Bad ISC Valve? Trouble starting...

[jefe]

91 3sfe automatic with 297K miles.

The car only starts when I press down the gas pedal. Is this the ISC valve (alternativel Idle Air Control Valve?)? I checked the resistance and it measured 19 ohms. (The reference range in the manual says 16.0-17.0 ohms).

Difficulty starting happened after disconnecting the exhaust as described here: Can starting car with exhaust disconnected cause a problem?

Anyway, since posting that thread I:

1. Verified spark to all 4 plugs.
2. I also checked: High tension cords on distributor cap, Resistances of primary coil, secondary coil, pickup coil and Distributor air gaps are all OK.
3. Checked for diagnostic codes - Normal
4. Removed Cold Start Injector Pipe, and jumped the +B and FP terminals of the diagnostic connector - Fuel squirted out, so I think that's OK too.

After all that, I re-connected the exhaust and re-connected the large Rubber Hose that connects the air filter to the throttle body & got the car to start by pressing down the gas pedal while turning it over.

On the Troubleshooting guide page FI-11, I think there is a misprint. There is a box for "Does engine start with accelerator depressed" and then there are 2 arrows leading from the box that both say "No". I think the one pointing right should say yes.

So, bottom line - should I replace the ISC valve, and would trying to start it without the exhaust (and/or hose from air filter) cause this problem?

Thanks.

[white90dx]

I don't see how removing the exhaust (post manifold/cat, right?) can affect the motor in any negative way.

When you checked the cold start injector pipe, did you pull the fuel line off, or did you check that the cold start injector itself is spraying fuel? I would suspect the cold start injector system (probably the time switch on the water outlet neck) before the ISC for starting problems.

-Charlie

[jefe]

Originally Posted by white90dx

I don't see how removing the exhaust (post manifold/cat, right?) can affect the motor in any negative way.

When you checked the cold start injector pipe, did you pull the fuel line off, or did you check that the cold start injector itself is spraying fuel? I would suspect the cold start injector system (probably the time switch on the water outlet neck) before the ISC for starting problems.

-Charlie

I only pulled off the line, not the injector itself.
I was only suspicious of the ISC because that's where the factory manual troubleshooting guide points me for "Does engine start with accelerator pedal depressed" on page FI-11

So to check the injector I just remove the line, then the injector, then re-connect the line to the injector and short the FP and _B again, right?

Thanks, and glad to see you in this thread!

[white90dx]

You should be able to remove the cold start injector without removing the fuel line to it. It is a little unsafe to have fuel spraying over the engine, so I would suggest trying something else to diagnose first.

The cold start injector gets power only while cranking the motor or while the motor is cold due to the cold start injector time switch. Search on here for directions on how to diagnose a cold start injector issue.

-Charlie

[jefe]

Originally Posted by white90dx

You should be able to remove the cold start injector without removing the fuel line to it. It is a little unsafe to have fuel spraying over the engine, so I would suggest trying something else to diagnose first.

The cold start injector gets power only while cranking the motor or while the motor is cold due to the cold start injector time switch. Search on here for directions on how to diagnose a cold start injector issue.

-Charlie

Thanks Charlie. I checked the injector cold start valve itself last night, similarly to how it is described in this thread:
Post #7

The injector cold start valve itself was covered in black debris. I cleaned it out and reconnected it to the supply and there was no spray from the injector cold start valve (when the FP & +B terminals were shorted).

Am I correct in assuming I need to replace the injector cold start valve? Or can it be soaked in anything overnight to try to salvage it?

($148 !! @ autozone: Cold Start Valve)

Also, the part the injector cold start valve inserts into had a lot of black debris around the opening. I cleaned it out as far as I could reach in, but do I need to remove & clean this whole part too?

[white90dx]

While you were doing that test, were you powering the cold start injector directly? Without the Cold Start Injector Time Switch active, you won't get any fuel spray with just Fp and B+ jumpered.

You can clean the cold start injector in carb/throttle body cleaner or similar, I would imagine. Only soak the part where the fuel sprays from, not the solenoide side of it.

I would suspect the Cold Start Injector Time Switch, not the Cold Start Injector at this point still (unless you did power the injector directly from the battery). Sadly the switch is expensive, but I have an extra working one you can have if that turns out to be the problem.

-Charlie

[jefe]

I didn't realize the switch needed to be directly connected to the battery.

I had figured if the supply line to the cold start injector valve was pumping gas when it was disconnected from the cold start injector valve, that the gas should get pumped through the valve when it was connected.

I'll try it and report.

Thanks.

[white90dx]

Originally Posted by jefe

I didn't realize the switch needed to be directly connected to the battery.

I had figured if the supply line to the cold start injector valve was pumping gas when it was disconnected from the cold start injector valve, that the gas should get pumped through the valve when it was connected.

I'll try it and report.

Thanks.

Whoa, wait!

The Cold Start Injector is on the manifold, and acts much like a standard fuel injector - spraying fuel when it has fuel pressure behind it and power to its internal solenoid.

The Cold Start Injector Time Switch (on the water outlet neck) supplies power to the Cold Start Injector when the motor is cold and while the motor is cranking.

To test the Cold Start Injector, you need to give it fuel pressure (Fp and B+ connected, key 'ON') and power the injector (from the battery). It is a reliable part and doesn't seem to fail very often.

The Cold Start Injector Time Switch, on the other hand seems to have problems fairly often at this age... You will want to check if you are getting power at the Cold Start Injector plug while you are cranking the motor - that is the easiest test.

-Charlie

[jefe]

Hey Charlie,

Sorry if don't have these terms right! I did a search and in this thread, the part is called the cold start injector:
Check Post-#7

This is the part I am talking about:


This is the exploded view:


When I had the hose disconnected from the part, ignition turned to on and jumped +B & FP, gas came out of the hose.
Next I disconnected the part and I reconnected the hose to the part itself (ignition to on, and +B & FP jumped) no gas would spray out of the part.

After your earlier comment I thought I needed to check it this way next to see if gas sprays out of the part:


Not sure now...

[white90dx]

Originally Posted by jefe

When I had the hose disconnected from the part, ignition turned to on and jumped +B & FP, gas came out of the hose.
Next I disconnected the part and I reconnected the hose to the part itself (ignition to on, and +B & FP jumped) no gas would spray out of the part.

After your earlier comment I thought I needed to check it this way next to see if gas sprays out of the part:


Not sure now...

Sure, we are getting closer... Fuel coming out of the hose just means that the fuel pump is running (which is good to know...).

To get the Cold Start Injector to spray fuel, it needs fuel pressure and power. Jumpering Fp and B+ does not supply power to the injector, only the pump. In normal operation, power is supplied to the Cold Start Injector by the Cold Start Injector Time Switch that is located on the water neck.

...

Actually, I just checked the diagrams - more correctly, cranking the motor supplies power to the cold start injector (black wire) and ground is supplied by the green wire through the time switch when the motor is cold (<30*C / <86*F).

While the motor is cold, you can make sure that there is connectivity/conductivity between the green wire at the Cold Start Injector and ground (at the water neck).

-Charlie

[jefe]

Hey Charlie,

Still haven't got this figured out...

I got the cold start injector to spray (jumped Fp & +B, and powered the injector directly.

Then I checked the Cold start injector time switch:
STA-STJ tested at ~47 ohm (spec is 25-45).

The factory manual wasn't clear to me & I wasn't sure if I was supposed to check STA-Ground or whether that was only for the 2VZ-FE.

Anyway, I checked STA-Ground = 8 ohm and also checked STJ-Ground = ~45 ohm.

Then I was trying to figure out how to do what you said earlier...

Originally Posted by white90dx

Actually, I just checked the diagrams - more correctly, cranking the motor supplies power to the cold start injector (black wire) and ground is supplied by the green wire through the time switch when the motor is cold (<30*C / <86*F).

While the motor is cold, you can make sure that there is connectivity/conductivity between the green wire at the Cold Start Injector and ground (at the water neck).-Charlie

The cold start injector doesn't have any colored wire visible - only a larger black wire coming into it. The cold start injector time switch does have 2 separate colored wires coming into it: green and black. I tried checking for voltage across STA-STJ while cranking but didn't measure any.

I also checked resistance from STA to the prongs in the connection on the cold start injector. The left prong - STA measured ~3ohms. The right prong - STA measured ~30 ohms.

I am lost!

[white90dx]

Ok, at least we know the cold start injector is working. Now you just need to see if it sprays fuel while you are cranking the motor.

Does the motor stay running after a little coaxing when you start it?

-Charlie

[jefe]

Originally Posted by white90dx

Ok, at least we know the cold start injector is working. Now you just need to see if it sprays fuel while you are cranking the motor.

OK, will do.

Originally Posted by white90dx

Does the motor stay running after a little coaxing when you start it?

Yes, it'll start if I hold the accelerator down, then it runs fine. If I run it for a little bit & shut it off, it will usually start again without having to hold down the gas pedal.

[holmesnmanny]

Does it spew out a lot of black smoke when you start it after having held down the accelerator?

[jefe]

Originally Posted by white90dx

Ok, at least we know the cold start injector is working. Now you just need to see if it sprays fuel while you are cranking the motor.
-Charlie

The Cold start injector does spray fuel when I am cranking the engine.

After verifying that, I tightened the big black rubber hose - which previously was connected but not tightened to the intake manifold/throttle body (?). The car seemed to start pretty normally, but then had some stalling issues (see below). Could not having the air intake hose tight or having it disconnected caused any of the difficulties starting?

Stalling: So, after starting OK, when I tried to put into gear it stalled. This happened a few time in forward and reverse. After about 3 or 4 stalls, I left it running for awhile (~45 minutes cause I got busy with other stuff and wanted the battery to charge up again anyway). After that I drove it normally without any stalling. This morning it started cold fine, and did not stall when I put it into forward and drove a few feet and then reversed a few feet. I plan on doing some more test driving on Thurs or Fri.

Originally Posted by holmesnmanny

Does it spew out a lot of black smoke when you start it after having held down the accelerator?

Yes it did (actually more grey smoke than usual to be exact).
Also, I noticed that after leaving it running as described above, I backed it into the garage and turned it off. Then I restarted it and noticed it sprayed a bunch of blackish water from the exhaust. I only happened to notice because it was backed up within a few feet of some other stuff in the garage. I touched this discharge and it seemed like water...