Very rough running

Help I need help. I have a 1985 Mondial cab. QV door plate mfg date july 1984. Saturday I was out driving stopped for some food and car was running great, went in came out and started the car it was running great then it lost power in 1 second no warning at all. it sounded like it was running on only half the motor. I checked the coils,wires,changed the plugs,run the car with a inline ignition spark tester all was good.I read on here about the Frequency valve do I have one and what dose it look like. I removed the wire from the O2 valve and there was no change,Removed the hose to the Advance electronic module and the car runs up a little but dose not fix the roughness,plugged the hose and inlet went for a drive and it would run great for a 5 to 10 seconds then back to bad, I have the car jacked up and the wheel well removed to remove the crane censer but before I do that I thought, I'd ask for some help!!!! If you guys could give me any advice I would be grateful. Nov.2011 service was done-belts ex.

 

Here's a thread detailing a similar problem.
http://www.ferrarichat.com/forum/showthread.php?t=371457

FYI I never use the search function in any forum because the engines aren't that good. I always use Google instead. Type frequency valve: ferrarichat.com in Google and away you go.

 

If your '85 Mondial QV is a US version = yes; if euro version = no.

PS Give shout if you can't find a thread showing the FV location.

PPS If you have spark on all 8 cylinders, there is nothing wrong with the (crank) flywheel sensors.

 

Thanks for the reply, I have an update the rough running only starts after warm up. When I start the car it runs up then throttles back 2 times and rough running begins, any idea what it could be? thanks, Bob

 

If you've confirmed that the frequency valve is operating, the next area to investigate on your K-Jet with Lambda system would be the thermomechanical-hydraulic analog computer (aka, the warm-up regulator) and the various pressure levels -- i.e., regulated supply pressure, cold control pressure, and warm control pressure.

Have you confirmed that the frequency valve is buzzing/operating?

 

Thanks Steve and yes the frequency valve is buzzing. I,ll move on to the warm up regulator and pressure levels. Also should I hear a change in engine speed when I unplug the relays for the oxygen sensor system, control unit for TWC thermo couple, throttle micro switch and the electrovalve controlling cut off valve. Because when I unplug them there is no change in engine performance.
Thanks, Bob

 

Can you please clarify what publication that you are getting these relay names from? If it is the US Mondial QV wiring diagram page 4, the only one that would have noticeable effect during warm-running would be the first (assuming that this is the protection relay) -- the FV should stop buzzing when unplugged, and the engine would run weakly (lean). But this is on a good-running engine -- if the engine is already running very badly (for some other reason), the effect may, or may not be apparent.

 

Steve I got the names from the Mondial Quattrovalole U.S. Version 1984 models Page 105, Cat.308/84 - n.600

 

update: Today I was going to put the drives side rear wheel back on my car. It was off to check the crank flywheel sensors. Before installing the tire I started the car and removed one hose at a time to the Digiplex/ digital advance ignition system, there was some change in the engine, the RPM's when up a little. The hose was run all over the place to get to the unit so I pulled it out and reinstalled it, put the wheel well back in and put on the tire. I started the car to move it over in the garage and it was running great not just good but great. Drove out the driveway, down the road, ran great for 20 min then back to the same rough running as before. The hoses to the Digiplex unit are all new. Any ideas ?

 

Check the spark plug extenders for tiny burn marks from arcing. It looks like a tiny black spot on the thicker side of the extender. Tiny mark that is incredibly power robbing and can be impressively intermittent.

 

Update: Today I removed all the spark plug extenders all I could find was one small black spot on # 1 cylinder. It was the size of an O in this text. The wires were new on 11/11. I was thinking it was nothing because the wires are new. Better be safe than sorry I taped all of the extenders with rubber (not PVC) electrical tape made for hi voltage lines. started the car and it was running great. Went for a road test for 90 min. shut the car off waited 30 min. started the car, went for a drive and it is still running great. When I got back I removed the tape from # 1 cylinder and the rough running started again. I would like to thank all who replied to my thread with all the good advice. As being this is my 1st. Ferrari I am grateful.
And as Mr. JGoodman would say, It's all good!!!!!

 

That's great news. I did the exact same thing to fix mine with the electrical tape until the new ones arrived. And I think my arcing was also on cylinder 1. Very interesting.

Now I have a favor to ask of you. With the time and money you just saved, please join F-chat, post some pictures of yours, and then spend the next several years not only driving, but also sharing all of your great experiences with your fellow Mondial brothers, and come join us and play at Mondipalooza next year. Deal?

 

That is indeed exciting news. Now you can say it wasn't running right and you fixed your Ferrari yourself