Idle and acceleration

[kyle79]

Hello Everyone, this is my first post and it's a long one! I've been driving my "new" 1982 Fuel injected spider for about 6 months now. I've read through many forum posts and service manual chapters to learn what I can about this engine and the fuel injection system. I'm happy with the car and I'm glad that it's running well enough for cruising around. I even taught my girlfriend to drive it last night, her first time with a manual and she only killed it a few times and the transmission and clutch are still intact.

It starts, runs and idles pretty smoothly most of the time, but I've got 2 issues. First, the idle seems to change quite a bit and somewhat randomly. Sometimes it idles right around 900, but then sometimes it's more like 1200 but without changing anything. It doesn't seem to be directly related to how warm the engine is either. The other issue is that it doesn't seem to accelerate smoothly, especially around 2,000-3,000 rpm... it does have decent power (although I've never driven another fiat so I don't really know what normal is). What happens while accelerating is that it "pulses" for a half a second or so with INCREASES in power as you are getting up to speed. That's what makes me think that the power most of the time is low. It's enough that it's very noticeable to a passenger also. The pulsing doesn't happen unless it's under load.

I do need to give it just a little gas when it's cold to get it started but once it's warm it idles fine, but I can't get it to idle below about 900 rpm.. it makes a sucking sound and then dies if I turn the idle screw in further... what should the minimum idle speed before it dies? I'm checking idle speed with a handheld meter that shoots off of a reflective strip on the crankshaft pulley (I don't trust the tach too much). I adjusted the idle speed as best I could according to the procedure in Brad Artigue's guide... when it's at 900 or so rpm, the idle screw is almost all the way in, and the thottle plate seems to be almost closed. Also, to get the TPS is adjusted where it won't make the relay under the dash click I had to turn it to the max position against the thottle (hope that makes sense).

I orginally suspected vacuum leaks and changed all of the hoses and replaced the vaccum advance module. I checked the torque on all of intake bolts, and then sprayed carb cleaner all around the intake side of the engine and all vaccum line including near the injectors to see if I could get a reaction but nothing. The was a small crack in a fitting on the plastic intake "boot" which I repaired. I don't really know how else to inspect further for leaks. I cleaned and tested the Aux air valve, and tried plugging the hoses to and from the valve to rule it out but it seems to work fine.

I replaced the fuel filter but haven't checked the fuel pressure, but it will run at pretty high rpm on the highway just fine so I don't suspect that is my issue.

I checked and adjusted the timing. The vacuum advance module was broken (and plugged off by PO) and the timing was way off, so I reconnected everything and adjusted it to 10 degrees with it idling warm at about 900 rpm.

I checked the voltage at the coil and it was ok, checked the cap and rotor and they are good, plug wires are in good condition, just replaced spark plugs. I also had to adjust the gap on the distributor pickup, but it is to spec now and the wires are in good shape.

The air flow meter bad been opened previously and the cap is gone from over the allen screw for the idle mixture which means that someone has been messing with it at some point. The resistor strip in the AFM is worn, but it seems to move very freely (too freely?). I cleaned the strip with rubbing alcohol and put the cover back without adjusting the spring or the idle mixture screw.

I just replaced the oxygen sensor and drove about 10 miles but nothing happened. I found some instructions for how to adjust the idle mixture and spring tension by watching the o2 sensor voltage but I'm hesitant to go there. Given that it was already opened up though, someone might have messed with it and I need to get it back to spec.

I don't notice anything from the tail pipe except some smoke once when I started it after it had been sitting for about 3 weeks. There is a slight gas odor at times when I start it but not after that.

A previous owner added a switch on the dash which I was told was "like a choke" and needed to be used when it was cold. I don't know what it is even connected to and I have never had to use it but maybe it's a clue as to something that was messed up in the past?

I still plan to adjust the valves as they tick a little, but nothing major. I haven't checked the lash.

The odometer says 127,000 but I don't know if that can be trusted because the glass on the speedometer assembly looks much newer than the tach.. it could just be that the tach was replaced with one from an older car.

It doesn't run too hot, and it's getting about 19 mpg in town. I haven't driven it more than 15 miles or so at a time on the highway yet.

Thanks for any tips on what to check/replace!

/Kyle

[narfire]

Holy crap...you pretty much covered everything that can affect the FI except..... wait for it....

Does the brake booster make any noise when the engine is running or when you apply brakes? The diaphragm is a source of unmetered air which can cause the grief you are dealing with..

Also you touched on it regarding the AFM. you cleaned the track but after I moved the pickups a half a mm to a clean part of the track all my idling issues and crap acceleration at 1-3000 rpm went away.
The 1-3000 rpm is were the engine has spent a lot of its time and will wear the start of the contact strip more than the rest of the strip.
Go back in there and loosen the clamp screw and move the arm up or down just a hair so the pick up is running on a clean section of the track.
good luck.
Chris

[redcars]

On your not to be able to get it below 900 RPM try replacing the O-ring that goes around the idle adjustment screw. On the rest of it you have covered it pretty good.

[kyle79]

Thanks for the tips! I disconnected the brake booster hose, and after I plugged it I could hear a small leak from the small hose going to the evap container... fixed that up, and while I was down there realized that the first fuel injector connector was broken and just barely plugged in... got that taken care of, started over with idle speed settings and pushed the arm on the AFM down just a bit too... It's running GREAT now!

I hooked the brake booster back up and it doesn't seem to be causing any issues, it's not much fun stopping without it. I guess I had a combination of little things, plus the big thing (the injector)... got my fingers crossed that it keeps it up.

Thanks again

Kyle