Cutting Out, Bad miss- Help Needed Options

[dr914@autoatlanta.com]

I would first replace the points condenser and set dwell timing, as the points fire the spark plugs and the injectors. Also check the grounds at the top rear right of the block and the resistor block. Finally install a fuel pressure guage and make sure it stays steadily on 35 lbs

Frustrated by a Bad Miss. hope the 914World Experts can help me out!

On my 1975 914 (1.8) I have had a sporadic bad miss for the last 6 to 8 months. Here are some of the details.

- it’s been doing this for at least 6-8 months. Some days doesn’t miss at all. But today it was bucking so hard I didn’t know if I’d make it home. This was the worst it’s ever been!

- When it misses it feels like it’s bucking, that is, doesn’t feel like one cylinder miss but total cut out.

- it’s worse under a load, e.g. when going up a steep hill.

- In the driveway today I could rev it up and hold it while standing still with no miss. Didn’t matter if I held it at 2,000, 3,000 revs- didn’t miss.

- not sure if fuel or electric issue. Any tests I could do to determine?

- Does it in all gears.

- The Tac does NOT fluctuate when it cuts out.

- The lights and radio do NOT flicker or stop.


Any suggestions would be greatly appreciated. Thanks in Advance!
PDXBob

[PDXBob]

Thanks Clay and Dr914. Gives me A few more things to check. It shouldn’t make much difference, but thought I’d mention my 914 came with a Pertronics Igniter ignition system.

Dr914 your “700” book very helpful and explained to me why on distributor I have a short hose to nowhere!

[PDXBob]

Ok, so I checked out my TPS and inspected and fixed a coupe of ground wires. But I still have the bad miss, bucking, cutting out or whatever you want to call it.

One thing that I recently noticed is it seems to be really bad after the engine heats up. So, Clay and Dr914 mentioned ballast resistor and I just ordered one. My thinking is maybe the ballast resistor is breaking down when engine hot.

Is this logical, and is there some other likely cause for bad miss that is affected by heat?
Thx, PDXBob

[JeffBowlsby]

Our original engine bay harnesses are 50 years old now, and often are worn out. Have you inspected the condition of your FI and Ignition harnesses? Engine bay harnesses are maintenance items and must occasionally be replaced to avoid problems like you are experiencing.

With the harnesses connected and the engine idling, is there any change in the engine performance when you wiggle each branch and connection? You might also try this at night or darkened garage to observe for any visible lights in the darkness while the engine is running.

Are sections of the outer casing broken or missing exposing the wires? Are those wires brittle or the individual insulation on each wire cracked or broken?

Are any exposed wires pliable not brittle or with cracked insulation?

What is the visual condition of each of its wire terminal connections like? Remove each connection from its component and inspect each wire terminal at each connection. Are any of the wire terminals munched (bent, distorted or pushed back out of their housings), dirty, corroded or broken?


Post here if you find any questionable connection.

[Osnabruck914]

Every time I have had those symptoms, it was simply a loose connection at the coil.

Osnabruck914

[brant]

The fact that you had to repair a few connectors makes it highly likely there is a broken wire or additional connector that needs repair

I’ve pulled the FI or engine harness in the past
Test every circuit. Repair as needed

[brant]

Duplicate post

[PDXBob]

I still have the cutting out (bucking) issue and have done stuff like made sure grounds are connected, new plugs, checked for vacuum leaks. A couple of you suggested it may be a ballast resistor breaking down, so I got a new one from AA. But I can’t see where my old on is located. I have a 1975 914 with L-Jet fuel injection and a Pertronix Ignitor system replacing points.

Where is ballast resistor hiding?