Idle Problems

[ososbob]

Once again a question for the Fiat Guru's. First off I must say this site is always a wealth of knowledge and is a great asset. I have problem with my idle, simply it's rough. I have recently rebuilt the engine (2.0 FI), I did do some headwork mostly port and polish the head, resurface and new valve guides. Had the valves reground and seated by my local machine shop. I checked the valve clearance on the exhaust side to be sure I set it correctly during reassembly, and they all checked out (either .018 and .019). I will assume the intake is correct as well. I can get it to idle but it's rough almost like I have a hot cam in the engine. The engine runs outstanding at higher RPM's. All plugs and wires have been checked and the timing is set at about 10 degrees BTD. One other symptom that is interesting is when it's at idle (1000 rmp) I do not have enough vacum to support my breaks. I know this as when I drive it and come up to a stop light, if I push in the clutch and let the engine idle down and apply breaks, the breaks do not work like they are supposed to. Could my idle problem be a vacum leak from the brake servo? I also suspect the fuel pump as well. I know the fuel pump is working but my kid had a 88 camero and had problems with idle very similar to my fiat. I tried all kinds of things with it and in the end when I replaced the fuel pump, it solved the issue. Any input is greatly appriciated.

[So Cal Mark]

low vacuum sounds like a cam timing issue

[ososbob]

I'm positive the two cam marks are lined up. Mark do you have any suggestions on what to check?

[So Cal Mark]

while idling, I'd remove one plug wire at a time from dist cap to see if the problem is one cylinder or all of them. Low vacuum is usually cam or ignition timing

[SLOSpider]

I would start to make sure your Throttle Switch is adjusted right and the idle speed setting is adjusted properly a 1k rpm is a little high. Turning the throttle adjustment screws can make a difference. If those are ok as mark said if it has a rough idle an easy check is remove one wire at a time and see if any do NOT make a difference in idle. If you find one that seems to not effect idle then start by checking that spark plug if that is Ok then I would check the injector connector at that cylinder. You can do the same test with it running removing one connector at a time and see if it effects idle. You can also plug the line to the vacuum booster and see how it idles. If plugging the booster line seems to fix it then check the one way check valve that is plugged into the booster the hose goes on. If not I would plug off the vacuum line going to the idle air motor and see if that helps. if so you idle motor maybe faulty leaking too much air. I would also spray some starting fluid around the intake plenum (should have a gasket there ) to lower intake manifold, base of intake manifold, throttle plate area, intake hose.

[ososbob]

Thanks for the suggestions, I will give those a try tomorrow.

[majicwrench]

diaphram in brake booster could be bad, creating a big honkin vacuum leak AND not helping with brake boost. With engine running, pinch off line see if idle changes.
If engine runs "outstanding" at higher revs engine itself likely sound, as would be the plugs and wires, injectors etc.
I am not fond of pulling wires off dist cap. Coil produce voltage that has to go SOMEWHERE once you pull wire out voltage will jump to whatever it can, the next post in cap, the - or + term of the coil etc potentially damaging things.
Take 4 small hunks of fine wire (2-3 "), stick em in alongside the wires in the cap so they are now sticking up where you can get to em. Now with engine running short each cylinder by touching you little wire with another grounded wire of some sort, a test lite works fine. No sparks flying around.
Keith

[ososbob]

Update, well I tried just about all of the suggestions and none really helped. Pulling each plugh wire affected the idle (worse) the same. So I took off the plenum pulled rechecked the valve gap for intake side. All gaps are .016 or .017 except cylninder number 3, its .019. They are all within specs though. I did retighten the the cam housing bolts. I could not find a torqe spec on those so if anyone knows what they are supposed to be torqed to please let me know. I did three other things. Replaced the old plenum gasket with gasket sealant, pulled the AFM and set the arm so it actually turns off the fuel pump at full close (I faily certain this is the way it should be) and turned the screw on the AFM all the way closed (this is the screw that usually is pluged so you cant mess with it). Oh yea, the battery died on me so I had to buy a new one. Started the car and now it idles much smoother at 1K RPM, not perfect yet but close. Reset the timing to 8 degrees BTDC. If I try to get the car to idle lower it just wont run. Not sure what I did to make it smoother but it's is alot better. Vacum seems better as well. By the way I'm posting some pics under my restoration thread, if anyone is interested. By the way Mark, I'm really thinking about your $550 distributor upgrade, If I install it will I pass a California Smog test?

[4uall]

You mentioned about putting the idle screw all the way in. I believe this is the correct method

Idle Speed Setting.
Run the engine to normal operating temperature. On cars with automatic transmissions,
set the parking brake, block the wheels, and put the transmission in "D". Completely
seat the idle speed screw. Loosen the accelerator linkage stop screw retaining nut and
adjust the stop screw to achieve 800 to 900 RPM on manual transmissions and 700 to
800 RPM on automatic transmissions.
Lock the accelerator stop screw with the retaining nut. Use the idle speed screw (1) to
set idle at 850 to 900 RPM on manual transmissions and 700 to 800 RPM on automatic
transmissions. If idle speed cannot be reached using this procedure, fully remove the
idle speed screw (2) and clean the orifice and the screw itself using a high pressure
spray cleaner (carburetor cleaner is fine).

[ososbob]

The mixture screw located on the Air Flow Meter is the one I was talking about.

[So Cal Mark]

technically the ignition system is not CARB legal but we haven't had any cars failed due it's presence

[ososbob]

Well, if I get it and fail because of it, I just may go to a smog referee, shouldn't be to hard to convince DMV, efficiency means less emissions.

[SLOSpider]

Referee wont don't anything Bob. They are **&^%# when it comes to smog. No Carb number no pass. Had a guy take Carb headers and notch them to clear his frame. Because he "Modified" them they wouldn't pass it. Easier to put the other distributor in if questioned. I have a Chevy truck from texas with no smog on a 454 Im trying to sell for a friend. If not got to try and track down all the smog equipment to get it to referee.

[SLOSpider]

Bob if you want to come out to Lompoc to take a look you can. Or it will give me a reason to ride the motorcycle out.

[majicwrench]

If you used some sort of silicon sealant on intake plemum it will not last, gas fumes will ruin it. Get a gasket, no sealer on it.
Keith