Mystery MISFIRE: 1995 Buick Riviera Supercharged V6! 

I remember when these super charged GM cars came out, also in the Pontiac form they were rockets for the day. Great diagnostics Ivan. 🏆👍

That engine was one of the best that GM ever made. A few tweaks like for the water neck and such, and they last forever.

These 3.8 supercharged "grandma" cars were the best kept secret in the used car market for the longest time. Now with the used car market craziness even these sleepers are hard to find at a reasonable price. I still see these a lot here in the Los Angeles suburbs.

Ivan I have worked at a GM dealership in the 90s and we had lots of problems with ECM's. The neat thing that one mechanic whenever he had a problem with the engine they suggested a cap test as you did. Every vehicle he got to work on seems like he could tap on it and it would glitch. Every vehicle I got to work on I could tap till a ECM was flat and had never stopped. He must have had the Midas touch for tap control oh just a just A to comment on the days and uh. We did have a lot of board problems. And your diagnostics was spot on and we never used scopes in the day and we would have found that stuff out too but you are much more advanced in this diagnostic world. You are doing a great job and teaching us some good info thanks Ivan God bless

Had one and loved it. Out in the boonies on the ND border I set the cruise at 100mph and left it there for 15 minutes. It drove like a dream at 100mph but I was scared for my license the whole time. Good times!

That's a neat touch how the PCM connectors are red, white, and blue. They echo nicely with the red, white, and blue shields in the Buick emblem.

I had the same problem with a Bosch Motronic for a 1998 Citroën XM. At that time it was due to a defective ceramic capacitor in the MOSFET driver for the injector.

Very interesting! I saw this before on my 2005 Honda Civic. One day, the ECU just stopped firing the number 4 fuel injector for no known reason. Couldn't afford a replacement ECU and programming, so I jumped the signal wire from the number 3 injector to the number 4 so they both fired at the same time. Surprisingly it actually worked perfectly fine for over a year until I could replace the ECU. I expected that putting twice the normal load on the number 3 injector driver would burn it out, but somehow it never did.

Great videos as always. That 95 3800 engine has several issues. 1. The tailpipe looked oily wet. That is caused by bad valve guides. GM bulletin on that. 2. His supercharger is going bad (growlish sound) did many. 3. The crank sensor and MAF were notorious for going bad with odd issues with engine. 4. Did many many water pumps. 5. Those aftermarket Napa plug wires and coils are junk. Replace with GM OEM. Did many many re-replacements on this.

Just an observation as a tech, battery life out west in hot climates is about 2 years, I noticed a 2014 sticker, frigging unreal. I see no misfire counter but you can see a weak cylinder. That is a cool car!

SFI and C3I. My wife had an 86 Buick LeSabre 3.8L SFI and C3I. The engine mechanically was great, the rest of the car was a rolling intermittent (electrically speaking) on 4 wheels! This car brought back some good, but mostly bad memories. Lots of electrical problems! Good call Ivan on the PCM. The 86 LeSabre had an intermittent PCM.

Buick Rivera. The Mexican Buick.

Man, would have never thought it needed a new PCM with only 27k miles on it. That was probably a parts Canon special before you got to it. Great job!

I’ve been a fan for a while. My favorite is no parts required. And you take something apart and fix it. Like the clutch pedal switch. I bought my son a Toyota Corolla. We have to push the clutch pedal hard to the floor to start it. I left it alone. It’s fun to watch people try to start it. My brother who is pretty sharp said it’s got a dead battery. Ha ha.

Although It`s A Bit Of A Pain Accessing The PCM Under The Dash i Prefer It That Way Compared To When They Place Them In The Engine Compartment Environment Good Call On The PCM 👍

Wow, 3.8 supercharged motor. That's bulletproof motor that gm ever made. Whatever abuse you throw at it, it'll keep on going lol!! Good old days!! Great diagnosis and cool waveforms! You nailed it right. Pcm going shitty! Wow, great video Ivan!

I want a tour of the Jag in the back ground! Great troubleshooting...

Just had to comment on this one. I own a 1995 Riviera 3.8 SC like this one only blue. Had it since it was new. I have changed the PCM TWICE. The first time it was a problem with the EGR circuitry. The second time it was the MAF circuitry. Whent through a lot of diagnostics to finally come down to the PCM, but I couldn't believe it when the second one failed. My car only has 52K on it so its now from a lot of driving. If the horn ever starts to honk on its own, it's the airbag cover shrinking and compressing the laminated horn contact sheet under the cover. It took three sets of burned up horns and dead batteries before I could reproduce the problem and fix it. Problem is there are no parts out there so it gets the relay pulled whenever its parked now.

Great work Ivan! Love how GM made an "odd" car even more so with the bazar IP, the battery under the seat (unusual for that time in a sort of regular car). The Riviera was always GM's styling car... kinda the early 70's boat-tail look again. The Riviera, you either loved it or hated it's styling. Fun video!

Good call Ivan. After my seeing those melted wires at the #4 injector, I was more than ready to call a short and would have gone down that rabbit hole trying to find where those melted wires ended.

Great work! That system is hard to follow. I lucked up and properly diagnosed a failed ignition module on my mother-in-law's Park Avenue.

Brilliant analyse again. Shows that experience and knowledge of your tools is essential.

Good job on the diagnosis! Even though the car only has 27k on it, I've experienced cases where electronics can still age and give problems with little actual use. I've had a few Buicks and three of them had run issues that the only final fix was changing the ECM, after the parts cannon was fired.

HA. Ivan fixed this guy problem and suddenly .. there's no gas for just a little test drive .. This was going to be nice test drive with this american V6-supercharged👍

Great diagnostics again Ivan.keep them coming.

Hey Ivan. I also do automotive electrical and diagnostic work for a living. I recently helped out a neighbor with a mystery misfire on a 2001 Windstar. (Yeah there are a few still on the road.) But I had no equipment with me. Found cylinders 1 and 4 had spark but weaker than the rest. With a rusty screwdriver we found that those cylinders could only jump a quarter inch gap. Where as the rest could go well over an inch. This van has been at two shops. Lol. The coil pack was new, but shorted and junk.

I looked at the interior and thought GM did a great job with this car it looks in great shape for 25 years, 25K and I would assume a garage given the lack of interior wear and tear would do it. Probably not too sophisticated electronically but electronics, rubber, plastic age, I would not expect mechanical unless you suspect it was sidelined years ago after someone drag raced it and broke something. I would swap injectors if it isn't too hard, check the control signal on 2 connectors without the injector plugged in. If a signal is sent when unplugged they should be the same check at the computer.

I can’t even watch this whole video without commenting how awesome these cars are. Absolutely world class seats and interior. Sooo comfortable and quiet. She even honks pretty good and reliable

Have a great day Ivan. Great video.

I was thinking a corroded wire from #4 injector to the PCM. GM usually had an intermediate connector with all the injectors as another place for corrosion. That car looked pretty clean for a ‘95, so if not a corroded wire maybe rodent damage. I wasn’t expecting the PCM with such low miles, I wonder if that had anything to do with the parasitic draw… Great Job with the diagnosis 👍

I so enjoy your video's .. Your processes are logical and that in itself surpasses most all other videos.

I saw this car in the background of the last video and was hoping to see it! I love the content and you have me contemplating getting into auto diagnostics myself.

I was following you but then lost you when you were sure it was ECU, awesome Ivan another awesome fix! I will rewatch this one until I own it:)

Oh wow, I just commented on this car in the background of the last video. Man I miss my '95 Riviera, it was the same color with black leather. Damn. Edit: I would just about give my left kidney for that car. I wonder if the owner would take 6k for it??

Very interesting Ivan. Thanks!

Never got to see what the inside of the PCM looked like. I have to wonder if after 27 years, if an electrolytic cap puked its guts and was corroding the PCB. Time can be just as harsh as mileage.

Ivan, it comes to my mind that maybe a solder ball is rolling around in that computer and intermittently shorting it out. A crack in the mother board could have the same intermittent effect. Replacing the PCM is a tough call to make so your process to get there is greatly appreciated. Thanks for including your PICO waveforms. This really helps me to understand your process and to follow along to your conclusion. I guess I've seen enough of your waveforms that many are no longer squiggly lines to me but actually make sense. So about a third of the way through this video you threw up a waveform and I immediately had the thought "Well, that's not right" regarding the performance of the vehicle. So thank you so much. Thanks for Sharing!

I have a 1997 Riviera. and one often problem with mine is a vacuum lone elbow. It will crack in about 3 to 9 months and leak, and the car will run kind of rough when it happens. I assume the original rubber elbow in that spot was more heat resistant, or else someone before me moved or replaced some part in that area with the wrong angle of hose connector part. I had the power steering pump fall off my about 3 years ago and a few months after that the timing sensors had to be replaced. There was a problem with the bolts the factory used on the power steering pump, but I am way beyond a factory recall. However since the garage had to drill out the broken bolts, I wonder if the shaving dropped down and screwed up the timing things below it. Water under the bridge, and past history. Speaking of water. Yes, it is a Riviera and the inside kind-of looks a bit like the inside of a boat cabin, but don't try running it into a deep water, keep ant water below the door level. I was caught off guard 2 years back, when we had a heavy rain and I waited the storm out. However one of the storm drains was clogged and I was also on a side road that that road I was going to cross I did not realize had deep dips on either side. I saw other cars and truck going down the road and thought it was OK. Well I got through the first dip and over the main roan but the dip on the other side wen partly over the hood and about half way up the doors, and the car stalled. I was trough the deep part and the water did go down and I eventually got the car started, by that point some water was in the car. I pulled up the road and parked the car at an angle to let it drain out, problem was it had affected my driver seat motors. Long story short, I had to have my niece drive the car home for me because at one point the seat went up and forward the whole way almost trapping me. The power seat and the mirror control computer is under the driver seat, and it got wet and was screwed it up. Finally after calling several junk yards for several days I was able to get the control box, before they crushed these cars at the junk yards.

The good olé GM 3800 3.8L V6. Like some of their V8 engines GM should’ve kept this engine & gave it even more updates.

Looking well Ivan, the weather helps, beautiful here in central PA, must make your job so much more enjoyable when it's like this.

Every time I see a buick 3800 with mix match coils I think they were chasing an ignition control module.

Great video intro! 😂 I'd love to own a Riviera. They're just so cool and unique. Thanks for getting my friend's Vibe roadworthy again. She'll be really happy with the work!

These Rivys came out just before I started as a Tech for a Buick Dealership, I loved taking them for their NVIs, we had a 10 mile stretch we did our inspection drive and those supercharged V6s would cruise nicely, Ivan I wish we would have had scopes back then LOL, we had the Tech 1, a noid light, a test light and a Fluke meter back then, basic stone age equipment!! 🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣🤣

Good job sharing

Ivan : “ GM PCMs are pretty stout “ Riviera PCM : “ hold my motherboard”

Once the main problem is fixed definetly need some newgas and needs to be driven at least a tankfull

Very interesting case! You solved the mystery quite fast, but I wonder how long it would take without the Pico - back in the day, dealership would just swap parts until it worked :-)

You're a good man - to say the least!

Well done ivan. We had them years ago on fords they gave up on them blow motors right and left .but they were not hard to work on .sam good job

Thumbs up Rocket man ! You got that in pretty short order! Good & accurate!

Good old Red White Blue ECM. Back in the Day, We replaced many. Good Job Ivan. What about that Beautiful Jag?

Sweet car, thanks for sharing Ivan! Really would love to do a teardown on that old computer. Bad chip perhaps? Still good process of elimination.

Got a feeling it’s not going to be a mystery for long.

Sweet vid Ivan. To bad it wasn’t no parts required. I was hoping for a compromised wire, but you can’t win them all. lol.

I was beginning to suspect the ignitiion control module under the spark modules.

I was thinking burned exhaust valve or seat, which these SC engines were known for, but bad driver in an OBD1 GM computer? Yep. Seen that many times back in the day.

Sometimes on those older processors failures occur mainly due to thermal damage or burnt metallization, oxide or dielectric breakdown, contact damage, or junction damage.The most common ESD-induced failure mode, open, shorts, leakage or resistive shorts at input/output pins. So those 28-year-old processors are pretty old and go way past the shelf life of what they are tested for.

👋Sir very nice explanation, diagnostic

dude you are a real mechanic!!!!

Nice fix on the Buick Riv- eee - air - aaah

Back in about 1992 an old couple in my neighborhood bought a new Buick Park Avenue Ultra that was so beautiful,,, but 10 years later at about 80000 miles everything broke,, they were very unlucky,,, super charger took a dump,,, other issues,, air conditioning took a dump it was retrofitted to 134a but we're in Houston so it was never the same it didn't work... They had about $6000 in repairs into it and finally had to walk away.... It still looked new...

Even unused electronics have a shelf life. Age, not use probably killed the computer. It would be nice if the computers included a self diagnostic.

The best part about your videos is how you unmask those grease geniuses who do not belong anywhere near a vehicle due to their level of ignorance. Just looking at the coil replacement job on that vehicle shows you the level of mediocracy of who worked on that vehicle.

well done bro

Very nice car!

Sometimes it is the driver mosfet that's ill, Now if that was your car i'm sure you would have the top off that computer in 3 seconds flat and replace it :-D Mosfets are tough devices but they still fail (Me stating the obvious lol ). I've repaired too many switch mode power supplies, yep cooked mosfets.

Only thing hotter than Yankee bats is Ivan and his diag skills. Nice to see a historic vehicle in such clean condition.

We call these GM cars as having OBD 1.5 because the DLC is an OBD2 looking connector but you can only get live data with a Tech 2 or a really high end scan tool like your snap-on.

With the 3800's, it's almost always the ignition module.

Thanks for the great video. You commented how well it ran with a missing injector. If not mistaken, don't I remember that all 6 injectors fire on every pulse? If so, maybe the accumulated fumes in the manifold provide a little fuel to even the dead cylinder?

My first thought is that this is one model year before ODB2 was mandated (1996); did GM put ODB2 on this car before it was mandated? Second, my guess is A, shorted harness only because the car is 28 years old.

Thanks!

Those GM Memcals always fire up with only a couple of rotations , I had an old 4 cylinder one from the 80s and even though rust was the only thing holding the rear of it together - you barely touched the key and it fired up. It must be the method they use to fire the coils on crank.

My thought was that the injector might be high resistance and the PCM was seeing too low an initial current. To disprove this, what if you swapped just the writes between two adjacent injectors? They would fire at the wrong time sure, but you could at least prove the injector was good?

thats the good GM

That computer is not old; it is vintage

Fixed a few 90s cars by soldering new capacitors on the ECU board. Only works if the rest of the components aren't corroded too much.

Ivan, just a friendly point for reference. 1000 ma or 1000 mv is, 1amp or 1 volt. "milli" is one thousand. "micro" is one million. "m" symbol representing "milli" and "u" symbol representing "micro". 100 ma or 100 mv is, .1amp or .1volt. 26 mv is .026volt. and not .26volt. .26volt is 260mv or 26000uv. .026volt is 1/10 of .26volt. .026volt is practically zero volt and can be "noise" or crossover. This did not affect your diagnosis.

amazing thats all thats wrong with a car that old with so few miles, u would think the gas would be gumming up the injectors, must have drove it , like u said just enough to keep this loose , wonder what the oil, coolant, looked like, thanks for posting, parts required whant whaa!

I think this style coil pack secondary powers two plugs in an even fire wasted spark system. So the plugs are in series across the coil. Is this correct? The bad news is the problem is an injector driver in the ECM. The good news is the problem is an injector driver in the ECM. The driver is probably a discrete smart power device in a TO-220 package, if so the module can be repaired. Similar to a MLD2N06CL, but in the TO-220 package (3 Terminal Device). The device used in the original module is most likely a Harris Semiconductor smart power N-Channel logic level MOSFET with active clamp and current limit.

hard to tell by the video, but I think I hear valves a clattering, valve guides are probably smoked. they loved to cook the center injector coils, especially if ran hot from a coolant/thermostat issue. probably 20 others things I'm not thinking of. 🤔

I've had to call a couple computers and it's a very hard call to make in a 1990's car as there are so few good ones still in junk yards and most remans are worse than the one you pull out.

I was thinking--- cut that injector wire at the PCM and check the pulse with a scope at the PCM.. that way it eliminates the harness and if you still get a random signal -- then you have no doubts that it's the PCM that's the problem... If not, you could have ran your own long jumper wire with aligator clips and bypass the harness and see if it would still run the injector.. Actually a cooll looking engine setup though- being supercharged.

This video has me wondering: is there anything Ivan won’t work on? 😂

What erroneous behavior could be seen with a bad battery and primary power only from the alternator? The result negates this inquiry though could it ever be an issue?

Back about 1986, my next door neighbor had a 79 Buick Riviera with the turbo V6. He said the turbo had to be replaced every 30k miles!

Without further Audew, bad battery.😢 .. (but came back to life 😊).

That 15.2 volts was the jump pack. (I've had them SHUT DOWN alternators, until the voltage drops back to within thresholds, OR next start cycle!?)

Id rather have you test drive the E Type in the background.

I rate my chances better with the SU carbs on the E type in the background.

Sounds like intake manifold gaskets upper and lower these Buick 231 CID 3800 engines are notorious for this from 1995-2005.

Ivan. Enjoy your videos. Say I have a question I’m not that much of an auto mechanic but I noticed that you use a laptop in your diagnostics. Is it possible to hook up my computer to my diagnostic plug somehow on my car and do the diagnostics do I need a special program? How is that done in general? Thanks

Obd 1 is music to my ears

90's PCMs are failing due to bad solder joints and/or failing electrolytic capacitors. Such low mileage probably does more harm than good to the older PCMs

@11:00 is that an E-type in de background?

Please explain to me about the issues that I might encounter in a 1998 Riviera? I'm very tempted

I am guessing a bad , or several bad, solder joints on the ECM. Maybe a bad cap, but if it were my car, resoldering suspect joints would be the first thing.

Hey Ivan, happy Father's Day if it applies. Question, how are you able to use a scanner on an OB1 vehicle? I have a 95 Ford Explorer that I would love to be able to use my (Thinktool) on. I purchased the Thinktool after your recommendation a year or so ago knowing I would not be able to use it on my own personal cars but able to use it on the newer cars (OBD2) I work on from time to time mostly family and friends and some referrals. Is it possible to use the Thinktool on an OBD1 system? Are there other scanners out there that can be used on an OBD1 system? Thanks for sharing all the videos I've learned quite a bit since subscribing years ago. Keep up the good work!

I have gm 3.8 buick regal have problem may I send you video

Sucks brand new cars are sitting in dealership and independent shops because there aren’t enough diagnosticians in the US. It’s quite obvious we don’t have near the qualified diagnosticians to be able to fix them any more. Too bad they couldn’t design cars better after 2000. The quality went down the tubes and no one wants to cover their cars with warranties any more. I feel bad for the next generation of autoworkers.