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Engine idles fine but no power on acceleration?

Tiny
HMAC300
  • MECHANIC
  • 48,601 POSTS
Scan for codes a nd check fuel pressure with a gauge. Then check for a vacuum leak pump pressure should be 41-47 psi.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
I did not see where you had mentioned a fuel filter, you will want to do a fuel quantity test with the key on. Should be one liter in thirty seconds if I remember correctly. Lou
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
Cannot, fuel Schrader valve on this truck and does not codes stored check engine light will not even come on.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
Everything was good filter. It was the first thing, sorry.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Okay, if memory serves me you need to remove the fuel filter and install a T with a fuel gauge attached. Also, does the truck run bad only under load? Do you have a fuel injection service tool?
If so you may want to disable the fuel system and run the truck off the fuel service system. If it runs the same you know its not a fuel system issue. If it runs better then you know it is something with the fuel system.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
It runs the same I have already tried it.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Okay, well if you do not tell us what you have already done then how are we supposed to guide you in the right direction. :)
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Partially disconnect the exhaust from the manifold see if the engine runs better. You could have a partially clogged catalytic converter.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
JESSE1971
  • MEMBER
  • 2 POSTS
  • 1995 CHEVROLET S-10
95 S-10 4x4 4.3 Z TBI A/T 15000 mls. Runs fine when cold, once thermostat opens thats when the problem begins, it misses when idling in gear and stopped, [at stoplight] if I shift into N or P it dosn't miss but tach floats 100 rpms up and down. Misses with light acceleration but not with heavy acceleration. Service engine light has never come on. Oil is clean [no antifreeze leaking in] oil pressure is fine, I have already replaced intake manifold gasket, fuel pump and sending unit, fuel filter, plugs, wires, dist. Cap, rotor, ignition coil, O2 sensor, coolant temp. Sensor, removed egr valve and found no carbon clogging the valve. WHAT CAN IT BE? I need help from someone smarter than me because I'm out of ideas and money!
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
Check the coolant temp sending unit not the sensor. Also check the MAF or AIS if equiped with your model. Also a dirty IAT can cause this.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
I have done so much I have forgotten.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
JESSE1971
  • MEMBER
  • 2 POSTS
Truck doesn't have MAF AIS or IAT did you mean IAC? Coolant temp sending unit seems to be working warms up to around 200-205, once thermostat opens drops to around 150 then stays steady between 150 and 170 which is normal however before this problem thermostat opened around 190 then dropped to 150. I don't know if this is related, seems like it. Cooling system is clean, good flow through radiator. Feels like a sensor is cutting fuel to injectors but no codes have been set. Tried a new MAP sensor today, runs even worse engine surges 1000 rpms at idle, service engine light comes on and goes off, can't accelerate at all without engine stalling. Starts right back up but still can't touch gas pedal without stalling. Put old MAP sensor back on.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
Okay, just got back from trying that no differences.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
BLACKOP555
  • MECHANIC
  • 10,371 POSTS
No I meant IAT, Idle Air Intake is located on the manifold.

I think were looking at a thermastat problem. Take it out and examine it, see if it opens when heated up with a hairdryer if not get a new one.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Forgiven :)
so either remove the o2 sensor and install a back pressure gauge or partially disconnect the exhaust and see if it runs better. You should never have more then 1-2 psi back pressure. Pretty sure its under one psi.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Okay, well if you ruled out exhaust and fue. I would take a closer look at the distributor and check the play of the shaft the rotor sits on. Also, the condition of the pick up coil. Not sure if I seen that you replaced that or not, but it sounds like you may have ignition breakdown. I would take a closer look at the distributor. Lou
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
No distributor has two coil packs and in two and a coil module.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
And I have replaced both.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
LOU P
  • MECHANIC
  • 118 POSTS
Oh sorry, thought this was a distributor style still. If I can come up with some better information I will reply back. I am sure another tech here has run across this and should chime in. Lou
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+1
Monday, December 14th, 2020 AT 9:24 AM (Merged)
Tiny
WESWALKER88
  • MEMBER
  • 15 POSTS
Thank you.
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Monday, December 14th, 2020 AT 9:24 AM (Merged)

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