Have 95 Cutlass Supreme and this morning it had a slight virbration (kind of like a small quick surging) when accelerating. It has 120K miles and is on it's 3rd tranny and has some trannny shifting problems at around 40mph. When not in gear the vibration is barely noticeable, but once it is put in gear you cna feel it a lot more and when the accelerator is pressed you can really feel th vibration. The vibrations is a lot less noticeable when not accelerating. Once speed is above about 25 I do not notice the vibration. It feels sort of like the engine is "missing" but the tach appears pretty steady. Acceleration is also somewhat weak (has had a bit of a hesitation for quite a while).

Any suggestions.

I would do this in this order.

1. Check the Air charge temperature sensor. It is usually located inside the air filter box. Just clean it and spray some throttle body cleaner and let it dry.

2. Remove and clean the IAC (Idle Air Control solenoid) with a throttle body cleaner and a brush. Clean the spot where the IAC goes in the throttle body.

3. The TPS might have some dead spot. TPS can't be clean but just have to replace it.

4. Check each spark plug wires and make sure they are not touching each other or touching the engine block. It might be cross-firing. Use a spark plug wire separator and some tie wraps.

5. Check the Crankshaft Position Sensor (CKPS) wire and make sure it is not rubbing on the engine block.

I replace plugs, plug wires, O2 sensor (thought is was suppose to have 2 O2 sensors, but I only found one) and cleaned the throttle body still running rough and is sluggish.

I don't know exactly what the IAC is, but I am sure I can find it if it is attached to the throttle body, I will try to clean it sometime and see if that helps.

Could you tell me where to find the Crankshaft position sensor and the TPS? I have no idea where they are is or what they look like.

I hope I get it figured out soon, I really don't want to take it to the oldsmobile shop they haven't done a very good job on anything for me in the past.

Thanks for your help.

IAC looks like this http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=GPS&MfrPartNumber=77910010&PartType=757&PTSet=A
Located on the top-side of the throttle body intake.

TPS looks like this
http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=GPS&MfrPartNumber=7793651&PartType=280&PTSet=A
It is just below the IAC.

CKPS looks like this
http://www.partsamerica.com/PartDetails.asp?SourceArea=&SourcePage=SEARCHRESULTS&MfrCode=GPS&MfrPartNumber=CSS7&PartType=762&PTSet=A
It is located behind the engine and accessible from underneath.

Cleaned the IAC and it appeared to help a little, but that could be that the idle speed went from about 800-900 to about 1100-1200.

Since there was a change when I cleaned the IAC, do you think that it might need replacing?

Again, thanks for all your help

Before you start replacing anything, I've come across some thread and in addition to IAC, TPS, CKPS, they have fixed it by just cleaning the MAF (Mass Air Flow sensor located right after the air filter box) or ACTS (Air Charge Temperature sensor located on the air filter box side)

I'll definitely give that a try. I am beginning to think it might be a clogged injector because it is now running slightly (very slightly) better and I did add some injector cleaner to the fuel. Along with cleaning the items you suggested I will probably add another dose of fuel injector cleaner with a few gallons of high octane fuel and hopefully that will take care of it.

Thanks again for your help.

they have fixed it by just cleaning the MAF (Mass Air Flow sensor located right after the air filter box) or ACTS (Air Charge Temperature sensor located on the air filter box side)


I did not see either the MAF or the ACTS. The only thing between my filter box and throttle body is a tiny sensor of some sort located in the duct between the filter box and throttle body (could this be the ACTS?) and nothing on the filter box side.

While it appears all the things I have done so far have helped a little, the problem is still there. If it weren't for the fact that the symptoms occur while the car is in park I would think the problem could be tranny related. When accerating, quite often the car will shift hard or act as though it is having trouble shifting or figuring out what gear it should be in. This was a problem the car had before, but only at around 40-45 mph, now it occurs at lower speeds and you can definitely feel the vibration when accelerating in OD at around 50.

Since the car has 120K miles on it I will probably go ahead and change the IAC & TPS, since they are relatively inexpensive, and maybe that will help a little. If I can't get the problem pinpointed pretty soon I guess I will be left with little alternative than to put the car in the shop.

One of our vehicles has developed some missing problems and we can feel it during IDLE as well. The RPMs does not change.
We noticed that the spark plug wires was laying on the engine block and exhaust manifold. The spark plug wire was rubbing and shorting on the block. We use tie wrap and moved the spark plug wires away from each other and away from the block/exhaust manifold and the problem went away. So we knew it was the spark plug wires because the missing problem did not come back after we moved the spark plug wires away from each other/block/exhaust manifold.

Doubt it is a pug wire since I replaced the wires shortly after I started having this problem.