Hesitation and dipping voltage

[pattejam]

Hello,

For the past week or so, I have a hesitation that has gotten worse. The car still drives, but it feels like I am getting bad spark on a cylinder or something. It usually coincides with wet weather (which we are having). In the past, I pull the coils and put a little dielectric grease in the coil boots and it fixes the problem. This time it did not.

I have pulled the alternator and had it tested. I tests fine. The battery is new. Car starts fine. No CEL lights. A multimeter to the battery leads at idle show 14.1. Grounds look clean. Plugs are 6 months old.

The thing that is odd, is that even though voltage to the battery is fine at idle, the voltage gauge on the dash is dipping from 13 to under 12. The dipping in the gauge is in time with the misfiring I feel from the engine.

My question is, does the drop in gauge voltage indicate something specific that I have not looked at? Is this reading taken from the output current of the alternator or somewhere further down the line?

Thanks in advance!

 

[ftuhy]

It sure sounds like a bad connection somewhere.

Besides measuring the voltage at the battery, measure the voltage at idle in the egnine compartment - from the jump start connection to the engine block or the the frame ground at the igniter.

Let's see what that is, and I'll try to come up with further suggestions.

 

[pattejam]

Thanks. Voltage at the jump terminal is 12.5V. The misfire is coming from the passenger site exhaust, I can feel the pulsating from the muffler. Any ide which cylinder bank that is?

 

[ftuhy]

12.5 at the jump terminal and 14.1 at the battery during idle suggests the car is running off the battery at idle, and there is a 1.6 volt drop in either the battery cables, the ground lead, or both.

If you can get long test leads, next check the drop from the + battery post to the jump terminal. Then check the voltage between the battery ground terminal post and ground on the engine block. That will reveal where the biggest voltage drop is.

I haven't dug through the manual, but asusming you have a stock muffler similar to the one on my '96, and assuming the exhaust goes in one side of the muffler and out the other end (ie, it doesn't loop back to the same side of the muffler), my WAG is the passeneger side exhaust is from the front bank.

 

[pattejam]

I should check the resistance between these points?

 

[ftuhy]

No, check the voltage. Resistance is important, but in most cases is so low that an acurate measurment is difficult. Be sure to make the voltage measurement from the center of the battery post, not the battery terminals. That will help detect a faulty terminal.