Guys, I just got back from a two week vacation yesterday and decided to take the 308 out for a spin. She started up fine; after it was warmed up I decided to give it a bit of an Italian tune up. Everything was great. On the way back home I stopped off to get some supplies. Again, I fired the car up and it was just a normal start up; however, I came to a stoplight and the idle became rough after revving the car out to about 5k in second. Once I started off the car backfired at 3k I pulled off into a parking lot, turned the car off and waited about 10 minutes. I restarted the car and she was fine for the remainder of the drive home. Quick rundown on the car: 78 308 GTS Electromotive ignition Last major was April 2007 Any ideas?
Was it backfiring through the exhaust or "coughing" through the intake? (Be careful, if you don't know, don't guess, or you will be on a wild goose chase.) Sometimes you can get a stuck float valve on one carb that causes two cylinder to go super lean. Then car coughs like mad until the valve unsticks, which is usually soon. Backfires are LOUD as hell through the exhaust. Totally different than coughing through the carbs which you hear well through the intake on the passenger side. I had a float valve sticking on my 308 years ago. Every once in a while I would take a turn, the gas would slosh in the float bowls and push up the float, and stick the valve. The engine would consume the fuel in that carb, then the car would start coughing like mad for a few seconds until the valve unstuck. Then it would mysteriously go away. (Took a while to figure it out!) I rebuilt the carbs, replaced the float valves (which are standard parts on a rebuild kit as this is not uncommon in worn float valves), and the problem never came back. Birdman
I'm pretty sure its a backfire out the exhaust. I've always known backfires to be akin to my 12-gauge browning and that's how I would describe this loud bang. One friend of mine suggested its a component of the electromotive ignition. I drove the car to work today and on the trip up it was smooth sailing. At lunch the backfiring happened again. I repeated the same process of turning the car off for about a minute or two. The car was fine the rest of the day - I even hustled up to 110 without problem.
If you're getting a backfire like that it means unburnt fuel is getting into a hot exhaust manifold. That can cause all manner of problems, definitely need to get it fixed. I had this happen on another car and it blew out a plug on the pre muffler. Then then car sounded like an asthmatic linebacker. Mine was caused by the distributor being misaligned, so the timing was way off. You've got EM ignition? Check the pickup and see if it's become loose or misaligned, or the gap is too large. If the gap is off it can definitely lead to timing issues.
Agree with the previous poster. Check the pickup wheel and pickup for firing. I would do this manually by turning the engine by hand with the ignition in the run position. You should be able to hear the 'snaps' when the ignition fires. Before any of this, check all ignition wires top to bottom for correct resistance and cracks.
I checked all the wires after this initially happened. They're fine. I was hoping it was just a wire but no luck... besides the stuttering and backfiring were not consistently happening (which I would think is a possible sign of a bad wire). That being said I'm a novice mechanic at best and certainly not up on my electronic ignition system. Where's the best place to get replacement parts for EM ignition?
I wonder if one of those coils in the EM system is firing intermittently. Might check the wiring to all those coils as well. Not too familiar with the setup
have the same problem-well sort of-,had my points taken out for the EM, -plugs wires and everything replaced. Car coughs-sounds like little pops-my girlfriend says it sounds like a popcorn machine-I usually hear it in low gear going down hill, when I first start up the car. Tends to go away after the car warms up. Seems I only notice it when I'm driving through town-it's annoying as heck. I've also had the LOUD bang before-but fixed that with Birdman's Fuse blocks. Does anybody think it's a stuck Float? How can you tell the difference between coughing through the carbs or a back fire?
I have the Birdman setup. One of my buddies suggested the coil packs and in his experience with other electronic ignitions this is a problem he sees often; however, my buddy hasn't worked with this set up before. I'm hoping to get the car into the garage this weekend to look at it while I'm doing brake pads and an oil change. I'm really stuck on the idea of when I turn the car off then back on again that something is being reset in the electronics, a ctrl-alt-del if you will.
Nick, The EM system does not work like a computer -- no "ctrl-alt-del" reset happening when you turn the car off and restart. It is a relatively simple system: The timing wheel on the damper tells the sensor where TDC is. Basically, the timing ring has a number of teeth, and two consecutive ones are missing. The computer senses where the missing teeth are, and then judges the RPMs of the car by the speed at which the teeth pass the pickup sensor. Based on TDC each revolution, the computer fires the coils for each bank, and advances or retards the timing based on engine speed, based on a pre-determined ignition curve. I would check a couple of things. First, check the timing ring, make sure it hasn't moved on the damper. And check the pickup. Make sure nothing hit it, loosened up or shifted at all. I agree it is worth cleaning the ring and pick up to be sure. I personally doubt that it is the coil packs. They are virtually brand new and have worked well. You can easily check them with an inductive timing light. One coil serves two cylinders -- it is a "lost spark" system, firing twice per cylinder, once on compression, once on exhaust, since the corresponding cylinder is on the other stroke. If you remove the inspection plate at the top of the flywheel, you can check the timing with an inductive timing light with an adjustable timing. Easy to do. Assuming the ring, pickup and coils are okay, I'd check what Birdman was saying about the floats in the carbs. Webers are great, but they are prone to some problems, like the floats sticking. If you've never dealt with them before, have someone who is familiar with Webers do it for you. Too many things to screw up in there, not the least of which is dropping the little gromits into the carbs when you remove the air filter housing. From the sound of it, my guess would be with the carbs, and a stuck float would certainly explain it. Unless there is a loose wire on the EM causing you to lose signal, it is a pretty fool-proof system. Sticky carb float makes more sense. Steve
Hey Gang, If it's a backfire out the exhaust, it's not the floats. Sticky floats would cause a lean condition which would pop through the carbs. Don't go chasing things that are not likely the issue. That's why I asked where the backfire was coming from. It is not a "component of the electromotive" unless the EM is set up wrong or the trigger wheel has moved or something. I have an EM on my car and it's about the best thing I ever did to the car. It's very simple to use a timing light to verify the timing and that will tell you if this is a timing issue. If it's a backfire from the exhaust, it's probably timing or something related to the ignition. Check all your plug wires/extenders to be sure you don't have a flaky one. But check that timing! A timing light is cheap. Birdman
I haven't got the slightest idea how the fuseblocks would have fixed a backfire. As for the popping, put your ear to the intake on the passenger side and listen for the popping there. It is common for these things to pop a little through the intake when they are cold and not warmed up. It's a carb car man, it's old. It doesn't have all the fancy engine management stuff of a modern car to make it run perfectly when it's cold. The carbs are set up to make the car run right at operating temp. When the car isn't warmed up, you can't expect perfection. So do not waste your time trying to fix things that only exist when the car isn't warmed up. Once the car is up to temperature, does it cough?
Most likely a timing issue which could be brought on by poorly operating advance in the distributors, or a pair of dizzys that are not advancing together. But there are many things that "could" be the problem. You need to start with a timing light! Checking the timing is EASY!!! 1. Get a timing light with adjustable advance. Here's one at Harbor Freight for $30. 2. Hook the pickup sensor for the light to the #1 cylinder plug wire. That would the the cylinder nearest to the passenger side/rear of the car on a US spec car. (The one near the oil filler.) 3. Remove the inspection cover for the flywheel. It's the little cover right next to the oil filter. 4. You might want to turn the engine by hand to find the PM 1-4 Mark on the flywheel which is the TDC Mark for cylinder 1. Then put a dab of yellow paint on the mark. Just makes it easier to see. 5. Start the engine. The timing light will be flashing in synch with plug #1. 6. Adjust the timing on the light until it is flashing exactly when the yellow TDC mark is lining up with the pointer next to the flywheel. Now read the advance you dialed in from the timing light. Check against the spec in the owners manual. 7. Check at idle and several other RPMs. Now you can see if the advance is following the spec in the OM. 8. Fixing the advance if it's off is different depending on whether or not you have an electromotive or distributors. On a distributor, you can only really "set" the static advance. The advance curve is up to the mechanical advance mechanism being clean and smoothly operating. On the Electromotive, the static advance is set by the position of the pickup wheel on the crank and then the advance curve is set by the little trim potentiometers on the "brain." If you have a Ferrari with a factory electronic ignition, advance is not user-settable and should never be off (unless one of the sensors is flaky or dead). From the GT4 service manual (approx): 600 RPM (idle) 0 degree advance 1700 RPM 5 degree advance 3400 13 degrees advance
This is pretty much the sentiment echoed by all the engineers I work with - including one former 308 owner . I've got a few maintenance issues I need to deal with and plan to throw the car in the air next weekend. I have a major road trip coming up and need to have the car ready in two weeks for the trip.
I have not had a chance to check the car out yet. However, I have driven the car without incident. I'm pushing back my planned lift time due to an emergency trip I need to make. Likely will have it resolved within 2.5 weeks. On another note new brake pads and oil filter have arrived and am looking forward to changing everything out.
Just remember when you crawl underneath -- the one in the rear of the car that says "Cambio" is the TRANSMISSION, not the engine. The engine oil plug is the one further forward. It helps if the engine is a little warm, so the oil drains more freely, but doesn't have to be hot. And when you reinstall the plug, do NOT overtighten it. The temptation is to really pull on it. Don't. Get a nice fresh washer and tighten it snug, refill with oil, and check for leaks. You do not want to strip the plug hole by overtightening it.
