Dash Intermittent while driving

[KPW]

Tach is acting screwy (jumping high quickly) and a few times on a 45 minute drive today the whole dash flashed out for a second and caused a miss. Little worried about it dying on the way home.

Any ideas what this could be? Hot day today...




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[karlaw]

My no start car does something similar. I put new fuel pumps in, which the secondary was completely dead. My key switch still does not activate the starter, the starter is fine shape. So I hook up VATS bypass, turn key to run position, then jumpstart to purple wire, the car immediately starts to fire and barely runs for 4-5 seconds, then dies. Have to wait 10 minutes to retry.
Anyways, my speedo cluster goes crazy, and there is a bunch of clicking noises from glove box area at same time cluster is crazy. Each time the key is turned to run position, the cluster and glove box area noises do a cycle, then settles down. But car never starts.


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[KPW]

Here's some more info:

Stop #1: parked in the shade for ~90minutes. Door sill hatch release buttons don't function at this point. Center console one does. Did not check door locks. Leave the car parked and go about our business. Start it up to head toward dinner, and it's still acting funny (tach is erratic and wrong, low voltage at stop lights)

Stop #2: Low on gas, so stop to fill up. Put 15.8gal in, and car seems much happier (tach is accurate again, voltage is OK...standard C4 discharging feeling) Thinking maybe gas fixed the issue...but no logic so still skeptical.

Stop #3: Stopped for dinner ~5-10 minutes from Stop #2. Everything seems OK when we come back, and we drive 50minutes toward home with no issues.

Stop #4: Decide to stop for some ice cream as it gets dark. When we come back to the car, I start it up and flip the headlights on. As we start to drive away, I notice the tach flutter again, and the dash blinks out and comes back. We manage to drive the 10 minutes to home, with the dash blinking out and jerking the car a handful of times along the way.

Car is parked at home now, so I'm hoping to do some troubleshooting to figure out what's up with this.

Summary:


Dash goes blank (LCD and Gauges) while driving, jerks the car
Fuel up seems to help for a while...but ultimately no fix
Charging seems OK, radio stayed on throughout everything, battery and alternator are both new within the last 2-3 months.

Any ideas on where to start?

[conesare2seconds]

It sounds as though you are getting a total loss of electrical power when the dash winks off and the car misses. I would start by checking the battery terminal cables and the condition of the power distribution block behind the battery tray and the nearby chassis grounds.

[scottskill]

Do you have a good shop manual to start your troublshooting? If so start with CCM Flow chart troubleshooting.

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[Paul Workman]

Sounds like several circuits are involved, which makes think the common ground issue. Well, easy enough to kill many potential problems (grounding):

There are two major ground point lugs located at the back of the motor, right and left of center, below the MAP (see FSM for exact location). Clean them both with a wire brush or sand paper, and then coat the lugs with dielectric grease.

Once that is eliminated, we'll see what else remains...

Just my 2 cents:cheers:

P.S. Just to add, IF it were just the dash, I'd be thinking about that multi-pin connector at the back of the instrument cluster. (My cluster was flickering and the tach would jump around. That connector was "frosted" (oxidized), but some brushing and electrical circuit cleaner solved that issue.

[Ccmano]

Start with the simple stuff. What is the condition of the battery? These cars are very touchy about low battery voltage. You could have a battery that is just starting to short out. Do a battery capacity test. What is the voltage of the battery at rest and running?
H
:cheers:

[WARP TEN]

Start with the simple stuff. What is the condition of the battery? These cars are very touchy about low battery voltage. You could have a battery that is just starting to short out. Do a battery capacity test. What is the voltage of the battery at rest and running?
H
:cheers:
I agree on this. It is surprising how frequently a large number of electrical gremlins in ZR-1s come back to a bad battery. Then as Dom points out, grounding points are worth a look. Good Luck!--Bob

[Ccmano]

I just had one do almost exactly this. One day, started and ran normally, next day, no start, gauges going wild, alarm going wonky. Turned out battery was shorting. Voltage was low. Replaced the battery and has been perfect since.
H


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[lfalzarano]

Good article on chasing ghost problems
http://m.cloreinfo.com/?task=get&url=http%3A%2F%2Fcloreinfo.com%2Fsorting-intermittent-faults%2F


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[KPW]

Thanks for all the info everyone. I had a brief moment to check on some of the low-hanging fruit today.

Voltage key-off is ~12V, key-on is ~14.2V.

I have a quick disconnect on the negative battery terminal, and I had used it to cut power while I replaced the headlight gear bushings this weekend. When I checked it today, it was about a quarter-to-half turn loose...

Did a few quick checks, and the car seems relatively happy now.

Will have to confirm with a more extended drive, but I may be giving myself the dummy award this time around.
:sign5:

[Dynomite]

Thanks for all the info everyone. I had a brief moment to check on some of the low-hanging fruit today.

Voltage key-off is ~12V, key-on is ~14.2V.

I have a quick disconnect on the negative battery terminal, and I had used it to cut power while I replaced the headlight gear bushings this weekend. When I checked it today, it was about a quarter-to-half turn loose...

Did a few quick checks, and the car seems relatively happy now.

Will have to confirm with a more extended drive, but I may be giving myself the dummy award this time around.
:sign5:

Nothing dumb about having the Battery Disconnect Switch ;)
I have the Battery Disconnect Switch on ALL ZR-1s (Negative Terminal) with easy access barely opening the hood :thumbsup:

https://cimg6.ibsrv.net/gimg/www.corvetteforum.com-vbulletin/800x600-1/80-9b113ff3_2c27_4600_aba8_a9f3456647a4_1__0376abfa70 aaf09b0d8629d95f8f18f05d564abe.jpg

The Battery Disconnect Switch and Having an Operational Secondary Full Power Switch (https://www.corvetteforum.com/forums/c4-zr-1-discussion/3005470-tech-info-lt5-modifications-rebuild-tricks-500-hp-8.html#post1587653767)

[Ccmano]

Thanks for all the info everyone. I had a brief moment to check on some of the low-hanging fruit today.

Voltage key-off is ~12V, key-on is ~14.2V.

I have a quick disconnect on the negative battery terminal, and I had used it to cut power while I replaced the headlight gear bushings this weekend. When I checked it today, it was about a quarter-to-half turn loose...

Did a few quick checks, and the car seems relatively happy now.

Will have to confirm with a more extended drive, but I may be giving myself the dummy award this time around.
:sign5:


It's always the simple things that get you. Even professional technicians have a tendency to jump to conclusions when the simple answer is staring them in the face, don't feel bad.

Btw, 12 volts on a resting battery is on the low side. Should be more like 13 volts. I would have that battery checked anyway.
H
:cheers: