Bad hesitation after warming up

Tiny
AUSTIN KERBER
  • MEMBER
  • 1990 CHEVROLET SUBURBAN
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 199,000 MILES
So I have the SUV listed above with the EFI throttle body. When it is cold it runs great. As soon as the temperature comes up, a whole slew of problems happen. From a complete stop, if you mash on it, it will fall on its face spit sputter and shut off. I did some digging, and my own self diagnosing, (unplugging sensors) I got to the coolant temperature sensor, unplugged it, ran great when warm, terrible when cold. Plug it back in, it does the opposite, so I put a new sensor on it, still didn’t fix the problem. No other sensors fixed the problem, so I pulled the wiring harness, and went through it. Every wire, every connector, found an alarming amount of shorts, and bare wires, fixed properly, (soldering and heat shrinking) reinstalled, still horrible problem. Am I missing something?
Monday, June 24th, 2019 AT 6:25 PM

1 Reply

Tiny
JACOBANDNICKOLAS
  • MECHANIC
  • 109,758 POSTS
Welcome to 2CarPros.

The first thing I would suggest is to scan the computer for trouble codes. The vehicle has an OBD1 system and they are simple to check. All that is needed is a jumper wire or even a paper clip.

Follow this link:

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

Also, have you checked fuel pump pressure and the regulator? Here is a link that explains in general how it is done:

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Here are the manufacturer's specs for pressure:

FUEL PRESSURE
Ignition ON Engine OFF .................... 62-90 kPa (9-13 psi)

____________________________

Check these things and let me know what you find.

Take care,
Joe
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Monday, June 24th, 2019 AT 7:24 PM

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