Electrical(?) issue right before FFO!!

[ga.spyder]

took the car into town today,and noticed a pretty lumpy idle.After it was parked for a few hours,I started it for the return trip.I left the lot and it just didnt feel right.At the light the idle was all over the place.It seemed fine until about 6 miles from home,I caught the tach jump from 2800 to 4000 in 5th gear.Then it did it again and the revs actually dropped to about 2000.I pulled in the clutch and revved it.She backfired twice and continued on.She was fine for the rest of the ride.I also saw the temp guage jump up a little,then back down quickly.OK ,so ? Any suggestions.I will pull the dist cap and check the mag p/u for frayed wires.That was my first thought.I need to figure this out quickly!

[rlux4]

Bummer.
First off, I'm sure you have already, but after a backfire you need to check that your boot is still attached to the AFM. I don't tighten my clamp completely tight. In case of backfire, I'd rather put the boot back on than damage the flap. While you're there I'd check for smooth flap movement in the full range.
As for the crappy running. Check the wires on your coil. Because your tach is being affected I don't think it's in the distributor.
I'm still cogitating on this, if anything else comes to mind I'll get back to you.
Ron

[ga.spyder]

It is a little odd,Ron.The car has been running great.I did check the intake boot,it was tight.When I got home I fiddled with the wires to the coil,but I need someone to watch the tach to see if it is affected.The actual stumble and loud backfires are what concerns me.It did it once and then was fine for the rest of the ride.Any suggestions ..hit me! I am supposed to be at Virginia Int'l Raceway next Thursday,to run the car at Phil Wicks Driving Academy.I am also going to be an instructor for the ride alongs in the new Fiats that Fiat N.A. is bringing I need the car back to her normal self!!!

[RRoller123]

Leaky injector dumping too much fuel into a cylinder?

[rlux4]

The erratic tach behavior got me away from thinking fuel related. My thoughts are something is affecting the coil output which could show up in the tach reading. Also if the ECU gets the signal that the engine is running it will still open the injectors even if spark isn't getting to the plugs causing a back fire when the spark does get there. Did I understand correctly that the engine speed isn't jumping up and down like the tach showed?
Did you by chance have the ECU unplugged recently?
Ron

[ga.spyder]

Engine speed wasnt affected at all,just the tach jumping.The ECU has not been touched at all.The car has been running fine,with the exception of a little rough idle when cold.I have swapped AFM's recently but have driven the car a lot since then.The weird thing is it did it once and ran fine after.I am off work and headed to the garage to see if it is something obvious(yeah,right)

[spider2081]

The tach counts pulses or spikes of voltage. For it to count higher than it should it either had an intermittent internal problem or some sort of noise pules are getting into the brown/white wire feeding the tach and the tach is counting the noise. First I would make sure the connections on the coil are tight. Next See if the brown/white wire from the coil to the tach is routed close to any of the spark plug wires. Same is true of the distributor pick up wire that goes to the electronic control unit mounted behind the coil.
A cars battery is the primary filter for its electrical system. Battery terminals need to be clean and tight for its filtering function to work properly. So battery terminals then starter connections and then alternator output terminal are all possible noise sources.
My last thought. I have had my dash lights mess with both my fuel gauge and my temp gauge. The ground terminal on those gauges serves for both the gauge needle and the back lighting. A poor case ground on the instrument makes the instrument reading off when the dash lights are on. In my case the fuel gauge would peg beyond full and the temperature gauge would read about 10 hotter than with the lights off.

Hope this is a little help
Looking forward to seeing you at Freak Out

[ga.spyder]

I just made my way back from the garage.I found the positive wire from the ignition control module had a bare spot with wires poking out.It looks to have been under the coil mounting bracket.Very possibly it was grounding against it? Everything else looks good.Mag p/u wires were free and unmarked,all other connections are tight.I cleaned and sanded them all and coated with dilectic grease.Hopefully the problem was the bare wire.Could that make the tach spike? After the two spikes the car ran fine again,no issue.It is pouring down rain here ,so I will try to drive it later. Thanks,
Craig

[ga.spyder]

Could it be that easy? Took the car for a short drive and all seems to be fine.The throttle response even seems better! The idle has smoothed out,and everything seems to work Will take a long drive in the next couple days to make sure.Thanks for the feedback,especially my personal gurus Ron and Dave.You guys are the best!!!

[rlux4]

Great!
Now all you need to do is set the mouse traps.
Ron

[supplyguy]

Craig - My clutch fritzed out this week and I too am worried about FFO. I run a lot of marathons and this is similar - the week before a race I notice aches and pains that were never there before and wonder if I'm gonna make it. Not saying your backfire is hypochondriacal like me, but I suspect as many gear up for the drive to Charlottesville we will be extra sensitive to how our cars are running! Hope to see you there.

[ga.spyder]

Make sure to look me up.The hardest thing about FFO is that many of the people there ,you know only by their forum handle!The badges dont have a spot to put your forum name ,like we do with the badges for Fiatfest.Looking forward to seeing you there.
Craig

[mdrburchette]

Dang Craig, I hope you got that 82 running right. I'm going to pull you around that track at VIR by your nose and I don't need you falling apart on me. Looking forward to seeing you and Rose Wednesday. Try to make it early so we can get that rollbar installed.

[narfire]

I'm going to pull you around that track at VIR by your nose

I want pictures

Have fun peoples, It is definately on the bucket list. Just a really busy time of year here.
Chris

[mdrburchette]

You're in luck, Chris. I've given the picture taking task to my daughter Randi. We should get some pretty good pics of the whole FFO event!