1989 scottsdale efi doesnt want to idle

1989 scottsdale chevy 1 ton 4x4 7.4L 454 it has the tbi efi fuel system , it doesnt want to idle i checked the fuel pump 15 psi like the manual states, new fuel filter,checked for vacume leaks no luck .  the idle control valve is there a way to check those . the motor will excellerate ok , startes write up  

first... you will need a scan tool that can talk to the GM system...

second.. you need to copy and paste this link... then print several copys of the chart..

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/06/7e/6a/large/0900c15280067e6a.gif

if you with the engine cold... write the sensor readings from the scanner down on one side of the chart..

then bring the engine up to temp..    copy the data stream down again hot...    now you can examine what the ecm is doing...

i would also take a pair of needle nose pliers and try pinching off the rubber vacuum hose to the power brake booster....  

how dirty is the throttle bores ... clean usually do to the fuel spray..

with the engine off... open the throttle lever with your hand.. then see if it wiggles around any .. loose shaft in the throttle body can make for weird idle problems..



with the scan tool... this is OBD 1... some scan tools are available currently with obd1 and obd2 ... there are sometimes various scan tools on craigs list...


only one thing...  the idle air counts.. IAC... i like to see 20 to 50 with the   ECT (engine coolant temp) above 195F///

do you have any codes??????     you can jump the A and B terminal on the ALDL connector sticking out under the dash just above your knees;...    there are charts  to show you which one is which...

one thing... does not want to idle...   does that mean its stuck at fast idle...  or so slow it dies...???????  

i had two codes 32 and 44 one was  check connectors on ecm and o2 senser then second was check puel pressure and egr valve and vacume lines for leaks . i ordered egr valve and o2 senser and complete tbi ,im going to check the fuel pressure again new manual says 26-32 lbs i was wrong on 15 lbs make sure im doing it write.the truck will start write up it will fast idle when cold then when kicking down to regular idle it acts like its starving of fuel but you can see the jets spraying and when you accelerate it it revs write up sounds fine just whants to die when trying to idle thanks for the help gary  

code 44.. is where to start... but BEFORE starting to replace things...

i am taking that your truck is equipped with an air injection system...


there are places the air injection system hooks up to...

the upstream air injection system feeds into the exhaust manifolds upstream of the Oxygen sensor...


the down stream air injection system feeds air into the exhaust system just before the cat or in the sides of the cat...

if your truck is equipped... i would like you to find the check valves that are mounted on the pipes into the exhaust manifolds...  unhook the rubber hose that feeds into them... use another. chunk of heater hose and something to plug that hose.. so NO air can be pulled in for this TEST only.. this is NOT a fix .. this is a test...

disconnecting the air injection system and driving it will cause damage to the cats...

when the engine is first started... the air injection system pushes air into the upstream exhaust to burn off the excess hydrocarbons... and to help warm the cats...  once the system goes into closed loop... the upstream air injection system is turned off.. except under heavy enough acceleration to force the system into open loop...  

oh... close loop.. the fuel mixture is  set by the ecm looking at the oxygen sensors..

open loop.. the system runs in preprogrammed mode...

if the diverter valve gets its plastic internal valves melted... by excess back pressure, bad exhaust check valves.. a bad smog pump that does not put out enough pressure to keep the exhaust out of the system..

it will leak into the upstream air.. diluting the exhaust stream and causing the EXACT problems you have..

lean exhaust...    excess air in the exhaust...

failed EGR system... the system cycles the EGR valve and looks at the exhaust stream for signs the egr is working...  it does show up ... but when the exhaust is so diluted.. it does not.. so the system generates a code...

exhaust leaks will also cause this...

clogged cats also..

clogged cats will also show up as the intake manifold vacuum dropping as you slowly increase the speed of the motor without a load..



her is the trouble shooting charts for code 44...

http://www.fastbird93.com/diagnostics/dtc44p1.jpg

you will see the last thing to check is the air injection system...

there is the second page..

http://www.fastbird93.com/diagnostics/dtc44.jpg




here are the 4 pages for the EGR... but i wold really go through the 44 first...  fix any exhaust leaks...

http://www.fastbird93.com/diagnostics/dtc32p1.jpg

http://www.fastbird93.com/diagnostics/dtc32p2.jpg

http://www.fastbird93.com/diagnostics/DTC32%20Page1.jpg

http://www.fastbird93.com/diagnostics/DTC32%20Page2.jpg  

thanks for all the help wayne,ill check all the procedures you described ,on my catalytic converter theres nothing hooked up to it, i must have the upstream air injection, theres tubes screwed into the exhaut manifolds, in the manual they call it typical secondary air management system. the converter is about 5 yrs old but i never drive the truck but ill check the converter to make sure its still good not clogged.im new to computers so my kids will show me how to do that paste and copy and the scanning is also new to me so this will be a learning experiance, id rather work on my 67 camaro much easier thanks again for the help gary  

they call the air injection system.. secondary.. but ... the actual things work like i described... if its upstream of the oxygen sensors.. its upstream..

block off the check valves.. so no air gets in.. verify they are NOT ROTTED out..  that they are actually working..  

see what happens....  

it was the distributer. thanks for the help wayne 7122