'89 Riviera. Rough Idle, Horrible throttle response

[HighMileage230000]

I have a 89 Riviera. Mileage is 230,003. It has been running awfully over the last week. Within 30 seconds of startup it begins idling erratically (racing from 650 RPM to 1100 RPM) and it alternates from running very rich, to leaning out. It hesitates HORRIBLY during acceleration and shutters rather violently above 45 mph. Me and a friend pulled the plug from the number 1 cylinder and it has the large "AC delco" letters, almost indicative of original plugs, and it was also comparable with the diagram picture of a badly worn plug, as it has a rounded electrode and worn resistor.

Question would be:

Would plugs alone cause this much trouble?
-and-
How hard is it to do the plugs, factoring in those heat shields that are on the rear? Do I need a special tool to remove them?

[maxwedge]

Welcome to AF. Yes replace the plugs and wires by the sound of the condition, if the probem is still there, a full scan should be done to look at the o'2 sensor, maf activity, also check fuel pressure. These are all basic diagnostic steps for your condition. Sounds like poor maintenance was done, so everything in respect to a full tune up should be replaced. The rear plugs are just tough to get to , no special tools.

[2lazy]

Just went through the same thing with my 1990. At first I thought it was the cam sensor or magnet for it. Nope. Replaced wires, plugs, egr. Same. Died on me 2 days later in an intersection. Towed to my mechanic. Fuel pump is dead.

After speaking to him about this, and knowing alot about 3800s, its a pretty common problem around 130-150k. The fuel pump, oil pressure sensor and crank and cam position sensor all control the fuel pump. Check your fuel pressure! When summer comes, the temps in a tank skyrocket. This causes the margin fuel pump to sputter at first then slowly die. My car started with just small problems, like starting, to the occassional weird loopy idle. What happens is the ball check vavle wear out, and allows the fuel pressure to leak back into the tank. Eventually this ball check valve will get stuck, and when it does no more fuel pressure, and goodbye pump. Happened very similarly on my old 91 Lesabre I traded up from. Symptom : tries to die out more turning right then left.

SO CHECK THAT FUEL PRESSURE!

Best of luck!

P.S. Just noticed your car as well as my 90, both have a recall for the IAC motor. Might want to take that off and give it a good cleaning and lookover. Could explain your erratic idle and dummy light. Just food for thought.