2000 SSEi Drivability issues

[smokingfang]

I am new to this forum and i have tried to search for my issue, i have not landed on a thread that can help me and hence i am asking this question here.

2000 Bonneville SSEi

138000 KMS - Canadian Car

I had the random miss at idle when in park and car would rock a little bit.
I decided to do the plugs, wires and fuel filter. I replaced with AC delco stuff which was OEM.

Sometimes i feel the car is rocking when i am driving, its almost like a hesitation or a lurching feeling. It happens at random speeds. It does not happen when its cold or driven for less than 20 mins. When it starts to happen and i let go off the gas pedal the car shakes momentarily. If i press the gas pedal and release it right away i get this rocking i feel coming from the engine.

Other times i can feel a shake coming from the rear when i hit speeds of 100km/h or above.

Another thing to note, when i shift into D from P, there's a definite movement and you can feel the tranny engage, its more pronounced in this car now than before.
Tranny was rebuilt at 90,000 KMS.

I am guessing its something to do with either my mounts and/or axles.

How can i go about diagnosing this.
Suspension is tight, tires are a year old. I will re balance them, but i have zero shimmy in the steering wheel when going over 100km/h, i just feel a shake under the seat and coming from the rear.
Also not sure if bad engine mounts and/or axles would cause lurching. No clicking noise or clunks etc.

Any help is much appreciated

[Namrepus28]

It's funny, I've experienced most of the issues you have and despite throwing a considerable amount of time and money at the problems, one of them still persists.

For your random miss issue, I have two recommendations:

- Change the coil packs. (You could even get one and try different positions to troubleshoot instead of replacing all three)
- Change the small vacuum line that runs around the supercharger. (3800 Vacuum Harness)

If the problem persists after those relatively cheap repairs, then it may be the Ignition Control Module, but that's a more expensive part.

When you shift from D into P:

-Rear Transmission Mount

Relatively inexpensive and will likely help with that feeling. If you still feel significant movement, I'd recommend replacing the front mount. There's a inventive option over the stock ones that tend not to last very long, but it stiffens the ride a little. Ask harofreak00 about the "boat roller mount" if you're interested.

And finally the shaking:

-Good luck

Ha. But seriously I have been all over my car trying to solve my 110-120 km/h shake and it's still there. Wheel Bearings/Hubs, Ball Joints, Drive Shafts, New Wheels and Tires, New Inner and Outer Tie Rod Ends, New Rear Shocks (long shot, but had to try), New Passenger Side Engine Mount and Drivers Side Trans Mount, etc.

My mechanic's best guess was one of my new driveshafts wasn't properly balanced, but I just changed them and didn't want to tear it all apart to replace a new part.

One of the few things left on my list to try is my front shocks. We'll see about that in the summer. For now I'm just going to live with it.

The kicker is the cause of your shake might be completely different. It's common for this platform to have this problem, but the fix can be different from car to car.

If anyone else has any advice, feel free to chime in!

[AJT2004]

Some of the issues may not be suspension related, trying disconnecting the MAF sensor and see if things improve. It's OK to drive with it disconnected.
If the MAF is suspect try cleaning or replace with high quality (OEM) sensor.

[smokingfang]

Thanks for the input.

I will disconnect the MAF and test
Will also replace the coil. I have ordered one and will swap it around to see.

The shake bothers me less, i need to figure this miss first.

[smokingfang]

I tested the coils; i bought one new and tried to switch it around. Nothing.
I decided that it was time for coils and ICM anyway and got Delphi coils and Delphi ICM. Replaced it and applied thermal paste. Still the same.
Still got that bucking when doing constant speed. Thought i may as well clean the MAF. Cleaned it with MAF cleaner and right after installing it engine started to stumble bad. I thought it was adjusting, so i let it be. Took it for a spin and i got the P0102: Circuit low input.

I thought i had a bad MAF; got a new one and put it in. Still the same stumbling and now more codes. P0131 and P0171. O2 sensor and Lean on bank 1. Car stumbles a lot with the MAF connected so drove it with it disconnected. Engine runs exactly like before when i had the old coils, ICM and the old MAF connected.

What should be my next to do item?

My theory is the old MAF was dead but never threw a code; and after cleaning and subsequently replacing it the other issues are surfacing up. I smoke tested it and no leaks.

Note: When i re did the leads; i did not put the plastic insulation from the old ones on it. Could the leads touching be an issue? Before i did the leads and plugs i had same issues.

[Namrepus28]

Based on your codes, I'd figure out which O2 sensor that is and replace it.

I'd also run some fuel injector cleaner through the system, and as mentioned before change the 3800 vacuum harness just in case that's causing some of the issues. It solved some erratic idling on my car and the old line was extremely brittle and cracking when I removed it.

It sounds like your MAF may have been bad assuming the P0131 and P0171 codes didn't appear at all until AFTER you put the new one in. And if you cleared the codes after removing the old one and P0102 didn't re-appear then again yes I think you're on the right track assuming the old MAF was bad.

EDIT: ...And like you're deducing, now that you're using a MAF that works it is telling you your O2 sensor is out. Forgot to add that part.

Not sure about the leads.

[smokingfang]

I will check the wiring to O2 sensor, making sure its not in touch with the leads.
Any tips on replacing the O2 sensor. Where are the connectors?

I will also order a new 3800 Vacuum Harness.

Thanks.

Based on your codes, I'd figure out which O2 sensor that is and replace it.

I'd also run some fuel injector cleaner through the system, and as mentioned before change the 3800 vacuum harness just in case that's causing some of the issues. It solved some erratic idling on my car and the old line was extremely brittle and cracking when I removed it.

It sounds like your MAF may have been bad assuming the P0131 and P0171 codes didn't appear at all until AFTER you put the new one in. And if you cleared the codes after removing the old one and P0102 didn't re-appear then again yes I think you're on the right track assuming the old MAF was bad.

EDIT: ...And like you're deducing, now that you're using a MAF that works it is telling you your O2 sensor is out. Forgot to add that part.

Not sure about the leads.

[smokingfang]

Delete - Double Posted

[smokingfang]

Checked with Torque APP:
Both O2s are running 0.0V when MAF is connected.

With No MAF 0.8 and 0.9V

I redid the vacuum harness using plastic vacuum lines and some tees and other connectors i had. No vacuum leaks in the car, smoke tested.

Fuel pressure is 38-40 PSI.

So what is the recommended FP for these 3800 Series 2 SC?

Could it be low fuel pressure that causes the rough idle, misfires and the P0131 and P0171 codes when MAF is connected?

[96 SSEi]

yes, check the o2 sensor near cylinder #4 on back of engine - mounted on exhaust manifold maybe it got damaged when you did plugs
you can clean the throttle body.

for the rear shake, balance tires first. inspect the tires
are the weights there?
is there a bulge, damage?

[Namrepus28]

I will check the wiring to O2 sensor, making sure its not in touch with the leads.
Any tips on replacing the O2 sensor. Where are the connectors?

I will also order a new 3800 Vacuum Harness.

Thanks.

I haven't replaced the one on the back of the engine (I did the one down by the catalytic converter on mine to clear a code), but I'd recommend an O2 Sensor socket to do the job. It made things a lot easier, although it is possible to do the job without it.

The connector is just at the end of the leads coming out of the O2 sensor. Pretty straightforward, nothing to complicated when replacing these. The hardest part is usually getting the old one out.

[smokingfang]

O2 sensor is hooked up correctly.
Any tips on the fuel pressure reading? I have 38 PSI when in the on position or start.

I feel this is low. Should i look at replacing regulator first or fuel pump?

[smokingfang]

Update:

I checked MAF readings again with the new MAF. Turns out it was a similar looking MAF but not for the SC engine. I got the right MAF and no more codes.

Fuel pressure is still low IMO. I still have a slight hesitation under load at highway speeds.

I am reading 38PSI with vacuum connected and 42 PSI with vacuum off.

Anyone here know the spec for L67 SC engines fuel pressure?

My guess is the 50PSI is usually where it should be.

Will this mean a bad regulator or bad pump?

[Namrepus28]

I believe it should be closer to 50psi. There's a range, but I believe it starts in the high 40s, not the high 30s.

Could be either one. I imagine the regulator is easier to change out than the pump, but our cars do have a hatch to access it in the trunk. Or at least mine does.

I'd guess pump since you haven't mentioned anything about soot covered plugs, black smoke from the exhaust, or fuel leaking from the exhaust (which can go hand in hand with a busted regulator) but I'm only speculating.

Based on the age of the car, I'm not sure how much longer the pump will live on regardless. I know they were a common problem on the F-bodies with the N/A 3800 Series II.

[96 SSEi]

has the fuel filter been changed?
please remove the vacuum line from fuel pressure regulator - do you smell/ see gas in the line? if yes, change the regulator.

do you still have driveability issues?

[smokingfang]

Fuel filter is new. no gas when i remove vacuum line. Driveability issue still there with highway speeds, very slight jerking.

[smokingfang]

Update:

Put in a new FPR, now i have 50PSI key on. 48PSI engine running and goes up to 52PSI when throttle is applied
So i am ruling out fuel issue.
New MAF
New Coils
New ICM
New Spark Plugs and Leads
All of this is genuine GM parts or AC Delco.

Idle is solid when in Drive(waiting on red lights etc)
Idle is good but i have some shake when in Park
On driving i feel there's a jerking when maintaining constant speed. Thing goes like a bat out of hell, but its not enjoyable with that jerking.

Vacuum leaks tested again. I have a leak(very very minor) at the tube that goes from manifold to egr i think. But not sure if this is the cause.

What can i look at next?

[96 SSEi]

jerking at speed? is there a misfire? if you have scanner, check for misfire.

[Namrepus28]

Hey, your fuel pressure fix is great news. I know it didn't solve the issue you're hunting, but it's nice to see a concrete result.

I very much doubt a small vacuum leak at the EGR would cause the issue you're describing while driving at speed. It would more likely result in a rough idle, which doesn't sound like a problem now, at least when you're in drive.

Not sure what the cause could be at this point. Best of luck though. You've already made huge improvements to the reliability of the car with the repairs you've done thus far.

[smokingfang]

jerking at speed? is there a misfire? if you have scanner, check for misfire.

Its a very slight rocking feeling at speed.
no codes, scan tool does not show any misfires