stalling at idle 1989 chev 305 k1500

[woolfmaster]

Hi!
I am at the end with this truck!
1989 chev TBI 305 k1500.
No codes and many parts later still will not idle in closed loop. sometimes a stall in open. here is the list! fuel pump/filter,tps,iac,temp sensor,map,pvc.checked all vac lines. will idle in 3.9k mode??? and 10K mode. truck sat for 3 weeks and started this. runs down the road great! I am missing what is different in the 3.9K and 10K modes that it will idle in. I have a OTC 2000 scan tool...truck starts right back up...(no flooding) and idles 10 sec or so. as its dies i hear a rush of air in the TBI?? idle air opening?? or lack of fuel? or spark? I am burned out!!! Help!
Thank you for any help to get me on track! can give you any data from the scan tool!

Tommy

[2000CAYukon]

Have you replaced the TBI gasket (or at least inspected it)? It is common for the gasket to get sucked in at the back of the TBI.

What is the 02 reading on the scan tool? Has the 02 sensor ever been replaced?

//2000CAYukon

[2000CAYukon]

A bad EGR can also cause this. Try plugging the vacuum hose going to the EGR to see if stops the stalling. If it stops stalling, the EGR is bad.

//2000CAYukon

[woolfmaster]

Originally Posted by 2000CAYukon

A bad EGR can also cause this. Try plugging the vacuum hose going to the EGR to see if stops the stalling. If it stops stalling, the EGR is bad.

//2000CAYukon

Thanks!! I changed the O2 sensor today NO help. Also at the parts store got a new TBI gasket and a EGR gasket. I sprayed around the TBI with carb spray its hard to tell if there is a vac leak.(stalls so fast) I will change it and check the EGR valve... It acts like its lean..even in open loop stalls when put in gear R or D..or turning the steering wheel! no power in the engine. I tryed plugging the egr hose NO help.. someone said to me take it off and check for carbon...Long time ago i seen a burnt EGR gasket do the same thing! Thanks for the help! getting closer to the problem! Tom

[woolfmaster]

Originally Posted by 2000CAYukon

Have you replaced the TBI gasket (or at least inspected it)? It is common for the gasket to get sucked in at the back of the TBI.

What is the 02 reading on the scan tool? Has the 02 sensor ever been replaced?

//2000CAYukon

Changed the O2 sensor today. the old one had low cross counts and stayed rich and lean along time in closed loop at say 1000rpm... and voltage didnot change much..new shows good cross counts and not staying rich or lean for that long time with the old one... Got New gaskets TBI and EGR! Ready to fix this thing! Got the email of a post at 4:30 looked at it and was off to the parts store by 4:40! 15 miles one way! Thank you for the help!! TOM...

[2000CAYukon]

Clean the egr valve and make sure it is not stuck open. Also, a bad EGR gasket is basically a vacuum leak.

//2000CAYukon

[woolfmaster]

Originally Posted by 2000CAYukon

Clean the egr valve and make sure it is not stuck open. Also, a bad EGR gasket is basically a vacuum leak.

//2000CAYukon

You are right! I see my job for tomorrow! saturday!! EGR time! thanks!
Tom

[woolfmaster]

Originally Posted by woolfmaster

You are right! I see my job for tomorrow! saturday!! EGR time! thanks!
Tom

Sorry it rained all day! and I still have rain..first project on the 4th! Happy 4th! Thanks again! TOM

[woolfmaster]

Originally Posted by woolfmaster

Sorry it rained all day! and I still have rain..first project on the 4th! Happy 4th! Thanks again! TOM

Hi! OK! Here is what i did and found today..checked and cleaned the EGR new gasket...new TBI gasket...tryed to see if it was fuel or spark problem. acted like spark stopping at under 700 rpm..took out the dist module had it tested failed low rpm test! great put in a new one..Same thing! runs fine in back up fuel mode...(idle that is) is the ecm bad? and one more thing on the scan tool i get NO injector width 0r timming?? That's because its TBI not EFI or PFI?? Maybe a bad wire to the ecm? Plus won't show advance?? someone e-mail me the coil was bad? In open loop its stalls if you put in gear or even turn the steering wheel! No power! OK!! where do we test or look at now? the Dist pick up looked rusty and the module had rusty bolts and rust on it... Thank's again for all your good help! I know we can FIX IT! TOM

[woolfmaster]

Well today i took the new dist module in and had it tested.passed fine.also checked charging volts at the battery 14.3. I hooked up my scan tool to my 89 s-10 4.3..readings look the same.but the block learn stuff was different.(stayed around 128/130 ingterger) I did find my s-10 the TPS is too high .82v(idles good something more to fix)There was NO injector data guess that year and TBI there is no data. found out the ECM is the same number in my s-10. i may try it swap the chips and try it in the 89 k 1500.I am going to check the pick up tomorrow because one of the parts guy worked for gm 25 years and said if the pick up is so rusty (It's real bad)or going bad(weak mags) the output at low rpm could be too low for the module to read and use to fire the coil..and i will retest the fuel pressure. any other things i should look at???
Thank you !! Tom

[roadrunner_70]

Do you have a way to print out the Scan tool results? If not, write them down and type them here. Do them at idle cold, then at operating temperature. Also, describe the timing figures when you accelerate from idle. What is it saying about EGR function?

[woolfmaster]

Originally Posted by roadrunner_70

Do you have a way to print out the Scan tool results? If not, write them down and type them here. Do them at idle cold, then at operating temperature. Also, describe the timing figures when you accelerate from idle. What is it saying about EGR function?

OK i will write down the data from the scan tool. checked the pick-up coil cold was 850 ohm...right in the middle of the range. i looked at the egr function at idle NO... A GM parts guy(retired) said they had some bad Dist reluctors (weak magents and cracked ones)in the late 80's he said to check the output of the pick-up coil should be around 500mv AC cold..all that rust could lower the output below what the module can read or the weak magnets lowering it too low. he said the magnets putout less the hotter they get so test when its hot and stalling..sounds OK to me.I will try it!
Thank you roadrunner_70.

[woolfmaster]

Originally Posted by woolfmaster

OK i will write down the data from the scan tool. checked the pick-up coil cold was 850 ohm...right in the middle of the range. i looked at the egr function at idle NO... A GM parts guy(retired) said they had some bad Dist reluctors (weak magents and cracked ones)in the late 80's he said to check the output of the pick-up coil should be around 500mv AC cold..all that rust could lower the output below what the module can read or the weak magnets lowering it too low. he said the magnets putout less the hotter they get so test when its hot and stalling..sounds OK to me.I will try it!
Thank you roadrunner_70.

Hi again! tested the pick-up output was 230 mv ac cranking..sounds low and it was not steady 210-250... Is that the right mv??? Thanks!! tom

[2000CAYukon]

On my 90 K1500, I had a rough idle and miss when warm. A new pick up coil really helped and the mileage when from around 11 to closer to 14. The miss was gone and it was less than 20 dollars for the part.

Mine had gotten pretty rusty too.

//2000CAYukon

[woolfmaster]

Originally Posted by 2000CAYukon

On my 90 K1500, I had a rough idle and miss when warm. A new pick up coil really helped and the mileage when from around 11 to closer to 14. The miss was gone and it was less than 20 dollars for the part.

Mine had gotten pretty rusty too.

//2000CAYukon

NASA we have a FIX!

First thing Thank you all for your good help! The problem was weak magnets in the Dist. come to find out this was a untold(by GM) problem in 1989 cars and trucks. here is a link telling about it!!
http://www.mightyautoparts.com/pdf/articles/tt71.pdf

Hope this helps someone! the idle is fine and i eyeballed the timimg(need to set it pings alittle) I knew that 240mv was low..the new dist tested 800-1.2v ac....wow! just by hand you could get 1v+ the old one maybe 500mv. SO who would have thought it was Weak magents in the Dist?? Not me!
I have had a repair shop for 25+ years. Teached auto repair.turned down a teaching job with Nascar training center in NC! ASE master for 10+ years.and loads more ASE certs. I have M1g,M2g,P2,F1,T1.
I learned alot about GM TBI system tring to troubleshooting this truck!
Thanks again!! tom