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Idles great but no power when accelerating I'm showing code…

Customer Question
Idles great but no...

Idles great but no power when accelerating I'm showing code 43 have changed knock sensor distributor cap rotor pickup coil coil plugs and wires

Mechanic's Assistant: Is the power loss consistent, or does it fluctuate?

It is consistent

Mechanic's Assistant: What is the model/year of your Chevy?

94 Chevy

Mechanic's Assistant: Are you fixing your vehicle yourself? What have you tried so far?

Yes I'm fixing it myself have changed plugs wires knock sensor and sensor connector distributor cap rotor ignition module pickup coil

Submitted: 10 months ago.Category: Chevy
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Answered in 1 minute by:
9/13/2017
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago
kalamykid
kalamykid, Shop Owner/ Tech
Category: Chevy
Satisfied Customers: 5,492
Experience: I HAVE OWNED MY OWN SHOP FOR OVER THREE YEARS. I HAVE THE TOOLS AND SOFTWARE TO ANSWERE ALMOST ANY Q
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What is the year, make , model and engine size of your car/truck?

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Customer reply replied 10 months ago
1994 Chevy Silverado 5.7
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Have you tested the fuel pressure with a fuel pressure gauge?

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Customer reply replied 10 months ago
No
Customer reply replied 10 months ago
How could the fuel pressure cause me to get a 43 code
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

That will be the first thing you should do. If the fuel pressure is to low, the engine will run lean. This will cause a spark knock the knock sensor can pick up.

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Customer reply replied 10 months ago
We'll have to try that tomorrow and get back with you
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Ok. Just let me know what the pressure is, with the ignition switch in the run position, as well as running please.

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Customer reply replied 10 months ago
Ok thank you
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

You are welcome.

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Customer reply replied 10 months ago
Fuel pressure was good around 11 PSI while running I was told did not check it whip ignition off but change fuel filter anyway no change in engine performance still no power to accelerate once we're out of neutral
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Do you still have the pressure tester connected?

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Customer reply replied 10 months ago
No a friend tested it for me
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Did you test the fuel pressure with the engine not runing, ignition switch in the run position?

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Customer reply replied 10 months ago
No just told me it was good running about 11 PSI
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

I need to know what the pressure was with the engine not running as well as how long the pressure would hold.

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Customer reply replied 10 months ago
Okay I'll see if I can get that tomorrow
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Thank you. I am sorry, I know it is a pain but I need the data.

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Customer reply replied 10 months ago
Could not get the guy back to check my pressure so I replace the fuel pump did not change problem still it existed no power when accelerating but now I can't even start the engine have fuel but no fire I have replaced distributor totally coil plugs and wires
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Has the ignition ,module been replaced?

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Customer reply replied 10 months ago
I bought a totally new distributor with cap rotor pickup coil and ignition module
Customer reply replied 10 months ago
Totally discouraged by this thinking of changing it all out for a conventional carburetor
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

When you turn it over do the injectors spray fuel out of the bottom tips on both injectors?

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Customer reply replied 10 months ago
getting fuel from both injectors
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Do you have 12 volts at the pink wire on the coil and at the ignition module?

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Customer reply replied 10 months ago
not getting any fire from the coil to the distributor cap
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

So there is no power on the pink wire at the module?

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Customer reply replied 10 months ago
Pink wire on module has power
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Then the module has to be bad. It is not sending a ground pulse to the coil for it to fire. Where did you get the distributor, and was it a remaned or a new distributor?

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Customer reply replied 10 months ago
Got it from O'Reilly's... I thought of that so I switched the module out with another one that I had that had tested good
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

At the coil there are two plugs with pink wires and white wires. one plug runs from the coil to the module, and the other plug goes to the engine wire harness. Can you cut the white wire on the plug for the engine wire harness and see if it will start and run?

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Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Make sure to cut it so there is atleast 2 inches of wire at the plug so we can reconnect it if need be.

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Customer reply replied 10 months ago
Are you saying I should sever the connection for that wire
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Yes. It only runs to the tach, so it will not hurt anything. There has to be something interrupting the pulsing ground signal to the coil.

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Customer reply replied 10 months ago
Okay let me go out and try it I'll get back with you in a few
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

ok

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Customer reply replied 10 months ago
Sorry in my frustration I did not connect the wires to the used ignition module that I replaced in the new distributor as I went out to cut the wire I realize they were not connected connected them and the truck started right up with the old ignition module but back to my first problem it still has no power
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Did you test drive it after replacing all the parts?

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Customer reply replied 10 months ago
just drove it around the block and still no power dies out at about 15 to 1800 RPMs
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Is your truck an automatic?

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Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Can you unplug the knock sensors please? Your truck can have one, just in front of the oil filter on the drivers side of the block, or it can have a two sensor set up, one on the drivers side head and one on the back of the passenger side head.

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Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

After you unplug the sensors, test drive it and see how it runs.

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Customer reply replied 10 months ago
Okay I'll get back with you after I test it
Customer reply replied 10 months ago
Helped very little if any at all still has no power on take off but after 2000 RPMs she takes off like a jet
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Plug the knock sensor back up. try turning the distributor clockwise about 1/2 inch and see how it runs.

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Customer reply replied 10 months ago
Okay back in a few
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Thank you.

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Customer reply replied 10 months ago
No good only spits and backfires now when I attempt to accelerate
Chevy Mechanic: kalamykid, Shop Owner/ Tech replied 10 months ago

Then turn it back 1 inch. That will be 1/2 in. back to where it was and 1/2 in. counter clockwise.

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Customer reply replied 10 months ago
A little better but still sluggish until it gets to about to 2000 RPM's
Customer reply replied 10 months ago
here's a little additional information I don't know if it will help or not temperature gauge does not work and oil sending unit has been changed out but oil pressure gauge doesn't move until I attempt to accelerate
Chevy Mechanic: Jerry Newton, Chevy Technician replied 10 months ago
Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 5,694
Experience: ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Are you still having trouble with this?

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 10 months ago

This won't be associated with your gauge issues at all. The engine computer does not interface with the gauges on this truck.

The timing is critical on this truck. Do you have a timing light, and do you know how to set the ignition timing to spec?

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Customer reply replied 10 months ago
disconnect the tan and black wire set timing for 0 degrees .
Chevy Mechanic: Jerry Newton, Chevy Technician replied 10 months ago

OK, you moved the distributor earlier under the other expert's advice, is it set back to where it belongs now?

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Customer reply replied 10 months ago
it's back at zero
Chevy Mechanic: Jerry Newton, Chevy Technician replied 10 months ago

OK.

What I suspect is that you have a catalytic converter that is restricted. The way to test this is with an exhaust back pressure tester, it's a gauge that you connect where the oxygen sensor plumbs into the exhaust. Most people don't have one of these in their toolbox, but you can borrow one from places like Autozone, Advance, etc. at no charge. My next step, if your truck were in my shop, would be to test the exhaust back pressure. The allowable back pressure is 1psi, put the gauge on the exhaust system, and drive the truck until it acts up while watching the gauge. If the gauge goes off the scale when it acts up, the exhaust is plugged up and needs repair.

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Customer reply replied 10 months ago
Okay I'm still working at the moment will be home well the truck is in about 35 minutes truck does not have a catalytic converter on it but I did remove the oxygen sensor to see if that would help it run better.
Chevy Mechanic: Jerry Newton, Chevy Technician replied 9 months ago

OK. Mufflers can also plug up, it's still a valid test to run. I've even seen rodents build nests in the exhaust system and cause this problem, so I'd still run the back pressure test.

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Chevy Mechanic: Jerry Newton, Chevy Technician replied 9 months ago

Did you get this worked out?

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