LT1 is a little sick...

[GREZ28]

Well, I have a 95 Z28, not a daily driver (collector). I took it out today for a little cruise to a car gathering at Fuds in Turnersvile.. Car started to run rugh on me on the way, shaking at idle like I have a cam, but when I cruise its fine at a steady spead, press the gass, shakes and no oumf like it use too. U could feel, and hear the diference in the borla also. Anyway, when i start to slow down to a light backfires on me ones in a while.. No smoke.
I cant really think of what it could be.. Exhaust system borla, catco cat conv, edelbrock headers. Headers about 2 yrs old and that is when I did my platnm plugs and wires (Taylor)..
1 more thing that I could think of, maybe cause my car sits alot, I might have build up on the f-injectores. :-?
Anyone have any ideas or have experienced something like this?

[ar0ck]

Opti

[Firebird67dude]

Opti


I second that.

[bad64chevelle]

Opti...and then the platinum plugs...

[GP99GT]

4th on the opti

[GREZ28]

I guess the opti will be a pain in the a$$ to do hu.. Now is there anyway to know for sure if that is causing the problem?

[WildBillyT]

I'd start with the plugs. Are they Delcos?

[GREZ28]

No delcos for me. I went Bosch double plat on my car.. But in 2 yrs to go on me like that? How about the coil?

[GP99GT]

bosch plugs...change them

[GREZ28]

Well I guess eather way I will have to start with the plugs...
I dont like the idea about it cause this will be a pain to do on the LT1. I would rather do the opti than plugs if I knew it was that... Has anyone been able to it without trying to take other things apart to reach them? One side looks ok but pasenger side might be a pain.:|

[Firebird67dude]

Well I guess eather way I will have to start with the plugs...
I dont like the idea about it cause this will be a pain to do on the LT1. I would rather do the opti than plugs if I knew it was that... Has anyone been able to it without trying to take other things apart to reach them? One side looks ok but pasenger side might be a pain.:|


Do you have headers on the car? I have edelbrock shorties on mine and numbers 6 and 8 are the hardest to do. I forget what my boss did but he checked the opti with some consistancy thing? IDK, anyhow, Until you can get completely sytuck witht he car you can't really rule anythign out. Coils usually just crap out while the opti will do exactly what you discribing. The ICM might be going too. I just relapced everything on my car. Opti, wires, plugs, coil, and ICM.

[GREZ28]

Icm.. Another thing to ad to my list now..:willy:
67dude your making it harder on me damn it!!!:hammer:
Anyway, yep I have the same headers... How did you make out?

[j0n]

http://shbox.com/1/4th_gen_tech2.html#opti_test

plugs aren't too bad...just need to get creative with universals and extensions. also helps to kneel on the intake manifold

[hardline_42]

I just did the plugs on my LT1 yesterday. I did every single one from above except #7 (got it out from above but couldn't thread the new plug in). The hardest one was #8 (from above) because it's right by the O2 senor (stock manifolds) and it's tough to slip a ratchet on it. I used the plug socket and an open ended wrench on the end with wrench flats. I suggest you get comfortable sitting on the intake. It's actually pretty comfortable and the hood provides some shade. Standing next to the car leaning on the fenders is useless. I had Auotlite 106's on it and I swapped them for NGK TR55's. Stay away from Bosch's.

If the Opti has to get swapped and it's your first time, give yourself a good 2 days to do it. I suggest getting an Opti from www.all-ignition.com. I got a brand new Delco Opti with an upgraded cap for $150 and it's running strong since I installed it.

Another thing to check are the plug and coil wires. Mine were in pretty bad shape with some of the terminals rusted out. If you're gonna swap them out, I suggest getting some Taylor cut-to-fit wires or a roll of MSD Super Conductor and run them OTVC. You'll never have to deal with getting the passenger side wires between the block and the accessory bracket again.

[Pampered-Z]

Hardline_42 makes some very good points. I'd rule out the cheap stuff before I throw an Opti at it. Not that is couldn't be the opti, but why throw that money and time into an opti if it's not the problem.

Check for a burnt plug wire(2) and check the coil wire for corrosion at the coil, very common problem.

You said the car isn't driving often, how old is the fuel? Maybe some fresh fuel and a can of injector cleaner. What about the fuel filter?

I don't know why everyone is so down on the bocsh plats. I ran the +4s for years in my Z and run them in my DD and have no complaints.

[bubba428]

AC Delco or Autolite. SBCs DO NOT like Bosch plugs. the 3.8s love 'em but the 3.4s and SBCs(same plug) hate 'em. Now sense its been 2 years I would do a tune up, plugs, wires, fuel filter, injector cleaner (Lucas is the best), oil change while your in there. If that don't do it....Opti...

[WildBillyT]

AC Delco or Autolite. SBCs DO NOT like Bosch plugs. the 3.8s love 'em but the 3.4s and SBCs(same plug) hate 'em. Now sense its been 2 years I would do a tune up, plugs, wires, fuel filter, injector cleaner (Lucas is the best), oil change while your in there. If that don't do it....Opti...

Good advice, start with the cheap and easy stuff first.

Delco plugs can lose the platinum "pucks" which lead to too large of a gap. Worst of the group IMO. My 3.8 liked the Boschs so I'm with you on that one.

Redline SI-1 is the only FI cleaner worth anything IMHO.

[GREZ28]

PamperdZ, fuel is not old, couple of weeks, but during the winter I drop some Stable in there untill I break it out from the garage. It 1st came out I guess around mid April. I do drop in a the tank some inj-cleaner everytime I change the oil, but then again I might have forgoten to put one in this time. Fuel filter have not done that yet..
It looks like I will have to make a check list..

[Pampered-Z]

PamperdZ, fuel is not old, couple of weeks, but during the winter I drop some Stable in there untill I break it out from the garage. It 1st came out I guess around mid April. I do drop in a the tank some inj-cleaner everytime I change the oil, but then again I might have forgoten to put one in this time. Fuel filter have not done that yet..
It looks like I will have to make a check list..


Also Start the car at night and look for any sparking from the wires. I had a wire burn on the header and the spark was jumping to the knock sensor and it gave the computer fits. Check for burnt or loose wires.

BTW, how many miles on the car?

[bubba428]

Good advice, start with the cheap and easy stuff first.

Delco plugs can lose the platinum "pucks" which lead to too large of a gap. Worst of the group IMO. My 3.8 liked the Boschs so I'm with you on that one.

Redline SI-1 is the only FI cleaner worth anything IMHO.

Redline is pretty good but If its clogged injectors I would use the Lucas 1qt bottle. its pure petroleum product so over-concentrating WILL NOT hurt anything plus it has special top end lube in it for the valves and cylinder wall. I had a guy with a 98 Dodge Dakota with the same problem, and I told him to put the whole bottle that treats 100 gallons in 1 tank. 20 min later he came back and told me how fast he noticed the difference. And I had a firing issue with my Junk yard injectors...ran Lucas through them GONE.

[BonzoHansen]

Also Start the car at night and look for any sparking from the wires. I had a wire burn on the header and the spark was jumping to the knock sensor and it gave the computer fits. Check for burnt or loose wires.

BTW, how many miles on the car?A squirt bottle of water works wonders for finding bad wires. Something that will mist. I have an old windex bottle with water in it that works good.

[Firebird67dude]

SBCs DO NOT like Bosch plugs.


I disagree. the 93 loves em if the opti wasnt half retareded and liked to work but since that got replaced all is good. MY firebird I had also loved the bosch plugs. I guess its all opinion.

GREZ28, I sent you a PM

[GREZ28]

My 95z28 has 49.000mls on it..
Bubba, never tryed the lucas one but I will give it a shot..

[CALL911]

49,000 miles on a 12 year old opti (asuming its original) is probably average for it to go.

Plugs, wires (unless your Taylors are still looking good), coil are all fairly inexpensive and easy to change (relative to the opti). I think you've got the right idea trying all those first. I would also recommend staying away from Bosch plugs. I would even get a set of cheep old champions before I would go the Bosch route.

I doubt its your injectors. I have heard of guys breeching the 200,000 mile mark on their original injectors with no problem. Besides that, if it was an injector, it would probably run like crap all of the time, instead of at what seems to be low RPM's.

If all else fails, and it still runs like butt after the ignition items have been changed. I can pretty much garuntee you its the opti. When the opti goes, it usually fails at either low, or high RPM's (or in rare cases both) and gives similar symptoms of what you are describing. Sometimes it will trip a low, or a high RES failure code to your computer. A couple of things to keep in mind if you are at the point of changing the opti. #1, don't do just a cap and rotor. Be sure to just get a whole new opti. Personally I believe the Delco opti will perform well for years if it doesn't get wet, and is generally cheeper than the more built up ones like the MSD or Accell models. #2, and this is an important one. If you are changing the opti with those miles on the car, you probably should go ahead and change out the water pump as well. It may still be running good now, but the average life of them is about 50,000-75,000 miles, and when they go out, they will take out the opti as well, and it would really suck having to replace the new opti soon.

Having gone through several opti's in my 95 Z28's life, I can honestly say I have it down to a science (4 hours to take the old one out, and install the new one). It is a royal PITA, and I would rather cut my lawn with a pair of fingernail clippers than have to go through it ever again. Make sure you give yourself lots of time to take screaming breaks, and if you are over 21, I would also invest in some beer.

Good luck man!

[karr95]

I had a 95 lt1 Trans Am with 75K on the clock and your problem sounds exactly what mine was doing. Here is what happened...

I changed the plugs and all were good except the #8 plug, it looked like it was original (the other 7 were champions and this was a burned up delco).

2 of the wires were burned up pretty bad.

I am guessing that between the burned out plug and the 2 rotten wires is what killed off my opti. I was getting misfires on the whole passenger side of the engine.

Most likely you will have to do plugs, wires and the opti.

[GREZ28]

karr95 & Call911.. Well I am making my list, I think I am going to do the whole 9 yards by the end of the summer to get it over with. Opti is original, my water pump is about 2 yrs old, changed it my self. The new one might have 3-4000mls on it. It's just a mater of time and $ to get my baby on the road again I guess.
Beer? No prob on that!:cheers: :toast: :barf:
Firebird67dude, sent ya pm.

[bad64chevelle]

I had the Bosch's in my LT1 for a month...car started to run like crap, and when I went to pull the plugs out the Ceramic disintegrated as soon as I touched them...put the autolites in and never looked back.