Running rough

[john3313]

I'm still trying to get my "new to me" Spider running properly. Now it is just rough, and has a vibration noise in the back of the car somewhere. The rotor doesn't look too good, so I'm getting a new one. I'm thinking that I should replace the fuel filter too, if I knew where it was! By the way, it's a 1980 FI. Also, is it recommended to change the distributor cap if I change the rotor?

[chrisg]

i'd replace both unless you've got a cap that's brand new on top of a crapped out rotor (unlikely). That's pretty cheap insurance. While you're at it (and, not necessarily related to the running issue), you should check out the condition of the wires leading to the magnetic pickup inside the distributor...if they're bad/dried/burned/etc., add that to your list.

Fuel pump & filter sits under the left (drivers) side rear seat pan - very easy to get to once you know where to look.

[So Cal Mark]

is it rough at idle or all rpms?
Try removing the plug wires one at a time from the cap, while it's idling. The weak cylinder will not cause an rpm drop. Once it's pinpointed, then you can determine the cause; poor injector connection, failed injector, bad plug wire, fouled plug, vacuum leak, etc

[chrisg]

yep, same recipe as most cars....remember an ungrounded plug wire can fry the ignition control module, so mind that when you test cylinders.

[john3313]

This actually started when I bought the car. On the way home, after 20 miles it started trying to stall when taking off from a stop light. I let it sit for about 10 minutes then it ran great for another twenty miles or so. Same thing. I bought and replaced the ignition control module. I noticed that the wire going to the distributor had been spliced and the connections at the splice were stuck together. I separated those and re-taped them. The car seemed fine after that. My wife then took it to her parents house (not too far) and it just died after going over a speed bump. Now it runs rough as soon as it is started and smells like the fuel mixture is off. (It's fuel injected). It seems to smooth out at higher RPM's. I know that I need a battery, but I'm just guessing at this point what the problem is.

[rlux4]

You say it smells like the fuel mixture is off. Does that mean you're smelling fuel? You may have a cold start valve that's failed in the open position. Try unplugging the connector on it and see if that helps smooth things out and gets rid of the fuel smell. There's a small "C" shaped keeper on the connector you'll have to take off. Be careful of it while you do, it can drop or fly off pretty easily. Use a very small screw driver to lift the keeper out of it's seat.
Ron

[So Cal Mark]

I'd suggest you remove the spark plugs and inspect them. If they're all black, you may have a leaking cold start inj or a failed pressure regulator. If just one is black you may have a leaking injector

[john3313]

Update, I knew that I needed a new battery, so I pulled the old one and discovered it was a deep cycle marine battery! Off to Autozone I went and got the battery and a new set of plugs. I disconnected the Cold start as suggested. It just made the car harder to start and didn't stop the rough idling. I removed the plugs ( The first one up against the hood latch was a bear to get to). They were all pretty black and fouled. I put in new platinum plugs. The car now does about the same thing. It idles roughly and almost sputters when I try to give it more gas. It sounds like it evens out at higher RPM's. I'm going to replace the rotor and cap on Wednesday. This car is frustrating, it's in great shape without a speck of rust anywhere, if only the damn thing would run properly!

[So Cal Mark]

black plugs indicate a rich mixture. Besides a leaking cold start injector, you could have a leaking pressure regulator or a failed temperature switch. You're going to need a volt/ohmmeter and a copy of the FI diagnosis manual for specs to test the components. Personally, I'd steer clear of platinum plugs. Once they get fouled they rarely fire properly afterwards. The only advantage to them is that the electrodes don't wear so you get longer life.

[mdrburchette]

You may also have a vacuum line pulling in air. My 82 Devil X had a problem with rough running and carboned up plugs when I installed an air filter. It ran fine without one. I found a vacuum line cracked.

[john3313]

I put the new cap and rotor on last night and not a damn bit of difference. I think the next thing I try will be a grenade. Why in the hell did I buy this thing? Oh well, I guess I will go over it this weekend again looking for cracked hoses etc.

[So Cal Mark]

replacing ign parts won't affect a fuel mixture problem. That would be like shutting off the water at your house to address a blown fuse

[john3313]

Okay, that makes sense. I'm putting the grenade away. My wife did mention something though that was interesting. The day that it stalled out and started running really rough, she didn't see the speed hump up ahead and said she was doing about 25 MPH when she went over it. It died immediately. Something had to have been knocked loose. I'll go through it again, but I may have to find a Fiat mechanic. I know my limitations.

[john3313]

I think i finally found it. Tinkering with it tonight, I discovered two connectors and I'm assuming that when the wife hit the speed bump, one popped off and wasn't making a connection. It is the same type of connector as the cold start assembly has. I plugged it in and started the car. It didn't want to start at first but then fired up smoothly. The only problem is the little clip that holds the connector in place is missing. I'm sure they can't be too hard to find. I'll have to look at the shop manual and find out what it goes to. Thanks for all of the advice.....maybe I can take it out this weekend!

[So Cal Mark]

where is the connector located?