Engine stalling

[Leonard124]

Having a hard time tracking this one down.

Car is a 1980 with fuel injection. Started stalling a few days ago and can't figure out why. Always happens when I am accelerating from a stop sign. I pull over to the side of the road and after a few attempts starts right up. So far I have replaced the ignition switch and the ignition control module.
Checked the coolant temp sensor and all is okay.
Throttle plate switch also checks out okay.

Naturally all of these checks were done when car is running fine.

Anybody have any ideas?

Thanks

[RRoller123]

Bunch of possibilities, could bad\intermittent grounds to the injectors (grounds are attached at 2 studs on top of air plenum, driver's side, at rear), or a bad AFM.

Pete

[Leonard124]

I will check the grounds for injectors.

For AFM...how does one go about checking to see if it's malfinctioning?

Thanks

[RRoller123]

Make sure the door moves smoothly without hanging up or squeaking, and check the connector for obvious contact\wiring flaws or poor fit. There are a few posts about refurbing the door by sanding the inside of the housing. The arm under the top cap can be adjusted to ride on new TF resistive materials as well, but this doesn't at the moment seem to be the source of your symptoms.

Pete

[misterfiat]

A big issue with this older fuel injection system and age is vacuum leaks. CHECK ALL THE RUBBER LINES! The one to also check is the fuel pressure regulator on the rail, you will need more pressure/fuel at that point. May even be a weak or failing regulator.

Another simple thing is to change the in line fuel filter by the drivers side rear axle. May be a fuel supply issue too....is the tank clean/rust free?

Just from my own experiences...I would start there.

[So Cal Mark]

I would also check the pickup unit in the distributor. If the wires have become frayed, they can short out as the ignition advances

[Leonard124]

Door of AFM moves freely and does not bind.

Fuel tank has been refurbished 8 years ago(recoated) and fuel filter changed at that time (60 000 kms ago).
How often should I replace fuel filter?

Pickup wires are good(also replaced 60 00 kms ago)
Can it be something with the vacuum advance?

Vacuum lines to fuel pressure regulator replaced a few years ago.
Do these go bad(fuel prressure regulator)? Mine is still original.

Thanks for the help

[spider2081]

I personally feel 8 years and 60,000 KM (38,000 miles) is too long a time and too many miles between Fuel injected car fuel filter changes. 2 years or 20,000 miles is about what I would do. This would be after I cut open a filter with about 8,000 km (5000 miles) on it to inspect and see if it looks like the tank is not contaminated. I was taught to cut open filters and inspect the contents at every filter change.

[KevAndAndi]

I personally feel 8 years and 60,000 KM (38,000 miles) is too long a time and too many miles between Fuel injected car fuel filter changes. 2 years or 20,000 miles is about what I would do. This would be after I cut open a filter with about 8,000 km (5000 miles) on it to inspect and see if it looks like the tank is not contaminated. I was taught to cut open filters and inspect the contents at every filter change.

I agree. I would check there first. I would also put a fuel strainer upstream of the fuel pump (i.e., between the tank and the pump).

[Leonard124]

I will replace the fuel filter as soon as I can and try to see if there was crud in there.

thanks

[Leonard124]

I stiill did not get the chance to replace the fuel filter(will do it this winter), but was driving around yesterday and car kept stalling. I noticed that it always stalled when I shifted(when throttle was suddenly closed). I disconnected the throttle position switch and car stopped stalling. Drove around today with switch disconnected and no stalling.
So I decided to check throttle position sensor a little more carefully and when throttle is open it reads infinity, but when it is closed it is anywhere between 5-20 ohms. I thought this was a simple on-off switch...shouldn't have any resistance. If I open the throttle slightly it goes to 0 ohms. If I open the throttle a little more then it goes to infinity. Is my switch failing or not properly adjusted? thanks

[KevAndAndi]

Below is a cut-and-paste from my "Spider Notes" document that I maintain in order to maintain my sanity. Sometime, I have two versions of the same procedure, and that's the case here. The second procedure comes from the writings of Brad Artigue:

Throttle Position Sensor:
• With the engine off start opening the throttle (from the engine compartment).
o As soon as it starts moving, you should hear a click from the TPS.
• To check that the TPS is working correctly disconnect the electrical plug and with an ohm-meter check for continuity between the center pin and one of the side ones.
o Now move the throttle all the way open, and there should be continuity between the center pin and the other side pin.
o There should be no continuity between any of the pins in any intermediate position.

• Artigue: Unplug the throttle plate switch. Note the connector blades (on the plate switch, not the connector itself) are marked 3, 18, and 2.
o Connect an ohmmeter between terminals 2 and 18 of the switch.
o Loosen the two screws holding the switch in place.
o Rotate the switch clockwise until the ohmmeter indicates a closed circuit.
o Tighten the two screws and reconnect the switch.

[Leonard124]

Thanks Kevin. This is the procedure I used, but when I have a closed circuit(throttle closed) I am measuring some ohms(between 5-30).
I have a feeling it should read 0 ohms. The only thing I can think of is that the contacts are dirty. When I crack open the throttle, I hear the microswitch clicking and meter reads open circuit.

[KevAndAndi]

Thanks Kevin. This is the procedure I used, but when I have a closed circuit(throttle closed) I am measuring some ohms(between 5-30).
I have a feeling it should read 0 ohms. The only thing I can think of is that the contacts are dirty. When I crack open the throttle, I hear the microswitch clicking and meter reads open circuit.

It certainly does sound like dirty contacts. If cleaning them doesn't work, then a new TPS can be had for $65.