Engine stalling after warm up - 87 Silverado 350 TBI

[Snakebite]

I LOVE square body trucks and have owned quite a few. Currently trying to pass the torch on to my oldest son who will get his license next summer.

My 87' 1500 has run great for years but now it stalls after a few minutes of running. It cranks fine, takes gear and goes but as soon as you give it gas, it bogs down a ton and eventually dies. We just replace the entire TBI with a rebuilt one and it does the same thing. Parked, it still cranks and you can throttle it all you want, does fine. Only stalls when in gear and you press the gas pedal. Any suggestions?

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[4WDKC]

did you reuse the same sensors when you rebuilt it? Do you have a scanner to see live data from the ECM? Last but no least have you checked the fuel pressure?

 

[Snakebite]

No, sensors are new from the rebuilt unit. I do not have a scanner or a pressure gauge. I guess that's where we'll start next.

 

[ajd89]

Yeah check for codes i agree! Also I don't know that this is your issue but the coolant temperature sensor will really throw things off had to replace one in mine when it didn't run right

 

[ajd89]

No, sensors are new from the rebuilt unit. I do not have a scanner or a pressure gauge. I guess that's where we'll start next.

Don't have to have a scanner you can use a paperclip to jump the terminals on the OBD port and your check engine light will Flash with the codes

 

[Snakebite]

Thanks for the replies, I'll update as soon as I can.

 

[4WDKC]

Yeah check for codes i agree! Also I don't know that this is your issue but the coolant temperature sensor will really throw things off had to replace one in mine when it didn't run right

Paper clips only shows codes, this system is so old it can have bad sensors and never set a code, this is why live data is best.

 

[1987 GMC Jimmy]

Paper clips only shows codes, this system is so old it can have bad sensors and never set a code, this is why live data is best.

What do you use to see your live data? I have the four dollar homemade Chinese scan cable that uses TunerProRT on my laptop, and I have a 32 year old OTC scan tool that I use on my Caprice, but is there something else?

 

[4WDKC]

What do you use to see your live data? I have the four dollar homemade Chinese scan cable that uses TunerProRT on my laptop, and I have a 32 year old OTC scan tool that I use on my Caprice, but is there something else?

I have the DIY cable and TunerPro RT also, I also have a Snap On MT2500 I picked up at a swap meet for $50. Everyone thinks these scanners are expensive and hard to find and they arent.

 

[Snakebite]

Replacing the throttle position sensor and coolant temperature sensor now (recommended by someone with a similar problem). The fuel pressure is fine and the electronics to the TBI are okay.

If these two parts don't work, my last option would be the pump inside the gas tank I guess? lol, I'm running out of options!

 

[4WDKC]

Didnt you replace the TPS and IAC with tje new TBI? Did you do key on self test/calibration? If the the IAC is moving to far when warm it wont idle. The ecm operates on a open/closed loop system open loop is (IIRC) ignores the sensors and operates on preset values, when it warms up it goes into closed loop (IIRC) and tries to operate off the sensor values.

 

[4WDKC]

Replacing the throttle position sensor and coolant temperature sensor now (recommended by someone with a similar problem). The fuel pressure is fine and the electronics to the TBI are okay.

If these two parts don't work, my last option would be the pump inside the gas tank I guess? lol, I'm running out of options!

If they replaced them and still have those problems do you want to do the same things that didnt work for him?