I tested my Battery and Alternator today and found that both are running normal. 12.5V with car off on battery, 14.4V with car on, and 14.4V with car on and AC Full blast and Headlights on. But, the Volts on my gauge inside the car keeps dipping, from 14.4V all the way down to about 12.5V. Is this normal?? It does this when my car has been driven for about 45 min on highway then I come to a dead stop at a light or something, then my volts get a messed up and my gauge goes up and down between 14V and 12V. You think maybe I have a dying alternator or battery?? I have the stock alternator on my 2000 blazer 4x4 4dr. I have an optima redtop gel cell battery under the hood. Had that for about 3 years with no problems. I believe the alternator is a 105 Amp alternator. Says delco or something on it. The belt is in great shape. What else could be wrong? I have not replaced the spark plugs, wires, cap and rotor for 5 years now. You think that needs replacing? Shoud that solve the problem? I feel like my blazer is losing power. Has 106,000 Miles on it, low for this year blazer. It goes slow on the highway when speeding up, like from 50mph to 65mph. Takes a long time to get speed. Looks like I only gain speed when going down hills. Rpms seems weak on car. Any ideas or solutions? Thanks.

 

It is possible that there is a problem with the alternator or connections in the system. The alternator in your truck is PCM controlled. If the PCM doesn't notice the drop in voltage fast enough, it could result in a momentary deficiency in the alternator output for the current draw. There is a post around here somewhere that details rewiring the alternator to put it back to the old system voltage reference approach, removing the PCM from the control loop which can provide more consistent output at/near idle.

 

You think maybe I have clogged injectors or something?? Maybe the blazer is not getting enough gas into the motor. Those bottles of Fuel Injection cleaner, are they worth buying for high mileage cars? I used them before, starting at about 85,000 miles up until 100,000 miles, then stopped using it. Then I noticed my car is slow after I stopped using the cleaner. But, I did recently have the intake manifold gasket replaced. Could there be lost conpression or something? Thanks.

 

How did a discussion about volts move to one about injectors/compression? I don't think you have anything wrong with the engine itself. If the system voltage is dipping too low, it can affect other systems. I would concentrate on the voltage drop issue.

As I stated, you can rewire the alternator to work off of battery reference voltage instead of PCM control which may alleviate your voltage drop at lower RPM.

At the very least, you should disconnect, clean, and reconnect the wiring at the battery and alternator.

As far as running injector cleaner goes, I run a large bottle of Chevron Techron Fuel System Treatment Plus through each of my fuel injected vehicles at every oil change, regardless of mileage.

 

+1 to both of swartllk's post.

When was the last time you changed the air and fuel filters? If it has been a while. A new filter for both may restore/improve the performance.

 

Last changed fuel filter at 91,000 miles and just cleaned my K&N air filter yesterday. It was really dirty and I noticed a change in performance. Thanks.

 

My injectors in my sonoma were dirty so i took them out to have a look and the mist sucked so i put them back in and threw a bottle of GUMOUT full fuel system cleaner in ran it for a while. I had better power after 500 miles i checkd the injecors again and they were spreying nomaly. So gumout is good but alittle pricey