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Hesitation on acceleration when hot


Ian Goddard's Avatar
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07-12-02, 12:52 PM   #1  
Ian Goddard
Hesitation on acceleration when hot

Have a 1990 Chevy S 10 Blazer, 4.3, 4x4. Cold runs fine . When fully warm ,will occasionally hesitate/misfire on acceleration, or sometimes at normal cruise speed. Usually clears when kicked down. Temp normal on highway but rises quickly at stops.No coolant leaks. Tends to rough idle at stops when hot. Park/neutral helps but no cure. Gas mileage virtually unchanged since new. All cooling system comps cleaned/checked/changed. IAC cleaned and specs checked. TPS replaced.EGR valve to specs. O2 sensor replaced. Any suggestions?No diagnostic codes set. No obvious vac leaks. Air filter good. When it runs 'Normally' hot, it runs fine. Other times it runs as though its on 2 cylinders.!!Premium fuel helps a little but no major improvement. Could it be something that, when fully hot, intermittently breaks down? Fuel injectors? I hate parts swapping in the hope of a miracle.!!

 
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07-12-02, 03:15 PM   #2  
Joe_F
When was the last time it saw a tune up? How's the fuel pressure?

 
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08-18-02, 02:40 PM   #3  
Ian Goddard
Hesitation on acceleration. 1990 S 10 Blazer

Fuel pump pressure is to specs. Tune ups done religously. Checked again timing, MAP sensor and EGR system. All to specs. Any other suggestions?

 
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08-18-02, 06:10 PM   #4  
kinda sounds like it may be an egr opening to much causing it to hesitate at lower rpm, and cruise speeds, test drive it with the vacum line disconnected to the egr if the problem goes away replace it with a new a/c delco one.
have you checked the pug wires, and distributer shaft for excessive play?

 
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08-20-02, 10:15 PM   #5  
Has anyone tried to adjust the idle speed with the torx screw on the throttle body??? If so, it will cause a problem between the TPS to IAC communications (voltage). A mechanic with a scan tool can check the TPS voltage to the IAC.

 
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08-22-02, 07:40 PM   #6  
Ian Goddard
Re hesitation on acceleration 1990 S10 Blazer

BeJay. Tried plugging off EGR vac. No change . Distributor shaft side play, minimal. ( 0.oo6 at side of rotor).Dirty Dan. No one has touched the idle speed adjuster. I have owned it since new. Will check voltages per your suggestion. Something wierd is going on and I am willing to check any possibilities!! Thanks to all for your suggestions. Any thoughts are welcome. It's been driving me nuts for over a year.!! Surely mine can't be the only one that has had this problem?

 
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08-24-02, 05:46 AM   #7  
LG2
Hey, have you checked your water pump and coolant flow? If the pump veins are worn off, that could explain the overheating at stops, and possibly be causing the poor running due to overheating, even if it looks like it's cooling when driving. Tauruses have a lot of trouble with this, no leaks, but no coolant flow. Good luck!

 
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08-24-02, 05:54 AM   #8  
LG2
Hey, have you checked your water pump and coolant flow? If the pump veins are worn off, that could explain the overheating at stops, and possibly be causing the poor running due to overheating, even if it looks like it's cooling when driving. Tauruses have a lot of trouble with this, no leaks, but no coolant flow. Good luck!

 
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