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Old 03-18-2018, 01:41 AM   #1
Evkev7
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1990 TBI acts like it's loading up like a carb

K so my 90 Suburban has an on and off again issue of sort of stalling out just off idle, and sometimes at speed in town.
It's a 4 bolt main 5.7. Stock. I recently bought it back from a friend who put the engine in while he had it. It was running way bad when I got it back, acting like the fuel filter was plugged. I went thru a few filters then replaced all the sensors on the tbi from stuff from the junkyard, air idle sensor, EGR, throttle position. Seemed to totally seemed to fix it.
It's 99% better. But the off idle stumble is annoying.
It is on 35 inch tires with somewhat tall gears. If I drive in 2nd gear in town it doesn't do the load up thing. Keeping the rpms up keeps it happier.
Thoughts from the experts would be greatly appreciated.
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Old 03-18-2018, 09:43 AM   #2
ChevyTech
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Re: 1990 TBI acts like it's loading up like a carb

If it is loading up it could be running rich because of a bad coolant temp sensor.

There is testing information in post #11 of this thread:
http://67-72chevytrucks.com/vboard/s...d.php?t=379142

That thread can be found be looking in the frequently asked question thread from the top of this board.
http://67-72chevytrucks.com/vboard/s...d.php?t=445487
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Old 03-18-2018, 12:49 PM   #3
Evkev7
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Re: 1990 TBI acts like it's loading up like a carb

That's the one sensor I didn't replace cause it looked brand new when I got it. Tho I've noticed it has a slight leak at the thermostat housing; I suppose that could be allowing a bit of air there at the sensor once it's been running huh?
Ill test it today.
Thanks!
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Old 03-18-2018, 01:50 PM   #4
Bigdav160
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Re: 1990 TBI acts like it's loading up like a carb

This is where a good OBD1 scan tool is useful.

Where do you have your ignition timing set at?
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Old 03-18-2018, 08:08 PM   #5
Evkev7
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Re: 1990 TBI acts like it's loading up like a carb

It never throws any codes. I jumped the plug and checked that way.
Haven't checked timing it runs awesome 99.99 % of the time so timings not the issue. I put a coolant sensor in today just to see if it did anything. Its hard to pin down cause it's so intermittent. But it's also not a big prob cause it's so intermittent lol.
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