308 QV slow to rev

My thoughts:

Fuel line clog. Check the fuel filter(s) too. Is the pump okay? Can you rev past 4000 at idle? If yes, then that's it. If no, the trouble is likely elsewhere.

Exhaust restriction. I have no idea how your car is set up but a symptom of clogged/restricted exhaust is low power.

Have you checked the timing? A loose distributor may have you way retarded and that will severly affect power, if it runs at all.

Um....that's all I can think of off hand short of some major engine issue.

Ken

 

Sounds like timing. If the exhaust is getting overly hot it is likely too far retarded/not enough advance.

 

It sounds like you may have 1 bank of cylinders out. Pull a coil wire onbe at a time and see.

Dave

 

If a cat is overheating, it could be getting unburned fuel from one bank of cylinders not firing. I would check for spark on all cylinders first. With the cat getting hot, seems unlikely to be a fuel delivery issue, but of course I'm wrong quite often! Figure out which bank has the overheating cat and check ignition there first!

Inability to rev is a symptom of having a bank out.

Birdman

 

What he said. Put a timing light on a plug wire and see if one bank is out. Then go to the coil wires and test again. Rotors go south once in a while. If it is a rotor the plug wires will be dead but the coil wires will show spark. If the coil wires show no signs of life get an ohm meter and test the crank sensors. There are three, one for RPM the other for crank position for either bank. They should be 700 ohms or so, don't split hairs. They will either be near that or infinate.

 

If he had an entire bank out wouldn't it sound REALLY different too?

 

If it can run through the rpm range in the garage then this eliminates some problems such as timing, point bounce, etc. No pull when on the road sounds to me like ignition breakdown - coil, leads, dizzy, etc. If it falters more the more you put your foot down this is what I'd look at. Fuel supply could also be a problem but less likely with these symptoms IMHO.

With a bank totally out the idle would be crap. In your case the cyls are only going out when asked to do some work, not at idle.

 

Bruce:
The 3X8 have a 180 degree crankshaft and this combined with the firing order and the two distributor configuration causes the car to sound almost the same if it is running on only one bank. It will have much less power, but it will sound almost the same. I suspect this is your problem.

Like Rifledriver (he seems like a real pro) said, no need to unplug any wires--just use an inductive timing light and check front bank, rear bank, and coil wires using the light to verify.

If it is a one bank issue, check the plugs on top of the coils they get jarred and could get some moisture. You might try to wiggle the plugs around while the car is running, but be very careful of the high voltage wires. I understand the HV circuits have extremely high voltage and will cause pain if you conatct them.

Good Luck,

Mark

 

Oops, shooting my mouth off again. This makes sense in that despite having 4 cyls out the remaining ones are firing on a regular cycle (like a Subaru boxer flat 4?) and so it can still seem smooth enough. I'll have to try it - surely it would sound different on only 1 bank though, even if it is still relatively smooth?

 

Fuel, fuel, fuel! You're not getting enough fuel. Clogged fuel line, clogged filter, bad pump....your problem is likely one of the three, or some Ferrari specific fuel delivery thing that I'm clueless about.

But check for one bank out as well since it will only take a minute.

Ken

 

Ken,
I'll bet right now it is ignition and 50-50 is on 4 cylinders. Cats get hot from unburnt fuel, not too little fuel. Lean running would result in backfires through the intake. The motors will run smoothly with a bank out, but lower idle speed and, of course, little power.

Dave

 

Oh well, not fuel huh! If one coil is bad, I'd replace both; the other one would likely be ready to die as well. They don't last forever. Yes, switching them around is a great test.

Ken

 

I'm not sure I understand what you did. But if you tried what I think you said of course the motor won't run.

Its very uncommon to have a bad coil on a 4 valve.

Did you try what I said?

 

Did you take both the wires off the caps and coils and install them on the other caps and coils? If you only took the wires out of the coils and reversed them the car will not run.

I you are not in posession of the most basic diagnostic tools (timing light) this will be a very difficult and time consuming process.

 

Yes it is wrong, I will not go into a lesson here on the theory and operation of 4 cycle motors. Just do it my way.


Also you never, never run that motor with a plug or coil wire disconnected. You can and may already have cooked electronic components.

 

I had VERY similar symptoms on my 308 QV....there wasn't anything wrong with the fuel. There wasn't anything wrong with the coil/cap/rotor/plug wires/plugs. There wasn't anything wrong with the Cat, either.....the culprit wasn't even the air injection or a bad ground at the fuel pump or loss of vacuum. The fuel injection computer was causing the problem - started by a bad relay connected between the fuel injection computer and my O2 sensor. Because of the bad relay, the FI computer was getting bad/no data from the O2 sensor, and overcompensating - by dicking around with the air/fuel mixture. As a result, the car ran lean/rich, resulting in bad/incomplete combustion in the cylinders. This condition could dump unspent fuel into the headers/cat, cause crappy idle, and a loss of power from the engine.

 

Timing Light, Craftsman

Multi-Meters, Radio Shack

You should have both in your "war" chest.

I have this from Radio Shack and have had good results.