IAC clicking when diagnostics…

[Jwernatl]

Hey all - was resetting base timing and base idle-

When I grounded my ‘a’ to ‘b’ at my ALDL- (which sets the IAC correctly, so that I can set idle.)

Once I turned key to ‘on’ position (truck not running), I can hear the IAC clicking.

I figured it was ‘setting’ - I left the truck in ‘on’ position for 2 min - it was clicking entire time. Should it quit clicking after 30seconds or so?

Once I started the truck I set the base idle (timing at 0) with advance wire unhooked.

After all completed I turned truck off. But in ‘on’ position Leaving jumper in at ALDL- The IAC still clicking-

I then went around and pulled jumper Immediately the IAC stopped clicking.

Normal? Or should it stop clicking after 30 seconds or so (in the very beginning prior to setting base idle)?

Thank you all for your help in the other post concerning setting base idle.

 

[SirRobyn0]

I say normal. Well it's not really 100% normal, I'd say more like nothing to be worried about as long as the IAC seems to be functioning properly otherwise.

My experience with the old computer systems, it is not uncommon for one or more things to actuate (click) when the jumper is on the ALDL connector. I remember with the feedback carb systems, it was quite common for the mixture solenoid in the carb to click when the ALDL was jumped. Not all of them did it but some did.

So my vote is normal for your truck.

 

[Snoots]

IAC TEST

To find out if it's dead just reset the IAC.

First jumper pins A&B on the ALDL connector.

Then turn your key to ON. Now walk back and put your hand on the IAC.

You should feel and hear it clicking rapidly.

What it's doing is being commanded fully closed.

If it's not clicking rapidly = dead.

If it IS clicking then simply pull the electrical connector from the IAC.

This freezes the IAC fully closed.

Now walk forward and turn the key OFF, then remove the jumper from the ALDL connector.

Now walk back and reconnect the IAC electrical connector.

You have just reset the IAC to a known position for the ECM.

Now drive the car over 35 mph to relearn idle. The car should idle fine as it is but
get more accurate the more times you drive it over 35 mph.

 

[Jwernatl]

You have just reset the IAC to a known position for the ECM.

Now drive the car over 35 mph to relearn idle. The car should idle fine as it is but
get more accurate the more times you drive it over 35 mph.

Snoots - perfect great instructions on resetting the IAC. Thank you.

Yesterday, I ended up swapping the 02 sensor, knock sensor and the IAC. I also set base back timing at 0 degrees -

It's still acting funny. - Im going to drive it a few days see if it gets better but, the problem is - there is no constancy. —

two things really...

1. what is super weird - closed loop is majorly not consistent.

When it sits overnight, (closed loop engine temp under 140degrees Fahrenheit )
CLOSED LOOP - Morning cold start it up —> it runs so rich - it could choke a city the size of NY - it'll 'pop' like it's buring etra fuel too -

After sitting in the parking lot for 6 hours -(closed loop engine temp under 140degrees Fahrenheit )
in CLOSED LOOP - Parking lot start up —> it does great.


2. And, whats even crazier but, may be normal...

Yesterday after replacing the 02 sensor, knock sensor and the IAC - plus setting the base timing to ZERO -

once I had base timing at 0 degrees. I shut the truck off -
Plugged up the black brown adv wire
started truck
I wanted to see how much advance timing the ecm was giving the truck
Turned out to be about 14 degrees
With advance wire plugged up, and watching the timing mark -initally it shows 14 degrees, then starts jumping all over the place. - 8 - 9 degrees.

Is that normal or an issue with my distributor or maybe a short with the plug wires??

And I know all of youz like pics so here ya go….

 

[Snoots]

Disconnect your battery for about 30 minutes. Hook it back up and go. This should reset everything.

 

[gmbellew]

when you set the timing, was the engine up to full operating temp? if so, the above advice to hard reset by disconnecting the battery is a solid next step. if not, reset the base timing on a warmed up engine.

 

[Jwernatl]

when you set the timing, was the engine up to full operating temp? if so, the above advice to hard reset by disconnecting the battery is a solid next step. if not, reset the base timing on a warmed up engine.

Thanks guys I like it
- I just went out disconnected the positive side of battery. I’m sitting fat and happy on the couch so may leave it that way all night - hope it makes a difference-

Today on the ride to the house- it was inconsistent too.

Thanks again- I feel good about it.

 

[Bextreme04]

Thanks guys I like it
- I just went out disconnected the positive side of battery. I’m sitting fat and happy on the couch so may leave it that way all night - hope it makes a difference-

Today on the ride to the house- it was inconsistent too.

Thanks again- I feel good about it.

Do you have an ALDL reader? What does the CTS read when the engine is cold and when its hot? An engine in closed loop mode will fuel the engine for cold start based on what the coolant temp sensor is reading

 

[gmbellew]

I think the engine ALWAYS starts in Open Loop, even when warmed up. if it is warmed up, it will go into Closed Loop quicker than if it is cold.

 

[Jwernatl]

Do you have an ALDL reader? What does the CTS read when the engine is cold and when its hot? An engine in closed loop mode will fuel the engine for cold start based on what the coolant temp sensor is reading

When the truck was at operating temp, I checked the coolant temp sensor - unplugged it - idle went up.

But Maybe - just maybe, it’s going bad that’s why it’s inconsistent.

 

[Jwernatl]

I think the engine ALWAYS starts in Open Loop, even when warmed up. if it is warmed up, it will go into Closed Loop quicker than if it is cold.

I think it does too. When all the stars are aligned, if the truck is operating temp, on restart it’ll idle at 900/1000 then settle down to 700rpm.

Maybe my cts is going bad?

But that doesn’t give reason for such a rich ‘cold loop’ start up after sitting all night.

With no codes. Weird.

 

[SirRobyn0]

When the truck was at operating temp, I checked the coolant temp sensor - unplugged it - idle went up.

But Maybe - just maybe, it’s going bad that’s why it’s inconsistent.

I think it does too. When all the stars are aligned, if the truck is operating temp, on restart it’ll idle at 900/1000 then settle down to 700rpm.

Maybe my cts is going bad?

But that doesn’t give reason for such a rich ‘cold loop’ start up after sitting all night.

With no codes. Weird.

Unplugging the temp sensor and having a idle speed change is not a valid or accurate test, it is okish for some sensors but if terrible for CTS. All you know by doing that is that the sensor was reading some unknown amount and when you unplugged it, it slammed the reading to -50F, the computer riches the mixture and increases the idle to prevent a stall. If you didn't get a check engine light or a code from doing that then you know just how insensitive these systems are to variation. Yes, you can definitely have a bad CTS with no code or light. What does that system have to check it against anyway? Only the computers own logic. So if it sticks in one spot for enough drive cycles it'll set the code and light. It can't assume if your CTS is drifting readings that it's bad cause you could have a failing thermostat (not saying you are just giving you an example of why parameters were so loose in the old days). Modern systems have more checks and balances btw. Back in the day we'd be more likely to replace a CTS based on symptoms and monitoring it on a scanner than a code set. You could test the sensor by resistance but you'd need to find a temperature to test it at and the resistance it should have at that temp. If you can't read data and can't find a resistance spec then replacing with a known good unit might be the only way you'd know for sure if the CTS is ok or not.

 

[Jwernatl]

Ya know, I thought pulling the connection was brilliant.

However I see that you’re 100% correct - it reads resistance. It’s not off/on.

Let me swap that out - I’ll pick one up today -

It’s nuts,

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I’m telling you. This truck should purr like a kitten - it’s driving me crazy.

Any brands better than others?