[jj5428]

Car starts and runs awesome when cold for about 7 minutes then it starts to misfire on cylinders 1 and 3 when it warms up. Sometimes its just cylinder 3 after running for a bit.

If you give it ANY gas the misfires go away completely and the engine runs fine when it warms up.

Replaced the following:
upper intake manifold gasket
Ignition module and coils. 3 different ignition modules and coils from other cars that run fine.
MAF
MAP
Throttle body
Crank sensor AC Delco
Cam sensor AC delco
Plugs wires
PCV
Oxygen sensors
removed valve cover and rockers are both moving. no broken springs.
replaced all 6 fuel injectors AC Delco
replaced pigtail wiring harness for 1 and 3 fuel injector.
replaced PCM with a spare programmed vin with TIS2000
replaced EGR and stainless pipe to it

Did a compression test 160 psi both cylinders
did a leak down test 14-16% loss on the cylinders

What the heck else could be wrong with this thing?

Timing chain? Is there a way to check if its loose without pulling cover?
Harmonic balancer? If the rubber goes bad can it cause a misfire 3x 18x tone ring moving possibly?
weak valve spring? how do you check that?

I have access to a 2 channel pico scope new user barely know anything and I hooked it up to the cam and 3 x and 18x signals and do not see any weird anomalies. no dropouts when looking at it hot or cold.

does anyone have a good waveform from a 3800 they could send me or I can send my 3x and cam sensor captures for anyone to look at.

This damn car has me stumped any help would be appreciated.

Is there a way to just raise the RPM's by say 100 or 200 rpms then the problem goes away.

Thanks

 

[Sortaslow]

Check your alternator for AC voltage.Simply set your meter for AC and check for leakage.Worth a shot.

 

[dezldave961]

Don't tempt him to now go buy an alternator 😵‍💫

On a serious note, this is at the extreme end for classic cases of someone buying random replacement parts without fully diagnosing/troubleshooting the issue with appropriate data. I see this all the time, but people tend to post after putting more knots in the string they're trying to untie, first. We'll try our best to assist with experience on this platform, but it's ultimately up to the owner to implement whatever actions they do. The original issue still exists, from the sound of it, but you've also disturbed dozens of other components/connectors/sealing surfaces which may or may not be exacerbating the problem, or creating different ones.

The list is so long that it's now difficult to be helpful without knowing what's been touched that's relevant. Common issues are lower intake gasket, vac leaks in multiple common spots, ignition components at various spots, exhaust leaks ahead of O2, etc.... It's not ALL of these and more, but that's what I see being thrown at the wall instead of scanning the car, doing careful troubleshooting to save time/money/effort in the ling run, and eventually solve the issue directly. Swap-tronics or a binary approach can be useful, but it will take some thought to dig back int the right direction.

Hope you get it done, and learned something new about this car along the way.

 

[jj5428]

Don't tempt him to now go buy an alternator 😵‍💫

On a serious note, this is at the extreme end for classic cases of someone buying random replacement parts without fully diagnosing/troubleshooting the issue with appropriate data. I see this all the time, but people tend to post after putting more knots in the string they're trying to untie, first. We'll try our best to assist with experience on this platform, but it's ultimately up to the owner to implement whatever actions they do. The original issue still exists, from the sound of it, but you've also disturbed dozens of other components/connectors/sealing surfaces which may or may not be exacerbating the problem, or creating different ones.

The list is so long that it's now difficult to be helpful without knowing what's been touched that's relevant. Common issues are lower intake gasket, vac leaks in multiple common spots, ignition components at various spots, exhaust leaks ahead of O2, etc.... It's not ALL of these and more, but that's what I see being thrown at the wall instead of scanning the car, doing careful troubleshooting to save time/money/effort in the ling run, and eventually solve the issue directly. Swap-tronics or a binary approach can be useful, but it will take some thought to dig back int the right direction.

Hope you get it done, and learned something new about this car along the way.

I was throwing crap at the wall on this one because it was completely intermittent. It really didn't cost me anything but time because I have three of the cars and was doing swap-tronics. I get spare parts from the junkyard from low mileage cars that have like trees fall on them or get rear ended.

and Its's fixed.....

I banged my head against the wall trying to figure out how to use a picoscope for the first time 2 channel model and found it wasn't the timing chain.

I can't tell you what ultimately fixed it because I did three things at the same time.

1. Installed new upstream 02 sensor.
2. replaced alternator (from other car) when I put a volt meter on AC and went alt bat to neg battery it read 37.0 on 200 scale oddly enought the new alternator does the same thing. I thought this should be close to 0
3. This is what I think fixed it..... I took the valve cover off again and sprayed berrymans B12 down the pushrod holes of cylinders 1 and three. Did this several times and let it sit over night. Used probably half a damn can of it.

Still had misfires when I left to go to help parents it was a 5 mile trip. Checked at his house still a few misfires. Bummed out. Drove it home and went 30 mile trip and the misfires are gone! I think a couple lifters were sticking and the berryman's worked them free. I know a bunch of it is still in the oil and will be changing it.

Case closed hopefully.

 

[jj5428]

I was throwing crap at the wall on this one because it was completely intermittent. It really didn't cost me anything but time because I have three of the cars and was doing swap-tronics. I get spare parts from the junkyard from low mileage cars that have like trees fall on them or get rear ended.

and Its's fixed.....

I banged my head against the wall trying to figure out how to use a picoscope for the first time 2 channel model and found it wasn't the timing chain.

I can't tell you what ultimately fixed it because I did three things at the same time.

1. Installed new upstream 02 sensor.
2. replaced alternator (from other car) when I put a volt meter on AC and went alt bat to neg battery it read 37.0 on 200 scale oddly enought the new alternator does the same thing. I thought this should be close to 0
3. This is what I think fixed it..... I took the valve cover off again and sprayed berrymans B12 down the pushrod holes of cylinders 1 and three. Did this several times and let it sit over night. Used probably half a damn can of it.

Still had misfires when I left to go to help parents it was a 5 mile trip. Checked at his house still a few misfires. Bummed out. Drove it home and went 30 mile trip and the misfires are gone! I think a couple lifters were sticking and the berryman's worked them free. I know a bunch of it is still in the oil and will be changing it.

Case closed hopefully.

 

[jj5428]

I forgot to mention this beast has 241,000 miles on it so everything I threw at it probably would have went out soon anyway. I did learn a lot on this one and was just glad it wasn't the head gasket or timing chain. Guy I bought it from said he just did head gasket. If he did it was a long time ago.

One other thing I just thought of was before I replaced the alternator the turn signal would click at a random cadence. It was not consistent. After the new alternator that went away.

Now I want to get a 4 channel scope but good lord $1600 for a pico 4425? My 2 channel was only $99

Definitely found some new options on my scanner and next time around I will know how to tshoot better. Got my scope looking and the cam and 3x and 18x signals so no more random parts throwing for me.

Thanks for the help

 

[dezldave961]

Hope you got it, just stinks not to know the inciting incident for certain. I mainly still approach troubleshooting as a poor college kid like I was when I got my GTP 20yrs ago, so minimal parts buying and maximum evaluation/research time were key to getting it right once, with minimal downtime, if possible. That usually works for the younger coworkers I help out with their vehicles, as long as they're willing to see the bigger picture of it.

 

[jj5428]

I've had quite a few Grand Prix's and Buick Lacrosse's over the years and also learned how to fix them with broken transmissions. Done several rebuilds and a few where I just replaced the broken forward band.

I changed all this crap in a few days just wanted to get this one done only bought the car for $800 so if it didnt get fixed was just going to use it for parts.

This got me thinking how can you check for weak valve springs and lifters that are not working correctly? When I popped the valve cover it looked like they were working fine. They were all tight as far as I could tell. Is the only way a picoscope and a pressure transducer? I did test all cylinders on this car and they passed compression and leakdown tests before I started throwing parts at it. I did throw all the parts at it because the misfires were so random. Sometimes it would misfire on cylinder 1&3 sometimes 1 only sometimes 3 only. Was frustrating as hell.

Got lucky I guess and saw a guy on youtube that did the berrymans on a few lifters and was successful and gave that a try never would have thought of that. Video wasn't even on a 3800 it was a chevy truck.

Still ran good all day today drove it for a few hours.

 

[dezldave961]

Pretty sure our lifters are common dimensions with SBC's, up thru LS's and so forth, just a matter of internal valving differences based on requirements, etc. If that was indeed the fix, I'm guessing some previous owner wasn't kind with the oil changes/selection. There's so many of these cars still on the road, and 95% of them get treated like garbage, due to lack of funds and/or care.

Springs aren't going to be a major issue, aside from a freak break, as they're not being pushed to the limit like we run into with an aftermarket build using parts with less testing and lower margins of error than OEM.

Testing springs can be done with the same rig a shop would use, lifters not so simple, but there's a handful of typical misfire-causers on 3800's that are much less internal. People are quick to dig deeper into these than necessary, blowing past the common culprits, sometimes luckily fixing the issue on the way back up (wiring/vac/gasket sealing they re-set or repair during assembly, etc.). There's also new things being added to the list as more go past 20+yrs and 200+k with very spotty maintenance, or generic work done without 3800-specific issues addressed until they cause a problem.

We only get to see/help the few that arrive thru our pinhole view of the owners, but I always hope it keeps a few more on the road rather than the crusher.

 

[jj5428]

Here is the youtube video for the Berrymans its 11 years old. Hope its ok to post link.

I definitely like saving them from the crusher. I have bought a few that were going to get scrapped just because the timing cover was leaking and shops wanted $1500 to repair.

I never thought I'd tear into a transmission I've always considered them the fuse between the motor and the rear end But I kept driving/owning these cars that would get the bang slip into gear from a stop at completely random times and they also were so damn intermittent. Absolutely frustrating driving these cars when they do that. Gotta love the transmission shops $3000 we'll fix it every time. Car is worth $2000. Sometimes they just need an EPC solenoid.

Anyway first time I rebuilt one and it took me like 20-30 hours because I was triple checking everything and figuring out how stuff goes back in and getting a few new tools I crossed my fingers started it up and put it in gear and it moved. I'll never forget how good that felt. Now when I fix them it's kind of fun because it's not such a mystery anymore. Just take my time and put it back together with new parts that are broke.

Nice chattin' with you and thanks for the help.

 

[Jim R]

I'm wondering, is it advisable to replace the lifters in a high mileage 3800 when changing the intake manifold gaskets? My GS has 198K and ticks for several minutes when started cold. I just live with it for now, but since intake gaskets are such a weak spot, and mine are original, it's not a reach to think that I will have the intake leak sooner or later.

 

[srgblr25]

Car starts and runs awesome when cold for about 7 minutes then it starts to misfire on cylinders 1 and 3 when it warms up. Sometimes its just cylinder 3 after running for a bit. If you give it ANY gas the misfires go away completely and the engine runs fine when it warms up. Replaced the following: upper intake manifold gasket Ignition module and coils. 3 different ignition modules and coils from other cars that run fine. MAF MAP Throttle body Crank sensor AC Delco Cam sensor AC delco Plugs wires PCV Oxygen sensors removed valve cover and rockers are both moving. no broken springs. replaced all 6 fuel injectors AC Delco replaced pigtail wiring harness for 1 and 3 fuel injector. replaced PCM with a spare programmed vin with TIS2000 replaced EGR and stainless pipe to it Did a compression test 160 psi both cylinders did a leak down test 14-16% loss on the cylinders What the heck else could be wrong with this thing? Timing chain? Is there a way to check if its loose without pulling cover? Harmonic balancer? If the rubber goes bad can it cause a misfire 3x 18x tone ring moving possibly? weak valve spring? how do you check that? I have access to a 2 channel pico scope new user barely know anything and I hooked it up to the cam and 3 x and 18x signals and do not see any weird anomalies. no dropouts when looking at it hot or cold. does anyone have a good waveform from a 3800 they could send me or I can send my 3x and cam sensor captures for anyone to look at. This damn car has me stumped any help would be appreciated. Is there a way to just raise the RPM's by say 100 or 200 rpms then the problem goes away. Thanks

Head gasket anti freeze leaking into your spark plug it starts as a misfire just like that until the hole gets bigger and starts filing out your spark plugs soon as the pressure starts building antifreeze drips in the chamber and the misfire is the fire in the chamber trying to burn it up have four different cars develope the same problem replaced everything like you after all of that head gasket everytime