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When accelerating the engine bogs, misses, sputters and barely moves

Tiny
AMATHESON
  • MEMBER
  • 1988 CHEVROLET 1500
  • 5.7L
  • V8
  • 4WD
  • AUTOMATIC
  • 100 MILES
It will idle nice and smooth but when you put it in gear and give it some gas it bogs, misses and sputters and won’t hardly move.
It’s a throttle body injected 350 that has around 13 psi of fuel pressure.
Thursday, January 9th, 2020 AT 3:54 PM

13 Replies

Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
13 to 18 psi Is normal.
Do you have any trouble codes?

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

Rich
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Thursday, January 9th, 2020 AT 4:28 PM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
It has code 22- TPS, fuel cut off relay opened or shorted.
43- EST low circuit and ESC circuit problems.
44- lean exhaust on left (O2 sensor).
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Thursday, January 9th, 2020 AT 5:15 PM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
Okay, the 22 is a bad TPS. A bad wire or connection somewhere between the ECU and the TPS plug or a bad ECU. Test for a 5 volt reference on one of the wires at the TPS. If you have an analog multi-meter you can ohms test the TPS. You want to put the leads on the TPS set the meter to ohms and then turn the TPS and watch the needle on the meter. It should go up when you turn it and back down when you let it off. If the needle doesn't move or jumps at all while you move it then the TPS is bad.

The 43 is a bad knock sensor or bad ignition module. More likely the module.

The 44 is likely the result of the 22.

Rich
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+1
Thursday, January 9th, 2020 AT 7:25 PM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
Thank you. I’ll do the test tomorrow and see if it helps me find the problem.
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Thursday, January 9th, 2020 AT 7:36 PM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
If you are going to test the TPS you have to use an analog meter. A digital one will not work. FYI.

Rich
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Thursday, January 9th, 2020 AT 11:52 PM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
I have tested the TPS and it’s good. As I said the truck will idle great but if you let it set for about five minutes idling it will start surging and then shut off.
But If you start it up and put it in Gear it will run great for about 200 feet and then it spits and sputters like it’s running out of gas.
I cleared the codes and drove it and it did the same thing only this time it didn’t turn the check engine light on.
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Saturday, January 11th, 2020 AT 10:04 AM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
These are all symptoms of a plugged fuel filter or possibly a bad fuel regulator.

I would change the filter and see if its fixed, if not do a fuel pressure test with it running.

Take a reading at idle.

Then open the throttle all the way fast like you stomped on the gas pedal, The gauge should drop near 0 then bounce right back instantly to where it should be.

Then one more reading holding the throttle at about 3000 rpm and get that reading.

All 3 should stay in the 13 to 18 range. If not the regulator is bad or you have a weak fuel pump.

Make sure you change the filter before doing this.

Rich
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Saturday, January 11th, 2020 AT 11:46 AM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
I have checked the fuel pressure at the filter and put a new filter in it’s at 13 psi at idle and under throttle. As far as the regulator is it built into the throttle body? I don’t see an external one.
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Saturday, January 11th, 2020 AT 12:09 PM
Tiny
94 TRANSAM
  • MECHANIC
  • 680 POSTS
The regulator is inside the throttle body but if you say you did all 3 fuel pressure tests and they were fine and you have a new fuel filter then I would look at a possible weak spark or failing ignition module. Coil test posted below.

Also you said the TPS tested good but you said nothing about the other tests I posted. What were the measurements for them?

Them being, test for a 5 volt reference on the TPS and the ignition module.

Rich
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Saturday, January 11th, 2020 AT 2:51 PM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
TPS 0.83 to 5.53 while opening throttle slow with just the key in the on position.
And while the truck was running it maintained 5.1 to 5.53 as I brought the RPM's up
I was only able to test the fuel pressure at the filter. Is there another place to check it?
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Saturday, January 11th, 2020 AT 2:59 PM
Tiny
AMATHESON
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  • 8 POSTS
Also, I’m wondering if the surging after idling a few minutes could be the MAP sensor.
I have thought about replacing all the sensors just to make sure.
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Saturday, January 11th, 2020 AT 3:01 PM
Tiny
94 TRANSAM
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It is possible the MAP has gone bad. I have seen more than once on these older cars where the MAP fails and never throws a code. At this point my guess would be a bad MAP or ignition module.
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Saturday, January 11th, 2020 AT 3:19 PM
Tiny
AMATHESON
  • MEMBER
  • 8 POSTS
Thank you. I will replace both and see what happens.
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Saturday, January 11th, 2020 AT 3:35 PM

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