Ok i've searched enough, time to post...

Ok so to start i have a slight miss at idle on a 95 sc riviera fresh plugs wires coils rebuilt s/c LIM gaskets (GM and their plastic gaskets...). I'm a mechanic but am having trouble with this one. I put the car in gear and hit the gas the rpms increase to 2-2.5k and then its starts missing and pinging and it starts to retard the timing it will not go past 3000rpm i don't know wat else to try. i've searched these forums all weekend to try and locate the problem to no avail...

Any help is much appreciated ty ahead of time -Steve

welcome to the forum!

do you have any SES light? if so let us know what it is.
it sounds like a misfire under load to me, and if you have already replaced the plugs,wires and coils you might want to look into the MAF sensor.
first try unplugging it to see if the problem gets worse or stays the same. it may just need a cleaning, or you may need a new one.

Greetings!

How about the catalytic converter being stopped up?

Bert

Tried unplugging the maf and it got worse than it was, I tried cleaning the MAF out with the regular sensor cleaner. Do you think the missfire could be caused by the icm? but usually when they quit they just either won't run or run when they want to. The Riv hasn't shut off or hesitated. Just a steady missfire.

ahah i could try the cat to didn't think about that. I'll remove the 02 and grab the tester from work.
This thing is driving me bonkers it might be break time soon haha

My first thought was the cat converter. My next guess would be ignition, even if you replaced everything. The fact that you had it all torn apart might indicate a defective part or installation error. Maybe try checking each of the front plugs for spark.

well the end of the o2 is white like its been running way to lean for a while, the black and purple wire were burned through, and the plug end was mutalated by the exhaust manifold. (Just so its clear i didn't put this oxygen sensor in lol, i just bought this vehicle from a family friend.) i'm goin to order a new o2 sensor tommorow just because this one is mangled beyond any recognition and hey its worth a try. Still gonna check and see if the extra exhaust flow helps.


EDIT: All plugs have spark. No terminals were dirty/rusty. Used dielectric on all connections

ibmoses wrote:

Greetings!

How about the catalytic converter being stopped up?

Bert

This was my first thought also.
There is, or at least was on older cars, a way to check for a clogged exhaust with a vacuum gauge. I used it a couple of time to find double walled exhaust pipes that had collapsed internally? You might give it a try?

Well i put the pressure gauge on it and it is in the green, i was in high hopes of that helping. =/
My sig isn't comin up btw

I See you are the admin and now i know why ty man

Welcome. I had that problem when I cracked a spark plug upon installation. It was okay at heavier loads and low RPMs, but at cruising RPM it would buck and miss like crazy. I would go after ignition based on your description. Was it doing this before the plug/wire change?

Ok i figured it out it got worse when i started replacing coils sensors etc. but somehow one of the coils wasn't putting out enough (New Coil!!!) and the miss before all that is gone too. so i don't know wat i did to fix the original miss.

So your miss changed when you replaced plugs wires and coils? and exactly what sensors did you replace?

Plugs and wires are usually the culprit, very rarely a bad coil will surface as the problem, but it does happen

besides the coil, o2 sensor, IAC, TPS, and MAT(I had one lying around),

All i can gues is maybe i had the wires off and on enough maybe one of them has a bad spot. I might just replace the wires as defective for a new set at advanced auto. They are autolite wires and i usually don't have to many problems with em.

And kudos to AA and deek even though i had new coils, plugs, wires they stuck with one of those being bad =] They were right... But thank you all I'm so glad the car is ready for the road now. Took it for a test ride tonight and it rides like a dream with plenty of power.

deekster_caddy wrote:

So your miss changed when you replaced plugs wires and coils? and exactly what sensors did you replace?

Plugs and wires are usually the culprit, very rarely a bad coil will surface as the problem, but it does happen

In general or on these cars? Bad coils causing bucking and severe missing out is actually rather common

I think he was making the point that the plugs/wires are a more common solution, but they arn't that common i think i've replaced only a handful of coils in the 4 years i've been working at the garage.

Of course, he means on our cars. This forum referrs to Riviera engines.

I think Derek meant exactly what he said, and I would agree. It's rare that an OEM coil just goes bad. It's just a simple transformer, no moving parts. It doesn't even get warm. Each pack fires only 1/3 as often as a single coil would in an old distributor system, so they should last at least 3 times as long. I have all of my originals at 185k miles.

If a coil does fail, there's a good chance something else caused it, such as removal and reinstallation, or replacement. Ignition components are delicate and can be damaged by dropping or mishandling. Replacing with aftermarket parts such as MSD may shorten life because of the increased (unnecessary) spark voltage. Or it's possible a bad spark plug or wire set could short and burn the coil, but this is unlikely, as these components usually announce when they go bad before the coil goes.

By any standards i think this is the last pre 96 vehicle i'll own unless its pre 85. I took for granted how easy it is to just hook my 96 cavalier up to the scan tool and it pretty much tell me exactly what the problem is. and the chevelle well theres no sensors besides the pickup coil (HEI FTW!!).

charged95riv wrote:

besides the coil, o2 sensor, IAC, TPS, and MAT(I had one lying around),

All i can gues is maybe i had the wires off and on enough maybe one of them has a bad spot. I might just replace the wires as defective for a new set at advanced auto. They are autolite wires and i usually don't have to many problems with em.

And kudos to AA and deek even though i had new coils, plugs, wires they stuck with one of those being bad =] They were right... But thank you all I'm so glad the car is ready for the road now. Took it for a test ride tonight and it rides like a dream with plenty of power.

RIv standard ignition is actualy a very hig energy set up. My guess is Autolite or other "standard" wires will work but not very long especially if a connector gets buggered. Easily happens on installation.

Your best value would be Delco wires at a discount, try rockauto.com.

Magnecor standard wires (the 7mm ones) will work for-flipping-ever, they cost a little more but only a little. www.magnecor.com. I use Magnecor 8MM, have over 100,000 miles on them with no problems.

Albertj

I did mean that rarely do the OEM coils actually fail. Often they are replaced as part of an improper diagnosis.

I worked at an auto parts store counter for quite a few years (15 years ago) and every time I sold a coil I said 'I doubt this is really your problem' and sure enough, every one of them came back for a different part before they were finished with their repair. I know that coils do occasionally fail, but in 20 years of turning wrenches and helping many many others, I've never witnessed firsthand a _bad_ coil.

Albert: Thanks for the suggestion I might give em a try, but i can get ac's at cost so idk. Might be worth it if i only replace even every 50k but if they would save my coils, hmm i have to think about this one, i really hate to delve into anything i haven't used before. =/

Deek: I agree deek and like i said i've only replaced a couple. (corsicas and berrettas are known for it because of valve cover leaks, any coil that was mounted on the block due to oil or coolant.)