The Oldsmobile Connection

[andrewk]

Hi all-

I hope I can bounce some ideas of any W-body owners, or anyone for that matter.

My Lumina (1991, 3.1) has been acting strange lately. I have been experiencing what I believe is a misfire at high RPM, after the engine is at full operating temp.

What is happening is when I go to pass someone on the highway, or merge onto the highway, the car hits about 4k RPM, and then it acts like it drops a cylinder, and the RPM rises very slowly, and it is obvious that the car is not running right. It sounds like a misfire, and the car loses power, but I don't know for sure if it is a misfire. Once I let off the gas, and let it go under 4k, it will act normal. It gets worse the longer I drive it.

If I put the car in neutral, I can rev it all I want, but when there is a load, it will act up like this. When the car is cold, it will not do this.

Right now it is pretty cold here in IA, and my usual place to work on my car is unavailable for the time being, since the owner of that shop is down south where it is warm. So I haven't done anything to the car since this started happening, which was about 2 weeks ago.

My first thought is spark, but I was hoping I could get some ideas from you all before I start working on it, which should hopefully be in a week or so, whenever my shop connection returns north.

Any thoughts? Is there more information I can provide?

Thanks all,
Andrew

[91parkave]

Does this happen at a certain throttle position as well or just 4k +?

Do you have access to a scan tool? If so i would do it again so you can view your engine data and help pinpoint the exact problem.

[andrewk]

91parkave wrote: Does this happen at a certain throttle position as well or just 4k +?

Just at 4k+ as best as I can tell. Granted, the throttle has to be past half to get the engine to rev that high, but with the pedal that far down, it will go to 4k before it acts up.

Quote: Do you have access to a scan tool? If so i would do it again so you can view your engine data and help pinpoint the exact problem.

I don't at this time, my shop connection may have one, but he is still down south.

Will an OBDI computer provide real-time data like that? No MIL light comes on, and there are no codes stored.

[91parkave]

yes you can log runs you make with some of the Actron scanners out there, Of cource not as detailed as a obd2 scan but detailed enough that it might show where your problem might be. When you get a chance to test, go for the usual suspects, plugs,wires, ICM, hopefully its something simple, best of luck to you.

[88 Coupe]

andrewk wrote: ........ about 4k RPM, and then it acts like it drops a cylinder ........
Exactly the same RPM? Only one cylinder?

andrewk wrote: ........ when there is a load, it will act up like this ........
A faulty plug and/or wire can cause a load miss.

Paper clip works on OBD1 systems.

Norm

[andrewk]

88Coupe wrote: Exactly the same RPM? Only one cylinder?

Give or take 300 RPM, yes. Once it happens, it will continue to happen at a lower RPM, but it is always when I am accelerating that it acts up. If I let off it will idle fine, and does not sound like it is misfiring.

I can't be sure that it is one cylinder, but I think it is only one cylinder.

We are in for nice weather tomorrow, I will check my plugs and wires.

Quote: Paper clip works on OBD1 systems.

I think he meant either a scan tool that will provide a data stream of the ignition and fuel delivery events, or the home-made equivalent, which is a ALDL cable that you can plug into a laptop and you can run a program that will do the same thing as the commercial scan tool.

I don't have access to either at the moment, so I will use some common sense and my VOM.

Thanks for the reply,
Andrew

[88 Coupe]

andrewk wrote: ........ I think he meant ........
Yes, that would be what he meant. Obviously, it was not based on the information you had already given.

From your first post:

andrewk wrote: ........ my usual place to work on my car is unavailable ........
Wouldn't that include his diagnostic tools?

andrewk wrote: ........ I don't have access to either at the moment, so I will use some common sense and my VOM ........
And any available paper clip/jumper wire.

If it is ignition, you won't get any codes. If it's not, you might even get some help.

Norm

[91parkave]

Just to clarify for anyone reading,

I recomended a Scan to log fuel/ignition as he drives so he could get a clear picture of what's going on when this happens, a Paper clip will not show anything unless the check engine light is on, or the computer has a stored code, which is not the op's case. Weather or not Andrew's shop connect is down south is irrelevant to bring back up at this point. as said before best of luck and hopefully its something simple..

[andrewk]

Hi all,

So far, this is what I have found. I got out my fancy hi-dollar scan tool (paper clip) and jumped the pins. No codes were stored. I took my VOM and started checking plug wires. When I got to #3 cylinder, the plug wire made a nice crunching sound when I pulled it off the plug. The wire end stayed on the plug. I inspected the wire, and tested it, and it was still in an acceptable range, so I crimped on a new end, and reinstalled. I didn't do the back side, because I didn't have the tools to crank the engine forward, and also because I didn't have time after work.

I drove it home, and drove it pretty hard after I got it warmed up. So far, I seemed to have fixed the problem. I'll know for sure whether or not it is fixed on Thursday, when I have to take a small trip to Des Moines.

I think you hit the nail on the head Norm.

Thanks all for the replies so far,

Andrew

[88 Coupe]

91buickman wrote: Just to clarify for anyone reading ........
And just to clarify 91buickmans clarification.

91buickman wrote: ........ a Scan to log fuel/ignition as he drives so he could get a clear picture of what's going on when this happens ........
Again, 91buickman is a bit late. Here it is again:

andrewk wrote: ........ a scan tool that will provide a data stream of the ignition and fuel delivery events, or the home-made equivalent, which is a ALDL cable that you can plug into a laptop and you can run a program that will do the same thing as the commercial scan tool ........
Not only is it more clear, it is more complete. I do not see where any "clarification" is needed.

91buickman wrote: ........ a Paper clip will not show ........
What it will not show, has nothing to do with anything.

91buickman wrote: ........ unless the check engine light is on ........
If it is not illuminated, it is not showing anything.

91buickman wrote: ........ or the computer has a stored code ........
As explained above: If it does, it can be retrieved with a jumper, such as a "paper clip".

Here it is again:

88 Coupe wrote: ........ If it is ignition, you won't get any codes. If it's not, you might even get some help ........
Using a "paper clip" andrewk has 24 codes at his disposal. Any one, or combination, might (or might not) have been helpful during his diagnosis.

91buickman wrote: ........ which is not the op's case ........
Not possible for anyone to know, without accessing the system. By using a "paper clip".

91buickman wrote: ........ Weather or not Andrew's shop connect is down south is irrelevant ........
The "Scantool", in question, is being stored in that shop, and he does not have access to it.

That makes it about as "relevant" as anything can be.

Norm

[88 Coupe]

andrewk wrote: ........ I think you hit the nail on the head ........
Just another lucky guess.

Norm