Loss of power when warmed up, but turning it off and on again is fine?

BRAVO97779

MEMBER
1997 CHEVROLET BLAZER
4.3L
6 CYL
4WD
AUTOMATIC
224,922 MILES

I have a new fuel pump (even though it's the rth one in 15 months) and it seems like it is struggling to work when warmed up. If I take it easy it will lose power in 7 minutes. If I accelerate hard it will lose power in 4 minutes. If I keep the peddle to the floor it will give bursts and the rpm jump up and down giving quick thrust after thrust. Now, if I turn the key off and on it will have no problem delivering 100% acceleration for a minute or two before dropping g right down. I turn the key off and on and it does it again. I changed the relays and that did nothing.

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

What you described sounds like it could be related to a partially clogged catalytic converter. Do me a favor. The next time this happens, inspect the converters to see if they are red hot. Also, pay attention for odd odors from the exhaust as well.

Take a look through this link and let me know if anything seems to mirror what you experience:

https://www.2carpros.com/articles/bad-catalytic-converter-symptoms

One other thing. If the check engine light is staying on or flashing, have the computer scanned for codes. Most parts stores will do it free of charge. Let me know what codes are found.

Take care,

Joe

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Wednesday, April 12th, 2023 AT 8:29 PM

BRAVO97779

MEMBER
5 POSTS

There is an oder like burning oil.
Now there is a smell of gas
I have code P0440.
The cat isn't red hot.
It's temperature is 346 engine side and something like 480 on exiting end.

The engine is now rattling and knocks at low rpm. It's jumping around a little too.
I changed the air filter because the last one was years overdue and I hope that didn't harm anything. I'm about to put in a new fuel filter.

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Thursday, April 13th, 2023 AT 9:53 AM

JACOBANDNICKOLAS

MECHANIC
109,755 POSTS

Hi,

The idea that you hear a knock at idle has me concerned. Check the engine oil. Make sure fuel isn't mixing with it. If it is, drain it and refill it with fresh oil.

Next, I need you to check for an engine vacuum leak.

Here is a link that explains how it's done:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If nothing is found, next I need you to check the fuel pressure to see if it is within spec.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

If you look below, I attached the diagnostics and directions from my manual related to pressure. See pics below

If the pressure is high, we need to check the fuel pressure regulator. It is located under the upper intake manifold. If you are able to access it, disconnect the vacuum hose, and make sure it is in good condition and no fuel is present in it.

Let me know what you find and certainly, since you smell fuel, check the engine oil and make sure there are no visible leaks. Low fuel pressure will cause it to run like this as well.

Take care,

Joe

See pics below.

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