Engine sputter on decell.

[ragtop2000]

I finally got the car a week ago. I was able to fix most of the initial problems with the help of this forum and my shop manual. I can see why you guys love these cars so much. It just loves the twisty country roads here in PA. When I first got the car the distributor was off badly. I was able to turn it and adjust the idle to get the car running fairly smoothly. The only issue I have is the engine sputters occasionally when I let off the gas to slow down. It doesn't affect the performance and doesn't back fire or stall, it's just annoying. Is this a timing, tune-up or exhaust issue, or is it user/shifter error? It is a 79 Spider with all the emissions crap still on it. I am eventually going to upgrade the carb, but is there a recommended way to by pass the emission stuff for now? What should my next step be to upgrade performance. She's going to the inspection station tomorrow. I hope there isn't any surprises!

Thanks,
Jon

[Danno]

let me verify. it does idle fine when warm, correct?

[ragtop2000]

Up until today she started right up and the idle was fine just the sputter when I started to slow down when approaching a stop sign. This morning she wouldn't start. I haven't had time to figure out why. The battery and charging system seem to be ok so it must be a spark or a fuel problem. I will check it out later today. Thanks!

[manoa matt]

That sputtering on deceleration means the fast idle system is out of adjustment or non opperational. If you are standing on the drivers side looking over the fender into the engine. There should be two white or cream colored electrovalves on the drivers side engine bay wall, at least thats where they are on my 78. Each electrovalve should have a hose going in and comming out.

The fast idle electrovalve should be the one more rearward with the larger diameter hoses. Near the electrovalves should be a push button switch. The switch is to test the system.

For the fast idle electrovalve: The hose comming out the back should go to a port on the intake manifold. The hose comming out the front should go to the carb on the front passenger side. Right above where the hose connects there should be an adjustment screw.

To test the system: You will need a 2nd person to watch the tachometer OR for more accuracy use a dwell/tach analog meter that hooks up to the coil. Start and warm the car to normal opperating temp, fan should cycle and turn off twice before its fully warm. With the engine running, pull the accelerator linkage so the RPMs get above 2500. Push in the button and hold it, while holding the button let go of the accelerator linkage. The RPM's should drop to between 1550 and 1650 I adjusted mine to 1600 RPM. To adjust, turn the screw out to increase RPMs, turn the screw in to lower the RPMs.
The screw has to be turned out pretty far.

This is probably the last thing you would want to adjust on the carb. First would be to check the timing, idle speed, and idle mixture.

If the system is innoperative then check the wiring at the electovalve, the switch, the switch at the clutch pedal and a switch on the passenger side of the transmisson. Another possibility is the fast idle diaphram is torn or broken which would indicate the carb needs to be rebuilt with new gaskets/diaphrams. Unfortunatly that carb is not worth the rebuid kit.

The first upgrades that should be made would be to accquire an intake manifold and a 32ADFA carb from an 1800cc engine.
However if PA requires emissions compliance then they may not let you alter and upgrade the carb eventhough it would probably reduce emissions and get better mileage.

Matt

[ragtop2000]

I can't thank you enough for your help Matt. She is at the shop right now getting inspected. I will make sure they check the timing and adjust the idle for me. I hope that cures some of the problem. I will also check on the emissions requirements and if I can upgrade the carb. I have a classic plate on her so I think that lets me opt out of the emissions test here in PA. The mechanic is a great guy, but he is primarily a MG mechanic and works on Fiat's reluctantly. He is the best I could find around here. It should be interesting! Thanks again.
Jon

[TJC]

Be aware, though, that the fast idle electrovalve is only energized (i.e., it only bumps up the throttle stop) when either in third or fouth gears. It does not activate in fifth. It was designed to prevent the engine from going too lean on decels in order to help mitigate NOx emissions, but why it's not active in fifth during most of our highway cruising is beyond me.

So, if your decel popping is happening when in fifth gear, it might be a different issue.

[TulsaSpider]

Wow, Matt, thanks I found this info to be very helpful! Mine wasn't connected partially. The hose that connects to the rearward electrovalve on mine (78 1800) (which was just plugged up) is kinda amber/clear color, connects to the carb just below the acc pump it seems. Does that sound correct?
Clark

[So Cal Mark]

the hose you're mentioning should connect to the air cleaner connection for the crankcase breather

[TulsaSpider]

Hmmmm Ok I'll try that, I read somewhere on here that the hose for the T at the crankcase breather was a vacuum source from the manifold, so currently I have one hooked there, it comes off the manifold in a single connection, below the choke housing.... so where does this one go? Is this the one for the electrovalve? I'll switch them to see what happens, till I hear back from you!
Thanks
Clark

[TulsaSpider]

Mark, I just went down and tried to do that, however the hose won't reach back the crankcase breather port and it's bent perfectly to go on that rear housing, it looks factory. I have taken some pics.

Whaddya Think?
Below is the port(marked made in USA that comes off of the manifold that I am currently using at the breather T so where does this one go??

Below is a hose that comes off the manifold at the T where the brake booster is (hard to get a good pic) it goes into the frontward solenoid.

the next pic is coming from the motor side of the carb, the hose goes into rearward solenoid, the firewall side

There is one small one that is plugged up, next to the one that goes to the vaccum cannister on my non existant smog system
pic below

side view

general shot


oh and what's this thing that's in the top of the intake??

wow I need some coffee!
Time for musical hoses?? Which ones are correct, which ones should I simply plug??
I am gonna revert it back to how I had it until I hear back from you!
Thanks!
Clark

[pauljdav]

I am concerned with the large green wire in the pic with the fast idle switch on the fender. That is the power to your starter and the casing looks cracked. If that grounds out you will have a major short, possibly fire, definitely bad day.

If I am seeing the pics correctly, the amber hose should be hooked to the air cleaner from the carb.

The hose that hooks to the fast idle switch comes from the front of the carb, nearest to the engine to operate a vaccuum powered throttle pull.

My car fast idle is non existent from the PO, but I do not have issues on the decel. I have all vac lines plugged with the exception of the one under the accelerator pump that connects to the oil breather.

Good luck,
Paul

[bandit]

Hi Clark


The 1979 spider i own was completely stock when i purchased it from the original owner so i decided to install
a ADF off a 1800 and looking at the 2L manifold and carb and comparing chock sizing ect ect i thought i'd
try just install the ADF without the manifold (1800) blocking off and the smog stuff of course . It was a decent improvement
over stock . Most the guys here do the manifold and Carb but i looked at both manifolds and didn't think
it would be worth it to change over . This mod is a direct bolt on no mods needed .


If you want a ADF let me know i have one for sale .


Daniel

[TulsaSpider]

Thanks for the pointer on the green wire I will inspect it!!
On the ADF, I am new at this so it's a better carb? Less emissions?? I don't have the cash right now, I need a new top among other things.. send me a PM on how much you want for it.
Thanks guys!! I hope I tame my octopus soon!
Clark

[bandit]

Hi Clark

Well the 79 has one of the small carbs chock size wise ( with the largest engine )if you look down the
barrels of the carb then down a ADF you can see the difference clearly . The 1800 had more power then
the Carb Model 2000 Engines even though the 2000 Engine is Larger with that crappy carb they came with
it is so small the Engine just doesnt perform well . Not to mention all the valves on the carb and Vac lines
ect ect making even harder to work on the engine i wish i had both carbs so i could show you the difference
just in size alone those 79 are a monster of a Carb . I will take a photo of my car without the air filter over
the weekend .


Daniel

[TulsaSpider]

Mine is a 78 1800. What about gas mileage? I am assuming it would go down and that's a big reason I bought this car.