PCV and MAF were cleaned at the start.

I also cleaned the inside of the throttle body and the exterior parts as well as I could.

When I was looking for vacuum leaks, I smeared a film of RTV silicone around each
of the vacuum hose connections.


I'll try a swap of the TPS from the wife'* car. hopefully before she leaves to pick up the kids at school

Mike

Mike following your post with intrest !

I know you said this happens when under a load and at around 2000 rpms, what does it do not under a load, and at what water temp on guage?

D Ryan,

It happens right off idle, and you can notice it even at idle, particularly in drive.
The roughness is most noticible at idle to 2200 rpm under load. If you leave it in park and rev it
up a bit there is an intermittent drop out but not at the same level as under load.

Even a minor load such as a flat parking lot is enough to make it very noticible.
The temperature does not seem to have any effect. It does this whether warm or cold.

At higher rpm it seems to go away but I don't know if it is getting smoothed over
by the other cylinders, or if it actually disappears.

I've had a bad coil before on the 99 and it was instantly identifible as an ignition problem.
The secondary resistance was 1000x more than it should have been i.e 15 megohm vs 15 kohms
Replaced the single coil and it has run smoothly ever since.

This issue is nowhere near that rough, plus when the coil was bad,
it didn't matter what rpm, it never smoothed out.

--Wife took the good car Christmas Shopping so I can't swap parts till this evening.

Thanks,

Mike

OK, wife came back with the car.

OBD-II scanner said that it was not connected, we tried several times.
One counter guy said that because it is a 1995, it is OBD-I with OBD-II connector.
They used an Arctron orange 79$ scanner Don't know what to believe.
I've never had the check engine MIL light come on during any of this.
---the bulb is not burned out, key on lamp check is fine.

-------------------------

Fuel pressure tests were much easier to interpret --Just Fine!
46 psi Key on, not running
44 psi Regular idle
42 psi 2000 rpm load against brakes
51 psi 3100 rpm max load against brakes
44 to 50 back to 44 psi quick snap of throttle no load fuel pressure responded pretty quickly
53 psi remove and cap the vacuum line on the back of the regulator

This seems to be in the range of pressures described in other posts I've searched

-----------------------------------

One of my friends (heavy diesel equipment mechanic) thought it might be a dirty injector or possibly a transmission slip issue.
I'm not sure how to check for a dirty injector, but the transmission fluid is just under the
full line when warm and it doesn't smell burned to me. Beyond that, I'm at a loss.

----------------------------------------

I'll try to swap the TPS sensor from the 99 bonneville this evening after supper.
and get back to you guys with that result.


Mike

You say this is the second motor? Are your Torque Convertor bolts tight?

I have no idea. This has never been an issue in the previous
2-3 years and 40,000 or so miles since the engine was replaced.

I wouldn't think that they would suddenly come loose, but I really don't know.
Could breaking loose the harmonic balancer bolt by using the starter trick have stressed them??
I used my 1/2 air ratchet for the rest of the removal and replacement of the new one.
That was done about 1500 miles and 2-3 months ago.

Is there an access panel on the transmission that is easy to get to so I can give them a twist
with a wrench to see if any move??

Thanks,

Mike

Just a thought, I had a 93 SSE Supercharged, that would vibrate at 2000 but would only do it in Park or Nuetral, didn't think much of it, and it wouldn't shutter while driving.

The 3800 Has a counter rotating shaft that rotates in the opposite direction than you Cam Shaft, located just above the Cam, this counter shaft is driven by a gear off the Cam gear, the Cam gear has an Alluminum Cam Button that hold the Cam from wandering, I holds the cam in place by taking the space between the Timing Case cover and the Cam Shaft, I replaced my Timing chain at 130K and found that this Cam Button almost worn a hole in the Timing Cover causing the Cam to wander, this button could be worn or you are getting Chain bounce, the nylon guide on the tensioner wear out as well.

How many miles are on this second motor? if it'* over 100K I would replace the Timing Chain, it'* recommended at 110-125K

Mike
I have a 95 olds 3.1 it has the OBD 1 , but takes a reader to get the codes out, paper clip trick wont work here! Just any OBD 2 reader wont do it either! O'Ries Auto Parts is the only one that I could get to read it, They had a autoxray 2000 to loan out for a deposit. If you havent disconnected the battery sence the problem has occured it would be a good idea to get it read before you do. In this case the SES light is your best friend.

Having another car to swap parts with is priceless!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

I have read many posts where parts are just thrown at the car for the quick fix , This can get expencive fast and still not get you what you want.

Not quite sure what you mean!

Our you saying that the engine is not running right as soon as you start it (cold or warm) or that after the engine idels down, maybe a minute or 2 later?

Do you get a SES light?

Yep, just that.

Dead cold, key on, wait 2-3 sec for fuel pump, then start
Initial rev as engine starts. Settles to 1200 rpm or so.
With car in park, hands on wheel, you can feel a slight irregular drop out.

In drive at idle, more noticible missing, but not at a regular beat, like it was the same cyl.

Slight throttle, enough to begin to move car, you can feel it easily.
If uphill, or against brakes, it is very noticible up to ~2200 where it seems to either
smooth out, or it is lost in the increased tpm.

Freeway crusing at 55-65 mpg about 2000rpm, there is occasional surging or dropout.

In all cases, cold or warmed up, under full throttle it does not do anything wrong, just takes off smoothly

It has never shown a check engine light. The light works on key-on lamp checkout

================================================== =================

This problem is getting to me. I cannot afford to buy new parts at the drop of a hat.
I replaced one coil pack as it was obviously bad >10megohm secondary resistance.
Swapped parts with my wife'* 99 which runs perfectly. Problem remains with her parts--
--other two coil packs and the ICM. I swapped plug wires, and even bought new ones since there
has been so much feedback on bad plug wires---still cutting out.

The only new evidence is that when i dismounted the IAC to clean, it seemed to be fully extended and
was pretty dirty, which takes me back to the vacuum leak idea again.

I don't know how to remove the fuel injector rail and injectors so that i can pull the upper plastic
intake manifold to put a bead of RTV silicone around the plenum. --I've removed and capped all the
vacuum hoses, including the brake booster (vise grips).

What haven't I checked, or missed??? I'm pretty much at my wits'* end


Thanks,

Big Mike G