350 TBI high idle

[Fleetwood]

I have a 1987 K10 with a TBI 350. I discovered a mistake in the wiring and fixed it and adjusted the idle properly. Now, when I start the truck up it idles at around 1000 rpm and when I switch it into drive and back to park it starts to idle at 1700 rpm. What do I do?

 

[JACK34]

Sell it. TBI trucks are junk. I sold my 94 it drove me crazy. Get a older truck with a carb on it.

 

[Fleetwood]

Also my IAC count start low but then I starts opening up and causing the high idle

 

[gmbellew]

might try resetting the IAC by forcing it closed. if the idle is high and iac is opening to make it high, something may still be off in the wiring. is all the other sensor data tracking normal?

 

[Fleetwood]

might try resetting the IAC by forcing it closed. if the idle is high and iac is opening to make it high, something may still be off in the wiring. is all the other sensor data tracking normal?

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[Fleetwood]

might try resetting the IAC by forcing it closed. if the idle is high and iac is opening to make it high, something may still be off in the wiring. is all the other sensor data tracking normal?

Above is a picture of the sensor readings. As far as I can tell, they all look fine. Also, I found a ripped vacuum elbow going to the charcoal canister and I plugged that temporarily and nothing changed (ill buy another elbow and fix this but I figured plugging the hole for a minute wasn't a problem). Today I bought a vacuum gauge and hooked it to the smog valve line and it was reading around -19 inHG steady at idle. I sprayed stuff around the base of the throttle body and that didn't change the idle either. Does this still sound like more of a wiring issue? Can someone send a schematic to double check mine?

 

[gmbellew]

check to make sure the vac lines are on the throttle body correct per the sticker on the core support. the charcoal cannister should not have vac at idle, only off idle. the egr solenoid and MAP have vac always.

looking at your coolant temp and open loop status, it isn't warmed up. does it idle high after it is warmed up? if so, screenshot the data then.

 

[JACK34]

Take the IAC out and put it in a paper bag. Go inside and get one piece of Bologna. Go back outside and grab the paper bag, stand on one foot and eat the Bologna.

 

[Fleetwood]

Take the IAC out and put it in a paper bag. Go inside and get one piece of Bologna. Go back outside and grab the paper bag, stand on one foot and eat the Bologna.

Will a plastic bag work too?

 

[gmbellew]

so much hate, Jack34, so much hate. I realize you had a bad experience with TBI that you couldn't get resolved and sold it. Like mom always said, if you aren't helping things you are hurting things. just let it go, stop trolling the TBI posts, and go enjoy your carb

 

[JACK34]

so much hate, Jack34, so much hate. I realize you had a bad experience with TBI that you couldn't get resolved and sold it. Like mom always said, if you aren't helping things you are hurting things. just let it go, stop trolling the TBI posts, and go enjoy your carb

Well now you ain't gotta run me off. Sometimes ya gotta laugh, how is that hurting things?

 

[SirRobyn0]

Well now you ain't gotta run me off. Sometimes ya gotta laugh, how is that hurting things?

It's not necessarily hurting things, but it isn't helping the OP either....

@Fleetwood I assume if you plug off the IAC passage the idle will come down?

If that is the case then it's on the computer side. If the idle is still high with the IAC port plugged, then it's a mechanical issue such as a vacuum leak or miss adjusted throttle stop, stuck EGR ect.

If it's on the computer side pull the IAC valve out clean the seat out in the throttle body and install a new IAC valve.

Make sure the timing is set correctly.

Also don't forget that these engines learn their idle. You need to warm the engine up and cruse at about 40 - 45mph steady for a bit. I think you need something like 5 seconds.

Looking at your read out I'd be looking at that open loop and low coolant temp. If it won't fully warm up, it'll never properly learn the idle. So then a thermostat maybe in order or possibly a temp sensor.

Hopefully some of this is helpful.

 

[JACK34]

It's not necessarily hurting things, but it isn't helping the OP either....

@Fleetwood I assume if you plug off the IAC passage the idle will come down?

If that is the case then it's on the computer side. If the idle is still high with the IAC port plugged, then it's a mechanical issue such as a vacuum leak or miss adjusted throttle stop, stuck EGR ect.

If it's on the computer side pull the IAC valve out clean the seat out in the throttle body and install a new IAC valve.

Make sure the timing is set correctly.

Also don't forget that these engines learn their idle. You need to warm the engine up and cruse at about 40 - 45mph steady for a bit. I think you need something like 5 seconds.

Looking at your read out I'd be looking at that open loop and low coolant temp. If it won't fully warm up, it'll never properly learn the idle. So then a thermostat maybe in order or possibly a temp sensor.

Hopefully some of this is helpful.

I tried to help the OP I said sell it. I know this forum technically covers TBI trucks but the GMT400 site is amazing.

 

[Fleetwood]

check to make sure the vac lines are on the throttle body correct per the sticker on the core support. the charcoal cannister should not have vac at idle, only off idle. the egr solenoid and MAP have vac always.

looking at your coolant temp and open loop status, it isn't warmed up. does it idle high after it is warmed up? if so, screenshot the data then.

It's not necessarily hurting things, but it isn't helping the OP either....

@Fleetwood I assume if you plug off the IAC passage the idle will come down?

If that is the case then it's on the computer side. If the idle is still high with the IAC port plugged, then it's a mechanical issue such as a vacuum leak or miss adjusted throttle stop, stuck EGR ect.

If it's on the computer side pull the IAC valve out clean the seat out in the throttle body and install a new IAC valve.

Make sure the timing is set correctly.

Also don't forget that these engines learn their idle. You need to warm the engine up and cruse at about 40 - 45mph steady for a bit. I think you need something like 5 seconds.

Looking at your read out I'd be looking at that open loop and low coolant temp. If it won't fully warm up, it'll never properly learn the idle. So then a thermostat maybe in order or possibly a temp sensor.

Hopefully some of this is helpful.

Just went for a drive and it warmed up and switched to closed loop. With the IAC unplugged it idles like it should. Once it was warmed up it would idle at 1000 rpm in drive completely stopped. When I shifted it into park, it started idling at 1450 rpm and slowly went back down

 

[Fleetwood]

check to make sure the vac lines are on the throttle body correct per the sticker on the core support. the charcoal cannister should not have vac at idle, only off idle. the egr solenoid and MAP have vac always.

looking at your coolant temp and open loop status, it isn't warmed up. does it idle high after it is warmed up? if so, screenshot the data then.

Here are some pictures of the sensors when it is warmed up. One is stopped in drive and the other is in park aft

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er driving around a bit