engine bucking and sputtering intermittently.

Just picked up a 96 supercharged Riviera with 188,000 miles on the clock.The car is running like crap or great depending on what mood shes in.It ildles pretty decent but when you get it under a load such as going up a hill it starts to buck and jerk on certain ocations.other times it does just fine.Sometimes when you get take off it will start sputtering and then catch up and run fine until it throws its next "fit".Ive put in new Ac delco plugs and wires,new BWD coils and the module they sit on.Ive also put in a new fuel filter and repaired some bad spots in the wiring insulation caused by a power steering fluid leak.when all this started it was throwing a number 4 misfire code and after I changed the coils it went to the po300 random multiple misfire code.also the car has no catalytic converter and hasn't in years.other than that its completely stock.thank you in advance for any help with this problem.

YAY! Random misfires are fun! If you have access to a good diagnostic scan tool, hook up to the car and monitor the misfire counter to see if the misfires are prominent in one bank of cylinders, or 1 cylinder that's misfiring more than the others.

Check to see if the PCV system is working properly. Check all vacuum lines. Check your LIM and make sure it's not leaking coolant and/or oil into the engine. Pull the spark plugs and note the condition. Make sure your MAF is not malfunctioning when it gets hot. Monitor (with scan tool) the CKP and CMP sensors to make sure they aren't malfunctioning. Check fuel pressure. Check the ground for the ICM (underneath the ICM bracket behind the tensioner)......

There are many things that can cause P0300. Without being there to help, only thing I can do is tell ya what to check......

I'm going to throw this out there cause I had a similar issue 2 years ago. At the time, did exactly what you described, and I was 300 miles from home so I took it into a shop and they diagnosed as a misfire and recommended a full $500 tune-up.

I called BS since I've replaced all my plugs, wires & coil packs under 10,000 miles earlier. Limped it home and just never throttled it. Did some research and since it always seems to happen when the Supercharger was kicking in - I replaced the coupler and that solved the problem (it was making a terrible noise at the time).

So there you go. The current mileage puts you inline for some SC work. Hopefully that helps

Did your car throw the code when the SC coupler went bad? A couple of days ago I replaced the serpentine belt and the SC pulley made a clanking noise when i turned it by hand. It also makes a clunking sound when the car's engine is shut off. I have an Actron auto scanner plus code scanner, but just not sure how to use some of the features on it. Vacuum lines appear to be in good shape. What am I looking for when checking the MAF, it isnt throwing a code? Thanks for all the help so far. BTW, whats a good source for the SC coupler?

Everything you've done so far was in the right direction, and I agree with most of Abaddon's ideas, too.

Since you've already thrown some money at it, the next thing I'd do is the cheap-and-easys: check the fuel pressure, and the fuel pump connections on the top of the tank beneath the access-plate in the trunk, and on the speed-control module in the left side of the trunk.

2nd, I'd get some MAF/Electronic cleaner and remove & clean the MAF sensor. There are several threads on this, just search for 'mass'. Spray it gently, from like, a foot away, so as not to damage it.

Finally, but most distressingly, it could be cause by a leaking intake manifold (LIM) gasket... Definitely check the color/clarity of your motor oil.

A bad cam sensor will usually throw a code, but the crank sensors are notorious for not doing so. I don't know how to 'monitor' the crank outputs, but I'm betting Scott does.

Engine oil looks good, best I can tell. The car starts up great. No codes on the crank or cam sensor but that whole area was saturated from the PSF leak. Had to tape up a couple of spots near the CAM sensor connector. BTW this is also making the traction control act up. Going to check the fuel pressure tomorrow if I can find something to do it with. Any recommendations as to what kind of cleaner to use on the MAF? Also, do you know any sources for a wiring harness or connectors, Im not expecting my tape job to last too long?

Looking at the dipstick, it will look fine. Pull the Oil Cap and look at the bottom of it. If it's full of brownish foam, that's an indicator that the LIM is leaking internally and the oil and coolant is mixing. This also happens to the Radiator cap....Externally oil and/or coolant can/will pool up in the valleys of the LIM, between the fuel injectors and the S/C. It usually happens on the "ends" near the TB and the S/C snout. Mine leaked down the front head and transmission, but I don't think this is causing your problems.......

You mention the TCS is "acting up". Is this happening at the same time the other problems occur? Do they all come and go at the same time? If that's the case, you have a serious wiring debacle, a PCM that can't make up it's mind, or an Ignition Switch that's getting weak connections internally. However, these are mere suggestions conjugated by the information you are giving us. I really wish I could be there to witness what is happening......

I've had quite a few cars (customer vehicles) with your problem, and all I do is check what we are all suggesting. P0300 is a shit code, I hate it. Every time I scan the car and see that code, something flys across the shop. It literally could be almost anything. Just start with the basics and work down the tree. Sometimes it's a simple find/fix, other times it's 2 days worth of probing, scanning, meter-reading, wire jumping, swearing, and more-than-usual smoke breaks. Be patient....

As for monitoring the Crank Signal. Really the "only" way is to watch the CRANK SIGNAL (which lists as yes/no) on a diagnostic scan tool while driving. You can even set the scanner to take a Snapshot and record what happens when P0300 sets. Watching to see if the CRANK SIGNAL changes from yes to no when the car acts up would tell you if it's a CKP issue. OR, if you really wanna get creative, you could wire up your meter (set to AC Voltage) to the Signal Wire, and somehow route the meter to the cabin so you can read it while driving. You'd then of course have to watch the meter during "no problems" driving in order to establish the "baseline". If the car acts up, and the "baseline" is broken, you know where to look. I've had to do many weird things to try and diagnose cars.....

96blackriv wrote:

Did your car throw the code when the SC coupler went bad? A couple of days ago I replaced the serpentine belt and the SC pulley made a clanking noise when i turned it by hand. It also makes a clunking sound when the car's engine is shut off. I have an Actron auto scanner plus code scanner, but just not sure how to use some of the features on it. Vacuum lines appear to be in good shape. What am I looking for when checking the MAF, it isnt throwing a code? Thanks for all the help so far. BTW, whats a good source for the SC coupler?

You can get a Kit that includes the coupler, synthetic fluid and the proper sealant to reseal the snout from Intense Racing.
ZZP sells everything also.

TC problems are occurring at the same time the car starts acting up,the light will begin flashing and then stay on for a while.under acceleration or lack there of,the mil light will flash when the miss happens.ordered the zzp coupler kit last night and gonna start running things down with my multimeter and scanner tonight.any suggestions on a sight that will explain using the scanner while driving.mine has a feature that is like a digital dashboard but with a lot more info.Instruction manual is kinda vague and doesn't tell what all the sensor numbers should be reading.One more thing if I could find a good wiring diagram of the coil pack harness or the whole under hood harness that would be helpful as I haven't been able to find any books on the riviera in the parts houses in my area.

I'd turn off the TC and try running it. my first guess is a wheel speed sensor.

I would guess the TC/ABS and SES lamps are not related. Seems like two separate problems causing some confusion.

his first listed symptoms matched my bad fuel pump issues from early this year, but the TC does add a little confusion for sure.


when my car did this with a bad fuel pump I could hear it screaming from the rear, but not all of them do this. something else to watch for, I guess.

96blackriv wrote:

TC problems are occurring at the same time the car starts acting up,the light will begin flashing and then stay on for a while.under acceleration or lack there of,the mil light will flash when the miss happens.ordered the zzp coupler kit last night and gonna start running things down with my multimeter and scanner tonight.any suggestions on a sight that will explain using the scanner while driving.mine has a feature that is like a digital dashboard but with a lot more info.Instruction manual is kinda vague and doesn't tell what all the sensor numbers should be reading.One more thing if I could find a good wiring diagram of the coil pack harness or the whole under hood harness that would be helpful as I haven't been able to find any books on the riviera in the parts houses in my area.

The only place to find books on these would be to go to Ebay Motors and look for used OEM Factory Service Manuals.
If your car is a 1996, I happen to have a set I bought for someone at the same time he found and bought a set.
Anyway if your interested in a good used set of FSM's let me know.
Either PM me or email me. I'll have to look up my receipts and see what I paid, don't know off the top of my head but I'll guess at no more than $60.00 shipping included.
I am not trying to make any money, just recoup what I spent.

96blackriv wrote:

Did your car throw the code when the SC coupler went bad? A couple of days ago I replaced the serpentine belt and the SC pulley made a clanking noise when i turned it by hand. It also makes a clunking sound when the car's engine is shut off. I have an Actron auto scanner plus code scanner, but just not sure how to use some of the features on it. Vacuum lines appear to be in good shape. What am I looking for when checking the MAF, it isnt throwing a code? Thanks for all the help so far. BTW, whats a good source for the SC coupler?

Yes it threw a code. The symptoms you described are inline with my issues (minus the TC lighting up). If your hear a grinding on engine shut off, then regardless of whether it's the source of your issues, your SC coupler needs to be replaced.

Ok, IGNORE THE TC LAMP for now. A bad hub or TCS problem is not going to happen at THE EXACT SAME TIME as the other symptoms, or go away for that matter. A bad hub is a bad hub, the TC lamp would stay on......Focus on the misfire issue.

I agree because the car does the exact same thing when the ABS fuse is pulled out.

96blackriv wrote:

Did your car throw the code when the SC coupler went bad? A couple of days ago I replaced the serpentine belt and the SC pulley made a clanking noise when i turned it by hand. It also makes a clunking sound when the car's engine is shut off. I have an Actron auto scanner plus code scanner, but just not sure how to use some of the features on it. Vacuum lines appear to be in good shape. What am I looking for when checking the MAF, it isnt throwing a code? Thanks for all the help so far. BTW, whats a good source for the SC coupler?

If it does not have a wire to it (the SC does not) it will *not* throw a code.

The SC pulley is not supposed to make noise when you turn it by hand, so this one is a no brainer -- fix the coupler now before it drives you nuts. There is a write up on how to not only on this site but if you use Google on the internet you'll find several that tell you just what to do - in addition, instructions come with many of the kits that are sold on line for this.

As for the scanner - RTFM (read the fine manual). I bet you can find a manual to download on line if you don't have it. You definitely want to use data logging or snapshot ability while driving, Abaddon must have an abansoned stadium parking lot he goes to to do that diagnosis - watching any meter while driving is just asking for trouble unless you're Abaddon or a pro like him.

After you get this stuff fixed you can take car to dealer and for 1 hour or less charge (an hour would be around $70 - $90 I think) thye will pull the codes and tell you which hub you have to change. Do the change yourself, there are great instructions on this site and the dealer mechs know the dealers charge an awful lot for the job, very little of which the techs actually get because if it goes smoothly and you are using the right tools it does not take all that long.

Best of luck and let us all know how it goes. .Keep those questions coming.

Albertj

Let me clarify on the TC issue.the light only comes on when pulling hills after the car starts acting up.i believe I read on here somewhere that a misfire can temporarily turn off the TC which leads me to believe that its fine just reacting to the other problem.The new upgraded coupler is on its way so i' m going to change it out and re evaluate.I'm also going to pull out the injectors and inspect them as well .

albertj wrote:

As for the scanner - RTFM (read the fine manual). I bet you can find a manual to download on line if you don't have it. You definitely want to use data logging or snapshot ability while driving, Abaddon must have an abansoned stadium parking lot he goes to to do that diagnosis - watching any meter while driving is just asking for trouble unless you're Abaddon or a pro like him.
Albertj

Oh, I'm sorry. I didn't realize that doing circles in a parking lot would make an intermittent uphill/under a load concern arise so fast! I'll try that out next time.......or maybe I'll just guess at what's happening.......

96blackriv wrote:

Let me clarify on the TC issue.the light only comes on when pulling hills after the car starts acting up.i believe I read on here somewhere that a misfire can temporarily turn off the TC which leads me to believe that its fine just reacting to the other problem.

That's why I said to ignore the TC light for now.

Abaddon wrote:

albertj wrote:

As for the scanner - RTFM (read the fine manual). I bet you can find a manual to download on line if you don't have it. You definitely want to use data logging or snapshot ability while driving, Abaddon must have an abansoned stadium parking lot he goes to to do that diagnosis - watching any meter while driving is just asking for trouble unless you're Abaddon or a pro like him.
Albertj

Oh, I'm sorry. I didn't realize that doing circles in a parking lot would make an intermittent uphill/under a load concern arise so fast! I'll try that out next time.......or maybe I'll just guess at what's happening.......

96blackriv wrote:

Let me clarify on the TC issue.the light only comes on when pulling hills after the car starts acting up.i believe I read on here somewhere that a misfire can temporarily turn off the TC which leads me to believe that its fine just reacting to the other problem.

That's why I said to ignore the TC light for now.

Abaddon I apologize, must have misread your post.

96BlackRiv, you might want to get a logging scanner such as Alex Peper's Car-Code. Software is free for download and Alex sells dongles that work with most Windoes-type computers. See http://www.obd-2.com for info. Peper is a little eccentric but his software works. You can get it running then set the laptop in the passenger footwell and let it log the data. Then you can get back home/shop and play back the log, reading it to catch problems.

Albertj

just scanned the car again and a new code popped up. it was the po1406 egr pintle code.not sure if its related but I thought id throw it in.My SC coupler came in the mail this afternoon so its off to the garage I go.

update:cleaned the MAF sensor,replaced a brand new cracked spark plug,ditched the spark plug heat shields,fixed a couple of vacuum leaks and the p0300 cleared.While I was at it I put in my new coupler and boost bypass valve,both from zz performance.Now its time to finally get to enjoy the car I spent 10 years trying to buy.Thanks for all the help and suggestions. Special thanks to Kyla at ZZ performance for tracking down the needle in a haystack boost bypass valve at a reasonable price.

96blackriv wrote:

update:cleaned the MAF sensor,replaced a brand new cracked spark plug,ditched the spark plug heat shields,fixed a couple of vacuum leaks and the p0300 cleared.While I was at it I put in my new coupler and boost bypass valve,both from zz performance.Now its time to finally get to enjoy the car I spent 10 years trying to buy.Thanks for all the help and suggestions. Special thanks to Kyla at ZZ performance for tracking down the needle in a haystack boost bypass valve at a reasonable price.

Over time you may find you wish you'd left those heat shields on the back bank of plugs.

if the heat shields are *really* a problem you likely need new wires.

Albertj