Fuel or ignition problem?

[76L82]

Talk about Friday the 13th!

I was into a 20 minute ride to work today on the Interstate...everything going well...until the car started to 'lurch' and 'lunge' as if it was running out of gas. I was running at about 3200 rpm and going about 67 mph when it all happened.

However, there was plenty of gas in it. So I lifted my foot off the gas pedal and coasted a bit. I put my foot back on the pedal and kept the car at about 60 mph around 2500 or so rpm. No lurching or lunging. Thinking it may have 'swallowed' something it didn't like, I pulled off the highway and headed to a gas station. I hit 2 traffic signals and the car seemed to be fine again...chalk it up to Friday the 13th gremlins!!

I filled it up with super premium and then got back on the road. Everything's going fine until I try to see if I can get it to do it again...sure enough, 3rd gear around 3200 rpm..the car starts to lurch and lunge again.

I drive it to work another 10 miles or so at low speeds...no problem...doesn't hiccup, sputter or anything. I pop the hood. All the plug wires are intact and where they need to be...no leaking fuel around the carb...hummmm.

I am wondering if there is a problem with the fuel system...accelerator pump, fuel pump ...or is this an ignition problem...distributor, coil, etc.

Of course the inevitable happens...on the way home from work I could swear it is now running rough, has lost a lot of power and dieseling when it never did...

Any thoughts? I have started to worry that I may have lost a cyclinder or something...

 

[MaineShark]

For what it's worth, a buddy of mine had similar symptoms in his BMW. Turned out to be a broken ignition wire. I think the wire between the coil and the distributor, but I can't be certain (was a few years ago, and I never really paid much attention to BMW's )

Might be something to check out.

Joe

 

[c4ever]

Sounds like what happened to me one morning. Fuel pump. Easy enough to check.
Carlo

 

[76L82]

Thanks guys! I have a list to check the fuel pump and wires form the coil to the distributor. I also found that the Temperature Vacuum Switch (TVS) coming off the top of the block had ripped away from the threaded port...that can't be good! My manual states that this switch controls the vacuum to the EGR and distributor and when malfunctioning..retards the distributor advance...learning something new all the time!

MaineShark - Where do you hail from?? I am in the WTVL area. I was wondering if there is a state Vette club?? I know there are quite a few Vette owners up this way that wouldn't mind a summer get together.....

 

[MaineShark]

MaineShark - Where do you hail from?? I am in the WTVL area. I was wondering if there is a state Vette club?? I know there are quite a few Vette owners up this way that wouldn't mind a summer get together.....

I'm way down south. Just a little bit north of the NH border.

There is a group called "Vettes of Coastal Maine" that I'm aware of. One of these days, I'll need to dig out the membership application that they sent me, and join.

I think a meeting sometime in the summer is a great idea. Quickjagg suggested the MDI area, although he may be biased, since he lives there. Once I get my Shark re-assembled, and the weather warms up and dries out a bit, it'll be easier to discuss when&where. Personally, I think it would be great to get people from different (but adjoining) areas, and make a trip along those great back roads that everyone knows of in their area. That would help avoid the tourist traffic.

Joe

 

[76L82]

Joe - Sounds like a great idea!! Please keep me posted!

Mike

 

[Tom Bryant]

An EGR valve sticking open will cause a rough idle but won,t be noticable at road speed. Change out that fuel filter while you are at it. Check the old one to see what is inside it. Looking for rust scale here. Might have enough blockage that it won't allow enough fuel for sustained 3200 rpm running.

Tom

 

[motorman]

look at the plugs,dark means ignition problems and white means fuel problems.

 

[cntrhub]

Sounds like you are draining the float bowls faster than the fuel can get back in the carb. Did you ever replace the filter that is in the carburetor?
It rides fine when you are just riding on the streets. Low RPM, no need to pull a lot of fuel out of the jets.
Rough running will cause a lack of sufficent fuel ratio too.
Check fuel filter at the carb and if there are any more filters between the tank and fuel pump.
Checking fuel out-flow of the fuel pump is the next test. Dangerous as it my be to do this, you have to find the flow rate specs for this on the net, or if someone here can post it for you?
I'm going to guess it's fuel first rather than ignition, since the car is running all the time and not really mis-firing at all speeds. I agree with Tom. Check that filter area for debris.

 

[Jack]

As Joe mentioned ... coil to dist. Your 76 has HEI so coil sits directly on top of rotor button ... just pop coil cover and lift out coil ... look for water /smutz where coil & rotor button mate. However, my first thought is that your ignition control module may be going south (small plastic critter inside dist ... held in w/ 2 screws ... has plugs on both ends). Very cheap, quick & easy to replace. Local parts house, "Standard Ignition" pn LX-301 ... or ... “Wells” pn DR100 ... under $15. Smear some dielectric-heatsink grease on module mount pad and bottom coil seal ... grease usually packaged with new module. Don’t waste your money on a “hotrod” module ... OE-type is aok.
JACK:gap

 

[76L82]

You guys are awesome!! I have my list in hand for what to look for and when I get a chance this week I am going to take a crack at it.

As a foot note..I purposefully drove around for a good 30 minutes and never took the car up over 3000 rpm...man talk about defying temptation..anyways, it ran great without a stumble. Got a chance to give my Mom er first ever ride in a Vette...Priceless!

 

[cruzer99]

If I was a betting man I would bet on clogged fuel filters.:duh