I have a 1997 2-door, 4-wheel drive, 4.3L V6. Below is a list of parts I have JUST replaced and all parts are brand new ACDelco parts.

Currently my Blazer "RUNS LIKE A DREAM" (better than it ever has before since I've owned it) but has intermittent bog downs, that happen randomly about every 5-10 minutes. For 1-second it will seem like it's "starved for fuel", and I can see the RPM gage dip down to ZERO for just 1 second! But if I press on the accelerator it's OK again. It has not stalled in this past week of driving it since all the parts were replaced. There are no warning lights on anymore.

(1) - Fuel Filter --- Replaced the fuel filter with a brand new ACDelco fuel filter.
(2) - Fuel Pump --- Replaced the fuel pump with a brand new ACDelco fuel pump.
(3) - Gas Tank Cleaned --- the shop emptied, cleaned, and replaced with fresh fuel at the time the fuel pump was replaced.
It ran a little better, but literally in 2 days the "Service Engine Soon" light was back ON again.

(4) - Engine Wiring Replaced --- An expert electrician who has worked on hundreds of GM trucks replaced all the wires in the engine
as the repair shop had determined there was an "electrical problem". It ran better, for a few days. Then started stalling out AGAIN!

*** Since it "ran better" with the engine wiring replaced, and has continued to "run better" since, I can not say the repair shop did anything wrong,
but they did not fully fix "the problem" --- since the Blazer "Service Engine Soon" light came back on after only 1 day.

At that point, I decided to use my own code reader to read the CODES because the repair shop was too busy to take my Blazer and the "Service Engine Soon" light was still coming on.

P0172 and P0175 are diagnostic trouble codes (DTCs) that indicate a rich fuel mixture in a vehicle's engine:

• P0172: Indicates a rich fuel mixture in Bank 1 of the engine
• P0175: Indicates a rich fuel mixture in Bank 2 of the engine

A rich fuel mixture means there's too much fuel in the exhaust stream or too little oxygen in the exhaust stream. The oxygen sensor alerts the system when the condition is too rich.

I decided not to return to the repair shop, because they were repeatedly not solving the problem.
So instead I had help from a friend who is a certified mechanic who replaced all of the following parts within 1 week (last week).

(5) - Oxygen Sensors --- Replaced all 4 with brand new ACDelco Oxygen sensors.
(6) - MAF --- Replaced MAF (Mass Air Flow Sensor) with brand new ACDelco MAF.
(7) - Spark plugs --- Replaced the sparkplugs with brand new ACDelco iridium sparkplugs.
(8) - Wires --- Replaced the wireswith brand new ACDelco wires.
(9) - Rotor --- Replaced the rotor with brand new ACDelco rotor.
(10) - Distributor Cap --- Replaced the distributor cap with brand new ACDelco distributor cap.
(11) - Coil --- Replaced the coil with a brand new ACDelco coil.
(12) - ICM --- Replaced the Ignition Control Module with a brand new ACDelco ICM.

All of the above parts are brand new ACDelco parts replaced within the past week, and currently my 97 Blazer "RUNS LIKE A DREAM" --- but just has these intermittent bog downs, that happen randomly about every 5-10 minutes. For 1-second it will seem like it's "starved for fuel", and I can see the RPM gage dip down to ZERO for just 1 second! But if I press on the accelerator it's OK again. It has not stalled in this past week of driving it since all the parts were replaced. There are no warning lights on anymore.

Here's a list of some possible causes of these intermittent 1-second bog downs:
--- a vacuum leak ?
--- a clogged fuel injector ?
--- the fuel pump I installed is a defective part ?
--- any other ideas ?

 

Depends on how much diagnostics your willing to do to identify the actual problem and perform a targeted fix. There are many possibilities. I would:

1. Do the ten minute fuel pressure leak down test. If thats OK travel with a fuel gauge attached to the shrader and taped to the windshield to see if you are getting a fuel pressure drop out
2. Monitor the voltage on the ICM and coil pink wires during an event
3. You can also watch the overall system voltage at the cigarette lighter
4. Get your 4 fuel trim numbers at idle and again at 2500 rpm
5. Graph your O2 sensors and make sure that they are switching properly
6. Watch all the sensor live values during an event on a capable scanner

George

 

I just got burned BAD on a related problem, 95 S10 4.3, it had valve guide seals leaking that fouled a couple spark plugs.

New seals, cleaned plugs...the ECM was the problem, Id power cycled it while fixing the alternator and the ECM
' learned' bad data on bad plugs.

I pulled the two ECM fuses for 10 minutes, put them back in and it runs like new now after ECM ' learned' on clean, working spark plugs.

A bad ignition switch can do that too. It intermittently breaks contact. It may be too fast for a voltmeter to catch. An oscilloscope would catch it