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10/1/12 4:11pm - Original Message: 'Urgent Help Needed!'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 829
Guys, I need some opinions on something.  I drove the Vette this morning to my hometown of Yakima, WA for the funeral of a family friend.  Yakima is about 3.5 hours from where I live, Vancouver, WA.  Car ran like a top the whole way except there was an "occurrence" when I was about 20 miles from my destination.  I was cruising on a freeway, going about 70 or a little more when it suddenly started surging and cutting out.  Then there was a loud backfire.  I pushed the clutch in and started pulling over thinking the engine would quit and I was done, but it stayed running.  I gunned it a few times, put it back in gear and continued driving.  I kept it under 60 the rest of the way there and it ran fine.  Any thoughts???

My theory is either the coil or something else distributor related.  When the cutting out was going on the tach was going crazy.  Neither the coil or distributor are high end units.  I plan on replacing both (dist I may go back to the original after a rebuild) but I haven't yet.  I've also recently had problems with the three wires going from the dist body to the cap, especially the yellow one.  Can a loose connection there cause similar problems?  

Advice would be appreciated - I'm nervous about getting it home 180 miles tomorrow!  


____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/1/12 5:06pm - Reply: 'Re: Urgent Help Needed!'
Norsky Lifetime Member
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Twin Lakes, CO - USA

Vette(s):
SOLD - "The Toy" - 1970 Convertible
SOLD - "The Beast" - 1990 ZR-1 (#682)
"BLKBRRD" - 1978 Trans Am, 400ci/285hp, 4 spd, Black w/black interior, Hurst t-tops

Joined: 1/23/2002
Posts: 6712
I have to admit I'd be in the same boat as you, but I'm sure Joel or someone else well versed in the air, fuel and spark world will be along shortly to give you some advice.

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Jim Olson 

"The Toys"...!!!  Save the Wave!
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10/1/12 8:16pm - Reply: 'Re: Urgent Help Needed!'
F4Gary Gold Member
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.

Joined: 8/26/2006
Posts: 862
What year car?  Why would the tack go crazy when the engine ran rough unless it is an electronic glich.  At first I was thinking trash in the gas, stuck float, etc.

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10/1/12 8:23pm - Reply: 'Re: Urgent Help Needed!'
corvette440hp Lifetime Member
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Joined: 7/2/2006
Posts: 8205
Dave, many years ago I had a similiar problem with my MGB. I lost a screw for the distributor points plate. Of course, it fell right into the garage floor drain sump. I figured no problem, just get another screw. I put the screw in then later drove the car. The car acted like yours. When I finially made it home I checked the advance plate in the distributor. Sure enough it wouldn't move because the new screw was a little longer than the original one. I had to shave it down for my advance to work. Another thought could be that your fuel filter is plugged or your gas cap vent is plugged.........if you have a vented cap. I sure hope you can at least drive home at a slower pace to then look for the problem. 

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corvette440hp
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10/1/12 10:25pm - Reply: 'Re: Urgent Help Needed!'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
Dave, what kind of ignition system do you have?
It sounds like one of three things, or possibly a combo of all. Either the coil is in the process of taking a dump, the ignition module, or the pick-up coil.
I would at the very least change the coil and ignition module before making the trip back home, if at all possible.
Take the cap off, and have a look up inside of it, looking for anything that looks like spark damage, corrosion, or melting. Take the ignition rotor off and look at the bottom of it, and see if you see any lightning bolts going fromt eh center, out towards the two screws that hold it on. Check the little carbon "tit" in the center of the cap for breakage, or other damage.
ANY problems with any of these parts will lead to coil failure, and coil failure will lead to module failure.
Make sure all of the terminals on the coil that fit into the cap, where the wires plug in are seated properly, and that the 4 screws that hold the coil into the cap are nice and snug, but not too tight. Definitely make sure the ground strap and dogleg terminal for the coil are present, and connected correctly.
Hope you have tools to do all of this on the road....


____________________________________
Joel Adams
C3VR Lifetime Member #56    
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             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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10/1/12 10:31pm - Reply: 'Re: Urgent Help Needed!'
Case75
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, - Canada

Vette(s):
1975 Corvette 383 stroker w/Patriot 190 heads, Eagle stroker kit, Comp 279TH7 cam, DUI distributor, Edelbrock 7116 intake, Edelbrock 1806 carb, Hedman Hedders, TH400 w/TCI Breakaway 2400 stall, Transgo 1-2 shift kit.

Joined: 6/19/2012
Posts: 230
Back in June I had the plug wire to #5 cylinder burn up. It didn't happen immediately, It took a couple of weeks to become very apparent what was wrong. Car started having a rough idle, then it would stumble under hard acceleration, eventlualy it started to backfire through the exhaust and I could feel it under my feet. Checked the timing, carb, etc. Started checking plug wires and there it was; it had burned through the insulation right at the boot connection. New plug wire and problem went away. Mind you, I have headers on mine and that is what burned up the wire. I see you have the cast manifolds so heat shouldn't be as much of a problem. Looking forward to the solution...

____________________________________
 
Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
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10/2/12 1:40am - Reply: 'Re: Urgent Help Needed!'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 829
Thanks for all the suggestions, guys.  First of all, pretty sure it's not fuel or one individual cylinder.  What I felt was a complete cut-out on the primary side of the ignition, reasonably sure.  And when I said the tach was going crazy, I meant it was dropping down to zero and then bouncing back up to normal RPM's during the cutouts.  So to me that sounds like complete loss of voltage on the primary side.  

I should have been more specific on what I have for an ignition system: essentially stock HEI.  The distributor is a billet aluminum unit similar to those sold by Jegs or Summit under their brands.  Nothing special.  Module is an Accel unit that is probably about 5 years old but very few miles.  Coil is about the same as the distributor, they might have even come together as a package.  Cap and rotor (red w/ brass terminals) seemed to be in good condition when I installed everything after the engine rebuild in August.  

Here's what I'm going to do:  bought a new coil today, higher end Borg-Warner unit.  Took the cap off and there is some scoring on the terminals so I think I'm going to replace that and the rotor tomorrow before I go.  On the fence about the module.  It's a good quality unit that hasn't seen much use.  Maybe I should buy a replacement and then return it if I don't need it?  Joel: I thought module failures almost always caused a complete no-run situation?  Could the module cause an intermittent problem like this?  I was stranded once before by a module; ended up getting it towed to my house because I didn't know what the problem was at the time.  Other than that stuff, I'm just going to put everything back together and make sure all the connections are perfect.  And say my prayers.  

Thanks again for the help, everyone!


____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/2/12 7:30am - Reply: 'Re: Urgent Help Needed!'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
Ignition modules are electronic...they can fail in many ways. You're right in that they do usually fail when hot, completely, and then work fine again when cooled off. I think you're on the right track, however, with the coil/connections. And..you know how I am about "new"....it don't mean diddly! LOL
Cap/rotor/coil/module failures can occur at any time, and rarely do they fail close to home. Double-check all of the connections at the dist, too, including the 12v power in connection, the connection for the module, and even the tach. A loose connection at the cap can cause weird stuff, too. Hope the coil takes care of it...or at least gets ya back home safely. Thumbs Up

____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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10/2/12 10:49am - Reply: 'Re: Urgent Help Needed!'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 829
Thanks for the vote of confidence, Joel!  Interesting you mentioned the tach connection.  For about 1/2 hour before the incident, the tach started acting funny.  It read low for a long time (2500 at 70 when I know it's more like 2900) but sometimes it would bounce around between the two.  I figured it was the tach filter that needed to be replaced - the board is brand new (yep, I know what you think about "new, though).  I'll make sure that connection is solid before I get on the road.  Just waiting for the auto parts store to open.  

FYI - I'm at my parents' house right now so at least I have access to my dad's garage and tools.  Hopefully there's no road-side repairs involved in this little adventure.  


____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/2/12 1:20pm - Reply: 'Re: Urgent Help Needed!'
daveo76
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 829
Well, there's a new cap, rotor and coil under the hood now and a module in the front seat, just in case.  All connections are solid and the car is running good.  Tach is steady at 3K and above.  Probably won't know until everything is good and hot, though.  

I'll post when I get back, safe and sound!


____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/2/12 8:04pm - Reply: 'Re: Urgent Help Needed!'
daveo76
Standard Member
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Vancouver, WA - USA

Vette(s):
1976 Silver/Firethorn. L48, 4spd. Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.

Joined: 8/25/2005
Posts: 829
Made it home and car ran well the whole way.  Must have been one of the components I replaced (probably the coil) or maybe there was a loose connection that I resolved during the replacement.  Thanks again for the help guys!

Oh, and the other good news: 18 mpg on the way back!  Woo hoo!




____________________________________

 

1976 Silver/Firethorn.  L48, 4spd.  Original 2 bolt, vortec heads, 9.4:1 CR, Speed Pro Cam: 224/224@0.050, 112 LSA, Eagle Steel Crank.
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10/2/12 9:15pm - Reply: 'Re: Urgent Help Needed!'
corvette440hp Lifetime Member
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Joined: 7/2/2006
Posts: 8205
daveo76 said: Made it home and car ran well the whole way.  Must have been one of the components I replaced (probably the coil) or maybe there was a loose connection that I resolved during the replacement.  Thanks again for the help guys!

Oh, and the other good news: 18 mpg on the way back!  Woo hoo!Thumbs Up


DaveClap And mostly thanks to JoelClap Glad everything worked outThumbs Up

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corvette440hp
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10/2/12 10:08pm - Reply: 'Re: Urgent Help Needed!'
Adams' Apple Lifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas

Joined: 11/8/2003
Posts: 19447
  

Good to hear, Dave!!


____________________________________
Joel Adams
C3VR Lifetime Member #56    
My Link


(click for Texas-sized view!)
             NCRS

"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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10/3/12 8:11am - Reply: 'Re: Urgent Help Needed!'
Case75
Former Member
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, - Canada

Vette(s):
1975 Corvette 383 stroker w/Patriot 190 heads, Eagle stroker kit, Comp 279TH7 cam, DUI distributor, Edelbrock 7116 intake, Edelbrock 1806 carb, Hedman Hedders, TH400 w/TCI Breakaway 2400 stall, Transgo 1-2 shift kit.

Joined: 6/19/2012
Posts: 230
Glad it worked out well! Great mileage too!

____________________________________
 
Build Date: May 7, 1975. 383 w/267 RWHP/310 RWTQ
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