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Author Topic: 87 350 TBI problems  (Read 12535 times)

Offline scott87

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87 350 TBI problems
« on: October 07, 2010, 04:24:21 PM »
Hello this is my first post. I just got a 87 1/2 ton 4x4 TBI 350 and it seams to be loading up at low rpms when you take off. Just wondering where I should start. I will be giving it a full tune up anyways but I thought that I would see if anyone had an idea. Thanks, Scott
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Offline VileZambonie

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Re: 87 350 TBI problems
« Reply #1 on: October 07, 2010, 09:50:37 PM »
Any codes? Check the map sensor
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline scott87

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Re: 87 350 TBI problems
« Reply #2 on: October 07, 2010, 10:34:44 PM »
No codes, I think a friend has a motor that I can rob some parts off of so i will grab a map sensor off it. Do you know what years will work with it?
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Offline Layne

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Re: 87 350 TBI problems
« Reply #3 on: October 07, 2010, 11:47:46 PM »
I think the map sensors are all the same. I took one off my 83 citation and put it on a lumina and it was fine.
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77 c-10 - 77 400 86 700r4 "Emmy"
83 citation - 2.5L Four on the Floor!
88 sierra - reman 350 700r4 "Eleanor"
All normal practicality and rational money handling goes out of the window when it comes to my truck.

Offline scott87

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Re: 87 350 TBI problems
« Reply #4 on: November 04, 2010, 02:01:38 PM »
Well it took me a little while to get to it, but I put plugs, wires, cap, rotor, coil and map sensor on it and it still does the same thing. If you slowly accelerate it acts like it is loading up and when you let off it will almost die, but if you accelerate a little quicker then it runs fine.
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Offline VileZambonie

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Re: 87 350 TBI problems
« Reply #5 on: November 04, 2010, 02:26:51 PM »
Check the tps. No one told you to replace anything. You were supposed to CHECK the map sensor and report if there are any codes.
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74 GMC, 75 K5, 84 GMC, 85 K20, 86 k20, 79 K10

Offline scott87

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Re: 87 350 TBI problems
« Reply #6 on: November 04, 2010, 02:31:08 PM »
I got the map and coil for free and I was giving it a tune up anyways. I wasnt implying that anyone said to change anything, I just figured if I can get it for free I would replace it. Is there an easy way to test the TPS? And still no codes.
« Last Edit: November 04, 2010, 02:34:09 PM by scott87 »
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Offline Layne

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Re: 87 350 TBI problems
« Reply #7 on: November 05, 2010, 01:02:25 AM »
Un plug it and see if it acts any different. My 88 sierra sounded like it had a radical cam in it when I unplugged it
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77 c-10 - 77 400 86 700r4 "Emmy"
83 citation - 2.5L Four on the Floor!
88 sierra - reman 350 700r4 "Eleanor"
All normal practicality and rational money handling goes out of the window when it comes to my truck.

Offline scott87

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Re: 87 350 TBI problems
« Reply #8 on: November 05, 2010, 10:14:31 AM »
I tested the TPS and it seemed to have a dead spot in it so I put one on and it is still doing the same thing and not showing any codes. Also when you start it cold in the morning it will run perfect for a couple minutes.
« Last Edit: November 05, 2010, 10:54:29 AM by scott87 »
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Offline scott87

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Re: 87 350 TBI problems
« Reply #9 on: November 08, 2010, 02:51:08 PM »
Do you think it could be the fuel pump?
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Offline topp

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Re: 87 350 TBI problems
« Reply #10 on: November 08, 2010, 03:32:37 PM »
Check Fuel Pump Pressure at back of TBI unit...Should be above 10psi and no higher than 15...
Check your EGR Valve...
Mine closes slowly and prolly is dirty.  The symptom i get is runs poorly on acceleration and almost stalls when i come to a stop...
The poorly on acceleration could be described as loading up or breaking up on acceleration.  I disconnected the EGR and it runs 10X better...Gonna replace it within the next week....
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'90 Suburban TBI 350

Offline scott87

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Re: 87 350 TBI problems
« Reply #11 on: November 08, 2010, 05:49:38 PM »
Thanks topp, I unhooked the egr and it runs fine. Guess I will get one soon and replace it. ;D
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Offline topp

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Re: 87 350 TBI problems
« Reply #12 on: November 08, 2010, 05:53:24 PM »
Check the Solenoid first....
At idle, It should have NO vacuum on the EGR valve side...
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'90 Suburban TBI 350

Offline scott87

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Re: 87 350 TBI problems
« Reply #13 on: November 08, 2010, 05:57:47 PM »
I assume that is what the hose runs to from the egr valve?
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Offline Irish_Alley

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Re: 87 350 TBI problems
« Reply #14 on: November 09, 2010, 04:33:46 AM »

EGR vacuum solenoid works with the on-board computer to provide a calibrated vacuum source for the EGR valve.
When not replaced, vehicle may experience excessive flow or non-functioning EGR valve, engine dies at idle, failed emission test, high NOx emissions, surging at highway speeds and/or hesitation.
get in the zone
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