebay) and had to remove the oil cooler, hit my coolant temp. sender for the gauge and oil press. sender which I replaced in the process of doing the headers. I also put new Delco spark plugs in while I was in there. I put the heat sleeves on the spark plug wires (they cover about 6" of the end of the wire which is enough to protect any parts that may have been exposed to header heat). I had to put a union in the throttle bypass that someone before me did, but that really shouldn't have affected anything. I was very careful to drain coolant from the radiator and sender for the coolant gauge in a manor that kept it off the opti/distributor...but there is no telling about previous work before I bought the car.

Here are my questions now:
As soon as my header swap was done, it felt like it had no ***** below 4K rpms...which I thought would be somewhat normal as I just replaced the entire exhaust system from the manifold to the tailpipe, eliminating the cat., which would drastically lower my backpressure...resulting in less torque. I just wasn't expecting it to feel so dramatic. However, since then, I have also noticed it smells way rich, (but could be cause I eliminated everything emissions related including the cat) it backfires after I get off the throttle...usually from mid throttle or higher to zero throttle (figured it could be from the headers as well as they might magnify the sounds that may have already been there before), and it seems to misfire occasionally. I may be crazy, but the mis seems to be getting slightly worse the more I drive it. I could be paranoid too as I'm watching it like a hawk now. Could it be the opti? Would it gradually get worse or just die? It's is not bad either...just a slight little buck you can hardly even feel when it does decide to do it.

On a secondary note, about 2 weeks ago, I went to the store up the street, turned the car off, went inside. Came out, fired the car up and got about halfway home and the thing died. It was like it ran out of fuel or like the fuel pump shut off as when I went to restart it...just cranked. I finally pulled off to the side of the road, put it in park, cycled the key and finally heard the pumps (which I may not have heard as I was trying to restart it while still rolling before) and it started. Drove it home and never had an issue again. This is why I even question the opti.

Basically, the car ran fine before the header swap and I didn't really change anything and was extra careful not to get coolant on the opti/cap. However, that doesn't mean that the thing didn't just decide to die coincidentally either...especially since the car has 115K miles.

I checked to make sure the plug wires are all connected and they all seem to be on there, clicked in place...but one or two are pretty touch to really get leverage on, but they feel good. There's new plugs, sensors, coolant, cleaned the air filter, pretty sure the plug wires didn't get burned as I put the heat sleeves on from day one and didn't even fire the car until they were all in place. I use premium gas. Any other basic check things?

So what are the verdicts out there?

 

I know you said you checked the wires but check them 100% boot to boot side to side up and down. My friend had heat sleeves on his wires and still managed to burn on. One could be melted some could be arching. You could be pulling some retard from the LT's.

To check for arching wires take a spray bottle of water, with the car running spray the wires you will either see it or hear crackling from the water hitting the wires. Best to do it in the dark.

Might be due for a tune as well.

 

Yea, that was my next thought. I was worried that the longtubes might be messing with the knock sensor...especially if they are contacting the frame/chassis anywhere like they are on the K-member until I get new motor mounts. I was also thinking tune, but wanted to cover all the simple bases first...don't want to try and tune out a misfire if the problem lies in a wire or bad opti. Would it not being tuned allow a pretty consistent back fire like though? The backfire is separate from the mis as they happen at different times under different circumstances...the mis seems random and infrequent where the backfire can almost always be replicated under acceleration and immediate letting off the throttle.

I will check the wires at night next as well just to rule it out. Better to be safe than sorry and waste time trying to diagnose something elsewhere if the answer is right in front not being looked at :-p

 

My 94 TA kinda done the same thing. It started out with just a slight hesitation and got worse over time. I replaced the plugs and wires but no luck. Is it a six speed? If so put it in 6th gear running about 55 and mash the gas to the floor, if the car feels like the trans is going to fall out in the road, I would say opti. Also, is the check engine light coming on? Sounds like the opti to me but I am far from an expert.

 

No check engine light, but it is a '93, so OBD1 allows it run pretty terribly before deciding to kick on a light most of the time. It is an auto. so I have to be going over 45 to get lockout to feel for misfires...which I usually feel down low just the same as when in lockout, so I don't know. I will check the wires here one of these evenings to see if I have any arching issues and make sure the wires are on tight before getting too much further. If it is an opti, it's going to be a while before anything gets done about it. In fact, I will probably just yank the heads and intake off at that time and do the top end if that is the case...but no cash now, so that would be a long drawn out project there.

 

Another thought I was having...is it pretty likely that the stock cap and rotor could be the culprit or can they tend to last over 115K miles regularly? The kid before me replaced plugs and wires with MSD and Delco plugs, but I just realized in all his descriptions he never mentioned cap and rotor. Normally I would just replace cap and rotor with maintenance, but it is a little tougher to get to LT1 cap and rotors and I hear about many of these ignition set ups lasting into the 150K realm, so just thought I would ask before throwing parts and time at it if is more than likely something else.

This is from the same guy who must have bought the cheapest fuel pump he could find as the one he replaced his with was too small of a capacity, so I'm kind of glad he didn't replace the cap and rotor with some cheesy underpowered thing.

 

You can replace just the cap and rotor and it may or may not fix the problem. My advice would be go on ebay, find thepartsladi and buy a new delphi opti from her for like $285.

 

Yea, I ultimately would like to do that, but I am not in the position at the moment to be able to afford to throw parts at it right now. I wish this would have happened or shown signs of this issue before I threw on the headers and exhaust as I am now out of money and time for a little while. I think she will just have to sit for a bit until I have time and money again to tinker with it.