87 Fuel injection issue? With a/c heater fan - The 1947 - Present Chevrolet & GMC Truck Message Board Network

bsm78 · 01-17-2013, 07:20 PM

Have an 87 with 305. She runs good. Little rough idle, but pretty solid. No speed demon by no means.

Does idle rough and at take off could shut off when the ac or heater is on.
It will bog the engine until rpms get high enough to over come.

I have stepped on it with the fan off and then cut it on during acceleration, felt normal loss in power but nothing like at take off. Could this be a throttle body issue or what do you guys think?

motornut · 01-17-2013, 08:04 PM

Hi
87 shouldnt it have a solenoid to keep idle up?
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bsm78 · 01-17-2013, 08:19 PM

I am a very green shade tree mechanic. Im not sure. I just know its like it starves for gas when ac/heat is on and you have to baby the throttle to keep it from dieing.

pontgta · 01-17-2013, 09:10 PM

Could be the iac....idle adjustment, or fuel related......ses light on?
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bsm78 · 01-18-2013, 11:09 PM

Havnt noticed any lights.

Vbjunker · 01-19-2013, 07:53 AM

IAC
Any idea what the idle rpm is with AC off?
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Desert1957 · 01-19-2013, 12:30 PM

TBI or throttle body injection does not have a stepper motor for the throttle.

The ECM automatically adjusted the idle when the A/C or defroster is turned on. If the engine computer is not in "Open Loop" mode meaning all functions are working I don't think the idle function will work as designed.

Is you check engine light on? If so this might be some of the problem.

As mentioned above it never hurts to clean your IAC control once in a while.
Here is a picture of where is gets dirty, Try not to handle or move the plunger while disconnected.

Desert.

01-17-2013, 07:20 PM	#1
bsm78 Registered User Join Date: Dec 2009 Location: Hazlehurst, Ga Posts: 132	87 Fuel injection issue? With a/c heater fan Have an 87 with 305. She runs good. Little rough idle, but pretty solid. No speed demon by no means. Does idle rough and at take off could shut off when the ac or heater is on. It will bog the engine until rpms get high enough to over come. I have stepped on it with the fan off and then cut it on during acceleration, felt normal loss in power but nothing like at take off. Could this be a throttle body issue or what do you guys think?

01-17-2013, 08:04 PM	#2
motornut 78K & 79C Jimmys Join Date: Nov 2009 Location: Ottawa Ont CANADA Posts: 7,901	Re: 87 Fuel injection issue? With a/c heater fan Hi 87 shouldnt it have a solenoid to keep idle up? Posted via Mobile Device __________________ John 1978 GMCJimmy4X4-350/203 1979 GMCJimmy4X2-305/350

01-17-2013, 08:19 PM	#3
bsm78 Registered User Join Date: Dec 2009 Location: Hazlehurst, Ga Posts: 132	Re: 87 Fuel injection issue? With a/c heater fan I am a very green shade tree mechanic. Im not sure. I just know its like it starves for gas when ac/heat is on and you have to baby the throttle to keep it from dieing.

01-17-2013, 09:10 PM	#4
pontgta Registered User Join Date: Nov 2009 Location: Haines City FL Posts: 461	Re: 87 Fuel injection issue? With a/c heater fan Could be the iac....idle adjustment, or fuel related......ses light on? Posted via Mobile Device

01-18-2013, 11:09 PM	#5
bsm78 Registered User Join Date: Dec 2009 Location: Hazlehurst, Ga Posts: 132	Re: 87 Fuel injection issue? With a/c heater fan Havnt noticed any lights.

01-19-2013, 07:53 AM	#6
Vbjunker Registered User Join Date: Aug 2012 Location: Virginia Beach, VA Posts: 131	Re: 87 Fuel injection issue? With a/c heater fan IAC Any idea what the idle rpm is with AC off? Posted via Mobile Device

01-19-2013, 12:30 PM	#7
Desert1957 Registered User Join Date: Apr 2009 Location: New Freedom Pa. Posts: 1,335	Re: 87 Fuel injection issue? With a/c heater fan TBI or throttle body injection does not have a stepper motor for the throttle. The ECM automatically adjusted the idle when the A/C or defroster is turned on. If the engine computer is not in "Open Loop" mode meaning all functions are working I don't think the idle function will work as designed. Is you check engine light on? If so this might be some of the problem. As mentioned above it never hurts to clean your IAC control once in a while. Here is a picture of where is gets dirty, Try not to handle or move the plunger while disconnected. Desert.



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