Hey Gang,

87S4 with 120K on the clock has strange issue. I changed the coils, wires, caps, rotors and plugs about a month ago. After all of that, the car was not starting (cranking) as quickly as it used to. Then, it started to crank without much trouble. I wire brushed the connector on the Temp II sensor. The car was running great. Strong pull throughout the RPM range.

Monday I changed the oil and while looking around in the engine bay, I noticed the ground wire that connects to the driver's side coil bracket was not attached. I attached it and today, it ran as if it has a bad wire. Not necessarily running on fewer cylinders but clearly not fully engaged. Sort of a (hard to explain) rumble (not in a good way) when cruising. Car vibrates at idle and on initial takeoff, its sort of uneasy (not smooth). What are your thoughts?

 

Based on experience with my S4, you probably disturbed the coil to distributor wire which is likely corroded as was mine. Remove both coil wires for a careful inspection. Mike were green with corrosion, and one was cracked, arcing intermittently. This could give the symptoms you describe.
This would be step one for me.
Dave

 

I changed all wires including the coil to distributor wires. The ones I replaced were slightly corroded. I replaced the coils also.

 

Take off the grounding wire that you connected last and see if that makes the car run better.
Check to make sure the each wire is connected to the correct spark plug.

 

Still seems like a wire issue. Any chance two wires are swapped? Unsure of your sequence of events, seems that the rough running issue started when you reconnected the coil ground wire, correct?

 

Yes. It ran great before after I changed all of the above and cleaned the sensor

 

Cranking means whaa, whaa, whaa,........as it cranks on the starter motor no varoom, varoom. Starting is when the gasoline explodes and the engine goes varoom, varoom
I really have no idea what you are trying to describe.....

My best guess is it is running on 4 cylinders....two on each bank which correspond to one distributor and one coil. And sometimes NEW parts do NOT WORK.... very frustrating but it happens.

 

It eventually goes vroom but 5 or 6 what, whaa before vroom. After I cleaned the sensor, vroom after 2 what, whaa. The I connected the ground back up & now it's back to 5 or 6 whaa before vroom. Car feels weak while driving

 

do you have an inductive pickup timing light available ?? you can check each plug wire for spark...

 

No sir. Not available

 

Removed the ground wire and vroom in 2 whaa whaa. Still not running as smooth as I would like. Was about to drive it to DC this weekend from Memphis but I guess I will have to fly. Damn!

 

some auto parts stores will loan out tools ....

 

Thanks James. I'll have to borrow one and figure out how to use it. Am I disconnecting the wire at the plug or cap? Is there w write up on how to use the timing light?

 

just clamp an each wire. If spark it will light up.

 

I would put the old parts back one by one until you find the culprit that's causing issue with one rotor/disti or coil......as Jim said sometimes new parts can be bad out of the box.