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Jerry Newton
Jerry Newton, Chevy Technician
Category: Chevy
Satisfied Customers: 4829
Experience:  ASE Master Technician, L1, Master GM Technician. Over 20 years of bumper to bumper GM experience.
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Idles great but no power when accelerating I'm showing code

Customer Question

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
JA: Is the power loss consistent, or does it fluctuate?
Customer: It is consistent
JA: What is the model/year of your Chevy?
Customer: 94 Chevy
JA: Are you fixing your vehicle yourself? What have you tried so far?
Customer: Yes I'm fixing it myself have changed plugs wires knock sensor and sensor connector distributor cap rotor ignition module pickup coil
JA: Anything else you want the mechanic to know before I connect you?
Customer: No
Submitted: 1 month ago.
Category: Chevy
Expert:  kalamykid replied 1 month ago.

What is the year, make , model and engine size of your car/truck?

Customer: replied 1 month ago.
1994 Chevy Silverado 5.7
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
No
Customer: replied 1 month ago.
How could the fuel pressure cause me to get a 43 code
Expert:  kalamykid replied 1 month 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.

Customer: replied 1 month ago.
We'll have to try that tomorrow and get back with you
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
Ok thank you
Expert:  kalamykid replied 1 month ago.

You are welcome.

Customer: replied 1 month 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
Expert:  kalamykid replied 1 month ago.

Do you still have the pressure tester connected?

Customer: replied 1 month ago.
No a friend tested it for me
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
No just told me it was good running about 11 PSI
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
Okay I'll see if I can get that tomorrow
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month 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
Expert:  kalamykid replied 1 month ago.

Has the ignition ,module been replaced?

Customer: replied 1 month ago.
I bought a totally new distributor with cap rotor pickup coil and ignition module
Customer: replied 1 month ago.
Totally discouraged by this thinking of changing it all out for a conventional carburetor
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
getting fuel from both injectors
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
not getting any fire from the coil to the distributor cap
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
Pink wire on module has power
Expert:  kalamykid replied 1 month 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?

Customer: replied 1 month 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
Expert:  kalamykid replied 1 month 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?

Expert:  kalamykid replied 1 month 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.

Customer: replied 1 month ago.
Are you saying I should sever the connection for that wire
Expert:  kalamykid replied 1 month 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.

Customer: replied 1 month ago.
Okay let me go out and try it I'll get back with you in a few
Expert:  kalamykid replied 1 month ago.

ok

Customer: replied 1 month 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
Expert:  kalamykid replied 1 month ago.

Did you test drive it after replacing all the parts?

Customer: replied 1 month ago.
just drove it around the block and still no power dies out at about 15 to 1800 RPMs
Expert:  kalamykid replied 1 month ago.

Is your truck an automatic?

Customer: replied 1 month ago.
Expert:  kalamykid replied 1 month 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.

Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
Okay I'll get back with you after I test it
Customer: replied 1 month 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
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
Okay back in a few
Expert:  kalamykid replied 1 month ago.

Thank you.

Customer: replied 1 month ago.
No good only spits and backfires now when I attempt to accelerate
Expert:  kalamykid replied 1 month ago.

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

Customer: replied 1 month ago.
A little better but still sluggish until it gets to about to 2000 RPM's
Customer: replied 1 month 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
Expert:  Jerry Newton replied 29 days ago.

Are you still having trouble with this?

Customer: replied 29 days ago.
Expert:  Jerry Newton replied 29 days 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?

Customer: replied 29 days ago.
disconnect the tan and black wire set timing for 0 degrees .
Expert:  Jerry Newton replied 29 days ago.

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

Customer: replied 29 days ago.
it's back at zero
Expert:  Jerry Newton replied 29 days 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.

Customer: replied 29 days 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.
Expert:  Jerry Newton replied 28 days 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.

Expert:  Jerry Newton replied 18 days ago.

Did you get this worked out?