308 Erratic Engine Behavior Problem

Sounds like a fuel delivery issue. Check/replace the fuel pump. The carb bowls sound like they are not being filled with enough pressure. THat, or the power going to the fuel pump should be checked at different throttle openings to make sure it is getting even current and is not cutting in and out. That is my bit! Good luck

 

I would look closely at your ignition. I have had similar problems due to degraded plug extenders and wire insulation. It may be fine at idle but shorts through the insulation under higher load.

Just a thought. In my rather limited experience, every time I have blamed the fuel system I have been wrong, it was ignition.

 

I agree, the plug extenders could be a likely candidate as well. You could try removing the extenders and placing the plug wires directly onto the plug and see if there is a difference.

 

For some reason, an ignition problem is not coming to mind with this one. You have such strong components that even if the rotors were worn down a little, the MSD would not have any issue jumping the gaps.

The voltage at the fuel pump while under load is what keeps coming to mind with your symptoms. I hope it is that simple.

 

Sounds like plug wires are breaking down under load. Even though they are new you may have a bad connection in the dizzy cap.

 

Ding ding ding... plug extenders ... check for holes on the sides... if so need to replace...also could mean your wires look good on the outside, but are arcing when voltage goes up... had that happen on my QV.

 

Carbs have fuel bowls and dont instantly empty and refill. Your pump could quit and the motor would run a minute or so if the bowls were full.

I have found a lot of wires that shorted internally, and not just ignition wires, but 12 V power and ground leads. Check everything, including fuses and ignition key switch, and relays.

Check the grounds. There should be two flat uninsulated webbed copper straps from the engine to the frame on each side. Check the ground lead on the battery, it should be the same type of flat cable, but either way check for solid connection on the frame.

I would start from scratch and check the entire ignition system again, caps, rotors, especially for hairline cracks or carbon tracking in the cap. Also check the carbon brush, wire resistance, extensions, plugs. Check the coils too. And if your running points, even if just to fire the MSD, they still should be properly cleaned and gapped. If they were worn to far open or closed, it could cause your symtoms.

 

If it's fuel delivery, a lot of times you can rev to redline when parked, but not when driving. Have you tried revving the car when parked? If it exhibits the exact same symptoms both ways, I agree with the thought it's electrical somewhere. How's your fuse box? Any hot areas, burn marks?

Ken

 

Sounds like ignition issues with 1 or 2 plugs firing intermittently. When you eliminate the stock extenders, you will find it is very difficult to get the long wire extenders seated properly onto the plugs. Several things to check: 1. Be sure the wires are not bundled. 2. Check wires in the dark to see if there is any arcing. Sometimes you can actually hear the arcing 3. Wiggle wires while running, you never know. 4. Check caps for carbon tracks. 5. Replace condensers. 6. Review all the things written by the others. 7. Be methodical – you’ll find it. Good luck, we’ve all been there.

 

Ummm.... I was under the impression that this was a 308 engine... which I beleive they all had some form of extender... cause the spark plug does not rest at the very top of the head.... so the big long thing on the end of your wire is what I'm talking about....anyhow this is a common thing. before you start replacing fuel parts, I always check ignition stuff... you could also have some leaking oil on the inside of your distributer... I think the carb cars had this issue at times... the seals go after a while... This would be a pain to fix... my bet is still the extenders or an non seated plug end.

 

This indicates a fuel delivery issue, but it could be the result of an electrical problem. I would look at the fuel pump first and be sure it's getting enough electricity. Follow the entire circuit if possible; could be fuse box, relays, bad ground, etc.

It could of course be a clogged fuel line, filter etc. but you said you checked that out. Maybe you should recheck it? Your car has duel gas tanks with a crossover, right? Mine does too, and the T that joins the two tanks to the line going to the fuel pump was a major clog area for me when I first got my car; sediment coated the walls like a bad artery! Get a brass replacement if yours is plastic; modern fuels eat those things up.

Ken

 

I just went through that problem it was a burnt plug extender, I opted to use taylor 8mm wires and eliminate the plug extenders alltogeter it is fine now,they can make you chase your tail before you discover the problem thats for sure !!!!!!!!

 

Great idea with the sound card. Think i'd be frightened of vapourising my laptop!! What exactly was 'wired appropriately'?

I had a similar problem to yours but it was easy to find because as the car faltered the tacho went out as well. It turned out to be a faulty connection plug in the low tension side between the distributor and the Crane ignition box of tricks. Only happened under acceleration, cornering and bumps. Stationary it was fine. I replaced the plug with a high quality gold plated version, although just crimping the plug connections a bit firmer may also have worked.

Richard

 

he said he doesn't have plug extenders which is weird because every 308 I've seen uses extenders and yes I just replaced mine for exactly the same reason as the first post and obviously so have a few of us so it must be electrical .... have you tried a different set of leads, the ones you think are good may be breaking down under load ??

 

Thanks for the link Christopher. This looks like a fancy bit of software. I tried to write something similar using GPS tracking data from acceleration runs, but the sampling frequency was too low so by the time you got the velocity and the acceleration from the position data it was all getting a bit spikey, (either that or the Ferrari was just accelerating too darn fast ). This powerdyn has a really nice interface with power-torque graphs and so on, and even if it is not particularly accurate it should be fine for comparing different mods and settings to find the best set up.

Has anybody tried this on their car?

Richard