Still need help - Cold issues on an 82 - SOLVED!

[4babycar]

Ok, I am still having issues with the 82 and I am desperately trying to get things together for the local FLU ride on Sat!

The car starts and idles low and a bit lumpy. If you try to accelerate it will bog down and nearly die. If you let off the accelerator it will return to idle. If allowed to warm up, the idle and these symptoms go away and you can accelerate freely. I have checked and swapped 3 used coolant temperature switches that I have and the all seem to check out but the symptoms persist (all read ~1750ohm @ ~75-80F). One interesting note is that if the temperature switch connector is disconnected the idle is smooth and you can accelerate at will when cold.

Upon the advise of another friend, I replace the O2 sensor today but there is no change. I also swapped the AAR as well but it made no difference.

What next? I am desperate to get some answers in he hope of making the FLU ride sat. Please any help that you can provide would be greatly appreciated.

Thanks,
Michael

[So Cal Mark]

how is the fuel pressure? have you checked resistance of the coolant temp sensor?

[4babycar]

I have not checked the fuel pressure, as I have no gauge but I did verify the CS injector is firing and since the condition goes away if coolant sensor is disconnected and no alternations to the fuel delivery system, I deduced the pressure is OK. Please correct me if I am wrong.

The coolant temp sensor is the resistance that I spoke about and was ~1750ohm @75-80F.

[pooldoctorstl]

Please confirm...you say if allowed to warm up the problem goes away and the car runs great? Did this start suddenly or was it a gradual thing? Probably not O2 if it runs OK when warm, some guys here can correct me if I'm wrong regarding Fiats, but they don't have any affect until the engine warms up.

By the way, you are checking the temp sensor in the coolant tee between the cam pullys, right? (Not in the head by the plugs)

Jeff

[4babycar]

To confirm, yes the problem goes away when warmed up and runs well. I don't know if this started suddenly, as I have never driven this car. I got it for free in Jan and have been slowly working on it since then. The PO said it had an AFM problem but I swapped the AFM for a known good one and the condition is the same. With that I am expecting this condition has gone on for some time but I can't say for sure.

I didn't really think it was the O2 sensor either but it was a relatively cheap and quick swap to verify and no knowing the history it probably needed replacing anyway.

Yes, I am checking the coolant sensor located in the coolant T between the cam pulleys.

Jeff thanks for the input as I am trying desperately to sort this out before the weekend! What else have you got? I am open to any and all suggestions.

[So Cal Mark]

since you seem to be zeroing in on the temp sensor, have you checked the resistance of that circuit at the ecm with the harness plugged into the sensor? It's odd that the car runs well with the harness disconnected. Most cars will stall with the sensor unhooked.

[ORFORD2004]

I got the same problem but if i disconnect the temp sensor, the car run very rough. I suspect the auxiliary air regulator or plug injectors. But if the injectors are plugs, the car should not run well when is hot.

But for now, i finishes my interior because summer is the 21...

[So Cal Mark]

have you removed the spark plugs for inspection before starting cold? A wet plug can indicate a leaking injector or head gasket which could cause the trouble you've described

[4babycar]

Mark - I have checked the resistance through the harness for the ECU at the ECU plug and the resistance is the same, within a few ohms. I first confirmed continuity by shorting a wire across the plug and then plugged in the sensor and verified the resistance.

Are you asking me or ORFORD2004 about the plugs? Mine are dry before starting and I have solid compression 120 across the board with no visible signs of leaking or mixing of fluids and no colors or smells in the exhaust.

[pooldoctorstl]

What happens when you let the car warm up till it runs good, then unplug the sensor?

Unplugging the sensor makes the system go rich and as Mark says, the car will flood and won't run. So I agree, you need to check the fuel pressure. You can buy a pressure gauge kit for about $40 at most parts stores and because you will probably pay that to have a shop do it, you might as well own the tool for future use (on the next Spider you own).

Mark - Is it possible that the pressure is low and when warm the fuel demand is less so it runs OK, but cold it only runs with what would normaly be overly rich (sensor unplugged) condition to compensate for the low fuel pressure?

Also, just because the plugs are dry doesn't mean they are good. My 82 sat for 8 years before I bought it and got it running but it still ran bad. Even though the plugs looked fine, I put a new set in and it ran great, and still does. For what a set of plugs costs it wouldn't hurt.

Good luck,
Jeff

[So Cal Mark]

at this point I'd attach a voltmeter to the O2 sensor wire and see what reading you get as the car warms up. Since you don't have an air/fuel ratio meter, it's probably the only way you can see if the system is rich or lean. I realize the O2 sensor isn't heated, so it will have to warm up but it may give you an idea what's happening

[4babycar]

Thanks gentlemen, unfortunately, I missed being able to work all last night due to some nasty thunderstorms. Hopefully, I can get a chance to work today after work.

[4babycar]

I haven't been able to get my hands on a fuel pressure gauge and I forgot to check the O2 sensor output before it got too late to bother the neighbors.

Anyway, with the suspicion of a fuel pressure problem, it is likely the pressure regulator or the fuel pump? I have spares of each and for the price of a gauge, that isn't in this month's budget, I can swap in either of the other units. (I also verified that I can't get a loaner from the local auto-parts stores) Which should I start with?

[rlux4]

Michael, I have rigged up a liquid pressure gauge to use on the fuel line that I can send you as a loaner if you like. It has a nipple that will go in the hose to the cold start injector so it's easy to hook up. Let me know if you want it sent out.
Ron

[4babycar]

Thanks for the offer Ron. I got the extra fuel regulator tonight and have spent the last hour trying to remove the one on the car in question. I don't know what super-hero put that nut on but he needs to stay away from auto repair! I have been liberally spraying down with PBblaster so hopefully in the morning I can get it off and go from there. Either way, the Fiat will not make the ride tomorrow. I have arranged to borrow my parents 4WD Fiat (aka - Jeep Wrangler) so we still may attend. I need some kind of top down therapy, it has been about 2 months now.

Thanks everyone for your help and I will keep you posted.