Surge on rear bank 83 308qv

Recently developed a surge in the rear bank. Engine runs smoothly then a miss. If I disconnect the coil wire its obvious it's isolated to the one bank.

So, I swaped coils, ignition boxes, tested the crank sensors, pulled and non professionally cleaned the injectors (carb cleaner forced through with compressed air, they all were singing.

All the wires, plugs extenders, rotors and caps are new (even went back to original caps and rotors to see if there was an issue) no change. Have triple checked the vacuum lines.

Pulled the 1-4 crank sensor and it was filthy, figured as it is such a pain to change I would put a new one in so I don't ever have to do it again, no change.

I'm now back to believing its fuel vs ignition. It's only one back so it could be fuel distributor has a bit of dirt in one of the 8 sectors or I need for the injectors to be tested.

Tomorrow I'm going to check compression just to make sure no sticking valves.
I'm sure it's something stupid, just can't get it yet. Any thoughts, ideas or tests would be appreciated.

 

Yeah, I have spark at the wires and extenders. It intermittent, so thought it might be part of the brain or upstream of the coils, but nothing is pointing that way.

 

Yeah thanks, but I think I have mentioned twice now that I have spark at the plugs. Starting to focus on fuel pressure, injectors and compression.

 

Wires are cavis 400 classic. Spoke with Larry Fletcher today regarding some questions on the FD and some other info I had for him. Great guy and we swapped a few stories. Hoping FD is not going out to him and from our discussion, it's probably not as I'm getting good fuel flow at the injectors.

Checked compression, which came to 180 at all 4 cyls cold. Checked vacuum at the plenum seamed fine.

Tomorrow I'm changing the rpm CPS as I have a new one and it's part of the 1-4 bank wiring. Larry said he had one which was problematic, but tested fine.

Then will be pulling all injectors to have them cleaned and checked out can't hurt and will replace the rubber gromets. Did this with my boxer when I had it apart last year - sent out to washington.

I will get it resolved but it is throwing everything at me and a couple of buddies who have restored, built and repaired more cars than they care to remember. Plus it's the beauty of working on a Ferrari .. . . .muttering the recurring phrase of "how the hell do they expect you to get your fingers in there".

 

I did speak with Larry about WUR he said nothing would just effect one bank outside of the FD (ie: clogged port effecting 1 cyl) and or an injector.

 

Is it the entire motor or just one bank. If you pull a coil wire does the engine sound different front and rear?

I put in a new CPS in the 3 o'clock position, nada.so I have new at 10 & 3. 7 is for the front bank, so I will change it when it back to correct operation just so they are all new.

My injectors look fine no rust or corrosion on any. But I'm going to have them cleaned and checked and put in new seals. On that topic, do people put the new seal on the injector and then screw the cap down with the injector or screw the seal in the cap and then push the injector down. It's a QV so no circlips.

Yeah, last thing I will be doing is having the FD rebuilt. The fun continues.