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Odd Behavior - Any Theories?

chevyaddict

Well-known member
Joined
Jun 12, 2002
Messages
894
Location
Tucson, AZ USA
Corvette
1990 Convertible
Hi Folks. I've got some weird behavior going on. Tried to search but didn't find any threads. Three things are happening, which lead me to think it might be electrical but everything else is operating fine, and the car is running fine otherwise.
1. My RPM gauge is way off when I'm driving
2. Car is trying to die when coming to a stop and sometimes it does - it would more probably but now I'm throttling it when I come to lights so it doesn't stall.
3. When it goes to die my radio shuts off (maybe this is an artifact of just trying to preserve voltage for motor running)

The main problem is it wanting to die when I come to a stop. What was throwing me off was my RPMs were showing at 1200 but now that I realize my RPMs are way off, that explains that. So, are these two problems connected? They both started at the same time and it happens regardless of whether I'm running the A/C or not.

Thoughts?
 
Have your battery properly checked with a carbon pile load tester and check your charging system when running at about 2500 rpm's, it should be between 13.2V to 14.5V, use a quality voltmeter at the battery and not the dash gauge. Check your positive and negative cables for tightness at the battery and starter (positive) and negative (engine), both need to be clean and tight.
 
As LLC5 said check all cable connections. Especially where the negative cable connects to the engine at the front left side of the trans near by the engine oil filter area. Make sure the large group of ground(Black) wires there are also clean and tight. It is a major ground wire junction and WILL cause all kinds of weird thing to happen if not secure. Take it apart and clean all the connectors with a little sand paper. Make sure the "shakeproof(toothed-lock) washer" is intact.
 
My first thought when I read the message was "check the battery, and check the grounds". Obviously, I'm not very original in my thinking. :L I hope you get it figured out pretty soon.
 
Thanks everyone for your post. The tachometer problem stopped altogether - was just something weird that day and the behavior has minimized but I do agree with everyone's suggestions. I will tell you my negative terminal on the battery is semi-stripped... I was able to get it tight but probably not tight enough. It is a fairly new battery so exchanging it really isn't an option at this time. I thought that if the car was running the alternator would take over and then battery connection wouldn't be as impactful but it sounds like that thinking is off given what people said so very likely it is a bad grounding situation.
 
I will tell you my negative terminal on the battery is semi-stripped... I was able to get it tight but probably not tight enough. It is a fairly new battery so exchanging it really isn't an option at this time. I thought that if the car was running the alternator would take over and then battery connection wouldn't be as impactful.

A good connection at the battery is very important. Since you don't want to replace the battery, installing a Heli-Coil at the bad thread is probably your best option. Your alternator won't work right with a bad ground at the battery, and this might cause voltage "spikes" which could cause further damage to your electronics!

:w
 
Thanks everyone for your post. The tachometer problem stopped altogether - was just something weird that day and the behavior has minimized but I do agree with everyone's suggestions. I will tell you my negative terminal on the battery is semi-stripped... I was able to get it tight but probably not tight enough. It is a fairly new battery so exchanging it really isn't an option at this time. I thought that if the car was running the alternator would take over and then battery connection wouldn't be as impactful but it sounds like that thinking is off given what people said so very likely it is a bad grounding situation.



A bad battery with a bad or shorted cell could also cause your issues , you need to prove that the battery is good by a proper load test with a carbon pile tester even with a new battery, then proceed with diagnosis.
 
I will tell you my negative terminal on the battery is semi-stripped...

This took out my EBTCM, So you better get it repaired!

Sent from my SM-N920P using Tapatalk
 
Yikes!!! I guess I'll quite messing around with it and get it fixed. It was pretty temperamental today driving it.... almost died twice.
 

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