Something weird happened on the way home, misfire?
 

So I have a 77 targa that runs pretty great, although it leaks oil quite a bit, it's generally pretty reliable. Yesterday, on my commute home, I was cruising at around 80mph on the free way when it had a pretty major hiccup; the engine quit, the tach dove downwards, and the car almost felt like the brakes were on for a second; I felt flung forward. Then it resumed normal driving.

A few seconds later, it did it again. Then normal driving. Then again. Then normal driving.

When I got off the freeway, it acted normal and drove without any issues.

The hell? Any ideas?

Fuel pump relay, Coil, Speed/Reference sensor, dizzy - wiring to any of these.
just a couple of ideas.

If you have stock components, your problem sounds electrical to me. Is it ignition or fuel? Check connections at fuel relay which may have rattled loose. Then check the distributor and associated connections to the CDI and the coil. You may find something loose. The other place to look is at the 14 pin connector since this, or one of the pins, can rattle loose or become corroded.
On the odd chance that it not an intermittent electrical problem, when did you last change the fuel filter? A simple test is to remove it and try to blow through it. If it is unobstructed you can blow air through a fuel filter. Good luck on finding your intermittent problem.

I had a intermittent relay connection problem resulting in the exact same symptoms.

That the tach dropped to zero while you were still in motion and in gear makes me think power. Loose battery post? Bad ign switch perhaps. Maybe CDI going south too.

Had something similar happen. It was a loose multi-pin connector under the dash. Check all the black round connectors are tight.

Can you give more details on these connectors under the dash? For a middie, how many should I be looking for? Are they easy to spot and get at?

Thanks

Can someone post a photo or more instructions on this multi pin connector? It just happened again.

ADD,your car is telling you something ,the 6 posts above are telling you somathing, and give you great advise on possible issues related to the symptoms you describe.

Electrical work is not everyones bag,.....if so, park the car until you can get it serviced or you have time to diagnose further.

It may leave you stranded very soon because you may have ADD. ;)

PS I doubt this is the issue ,but while your ( or your mechanic) in there change the fuel filte ,and check the fuel accumulator if these have not been serviced in the last 5-10K mi.

I replaced the fuel filter when I got the car, maybe 5k miles ago. Doesnt' seem like a fuel filter, because it's an abrupt cutout for a split second, then normal.

I'm just looking for specifics on the multipin connector.

Driver's side? Passenger side? Under the dash? Engine compartment? Not sure which connector people are talking about.

Forget the fuel system.

Check the connectors in the engine compartment, check your ground straps etc etc.

Spark/Ignition it sounds like.

I had the very similar warning signals before my CDI quit. That sucker resulted in the ONLY time in 15 years I needed a tow.

So I'm troubleshooting this right now. Pulled the distributor cap, sanded the rotor a bit but it looked okay. Cap has a bit of carbon buildup but not bad. All connections in the engine bay seem tight so far, I found the multipin one in the engine bay on the driver's side.... but what connectors were people referencing under the dash? Anyone have more info?

I don't think it is my fuel filter, as the car runs ace for quite a while even at high RPM/speed.

I did notice my vacuum line running to my distributor was cracked/broken.

Fuel Pump Relay: Where is this?
So can anyone tell me where the fuel pump relay is? I have tried googling for it, but can't find where it is located. I also tried looking it up in my 101 projects book, no dice there either. I want to make sure that connection is secure since multiple people have mentioned it.

Multi Pin Connector Under Dash: Where is this?
I've been under the dash on both sides with a flashlight and I don't see any multi pin connectors. Could anybody provide more photos?

Battery Posts:
I actually know where these are. They are both tight.

Ignition Switch:
Seems fine. How would I diagnose this?

Intermittent Relay: Where is this?
Oldspool suggested this but I am not sure what he is referencing. Anyone?

CDI Box:
Is there way to diagnose this to see if it's the issue, instead of throwing money at it and replacing it? Is this a common failure?

Red relay in the front trunk is the fuel relay.

Tach going to zero is your big clue that it is electrical or ignition. If you haven’t done points, plugs, cap, rotor and wires in awhile, that would be a good start.

I had a similar problem that turned out to be the tiny wire going from the points to the distributor connector- only about an inch long wire and points looked great, but when I put an ohm meter on it and wiggled the wire, the meter numbers went crazy.

Permatune ignition boxes are famous for having intermittent issues, but they seem to do it from heat and run fine after cooling off.

Thanks! So I found it in the frunk, and pulled it out and plugged it back in. Is there a way to test it?

I agree, this seems electrical and not fuel related, given how abrupt it is and how intermittent.

I pulled the cap/rotor off this morning, they looked okay, I scuffed them up to make them a bit brighter and reinstalled. I have not done the plugs or wires though. I'm not sure I have points; I have a 77. From the 101 projects book, it says they only had points up until 1976. How would I check?

I have a stock CDI box, no permatune. Is there a way to test the CDI box to see if it is causing the problem?

Permatune was stock on many 77’s it would be blue if original. 78 was when points went away, you should still have them unless someone modified them.

Do a quick search of the parts section for points and there should be a picture of them.

The thing that really sucks is that you can’t fix what isn’t broken- intermittent problems can be a bear because if it’s running, you can’t troubleshoot it until it fails.

Just to clarify, the points are in the distributor under the rotor and possibly under a thin plastic dust cover just under the rotor, but most of the time that cover is missing.

Do you have a way to check the dwell or points gap?

Might also try wiggling the thin wire going to the distributor while the engine is running- careful of fan and belt spinning!

Good luck, electrical problems can bring grown men to tears.

Something weird happened on the way home, misfire?
 

If it’s an abrupt cut out and resume it points to electrical supply, not fuel or ignition downstream of the points.
I had a pesky no start issue that I finally traced to a failing relay that was part of a dodgy alarm install.
For yours I’d start with all the basics: clean all battery connections, ground straps and fuse terminals, then rule out all connectors to the CDI, distributor, etc one by one. There is a product called “De-Ox” that cleans oxidation from electrical connections. Chasing electrical gremlins is a process of elimination.


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Here's a pic of my CDI box, it is silver, not blue. Is there a way to troubleshoot this to see if it is causing the issue?

https://i.imgur.com/tmTcfie.jpg

The 101 projects says points went away in 1977, not 1978. Weird. Here is a pic of my distributor with the cap pushed out of the way:

https://i.imgur.com/2ROsTfc.jpg

There is a small light tan wire going from the harness to the side of the distributor body, with an electrical taped junction that grounds out on the engine tin. I checked the 1" black wire in the distributor with a meter and it's fine.