Engine surges at low idle

[roy]

Hi folks, just bought my first Fiat (79' Spider 2000), seems I've got a carb issue. Can't get the idle to run smooth, it either surges or dies after I give it some gas. Tried adjusting the idle mixture and idle speed but nothing really improved. Now I've got it idling at around 1100 rpm so it doesn't die when I'm stopping at a light etc. Any help would be appreciated.

[vandor]

1. Check for vacuum leaks
2. Make sure the idle solenoid works. It should click when you unplug or plug-in its electrical connections with the ignition on.

[dmwhiteoak]

Hey Roy, I had basicly the same problem with mine after i brought it home. What I found was a vacuum leak between the base plate and carb body.The carb body was worped. Also had no power to the idle/ low speed solinoid . Check out my thread ( surging at low rpm ) there is alot of info there. Hope it helps

[roy]

OK, so I've installed a carb kit with new gaskets etc, disconnected and blocked all the emission lines to the carb. I still have a slight surge but now I can't get it to idle smoothly below 1K rpm. Also when I apply gas and hold it the engine doesn't run smooth it sputters at bit. Any ideas?

[majicwrench]

As has been mentioned, the idle circuit can and will cause lots of issues.

If you unplug idle soleniod with engine idling, does engine die?( it should).

With engine off, key on, if you unplug idle soleniod does it click? ( it should)

If you look down carb throttle bores ( safety glasses, right?) is there fuel spittiing out of venturis??( there should not be)

Keith

[124JOE]

As has been mentioned, the idle circuit can and will cause lots of issues.

If you unplug idle soleniod with engine idling, does engine die?( it should).

With engine off, key on, if you unplug idle soleniod does it click? ( it should)

If you look down carb throttle bores ( safety glasses, right?) is there fuel spittiing out of venturis??( there should not be)

Keith

i used a 9v batt to test the soleinod

[roy]

Ok, unplugged the idle circuit and the engine quit, the solenoid clicks when I unplug it with the key on, there's no gas spitting down the throttle body unless I give the gas. I put new Boush spark plugs in today and will install new plug wires tomorrow. We'll see if that makes a difference, more to follow, thx

[124JOE]

how was the old plugs?
any burned or wet or black?

[roy]

Plugs looked ok, there was some black residue but no major build up the tips were not corroded, so I don't expect any valve problem issues.

[Fi8spider]

Hi roy I recently had a similar sounding problem with my 128 and went hell for leather chasing carbi problems. Did nearly everything you have done but still no joy. I had the HT leads checked and they were at fault,,,at least I've got an overhauled carbi now..

[roy]

Help me out, what are "HT" leads? I'm new to the Fiat world, thx

[majicwrench]

HT = HIgh Tension + plug wires.
Plug wires will not usually cause idle issues.
You done good, if the soleniod click, engine dies when unplugged, idle circuit is flowing like it should. HAve you adjusted the idle mixture??
If you rest your hand over carb when it is idling does idle improve??

[roy]

I'll have to check again but I do think the idle increased when placing my hand over the carb. Now I've got two gas leaks that I need to solve. The carb kit didn't include new gaskets and power valves, I'm assuming since I've disconnected the emission lines running to the carb these valves aren't needed but since they lead I need a fix. Looks like it might be some time before I can get things running again.

[roy]

I removed and plugged all emission stuff, stopped the gas leak and now it idles at around 900rpm, no more surges. I noticed that when I step on the brake the idle increases. Not sure what's up with that but I'll replace the connection from the boaster to the manifold just in case there's a leak. Not sure if this is a by product of taking off all the emissions stuff but now it seems my electric fan doesn't come on after the car runs for a while, any ideas?

[dmwhiteoak]

Do you hear a hiss as if the booster is sucking air when your not on the brake ? If so your diaphram in the booster may be leaking, as was in my case. I totaly took the booster out of the loop and solved all my other idle issues. Just plugged the nipple the hose to the booster was connected too. Just run mine with no power brake and then decided I liked it better.