TBI surging when idling after warm. Coolant Temp Sensor replaced. Cause?

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PlayingWithTBI

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Another thought, if your engine runs smooth when warming up, then does this when warm, you may have a "lazy" O2 sensor. Before it warms up you're running in OL then, once up to temp, it switches to CL and adjusts fuel trims based on O2 feedback.
 

thinger2

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Always start with year model engine transmission
The code(s) will reset. The only other thing the ECM resets is the INT (Integral AKA short term fuel trims) and BLM (Block Learn Multiplier AKA long term fuel trims). It'll run on the VE tables in Open Loop until it goes into Closed Loop, then it'll start working on INT and BLM based on O2 sensor feedback.


Driver's side for the gauge. Some later models with E-fans used a temp sensor in the passenger side for controls.
The code(s) will reset. The only other thing the ECM resets is the INT (Integral AKA short term fuel trims) and BLM (Block Learn Multiplier AKA long term fuel trims). It'll run on the VE tables in Open Loop until it goes into Closed Loop, then it'll start working on INT and BLM based on O2 sensor feedback.


Driver's side for the gauge. Some later models with E-fans used a temp sensor in the passenger side for controls.
Yep. But how about we not burn this guy.
Or each other.
A newbie came here for advise and got **** on becuase he hadnt reached some exalted level of ass kissing that made him worthy enough to dare ask a question from the holy exalted rulers of gmt400 trucks
You can not **** on people who want to get into the car world.
That will happen anyway.
That is racing boys.
Nobody owes you a ******* thing.
Nobody has to kiss your ass.
How about you big badass ******* help somebody.
I bet you wont do ****.
Prove me wrong.
 

thinger2

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Another thought, if your engine runs smooth when warming up, then does this when warm, you may have a "lazy" O2 sensor. Before it warms up you're running in OL then, once up to temp, it switches to CL and adjusts fuel trims based on O2 feedback.
I think we are really chasing people away by giving them deep tech advise first.
OBD1 is such a short lived and archaic technollogy and very speciallized.
When people show up asking for advise they really get **** on becuase they dont know **** all.
They are here because they dont know **** all.
That is the whole point.
Telling some new guy that his only hope is to buy 400 dollar scanner and learn how to use it before he needs to drive it to work monday to feed his family is such an egotistical petty small minded little chump ass rush for a somebody who gets off on dragging other people down.
You had a chance to reach out and try to help someone.
You used it to make yourself feel better by calling somebody out and show what a big man you are.
Weak.
Weak watered down weak.
Which one of you are gonna reach out and help this guy?
******* prove me wrong.
He needs his truck to work.
He isnt taking it to pebble beach.
Help him fix it
 

tayto

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you can datalog obd1 with $80 cable and free software. you can also pull codes with a paper clip. it's no ones job here to spoon feed anyone information. i think there was some good advice posted here, especially considering the lack of information. not sure who pissed in your cornflakes but maybe you should sit this one out.

also, not sure where you get that 1995 is standalone. The same PCM was used in '94.
 

Schurkey

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Trying to fix a computer-controlled system without being able to communicate with the computer is two steps away from futile.

A scan tool is as needed as wrenches and screwdrivers on computer-controlled vehicles. "Helping" someone without an ability to see what the computer and it's sub-systems (sensors, solenoids 'n' acutators, and the wire harness that connects 'em) is doing is how the Parts Cannon gets loaded. Every possible scenario is offered-up as a sacrifice; and every possible part is replaced until somehow they stumble onto the actual problem. This is neither efficient, nor economical, and in most cases is really bad for the mental health.

Two sessions with a shrink will pay for a decent scan tool.
And heaps 'n' piles of fixable cars that could have done people some good, got sent off to dirtbag politician's wet-dream of "Cash For Clunkers".

If Do-It-Yourselfers don't want to buy--or borrow--or rent--the needed tools, there are a jillion professionals ready and willing to do it...for a price.

Nobody asked me for permission to put computers in vehicles; and nobody asked my permission to sell them without incorporating a built-in scan tool and a full set of service manuals in the trunk. I--and we--have to play the cards we're dealt. That means investing in essential tools; or finding an in-person mentor who's appropriately well-equipped.

When I become Emperor of the USA, there's gonna be auto-repair courses offered in Adult Education programs and Community Colleges in every town big enough to have such a facility. All sorts of folks will have access to scan tools, alignment racks, oscilloscopes, and various kinds of specialized tools. Until then, folks gotta fend for themselves as best they can.



"OBD1" wasn't all that short-lived. It went from mass-production in '81 (and limited production before that!) until '95; probably post-95 in foreign markets.
 
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GoToGuy

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If you don't have energy to do a little research, reading on your own part, are you wanting to gain the knowledge of your vehicle, or just want a cheap quick fix with no effort ?
As for when questioned on codes, " none that I know of ".
So does have knowledge you can use a scanner. But does not want to purchase any, including a cheap one.
When criticized about that fact takes it to a personel level, rather than, " ooooh yeah shoulda check those".
So when you get called out on some omission, or mistake do you immediately go on the attack? As he did?
Your two post entry was overkill, and obviously you have had a bad experience.
One person wants answers, but how far does one
get when biting the hand that feeds you?
Good luck.
 

89Fleetside

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What year is your truck? If its a 94 and older its probably easily checked with a paper clip. if its a 94(maybe) , 95, it may be slightly more difficult, and a 1996+ isnt TBI if I am correct in believing that, so the attitude was because I thought you were being lazy. You seem to just not know about this , which is not lazy ness so I do apologize.
xc_hide_links_from_guests_guests_error_hide_media
It is an 89 Fleetside. I'll try the paperclip and see what codes it throws. I am assuming I can find a list of codes online without much searching.
 

89Fleetside

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Always start a question with year, model, engine, transmission.
These things changed so much over the years that we really need to know that.
Based on your user name Im going to assume that this is an 89.
Theorectically 95 and older are all OBD1 systems.
OBD11 is 96 and newer.
But, 95 vehicles are so odd that they are pretty much a "stand alone" one year only variation.
You can check for codes using the paper clip trick on an OBD1.
Really easy to do.
As long as you have not disconnected the battery or let it sit untill the battery went dead.
If you disconnect the battery on a ODD1 system all of the parameters that the ecm uses to control the engine are lost.
And so are the codes.
When you restart it again it needs to "relearn" from those inputs before it will run properly.
If this is an 89, it has two temp sensors.
One in the passenger side cylinder head.
That one feeds signal to the dash temp gauge
The other one is on the pass forward side of the intake manifold.
That feeds the ecm.
Whenever you crack a sealed system open you have to purge the air out of it.
If you pulled the head sensor and let it drain I gaurentee that you air in the cooling system.
If you pulled the manifold sensor and it was not full right to the top?
You have air in the system.
At hot idle I would be kinda surprised if it caused the ecm to firehose fuel like it is but it could be some ecm base module to keep it from being to lean.
Even over my crappy celll phone it looks like a major injector pulse issue.

Why did you replace the temp sensor?
What was going on before that?
Were you having problems before you replaced it or was everything fine untill after you replaced it?
Give us the back story with as much detail as you can.
I think you have maybe an air problem but you need to check fuel pressure for sure and set your timing with the dist wire disconnected.
Start with the basics.

Always start a question with year, model, engine, transmission.
These things changed so much over the years that we really need to know that.
Based on your user name Im going to assume that this is an 89.
Theorectically 95 and older are all OBD1 systems.
OBD11 is 96 and newer.
But, 95 vehicles are so odd that they are pretty much a "stand alone" one year only variation.
You can check for codes using the paper clip trick on an OBD1.
Really easy to do.
As long as you have not disconnected the battery or let it sit untill the battery went dead.
If you disconnect the battery on a ODD1 system all of the parameters that the ecm uses to control the engine are lost.
And so are the codes.
When you restart it again it needs to "relearn" from those inputs before it will run properly.
If this is an 89, it has two temp sensors.
One in the passenger side cylinder head.
That one feeds signal to the dash temp gauge
The other one is on the pass forward side of the intake manifold.
That feeds the ecm.
Whenever you crack a sealed system open you have to purge the air out of it.
If you pulled the head sensor and let it drain I gaurentee that you air in the cooling system.
If you pulled the manifold sensor and it was not full right to the top?
You have air in the system.
At hot idle I would be kinda surprised if it caused the ecm to firehose fuel like it is but it could be some ecm base module to keep it from being to lean.
Even over my crappy celll phone it looks like a major injector pulse issue.

Why did you replace the temp sensor?
What was going on before that?
Were you having problems before you replaced it or was everything fine untill after you replaced it?
Give us the back story with as much detail as you can.
I think you have maybe an air problem but you need to check fuel pressure for sure and set your timing with the dist wire disconnected.
Start with the basics.
Updated the post with relevant info. Changed the temp sensor as it was a cheap and easy attempt, but same issue after replacing.
 

AuroraGirl

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I'll check that out. Thanks.
you unlikely have a heated sensor, if you wanted to upgrade to a heated oxygen sensor , this would be wise. Unheated sensors live slightly shorteend lives compared to heated and also allow your truck to idle better. also the 1 wire sensors ground through the exhaust so if you had a poor connection from rust they would have unreliably grounds but a 4 wire conversion would allow you to ground it through the harness.
 
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