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88 s10 2.5L 5 speed TB
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Discussion Starter · #1 ·
Have an 88s10 with the 2.5 and 5 speed that will almost always stall out when slowing down or downshifting gears, always starts right back up . The injector above the throttle body is flooding the TB with way to much fuel and causing the truck to emit real thick grayish colored smoke out the exhaust pipe with the smell of unburnt fuel and a small pile of liquid forming around the end of the tailpipe . Have changed out everything but the TPS. Wondering if it’s that or something along the lines of the o rings on the injector are bad or something. Any help or advice greatly appreciated
 

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1994 S10 LS 4X2 with a 4.3 Liter V6 VIN Z
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62 Posts
I would try the TPS sensor as they are not that expensive to replace. If that doesn't work, then I would get the injectors tested to see if they are faulty. Also, put a noid light on the injector wire and see if it is on for a longer period of time than normal.
 

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88 s10 2.5L 5 speed TB
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29 Posts
Discussion Starter · #3 ·
I would try the TPS sensor as they are not that expensive to replace. If that doesn't work, then I would get the injectors tested to see if they are faulty. Also, put a noid light on the injector wire and see if it is on for a longer period of time than normal.

I just had someone else tell me there was a good possibility it may be the TPS sensor ,O’Reilly’s is gonna have it for me Monday and I’m going to replace it and see if it fixes the issue . Thanks for advice bud
 

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So have you already changed the Engine Coolant Sensor (temperature sensor for the ECM)? Have had lots of issues with them on my V6 rigs, so has my good friend who ran TBI Chevys for years.

The last one failed on my V6 Trooper, made the ECM think it was extremely cold outside, so it was dumping fuel into the engine. It actually ran better after unplugging the sensor. A trip to NAPA and about 5 minutes of wrenching fixed the problem after I got home from work.

Looks like your 2.5 uses the same ECS as my 60-deg V6's:

 

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1994 S10 LS 4X2 with a 4.3 Liter V6 VIN Z
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62 Posts
Unplug the Engine coolant sensor then and see. It should be right next to the thermostat. If that still doesn't fix it, then get the injectors checked and put noid lights on the injector wires and see if they stay on longer than normal. You might also have a relay that stays open longer than it should. It seems to be something electrical going on.
 

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88 s10 2.5L 5 speed TB
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Discussion Starter · #9 ·
Unplug the Engine coolant sensor then and see. It should be right next to the thermostat. If that still doesn't fix it, then get the injectors checked and put noid lights on the injector wires and see if they stay on longer than normal. You might also have a relay that stays open longer than it should. It seems to be something electrical going on.

alright man thanks I will put a new one in when I get off work and let you know if it fixes the issue . I’ve noticed another thing is when it’s colder it seems to do it worse and more frequently or if it’s real wet or damp outside
 

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Pull the air cleaner lid, fire up the engine and see if the injector is spraying cleanly. You can hook up a timing light and point it at the injector, the strobe effect will "freeze" the view.

There should be a nice, even, conical "fan" spray pattern. If you're seeing gaps in the spray or "dribbles", the injector needs to be reconditioned or replaced. Pull up your rig at Rockauto.com , they have some decent deals on reman'd injectors. Or you may have a local company that can clean/recondition/flow test your injector if it needs it.

Turn off the engine after the rig is warm, with the air cleaner lid off, see if the injector is leaking any fuel. Or fuel is leaking internally to the TBI anywhere.

At least your throttle body is simple, with just a single injector. Here's an inexpensive TBI repair kit with all the gaskets, O-rings, FPR diaphragm, etc you'd need to recondition the throttle body:

 

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88 s10 2.5L 5 speed TB
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Discussion Starter · #12 ·
Wish I could upload a video of the injector spraying fuel into throttle body . It’s not a consistent fan .. it’s almost like itl pulsate then dump an overload of fuel then it is all over the place with how much fuel its giving the TB
 
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