Power going on and off while the car is on.

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ThePope

New Member
Hi All. I recently did an LS swap into my 98 ek. Everything was working fine for about a week but now I seem to be having an electrical issue. After the car warms up there are sudden drops in power causing an irregular idle until it stalls. When driving, because of the power turning on and off at random intervals, the car is extremely jolty. The relay in (or next to?) the ecu clicks everytime there is a loss of power. I've checked and cleaned all the connections in the harness, changed the cap, rotor and coil, but the problem still persists. A couple days before this problem arose, I installed one O2 sensor on the head pipe but the second one on the cat is still disconnected from the harnes (the CEL is on but that was expected.) Could the O2 sensor in the head pipe cause a problem like this if the connection to the harness is bad or the O2 sensor is faulty? Any other ideas of what to check next?
 
check the timing. check all your grounds. check all of your fuses. start with the free adn easy stuff.

are there any codes? what ecu are you using?
 
Sorry, I didn't include this info in my first post. I checked all the fuses yesterday as well. I checked the grounds that are visible but I haven't checked the grounds that have been rewired to extend the 1st O2 sensor. It's supposed to be a P75 ecu for the 96-00 LS but I'll double check that as well when I get home this afternoon. When the problem started a couple days ago, my friend and I checked for codes. I don't remember the numbers but one was for the second O2 sensor (not hooked up yet) and another for an ignition problem, but it wasn't specific. Thats the main reason why I replaces the cap, coil, rotor and wires.
 
I believe they mean chassis grounds. Also check to make sure your neg terminal is TIGHT on the battery, you shouldnt be able to spin it around!!
 
if you changed the cap/rotor and all that, check the timing. check the grounds that run from the engine to the core support etc. i believe there sould be at least 3 or 4 grounding points.
 
The battery terminals are tight. That was one of the first things I checked. I'll double check for more chassis grounds as well as their connections. Could this problem be related to the wiring of the O2 sensor? Or is that unlikely?
 
The battery terminals are tight. That was one of the first things I checked. I'll double check for more chassis grounds as well as their connections. Could this problem be related to the wiring of the O2 sensor? Or is that unlikely?

If your reffering to the oxygen sensor, bank1 sensor 1, than it is likely if wired up incorrectly. Bank 1, sensor 2 is the oxygen sensor for the catalytic converter. As far as this causing your problem (being disconnected), it is possible as well especially with the ecu you are using.
 
If your reffering to the oxygen sensor, bank1 sensor 1, than it is likely if wired up incorrectly. Bank 1, sensor 2 is the oxygen sensor for the catalytic converter. As far as this causing your problem (being disconnected), it is possible as well especially with the ecu you are using.


The wire for the sensor on top of the throttle body was also extended about a week ago. If the connections are bad in this wire, could that also be the culprit? I'm going to solder those connections instead of using those crimping tubes when I get home.

If it is the wiring to the O2 sensor, would unplugging it from the sensor solve the problem at least temporally?

I think at this point it has to be a connection problem with the wires that were extended. It drove fine for days so maybe something came loose during that time.
 
Found the problem. There were two wires that lead to a sensor on the throttle body below the injectors, These were extended by whoever owned the harness before me, and they did a fairly lousy job, especially with the insulation. I cleaned up the connection and it runs smooth as ever. This weekend I'm going to do a thorough search for other bad connections just to be safe. This is something I should have done before I put it in engine compartment. Lesson learned. Thanks for your help everyone.
 
The wiring being F'd on a O2 sensor wouldnt cause a loss in electrical power....

If his battery warning light does not engage than its obviously not a low voltage problem from the source. When your main oxygen sensor is faulty or inoperative than it will (when driving) cause a "shudder" feel as if it was like a minor fuel cut, so to say.
 
Found the problem. There were two wires that lead to a sensor on the throttle body below the injectors, These were extended by whoever owned the harness before me, and they did a fairly lousy job, especially with the insulation. I cleaned up the connection and it runs smooth as ever. This weekend I'm going to do a thorough search for other bad connections just to be safe. This is something I should have done before I put it in engine compartment. Lesson learned. Thanks for your help everyone.

Just make sure you use the correct gauge wire and solder it and you shouldn't have any issues later on.
 
Well, it drove fine last night as I went to Pepboys to get some zip ties. I made sure it was fully warmed up before I left and had no problems. This morning, before leaving for work, I warmed it all the way up and drove about 3 miles without incident. As soon as I got on the free way the problem started to happen again, so I drove back home. Thankfully i can work from home but damn this is a bitch. I'm going to mess with the O2 sensor more today. What if the O2 sensors switched? If the plug for the second 02 sensor is in the first O2 sensor would that cause a problem? I can't find the second O2 sensor plug on the harness. The connections are there for it in the ecu so it should be there somewhere but...
 
Electrical crap sucks. I believe I found the problem. The main engine harness ground was loose. I spent a good amount of time last night and this morning looking at the engine harness layout online before I saw were the ground was located. Well at least it was an easy fix.
 
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