Hey LS1tech, first post on here just seeing if I can some advice on what to do. My car is a 95 A4 Z28, The car is stock minus, a magnaflow muffler on the stock cat back, Cat/AIR/EGR delete, a sorry excuse of a CAI, it's a crunched up k&n cone filter on a painted, skinny elbow (I'm assuming eBay) going to the MAF. I bought the car from a younger gentleman. I bought it at 143k and now after a year and a half it has 161k. As soon as I got the car it was running fine, it just needed some love. So I drove it 40 miles home, changed the oil/filter, it was pretty low on gas so i ran it out then filled it up with Shell and some gumout injector cleaner,flushed out all the nasty old coolant from the radiator and block to refill with green peak and also changed the plugs and wires with the factory replacement wires and NGK TR55s, and wow that was hard. On to my problems, the car has always ran fine and I've taken good care of it, regular oil changes always ran good fuel in it, made sure the opti has stayed dry etc, it still does run fine minus a few things. The AC never has worked but now the compressor is locking up putting a huge load on the motor bogging it down, it doesn't do this all the time and also the compressor makes this whistling noise at any rpm... I never really have drove it hard the only times I've put my foot to the floor are having to pass someone on the road/freeway or if I'm pulling out in front of somebody lol.. But here lately around peak RPM it'll bust out and stay there for 3 or so seconds, almost like a misfire. I figure it's the opti because it's the factory delco one at 161k. The last problem is no matter how many times I prime the fuel pump it will turn the starter over for a while before starting, then when it finally does it just stumbles for 5 or so seconds and then runs fine. It doesn't do this if the motor is warm, it'll fire right up if the motor is warm. Anyone know what these problems could be related to?

 

I would say check for spark and fuel. Make sure ur getting sufficient fuel pressure to the fuel rail, and make sure ur getting sufficient spark from an end of a plug wire, then maybe from ur coil. If theres a huge difference in spark, it could mean bad wires, and or the opti... but if ur getting the same spark from both, u could have a bad coil and or icm. Just simple things to check. Eliminate the easy stuff first...

 

Also check the coolant temp sensor (The one on the water pump NOT the one in the head). When this sensor dies it sends the wrong readings to the PCM and the car will have trouble starting either hot or cold. I had this problem myself personally plus the part is cheap. Don't immediately jump on the "opti is bad" band wagon as the opti usually is not the problem. I agree to check fuel pressure (Leakdown pressure as well) as that can cause problems just like this.

Also if the compressor was locked up the belt would screech and smoke like crazy. The compressor should not even be engaged if the A/C never worked. The pulley on the A/C pump will free spin when the A/C is turned off so that shouldn't be any kind of drag on the motor. Usually what happens when the A/C clutch gets old is that it starts "dragging" ever so slightly. It sounds like a whistle or like a metallic sound, it's very common on a GM with over 100k miles.

 

I replaced the one in the water pump a week or so ago when the problem really started happening alot more, spark is really good... Need to check fuel PSI and regulator. I just figured the opti could cause the high rpm miss fire. I'll probably put a AC delete pulley in soon. I lived the whole summer in FL without it...

 

I would try a new cap and rotor first (MSD one is vented and better built), 160+K is a lot of miles and it is a wear item.

 

I've been holding off on this due to all the fanboys of certain brands. Some people say MSD then others say those suck and OEM is the way to go. If it indeed turns out the opti dies, I'm probably gonna take my chances at 24x. I'd rather stay LTx over LSx. Not many people these days are still rolling with the underdog. Plus in my opinion people say things they don't even know about the LT1 or opti... If you take good care of it like I have and the previous owner they'll do fine.

 

Well it's $150 vs. $2000+ once you price it out; a stock LT1 is not going to see the sort of gains or fully utilize a 24x setup as a "built" LT1 that's capable of over 7K rpm.....IMO you would be better off and make more HP trading up to a LS1 car or do a full LS swap for that kinda $$ unless you have big plans for the car. But hey, it's your money!

I don't think you understand the difference in a "opti dying" and a bad worn out cap and rotor....there's 2 parts to the opti to go bad...the optical sensor is not always the culprit....

 

Honestly id probably try and get a used C5 of some sort. Sell and then save up a lot more cash! Lol I do understand, I was just making a point. Any cap/rotor suggestions?? I'm stuck between MSD or OEM remani.

 

I have the entire MSD opti with no issues....if you hold a stock cap and rotor in one hand and the MSD in the other it's obvious which is built better, and the MSD has an improved vent design that pulls in fresh air from in front on the TB on the rubber bellow and vent out through engine vacuum.

 

Very true. Kinda wish I would've went with one. I bargained out for a new old stock AC Delco unit... Local guy on craigslist had one from when GM still made them, rather than remanufactured them.
EDIT: OP, my car sat for TWO YEARS outside! And it was still fine, my old one was fine however it was also a high mileage part and i figured hey, I'm rebuilding the motor and I want it to be reliable so might as well. Your problem to me sounds like a opti cap and rotor or mate your fuel psi regulator.

 

Delco cap & rotor can be made vented pretty easily. You'd need a vacuum harness from any LT1 car that came with one, junkyard is a good place to find one in good shape. I live in NC and the MSD vacuum harness lasted for a year and a half before it dry rotted and produced a vacuum leak on the car in my sig. So here's the list:

1/4" straight vacuum connector for the cap
3/16" straight vacuum connector for the isolator
Vacuum harness (trim a little to fit the distances to intake elbow and opti)
Rubber T vacuum connector for the EGR vacuum port if you still have EGR
RTV

Vacuum is provided by the EGR vacuum port and goes to the cap
fresh air is from the intake elbow (drill a hole, grommet available at parts store)

The write-up in my sig is old and uses an 'F' style fitting on the cap. Pics below are of one I did with a straight connector.

 

I would agree with v8vette84... dont jump on the opti is bad bandwagon. Honestly it all depends what u want to do with ur car. U wanna race it, plan on doing heads, cam, high dollar engine mods, then i would suggest MSD (bout 500 bucks though) and if u just plan on doing a daily driver, and plan on keeping it maintained well, then a chandler motorsports (ebay) or any place like oriellys, autozone, or advanced auto, all make sufficient oem replacements, and most with lifetime warranties. Plus they are really super easy to replace... maybe and hour or two tops...

 

It's a daily. I'll never put a parts store replacement on there. I'll shell out the extra cash to get a quality brand Opti just for the reliability reasons. I tested everything and it's fine?!??!!!? opti harness maybe?? Fuel PSI was fine... Spark was good from the coil and all the wires and I even checked all the plugs!

 

Well there's no reliability issue in any of the optis to be honest. Unless u can score an opti with the original Mitsubishi optical... then ur money doesn't really matter. I've got one of the Oreilly's lifetime warranty I think from Borg warner in my 95 Z28 , and I think an advanced auto lifetime warranty for my 97 SS SLP LT4 either work just fine. Chandler motorsports offers them for 100 bucks, and the lifetime warrantied ones run about 200/250. I love MSD all day long. In fact all of my ignition on my 97 is MSD except the opti, and wires. Which both will come later on this winter, with new heads, cam, and intake. But as a daily driver, ur just fine with an OEM style, or even for a couple bucks more run MSD cap and rotor. Unless ur spinning 6k rpm or more, the stock opti will handle just about anything u throw at it. I'm running about 400hp to rear wheels, but I rarely use high rpm. So my opti handles what it needs to do my daily driving, and highway. Plus if u drop 500 plus into a MSD opti... then they are only warrantied for like 1 year, so something goes out... ur out 500 bucks. But these things do just fine as long as u understand them. They are just like any other distributor with a slight difference, but bottom line, just like anything else. As for fuel stock pressure is like 40-44 psi. And what color is ur spark. Example a buddy of mine has a 95 Z28 . He called me cause his car just died out. So he was getting great fuel pressure, and swore up and down his spark was good. When I went to his town (50 miles away) I looked and laughed. He had hardly any spark. That was from plug wire. Then we checked from coil. Weak. So I got him a new coil, and tested the ICM, ICM was bad, put it back together, and. She fired right up no problems on first try. Just an example though

 

Spark is very strong and bright white, fuel PSI is in check as well. FPR is dry as a bone. I understand the distributer, I've kept the opti very dry, haven't spilled any coolant on it.. Never submerged it or taken it through a car wash. I never said it was bad, I just figured as pesky as they are, at 161 original miles it might be showing a few signs of wear... So far everything has been fine the past few days except on startup it seems it turns over forever, finally fires up and stumbles and spits and after a few seconds of that it runs fine. And will run like a clock until you floor it, THEN upon WOT, it will misfire at redline and stay in gear until the shift. Then it's fine until the next shift. Other than that it's fine. It has NEVER died on me and it hasn't skipped a beat until at redline before a shift.

 

I can not stand this "Go LS for cheap power" talk. I feel that anyone who says this has never priced an LS swap... Around me its 2-3K JUST for a stock LS1 with accessories. That's ridiculous! Granted you can go with a 6.0 block for cheaper but people still think those are also made of gold. I can get an LT1 with accessories for like $200. ( I got a complete LT1 once for $50) No joke. Granted if you pop a cam in an LS you make 400whp but for the money you could go LT, get heads and a cam and you are at the power level of the LS with money to spare. Sorry not trying to get off track but I can't stand is when ppl say an LS is an easy, cheap way to make power. 2k wouldn't even buy you all the swap parts...

Back on track I have used 2 chandler units, one in my Vette and one in my Caprice. Both have worked flawlessly. They seem to be hit and miss but they are cheap. Don't but Advance or Autozone brands as my buddy has gone through 3 of them within the last 4-5 months. Currently he has an MSD unit.

 

This REALLY sounds like a fuel problem. What was your fuel pressure key on/engine off and fuel pressure at WOT?

 

That's why I said or trade up....as in sell your LT1 car and use those proceeds + $2000 to buy a LS1 car with 50 more RWHP and the better ignition system (and 100X aftermarket support and tuning). By the way, I bought a complete LS1 with a blown head gasket for $250 from a local dealership...there are deals if one looks hard enough!

I think you are the only person with any luck with Chandler optisparks...those are spotty at best

 

^Don't listen to this guy with this auto zone/advance whatever cheapo knockoff Chinese optisparks recommendation....or get ready to start replacing optis left and right!

Yeah, it's super easy to replace them , I just love pulling the WP and making a mess draining coolant, trying to line up the spline drive , and changing optisparks as often as oil changes.

 

You got real lucky then, I have looked at LS1's for years and I have never seen any for that low. The cheapest I have seen anything LS was an LS1 block for $500 and that was JUST the block. I wouldn't mind doing an LS swap but I have not been able to justify the price. Plus I do love when ppl say "the LT1 is junk" and then they get spanked by one. I do wish there was a better aftermarket for them. The chandler optis do seem to be hit and miss from threads I have seen on this forum but I have had good luck with 2 of them so I think that's pretty good.

It's unfortunate that the opti seems to be hit and miss no matter what the brand. Some ppl have new GM units fail, some have MSD units fail. I'm surprised not one company has come out with a SOLID opti spark. This day in age its inexcusable. Must be companies don't want to drop cash to develop a better system for a mediocre return seeing as there are not anywhere near as many LT1/L99's on the road anymore compared to 10 years ago. They spend their time/money on the new LT1/LT4 in the C7.