1987 Suburban Idle Issues

[shotrod69]

Months after. Did the iac in September. But I will give that a shot tomorrow morning and post an update

Jumped the pins and turned the key, the iac just hummed and never clicked. Touched the side of it with my hand to make sure it was what I was hearing.

 

[gmbellew]

Jumped the pins and turned the key, the iac just hummed and never clicked. Touched the side of it with my hand to make sure it was what I was hearing.

hmmmm....usually it starts to click when it is bottomed out because the motor is clicking over the little gears inside, or that's at least how I imagine it in my head. it may take 30 sec or so to close. you may want to pull it and see if it looks like it is jammed up or something. or maybe yours is just quiet?

if you have a scanner or ALDLDroid like I mentioned before, you can see the IAC counts....0 counts should be closed all the way.

I try to use AC Delco parts when I can for all the TBI sensors in the hopes they are better quality.

 

[shotrod69]

if you have a vacuum gauge, you may hook that up to the EGR port on the TBI and see if your vacuum is steady at idle.

and ALDLDroid with a blue tooth OBD1 cable goes a long way when diagnosing TBI issues. it's a slow computer system that only reports data every second or so, but it is still a lot of help.

Vacuum from egr port is 0, vacuum from air injection port is ~17.

 

[shotrod69]

hmmmm....usually it starts to click when it is bottomed out because the motor is clicking over the little gears inside, or that's at least how I imagine it in my head. it may take 30 sec or so to close. you may want to pull it and see if it looks like it is jammed up or something. or maybe yours is just quiet?

if you have a scanner or ALDLDroid like I mentioned before, you can see the IAC counts....0 counts should be closed all the way.

I try to use AC Delco parts when I can for all the TBI sensors in the hopes they are better quality.

Well it did a motor humming for a couple minutes,

hmmmm....usually it starts to click when it is bottomed out because the motor is clicking over the little gears inside, or that's at least how I imagine it in my head. it may take 30 sec or so to close. you may want to pull it and see if it looks like it is jammed up or something. or maybe yours is just quiet?

if you have a scanner or ALDLDroid like I mentioned before, you can see the IAC counts....0 counts should be closed all the way.

I try to use AC Delco parts when I can for all the TBI sensors in the hopes they are better quality.

pulled it twice and pushed the plunger in to reset it. Seems to be functional.

Would a bad icm or spark control be a culprits? I haven’t done those yet.

 

[shotrod69]

did you take it out of the bracket, or just wiggle it around in the bracket? I've had my line off that goes to the TBI and I don't remember getting a very strong fuel smell.

if you didnt remove it from the bracket, I guess you could take off both hoses, hook up a plastic hose to the gas tank port and blow and see if fuel comes out the TBI port or the vent port.

Took it out of the bracket, put air to it and doesn’t seem to be plugged up either

 

[gmbellew]

Vacuum from egr port is 0, vacuum from air injection port is ~17.

check to make sure your vacuum hoses are hooked up properly for your year. I think only the fuel purge cannister is ported vac on mine, but it is a 90 with no air pump. EGR solenoid doesn't let vac be appiled to EGR valve at idle, but my port for EGR always has vacuum.

 

[shotrod69]

check to make sure your vacuum hoses are hooked up properly for your year. I think only the fuel purge cannister is ported vac on mine, but it is a 90 with no air pump. EGR solenoid doesn't let vac be appiled to EGR valve at idle, but my port for EGR always has vacuum.

Lines match the picture, I know it’s running rich in general.

 

[gmbellew]

Lines match the picture, I know it’s running rich in general.

check your injectors with key on but no crank. make sure no fuel is dripping in or leaking under that condition. then check injectors with it running to look for a nice cone of spray.

 

[shotrod69]

check your injectors with key on but no crank. make sure no fuel is dripping in or leaking under that condition. then check injectors with it running to look for a nice cone of spray.

No leaks and the spray patter looks good. They’re new ac delco injectors

 

[gmbellew]

check these things if you think it is rich.

does the idle stumble cold or warmed up or both?

 

[Albrigap]

Re-torque the intake manifold.

if this helps, then replace the manifold gaskets.

 

[shotrod69]

check these things if you think it is rich.

does the idle stumble cold or warmed up or both?

Both, but only on restarts. Starts up fine cold. Even if all I do is run the truck for less then a minute. Sometimes reving it a little helps

 

[gmbellew]

Both, but only on restarts. Starts up fine cold. Even if all I do is run the truck for less then a minute. Sometimes reving it a little helps

hot restarts, or any restart? could be some sort of heat soaking issue, maybe the ICM is going bad or a bad connection in the ignition controls?

 

[shotrod69]

hot restarts, or any restart? could be some sort of heat soaking issue, maybe the ICM is going bad or a bad connection in the ignition controls?

Any restart, even running the truck for less then 30 seconds.

 

[Tanked]

I turned my idle screw to the lowest setting where it doesn't conk out. But if you're getting pressure in the tank means something Plumbing is not okay I would start there. Like an EGR valve

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