LaVy

iTrader: (5)

Hey guys, I've done a a lot of searching on here and reading the last two days, PM'ed a few guys with similar problems but can't really say I've found any answers yet to my particular problem.

I'd like to start off by saying last fall I installed a MSD cap and rotor, MSD coil, Moroso plug wires, and new AC delco plugs. This set up Fixed my High RPM stumble and hard starting problem I had. I put about 1,000 miles on it last fall, Parked it for the winter, Did a T56 swap and installed pacesetter long tubes while it was down for the winter months.

I started driving it again in mid march, No issues ran as strong as ever. The car sat outside Monday and Tuesday due to rain, On Wednesday the rain cleared up and I started the car, and took it for a drive. It ran good as always for the First 3-4 minutes Then It missed after I shifted a gear and stumbled, I kept driving it down the road and at low rpm (under 3k RPM) It would missed and stumble and I would let off and stop at a stop sign and it would Idle rough, The car would shake RPM's drop to about 5-600. I hit the gas and it smooths out. So Not knowing what was going on I pulled over into a gas station pop my hood, Checked all my plug wires, Made sure they weren't loose or hitting the header, Everything checked out to be okay. I start the car back up and it runs normal, Idles smooth. Start driving down the road and Again after 3-4 Minutes it would miss at low RPM's, started idling rough, and have the Occasional backfire when it misses around 2500rpm, If I hammer down the car runs as good as ever after 3k rpms all the way up to redline.

It doesn't matter if the car is warmed up or cold If i shut it off and let it sit a minute then restart it it will run normal for the first 3-4 minutes. I took my mechanic buddy for a ride and he thinks its the o2 sensor's possibly They could be the originals I never replaced them with new when I installed the headers just re-used my old ones. I know there is a lot of smart lt1 guys on here and would like some guidance before I start throwing pointless new parts on it. Thanks all help is appreciated.

dkishton1486

Hmm a few things pop up in my mind... Sat through winter.... Possibly bad gas.... Sat out in rain....Could be moisture in the opti.

LaVy

iTrader: (5)

I've ran about 5 tanks of gas through it since I started driving it last month. I thought it could be moisture in the opti, But It wouldn't run right all the time and it should of dried out with driving it. With the MSD cap and rotor it is the "vented" set up with 2 vacuum tubes going to the intake.

ss.slp.ls1

iTrader: (36)

Any codes? It sounds like the problem occurs when you switch form open look to closed loop. I would suspect your o2's or your MAF. You can disconnect all three, drive it around, if your symptom disappears, might as well replace the o2's since they are old and clean your MAF. Good luck.

LaVy

iTrader: (5)

thanks for the advice brother, i tried using my buddies snap-on scanner last night, but I'm stupid and couldn't even get it to turn on so I'll need his help. If it is bad o2's should the symptoms disappear if I unplug them? If I unplug the mass air flow sensor will it run right? Well I guess I'll run out there and try it now. Then I'll have my answer huh? lol, But yeah I'm taking your advice on replacing the o2's because it can't hurt nothing being that there old and I'll pick up a can of MAF cleaner, Then go from there.

If anybody else wants to chime in with there opinion on the matter or has any other priceless advice don't be shy haha thanks guys.

ss.slp.ls1

iTrader: (36)

New o2's would be good routine maintenance. Yeah, unplug them all and drive it. It may struggle to start or run after you unplug the MAF, it should only do that for a matter of seconds, keep trying to start it and it should fire right up and run. Good luck, hopefully you'll get some positive results.

LaVy

iTrader: (5)

Are Denso o2 sensors the same as the ac delco's?

dkishton1486

If I were you I would only run Delco's

ss.slp.ls1

iTrader: (36)

I've heard they are. But not sure. I'd get AC Delco's just to be sure.

LaVy

iTrader: (5)

On GM parts direct it has GM PART # 25312184 as a non returnable item, I'd hate it to be the wrong part and waste 120 dollars on it and 7-10 days before shipment? This dont seem like a deal I want to do is there a better place to get real AC delco o2 sensors? I know the dealer should be able to but there closed till monday now. Probably looking at spending the list price there too (119.43 a piece).

LaVy

iTrader: (5)

Local part stores can only get me Bosch and denso

clwz28

This is funny ,I was going to the track tonight,but not now my car is doing the exact same thing as yours,I took it to Oreillys and it has a (lean)o2 code+ (16)opti code,and its was raining when it all started,I had a spare o2 and tried it,and that did not fix it,I know its got to be the opti,I replaced it with a new cardone select over a year ago,good thing its liftime,but I am sure I will have to wait a few days for one.Let me know your fix.

LaVy

iTrader: (5)

Hey man, Last night I Replaced my o2 sensors with new ones, and took my mass air flow sensor apart and cleaned it with the CRC MAF sensor cleaner and Took her for a spin. PROBLEM SOLVED!

I also wanna thank ya ss.slp.ls1, You know your **** and were right on with your first thoughts

clwz28

I want to know if its still running good after you get some miles on it,I have another opti coming for mine,but the o2 I stuck in was just a spare and maybye its bad?keep me up to date I am going to be down a few days.

ss.slp.ls1

iTrader: (36)

No problem man, happy to help.

pythonwarrior1

I'm using Denso in my 94 firebird no problems no codes