dontmachme

i bought a sc400 thinking it needed a head gasket. but it turns out the guy i bought it from put two ignition wires on backwards. so i switched those over and it reved real nice but rough on idle. it needed a o2 sensor and an iac valve. it runs much better but still misses slightly. now before i did the o2 sensor and iac valve i threw some cheap autolite copper plugs in it just till i was sure it wasnt a head gasket. so my question is has anyone ever used the autolite then put ngxs in it and had it run better?

MooJohn

They're not that sensitive to the brand of plugs. Replace your vac hoses (about 8 feet of 4mm hose) and the distributors & rotors. They get very brittle after 20 years of use. You can do coils too but they are more expensive. The one on the driver's side is mounted absurdly well -- I mean comically bolted into place for something so lightweight. I refuse to unbolt the old coil there; I plan to zip-tie a new coil nearby and live with it that way.

You bought a new IAC valve? One that's $700 at the cheapest sources?! I took mine apart, cleaned it, and greased it.

xxtoobsxx

iTrader: (4)

I tell.everyone this...check your timing. Its very easy fiy these cars to jump a tooth or 2+. Everyone will then respond with "then I would have bent valves and my car won't run." Then I say the earlier sc400 have non interference motor. Anyway check your timing...if its spot on sea foam then tuneup!

dontmachme

no i didnt buy a new one i got one out of a boneyard from an 94 ls. and the 1uz is an interference motor. but your timing can jump 2 teeth and not hurt your valves. but even it the timing jumped two teeth the computer would compensate by advancing or retarding the ignition timing in relation to crank sensor so it shouldnt run rough like it does. and its not really rough the engine is pretty smooth its the exhaust that puffs like it has a misfire

MooJohn

The non-VVTi 1UZ is not interference.

Just putting that out there for those who read this (and bump this post 10+ years from now!)

Bassrocker

spark plugs are more then just brands they have different levels switiching from autolite iridums to NGK iridiums you wont notice mutch if anything at all however switching from autolite copper to NGK iridium you will swear your car runs like new again so it all just depends on what your starting with. the laser iridiums are great plugs that can keep up with all the other plugs in it's class but with much better effieciency. not sure how long they last tho because i have not had too much experience with that plug. if you want extreamly long lasting plugs i would say bosh platinum +4s will last forrever (unless ou have engine problems that fouls it) just read a bunch of spark plug articles recently comparing a bunch of spark plugs on the same vehicle and stuff like that trying to get to the bottom of what really makes a spark plug more expensive and how important spark plug selection is to making your car run better for work (i sell service at Pep Boys so i try to be as knowledgeable as i can to help my customers who usually don't know ANYTHING about cars plus a few months ago before working there i did not know much either ... i thought i did tho)

what i dont understand is how people have so much brand loyalty with something as mundane as spark plugs evryone has that one brand they are crazy about and that one brand they pick on. i can ask 6 different master mechanics and get 6 different answeres. some are crazy about NGKs others love autolite or ac delco. the most hated plugs seems to be bosch they curse at me every time i suggest those and i have no idea why there is so much hate on the bosch because every other auto part they make is exceptional so why would spark plugs be any different and ive allways used them on all of mine and my family's vehicles without any problems and the mechanics never give me a REAL reason why they dont like it they just all prefer other plugs.

MooJohn

For most generic engines, any generic plug will perform the same. That's probably true for the typical SC too.

That changes when you go forced induction. When you spend 20 years dealing with turbo cars and you learn through experience that NGK plugs work every time and the others give wildly different results, you tend to go with NGK from the beginning.

The hate for Bosch plugs is because they were the first to push the "Platinum = better" line and that isn't true in all cases. It will last a long time but most enthusiasts prefer performance over longevity.

Bassrocker

yeah seems like most brands offer iridium and platinum plugs now but yeah ngk is a god product but they have copper and platinum plugs so look at the material ngk copper plug is still just a copper plug nothing to see here

dontmachme

i guess my dilemma with myself is that different metal materials have different capacities to carry electricity . so if my ( our) 1uz's were built with double platinum plugs to perform on a 10:1 compression engine. so when i put a copper plug in there it might perform differently. i sell auto parts as well at autozone and i always say oem or better. i know you will notice a performance or mpg difference. my question is can the (correct) wrong plug be wrong enough to make it miss on idle

Bassrocker

It shouldn't missfire on brand new plugs as long as they are gapped properly even if they are cheap ones. People run cheap plugs when they are diagnosing problems all the time. I wouldn't put too many miles on cheap plugs tho and I wouldn't expect them to last long. From what I've seen on dynocharts an example was on a neon srt4 the best plugs they used (ngk) offered 4 horsepower and like 8.5 torque and let it peak about 150 rpm lower versus the oem plugs and they put some cheap plugs on the dyno and it was like 2 hp less. So granted its in a boosted 4 cylinder engine versus a high compression 8 cylinder engine through the gambit of plugs they used its just a 6 horsepower difference (so about 2% of this cars power is determined by plugs)

dontmachme

as i keep diagnosing my missfire. i came across something that was new to me and has me flabbergasded. i took the ign wires off the plugs on the right(passenger side) bank and it ran better than with them on. then i put them back on and took the left( driver side) bank wires off and it wouldnt even start. im leaning towards ecm or ignition module.

MooJohn

Do you have them in the right order? That's how I got my car for $800. It barely idled or drove but compression was perfect. Put the wires in the right places and it runs like a Lexus.

I mentioned the coils already. We've got brittle plastic distributors (and especially the rotors) and that can easily cause a misfire. It's only a few screws on each side but naturally they had to make it hard to reach said screws.

dontmachme

thats how i bought mine with two wires on the wrong cylinders. and the wires are good now all in order. but i hear a lifter noise on the right bank i think that might be my rough idle. the valve isnt opening all the way and the pressure isnt even with the rest of the cylinders even though on a compression check its all the same as the rest.

g4ebguy90

We got HLA right? Mine does it once in a while on a cold start. Just means one of them is not filled with fluid and has collapsed on itself. Really not a big deal at all, on a 4cyl you might misfire every now and then at moderate rpms. But a v8 I doubt you could notice at all.

dontmachme

no mine does it worse as it gets hot i know its a collapsed lifter. and if it wont pump up enough then of course you would be able to feel it. i just dont know the extent of how bad its collapsed. even a vacuum pressure gauge wont fluctuate its steady which makes me think the valves are opening evenly. its got me boggled