Won't stay running until warmed up

[dantye]

This problem just cropped up after more than 2500 pretty good miles. I have been through the Artigue tune-up and cold start tests, except for actually removing the Cold start injector to see if it sprays. It starts pretty easily, but within just a few seconds, the rpms drop off to zero and it will not stay running unless you hold the accelerator down. If you do so until it warms up, to op temp, then It runs fine and holds idle speed at about 800-1000 rpm. But if I adjust the idle speed COLD to where it will keep running, then when it reaches op temp, it idles at about 2000 rpm - even I know that is not a cure.

I'm somewhat concerned that a temp sensor may have been damaged in the recent overheating incident outlined in my post that started the following thread: http://fiatspider.com/f08/viewtopic.php?f=30&t=18217

Any pointers and "experienced guesses" would be appreciated!

Thanks

[rlux4]

Have you checked that your auxilliary air valve is opening? If you're getting it to idle cold by opening the air bypass screw you're doing the same thing the AAR does, giving the engine extra air in the mixture.
Ron

[ga.spyder]

I have exactly the same issue,and this is the second time for me.I am pretty sure it is the Aux air regulator(AAR).There is a way to test it,but I have forgotten the procedur.Maybe Ron,or someone can post that info.I havent bought a new one because I am being given an entire f.i. system,from one of my racing teammates.Mark does have them available.
If you read the manuals they instruct to go thru 2 heat cycles,then set the idle.I tried the same thing as you,and the 2K idle when warm is just a wee bit high!!

[dantye]

Have you checked that your auxilliary air valve is opening? If you're getting it to idle cold by opening the air bypass screw you're doing the same thing the AAV does, giving the engine extra air in the mixture.
Ron

I recently cleaned and adjusted the aux air valve and checked the voltage to it, but I suppose I could accidentally have warped that thin "plate valve" in it while cleaning and adjusting, and that and/or the brief overheating incident I referenced could have caused it to stick closed. It will be easy enough to check if that is the problem by opening the air bypass screw on the AFM, but I probably won't do it in the rain today.

Thanks for the tip.

[rlux4]

The AAR will operate without voltage going to it. The voltage is just to heat it to get it closed sooner. If you put it in the fridge for a few minutes you should see the triangular opening all the way open, warm it up and it should close fully.
Now that this subject has been brought up I'll say that I've considered replacing the AAR with a manual valve that would give me control of the auxilliary air, sort of like the old manual chokes used to do.
I may try it just to see how well it works if mine bites the dust.
Ron

[dantye]

The rain stopped, so I started it this morning - just sitting still - and could not get it to die! It's acting a lot like an old Chevy truck I had 25 years ago, where the only problem then was the fuel filter, but does that make sense with a pressurized FI system? Maybe I should have cleaned out the fuel lines when I had them out for floor welding and the gasohol has worked something loose while sitting over the winter. Weather is getting nasty again and we have family coming to visit, so I must leave it alone for a while.

Off topic, I somehow hit the emergency flasher button in all of this, and it won't go back - had to wedge it with a folded scrap of paper. ... I guess if you have a Fiat, you don't need a Rubic's Cube!

[dantye]

Feeling pretty stupid - all it was that the #3 spark plug boot did not get snapped all the way back after reassembly and clean-up. It finally shook loose, so it was running on 3 cylinders whenever it felt like it - which makes a steady idle RPM difficult, and tends toward a VERY rich mixture when you are rattling down the road and #3 DOES decide to fire! Finally discovered this when I took it out and tried to really open it up - thank God it was not a burned Valve!

[rlux4]

Oh man! I was this close to suggesting it may be the #3 spark plug boot.
Good going, thanks for the update.
Ron

[dantye]

Oh man! I was this close to suggesting it may be the #3 spark plug boot.
Good going, thanks for the update.
Ron

How often do you change fuel filters? It appears my memories of the fuel filter symptoms with my $75 '53 Chevy truck 30 years ago may not have been far off: Today, I took a 14 mile round trip to my oil change guy and the Spider purred like a kitten both ways. Opened it up a bit now and then with no problem. But it sat for 3 hours around lunch time. I dropped the Wife off at the grocery store and on a side trip, BEFORE gasing it up, it started gagging and choking and would die at idle every time. After gassing up it got even worse, but you could keep it running roughly if you just gave it more gas. The only way it will start now is to pump the gas, which should not be normal, so I will change the fuel filter ASAP. I will also change the plugs. The only other thing I considered was a sticky AFM, but the symptoms just don''t seem to add up. Hopefully it is not injectors - It has a new fuel tank, but who knows what could have been loosened up somewhere else in the fuel system.
Does this sound to anyone like anything other than a fuel filter?

[rlux4]

It may be fuel pressure. Without enough fuel pressure the gas will not spray out of the injectors, too low and it would just dribble. The way to check it is a pressure gauge on the line going to the cold start injector. Also, check the vacuum line going to the fuel pressure regulator.
Ron

[bradartigue]

Now that #3 is firing does the car run correctly?

[dantye]

Now that #3 is firing does the car run correctly?

Unfortunately not, as you may note from recent posts. But it's an honor to have YOU ask! (Either that or your manuals have made me more brave than I should be. )
We are having stormy days this week, so I think I will take this time to change the fuel filter and plugs and check the fuel pressure. It seems logical to me that, even with a new fuel tank, a car that sat for the better part of 22 years could clog a new fuel filter in 2500 miles or so. My arthritis will only take so much fiddly mechanical work at a time, so if it begins to look like injectors or the fuel pressure regulator or pump, I may turn it over to my mechanic - with the advice I've gathered here - and dump some bucks. He is a British car specialist, but owns an Alfa, has owned Fiats and maintains a few for "hands off" guys.

[bradartigue]

But it's an honor to have YOU ask! (Either that or your manuals have made me more brave than I should be. )

I'm reading back through your posts. You mention it will stay idle or start if you work the throttle. Understand that "pumping the gas" on a fuel injected car actually lets in more air, not gas, so you have to start thinking "I'm not getting enough air to idle" - not "I'm not getting enough fuel to idle."

It sounds like your car runs OK once you get above idle, so try this:

If your car won't run at all at idle but runs great at high RPMs then you don't have a fuel delivery problem, you probably are not getting enough air at idle. Check the idle speed settings and that your fuel pump is running. You can put a voltmeter on your fuel pump leads (use banana clips to extend the length of your voltmeter leads) and when you turn the key you should get 12V (or thereabouts, it's a FIAT, so maybe 11.2V!). If not then you likely have a bent rod in the AFM, which is extremely easy to fix, or your throttle position switch is screwed up.

[ga.spyder]

Thanks for posting that,Brad.I had a BMW mechanic(worked with Bosch inj. for years) cheat my AFM,to richen it a bit for some auto-x.Definitely made better power,but my cold idle is now non-existent.I too have to pump the pedal and keep revs up until warm.Your post jogged my memory that this is only since he worked with the AFM.I will now look toward the bent rod on the flap.Thanks
Craig

[dantye]

Went to start it this morning, and DEAD - Cause: The Hazard flasher button had responded to the weather and popped loose overnight! Not related to the running issues, but I had best fix it right.

I think Brad, as usual, has led me to the answer. I had to adjust the the arm in the AFM last year because the fuel pump was running whenever the key was in accessory position. At the time, I noticed a very slight bind in the AFM flap. My guess is that it has gotten worse or some junk has gotten in there - maybe from a backfire when the #3 plug wire was loose - and bound the flap tight enough to bend that rod again, because the fuel pump is again running in accessory position. The car is running worse and worse, so I will try to operate on the AFM before doing anything else. I will also run a compression test to see if there have been more serious changes - it was all within 10% on last check.
I should point out that the AFM bracket adapting the Cone air filter tilts the AFM downward a bit below the normal position, (see photo) but I don't see what effect that could have. I have put well over 100 miles on this spring, and the fuel pump ran correctly before the #3 plug wire popped loose, so that may have been the start of the problem. Is this analysis or just wishful thinking?