5.7 vortec hesitation and bog HELP *FIXED*

[travis mattson]

Hello I have 1997 5.7 vortec that bogs out under wide open throttle and half throttle.
Runs fine at idle and under 2500 rpm. Replaced fuel pump and regulator last year. Checked fuel PSI is 53 idle 58 throttle . Checked intake tubes and vacuum lines for leaks. Spray carb cleaner around air intake connections and no RPM increase. Checked all fuses.
Have the following codes.
P0303
P0430
P0102
P0141

 

[thegawd]

what happens to those fuel trims if you press and hold the brake? have you checked the brake booster? you can test it by pressing the brakes and watching those fuel trims.

Al

 

[travis mattson]

I'll check again at work should they increase?something to do with vacuum
Pressure or map sensor

 

[thegawd]

if the fuel trims start rising when you press the brake, I cant remember if it's short term or long term fuel trims but if they start rising your brake booster is leaking vacume. it will rise all the way up to 100% if its held long enough and then fall on its face when you let off and give it gas.

looking at the scanner i cant wager a guess. I just had a booster fail and when I replaced it the truck ran way better than before. I think I got used to its gradual decline but coming up to a stop sign it completely ruptured, it leaks around the plunger that goes through the firewall and you might hear it. when it completely failed it was extremely loud and I also blew the front passanger side brake line at the same time and it was kinda scary. take a look at that brake line if you havent, it's not visible from below and it sits on the front frame above the skid plate.

 

[Schurkey]

Hello I have 1997 5.7 vortec that bogs out under wide open throttle and half throttle.
Runs fine at idle and under 2500 rpm. Replaced fuel pump and regulator last year. Checked fuel PSI is 53 idle 58 throttle . Checked intake tubes and vacuum lines for leaks. Spray carb cleaner around air intake connections and no RPM increase. Checked all fuses.
Have the following codes.
P0303
P0430
P0102
P0141

P0303 = misfire on #3. A misfire, left unrepaired long enough, will cook a catalyst.

P0430 = Catalyst efficiency as read by O2 sensors

https://www.carparts.com/blog/p0430-code-catalyst-system-efficiency-below-threshold-bank-2/

P0102 = Mass Air Flow circuit low input

P0102 Chevrolet: Code Meaning, Causes, Symptoms, & Tech Notes

The Mass Air Flow (MAF) sensor is integrated with the multifunction intake air sensor. The MAF sensor is an air flow meter that measures the amount of air

www.engine-codes.com

P0141 = O2 sensor heater fault, bank 1 sensor 2

Code P0141 Chevrolet: HO2S Heater Performance Bank 1 Sensor 2 (With Video)

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the

www.autocodes.com

You've got two codes directly related to O2 sensors-- '430 and '141. How old are the sensors? Do they read appropriately on your scan tool? When I had O2 sensor heater codes, I just changed sensors, cleared the codes, and the codes didn't come back. MAYBE you will get lucky and discover that the catalyst efficiency code was really a faulty O2 sensor problem. Otherwise, you can expect to be installing a fresh catalyst or two.

How does the MAF look on the scan tool? Idle flow numbers look good, and they increase with more throttle? Any problems when the engine "bogs out"?

I've been told that misfire on #3 is common on Vortec engines with failed distributor caps. But you might as well check everything--cranking compression, plug condition, plug wire, cap, rotor condition. Checking the ignition side is easier than checking the fuel injection system--but if the compression is good, and the ignition system is OK, about all that's left is fuel and air.

In my driveway, I'd START with the '303--diagnose the misfire, and then replace all the O2 sensors if they have more than 50K on them, or show any sign at all of failure. Then verify the MAF. Clear all the codes, see if the catalyst efficiency problem fixes itself.

 

[travis mattson]

Thanks guys , went down now and it just cranks no start, ill replace 02 sensors and clear codes. I tried cleaning the MAF last night but it was pretty clean inside. Maybe I ****** it up. I unplugged and still cranks no start.

 

[travis mattson]

I got it to start on carb cleaner and idle, I looked down the throttle body and it has the stock skinny spider injectors, do you guys think the injectors are shot and causing the issues?

 

[Schurkey]

What is spec for fuel pressure; how does that compare to the current fuel pressure, now that the engine won't start on it's own?

Has your fuel pressure gauge been checked for accuracy?

 

[travis mattson]

I used one at oriellys had 55 psi, new Delphi pump last summer

 

[Schurkey]

Does it STILL generate 55 psi? What is the spec for fuel pressure?