It runs fine most of the time, but at higher throttle settings & RPM, like climbing a hill, power output is somewhat uneven.  Sometimes it's almost rough, but if you floor it, it usually evens out some within a couple seconds, and power will pick up.  The owner says on at least one occasion it was extremely rough when climbing a long hill, but I haven't observed that.  If you're watching the tach while this is going on (electronic dash, so tach is a segmented LED bar), it frequently jumps instantaneously up 1000-1500 RPM & back down, and the Check Engine light flashes for just a split second occasionally, both of which lead me to believe the problem is in the computer or electronics.  Anyone have an idea that might help track this down?

Is there a code reader I can get that might be able to give me some hints?

There is no scan tool for these cars. Under the steering column (you gotta remove the two plastic panels beneath the steering column) you'll see the computer with the three large connectors. On the computer you'll see a hole with an LED, this light will flash and display the codes when you turn the key to On.

Long flashes are values of 10, short flashes are values of 1. So 3 long flashes and 2 short flashes would give code #32, for instance. There will be short pauses between codes.

The computer only reads electrical faults, it will not indicate a mechanical fault.

You can find codes lists online as well as the service manuals.

I'd deal with the codes first, in the order the computer displays, if that doesn't solve it, then dig further into the service manuals. 

Edited February 3, 20251 yr by SuspiciousPizza

If your fuel filter hasn't been changed in a long time, it might help to change it.

5 hours ago, SuspiciousPizza said:

There is no scan tool for these cars. Under the steering column (you gotta remove the two plastic panels beneath the steering column) you'll see the computer with the three large connectors. On the computer you'll see a hole with an LED, this light will flash and display the codes when you turn the key to On.

Long flashes are values of 10, short flashes are values of 1. So 3 long flashes and 2 short flashes would give code #32, for instance. There will be short pauses between codes.

The computer only reads electrical faults, it will not indicate a mechanical fault.

You can find codes lists online as well as the service manuals.

I'd deal with the codes first, in the order the computer displays, if that doesn't solve it, then dig further into the service manuals. 

Thanks for that info.  The Chilton's manual I have has very sketchy info about reading the codes; it has the code list, but says nothing about where the computer or light is.  I'll check those next chance I have.

 

1 hour ago, kayakertom said:

If your fuel filter hasn't been changed in a long time, it might help to change it.

Probably a good idea anyway, but I'm not sure how a fuel filter could cause these symptoms, unless I'm missing something.

If you score factory service manuals be sure you get the sections you need. Don’t just buy sections 4,5,6 without being sure they’re to your benefit.

 

Usually it’s section 2 that’s the Engine or Engine/Transmission 

And you would be ok with getting any of the years around your car like 87-89 and I’m pretty sure you’ll have the info you need and then some. 
 

Plenty of us have it had them. Sorry that I got rid of all my 80’s pretty much. Good luck. You’ll be fine. 
 

Being an EA82T my first thought is to check air leaks and the O2 sensor but that’s based off of my limited experience with those and may not even be your cause. But it’s a good item to check off your list. That’s a closed air system. So it doesn’t want additional air. 
 

Again, likely not your issue. But may help for general maintenance. 

Two things come to mind for me - first was the EFI pump dampener is dead or non existent. Or the pump itself is not performing properly. 

The other thought - and it’s a bit of a long shot - is the coolant temp sensor doing some funny stuff. It starts ok? 

Here’s another thought - these have a knock sensor? It could be on the way out or picking up something else that’s not detonation, holding power back. 

Cheers 

Bennie

If your fuel filter is partially clogged, you'll notice it initially at higher rpm.

Another possibility is at least one of the 4 fuel injectors acting up and one possibility is a corroded electrical contact on an injector: