89 gmc runs rough.

cburcham73 · 08-22-2008, 07:50 AM

89 gmc truck,305,tbi. everymorning on start up the truck runs like ****,flooding,black smoke [etc]i have a code 45,rich exhaust.replaced the o2 sensor,iac,tps,ect,map sensor,fuel filter,fpr,egr valve has been blocked off for 5 years,so thats not the problem.i see i have a small drip from the driver side injector,but the spray pattern is good.the truck will run rough all the way to work ,15 miles,i cut it off and 10 minutes later i start it up it runs perfect for the rest of the day.could the ecm be going bad?

Case 7230 · 08-22-2008, 11:04 AM

I am no expert but could you unplug the injectors with engine running and see if fuel keeps flowing? Also could you check for vacuum leaks around the intake manifold and throttle body and the EGR valve? You can do this by spraying carb. cleaner or similar and listening for a change in engine note if the spray hits a leak. I`m sure someone else will chime in soon. Good luck with it.

leolkfrm · 08-22-2008, 11:11 AM

Welcome to the forum

Could be the temp sensor is starting to go bad making it run rich

87c10slammer · 08-22-2008, 11:13 AM

i would have to say it has something to do withthat leaky injector. if it sits overnight leaking then you are flooding the closest cylinder. it may take that long to clean itself out. perhaps it has a good spray pattern in your eyes but they may both be weak and that is the culprite. now as the motor heats up it will run better becuse the air is getting hotter coming into the intake and its less dense air. so you need less fuel to mix with this less dense air. take the air filter off after it has been running good for a while then take it around the block see what happens

cburcham73 · 08-22-2008, 11:19 AM

i havent tried unplugging the injectors yet. ive put my finger under them while the truck is off and there dry.and ive also replaced the temp sensor but no luck either.it seems to be temp related.i left my truck at work yesterday and i started it up an hour ago after sitting all nite and it runs perfect. i also reaplced all vaccum lines and sprayed all around tbi unit. no leaks. thats why i think maybe ecm.

cburcham73 · 08-22-2008, 11:22 AM

im going to take the injector out tonite and look it over. there is some o-rings in the pod im going to check.

wojeepster · 08-22-2008, 03:23 PM

I second the coolant temperature sensor or connection to it.

cburcham73 · 08-23-2008, 12:34 PM

wha-lah!!! is fixed. i discovered the o-rings in the injector pods were cracked and hardend. when it was cold outside {mornings} the o-rings would shrink and fuel was being pushed by the injectors,both of them. causing gobs of fuel to be dumped.when the tbi warmed up the o-rings would swell up and seal the gaps. needless to say two .25 cent o-rings later and the truck runs like a champ.

Case 7230 · 08-23-2008, 12:46 PM

Good man. Glad you got it sorted and posted the solution.

08-22-2008, 07:50 AM	#1
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 114	89 gmc runs rough. 89 gmc truck,305,tbi. everymorning on start up the truck runs like ****,flooding,black smoke [etc]i have a code 45,rich exhaust.replaced the o2 sensor,iac,tps,ect,map sensor,fuel filter,fpr,egr valve has been blocked off for 5 years,so thats not the problem.i see i have a small drip from the driver side injector,but the spray pattern is good.the truck will run rough all the way to work ,15 miles,i cut it off and 10 minutes later i start it up it runs perfect for the rest of the day.could the ecm be going bad?

08-22-2008, 11:11 AM	#3
leolkfrm Senior Member Join Date: Mar 2008 Location: N.Y. Posts: 1,456	Welcome to the forum Could be the temp sensor is starting to go bad making it run rich __________________ 4 wheels move the body 2 wheels move the soul

Thread Tools	Search this Thread
Show Printable Version Email this Page	Search this Thread: Advanced Search

Similar Threads
Thread	Thread Starter	Forum	Replies	Last Post
98 S10 V6 Runs rough when cold after 5 miles runs great?	STRAYDOG	Chevy Truck Forum	17	01-24-2008 02:44 PM
truck runs rough	chrisjordan	Chevy Truck Forum	4	04-04-2007 03:59 PM
Engine runs rough between 2k and 3krpm only	cody_321	Chevy Truck Forum	9	03-26-2007 06:41 PM
Hey all, new here & I need HEELLLPPP (runs ROUGH!!)	meimg	Introductions	5	09-27-2006 08:00 AM
94 K1500 Runs Rough When Cold	tdyer	Chevy Truck Forum	0	04-07-2006 06:32 PM

08-22-2008, 11:04 AM	#2
Case 7230 Senior Member Join Date: Dec 2007 Posts: 253	I am no expert but could you unplug the injectors with engine running and see if fuel keeps flowing? Also could you check for vacuum leaks around the intake manifold and throttle body and the EGR valve? You can do this by spraying carb. cleaner or similar and listening for a change in engine note if the spray hits a leak. I`m sure someone else will chime in soon. Good luck with it.

08-22-2008, 11:13 AM	#4
87c10slammer Banned Join Date: Mar 2008 Location: levittown pa Posts: 2,197	i would have to say it has something to do withthat leaky injector. if it sits overnight leaking then you are flooding the closest cylinder. it may take that long to clean itself out. perhaps it has a good spray pattern in your eyes but they may both be weak and that is the culprite. now as the motor heats up it will run better becuse the air is getting hotter coming into the intake and its less dense air. so you need less fuel to mix with this less dense air. take the air filter off after it has been running good for a while then take it around the block see what happens

08-22-2008, 11:19 AM	#5
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 114	i havent tried unplugging the injectors yet. ive put my finger under them while the truck is off and there dry.and ive also replaced the temp sensor but no luck either.it seems to be temp related.i left my truck at work yesterday and i started it up an hour ago after sitting all nite and it runs perfect. i also reaplced all vaccum lines and sprayed all around tbi unit. no leaks. thats why i think maybe ecm.

08-22-2008, 11:22 AM	#6
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 114	im going to take the injector out tonite and look it over. there is some o-rings in the pod im going to check.

08-22-2008, 03:23 PM	#7
wojeepster Senior Member Join Date: Nov 2005 Posts: 92	I second the coolant temperature sensor or connection to it.

08-23-2008, 12:34 PM	#8
cburcham73 Senior Member Join Date: Aug 2008 Location: williamsburg virginia Posts: 114	wha-lah!!! is fixed. i discovered the o-rings in the injector pods were cracked and hardend. when it was cold outside {mornings} the o-rings would shrink and fuel was being pushed by the injectors,both of them. causing gobs of fuel to be dumped.when the tbi warmed up the o-rings would swell up and seal the gaps. needless to say two .25 cent o-rings later and the truck runs like a champ.

08-23-2008, 12:46 PM	#9
Case 7230 Senior Member Join Date: Dec 2007 Posts: 253	Good man. Glad you got it sorted and posted the solution.