350pride

94z a4, and I just installed hotcam and rr. On the dyno car was breaking up in the higher rpms. Mechanic told me opti was bad, so I put a new opti on, and car worked like a champ for four days. Then all of a sudden car backfires really bad at 4500 rpms at wot. Does it in nuetral as well. So i take it home. When I try to crank it back up, there was no fire. Car just kept tring to start, but now fire.

Call mechanic back he said that it was the Wireing harness that goes into the opti that caused it to go bad. He said that it was probably corroded. So I took it off and looked at it and it looked fine. I checked it with a volt meter and all terminals where fine. I would just go and by another harness but the dealer wanted 150 for it.

So does anyone know what would eat an opti after a cam swap? BTW im only shifting at 6000 rpms.

Thanks for your help

anaik

Did you check the length of the cam dowel pin before installing the cam? It should be .620". I have also read no longer than .605". You could put a piece of clay in the opti slot and see if the pin bottoms out.

LT1_383

A longer dowl pin then required would do it but i would think a hot cam kit would come with exactly the right length pin. However, if you do need or want to try the harness. Casper makes an opti harness that is only about $30-$35. Works and even looks like factory. Not sure of their web address but Summit sells casper products.

350pride

well the hotcam comes with dowel pin setup for 96 and up. I have a 94. If the mechanic put it in, wrong then oops on his part. So does anyone know what the opti would look like if the pin was too long. I look down into the opti but I could not see any damage. Only thing that looked off was a little oil on the back of the opti, just a little though. So anymore Ideas. Oh btw can you check the lenght of the pin with out taking the timing chain cover and timing chain off??? Thanks for your responses

350pride

Im still having problems. Does any one have any ideas. Dowl pin length is fine. Just order new opti harness, in hopes of miracle. I need some more Ideas because im tired of taking this thing apart.

Does anyone think that I need to upgrade the opti to a MSD one?

bgmz282

This has been a constant problem for me. I can almost bet u money that one of two things happened. The rotor is in pieces because it came apart or the screws that hold it to the opti backed out. What brand opti are u using? If your buying aftermarket rebuild's from your local auto parts store your wasting your time. Go to the dealer,ebay or a parts store that carrys acdelco products and buy the GM opti. The MSD seems cool but i know a guy who bought one, put it on, and boom the next day its out. Buy the GM opti and take it apart and loctite those screws down and go on about your business.

bgmz282

AcDelco part number are .... 93-94 non vented #10457702 95-97 vented #1104032... good luck

350pride

the opti i replaced it with the first time was a GM one. striaght from summit. (the one that lasted for days)

kainZ

if his opti died the next day, he probably installed it wrong...

my guess would be that if its breaking up at high rpms you might check your plugs and wires and oxygen sensors before looking at the opti....

the only reason i can see for an opti to fail "at a certian rpm range" is mild corrosion and or something that isn't an inert gas present inside the opti inhibiting its ability to sense the cam's position accurately/precisely. otherwise, optis should work or not work, fairly predictably..

things like plug wires and the normal distributor part of the opti and spark plugs and o2 sensors that "wear" are more apt to have the kind of "not working well at high rpm" that you're experiencing......

though, i'd say usually for wires they'd work better at high rpm than lower, just because of the different resistances, etc.

note by work or not work, i mean they should just act crazy, or they should work.... there shouldn't be a method to their madness when they don't work... it shouldn't be a "opti doesn't want to work above 5400rpm" thing, unless, like i said u have some specific amount of corrosion causing that behavior..

btw im a lil drunk so don't mind my spelling

Injuneer

I think the inebriation may also have produced this statement:
What "inert gas" is normally present in the Opti that allows it to "sense the cam's postion accurately/precisely"?

3DFORMULA

I'm having opti problems as well I believe. On my way to work, shifting from 2-3, at about 4000rpm, flat lined as soon as I hit the clutch. I now have spark coming out of the coil but not out of the plug wires. Never changed the opti, its original so no improper install here. Is it probably just the cap and rotor? Disassembly starting this week to fix this issue on my '94 formula. Did just buy a '96 Z/28 turn-key yesterday, but if its a cheap fix I'll have 2 LT1 M6 cars to play with. Any hints? Thanks, Darrell

3DFORMULA

I'm having opti problems as well I believe. On my way to work, shifting from 2-3, at about 4000rpm, flat lined as soon as I hit the clutch. I now have spark coming out of the coil but not out of the plug wires. Never changed the opti, its original so no improper install here. Is it probably just the cap and rotor? Disassembly starting this week to fix this issue on my '94 formula. Did just buy a wrecked '96 Z/28 turn-key yesterday for the drivetrain, but if its a cheap fix I'll have 2 LT1 M6 cars to play with. Any hints? Thanks, Darrell