98 Lumina LTZ Electric "pulse"

[Lumina_in_Lansing]

I have a 1998 Lumina LTZ with 107,000. I have recently had a strange series of problems and was hoping the community could give me a few ideas.

Problem #1: My entire electrical system has a irregular, yet constant pulse to it. All electrical lights (dash, radio lcd, interoir lights, headlights) have a contsant pluse to them. This pulse occurs at all speeds and RPMs. The amount of load on the system has no effect on the pulse. Pulsing only occurs when car is on. When in accessory mode, pulse is not evident. Only when the car is running is there a pulse. Took it into a mechanic to test the alternator. Alernator is putting out constant voltage. It hs been suggested that this problem is due to a faulty ground, but no one can tell me where to find these grounds to check them.

Problem#2: Formerly an occasional nuicance, not becoming more of a common place. I notice that sometimes when I start my Lumina, my RPMs are high when driving as if she won't shift past first gear. My acceleration is almost non-existant when she runs like this. Pressing on the gas causes the engine to rev high, but still little to no acceleration. She doesn't overheat, not does she have a rough idle. However, she will occasionally idle high at a stop until about 1500 RPM then stumble once and fall to normal idle speed.

Had a similar problem with my Escort that turned out to be a leaky hose that was messing with the computer readings. Possibly the same thing occuing here?

Any thoughts would be appreciated.

[gw84]

welcome to AF! are you getting any codes?

[richtazz]

When you checked the alternator, did he just check voltage output, or did he put a diagnostic machine on it? A GM alternator can have adequate voltage and amperage output, but if the diode/rectifier bridge assembly is bad, will cause pulsing as you describe. The diode/rectifier assembly is responsible for keeping current constant.

On the high idle/no shift issue, check the vaccum line that goes to the trans shift modulator. If the line is cracked/split/disconnected, the vacuum leak will cause the high idle, and the trans won't shift due to inadequate vacuum. IF the line looks fine, check the inside of the hose for trans fluid residue. The diaphram inside the modulator could be damaged, which will cause the engine to suck trans fluid through it. If this is the case, your trans fluid level should be low.

[john51md]

Originally Posted by Lumina_in_Lansing

I have a 1998 Lumina LTZ with 107,000. I have recently had a strange series of problems and was hoping the community could give me a few ideas.

Problem #1: My entire electrical system has a irregular, yet constant pulse to it. All electrical lights (dash, radio lcd, interoir lights, headlights) have a contsant pluse to them. This pulse occurs at all speeds and RPMs. The amount of load on the system has no effect on the pulse. Pulsing only occurs when car is on. When in accessory mode, pulse is not evident. Only when the car is running is there a pulse. Took it into a mechanic to test the alternator. Alernator is putting out constant voltage. It hs been suggested that this problem is due to a faulty ground, but no one can tell me where to find these grounds to check them.

Problem#2: Formerly an occasional nuicance, not becoming more of a common place. I notice that sometimes when I start my Lumina, my RPMs are high when driving as if she won't shift past first gear. My acceleration is almost non-existant when she runs like this. Pressing on the gas causes the engine to rev high, but still little to no acceleration. She doesn't overheat, not does she have a rough idle. However, she will occasionally idle high at a stop until about 1500 RPM then stumble once and fall to normal idle speed.

Had a similar problem with my Escort that turned out to be a leaky hose that was messing with the computer readings. Possibly the same thing occuing here?

Any thoughts would be appreciated.

Good luck, hope its something simple, i tried fixing the same thing on a 85 ford pickup for my brother, new altinator/regulator, checked every wire within a inch of its life, over and over could not find why it was pulsing.Added grounds all over the place too. Found nothing.. Got aggrivated and went and bought a used mid 80's Chevy internal regulated altinator, modded the mount and put it on, no more problems, still i would love to know what was the problem, or maybe not..