Still chasing hesitation, backfire, rough running issue. 97 Bonneville SE 3800 series II N/A.
Sometimes car runs like a rocket and other times I would be afraid to try to pass a moped.
Question: How do you check the harmonic balancer - reason is would this cause an issue with the crank sensor?
Does the 3800 series II have balancer issues?
What is a balancer/pulley price wise?
How hard to change?
I can not get the car to set any codes no matter how rough it runs.
Scan shows no codes and no historic codes even though car will backfire through the intake and surge and shake.
Going to the local wreckers soon and pulling ignition coils, TPS,MAF,ICM, and EGR if I can find them then I will have spares.
What fuel preasure should this car have?
If car wasnt so damn nice I think I would demo derby it!
Thanks
Martin

Check your fuel pressure regulator on the fuel rail. Disconnect while engine is running, if fuel squirts out its bad. Also check to make sure your getting vacuum from that line.

Fuel pressure should be around 43psi if I remember correctly.

Does it idle ok, but grunt and grumble when under load, especially at high rpm?

Don't forget to smell the vacuum line, if you smell gas, the FRP is bad. You should have about 48psi. 46-52 is what your shooting for.

As for the harmonic balancer. It'* not hard to remove, here'* a write up. https://www.gmforum.com/mechanical-134/harmonic-balancer-replacement-286278/

I've only had one that fought me real hard. The rest I was able to break the bolt loose with a good breaker bar.

The stumble, hesitation backfire usually happens when you are at any cruising speed, 60,70, 80, 90 100,kms an hour and you apply throttle say to pass someone.
If you gradually give it throttle from start car will cruise right up to 160 ++ kms with no issue.
Seems to be only if your cruising and apply more throttle although although at times there is no hesitation and car just takes off like it should.
Hate to just start replacing parts and wish it would throw a code but it will not no matter how hard I push it when it acts up.
Are the hamonic balancers an issue on these 3800 engines?

Thanks

Have you scanned for codes? That sounds like the torque converter staying in lock up.

Scan shows no codes and no historic codes even though car will backfire through the intake and surge and shake.
Fuel pressure regulator- no leak from vac line and no odour of gas. TPS checks out on meter, very smooth on accelerate and decelerate.
The FPR and front fuel rail seems to be 1 piece along with the schrader valve, is this correct?
I will have to get a fuel guage on it and check pressure.
Harmonic balancer is very tight with no vibration.
When driving at 60, I stay on throttle and lightly touch brakes, RPM goes up about 200 so lock up is working, right?
Dan, if Wisconsin wasnt so far away you would have another 97 Dark Cherry dumped in your driveway LOL.
Thanks for all the assistance.
Martin

Sounds like FPR is fine, TPS is fine, torque converter is working.

I would pull the plugs and inspect them. If your having a problem with combustion it will show up on the plugs.

Have put in 3 sets of A/C Declcos, exact same issue. 2 sets of new wires, same issue. All plugs are clean.
The backfire through the intake has me thinking spark issue, but no matter how hard I push it with it surging, backfireing it will not set a code.
I unplugged MAF and SES came on so I know SES light works.
Going to have to find a garage around here that can drive the car with a scanner hooked up that will give a print out or graph.
Thanks again.
Martin

I have seen a clogged cat cause problems like this. When it'* popping back threw the intake it has me thinking gases are not getting out.

I thought cat also, but car will cruise 160 - 180 kms an hour and just did a 400 km drive at about 130 kms hr with no issues unless I wanted to give it sudden throttle. Feather throttle usually no miss.
Does not loose power on hills, where a car I had before would barely pick up speed and hills would almost kill it when the cat was plugged.
Maybe if I had your hood on mine...lol.