Codes P0174, P0171, and P0327. HELP!!!!!!!

I have a 1999 chevy truck (http://www.automotiveforums.com/vbulletin/#) with a rebuilt engine 4.3L V6. Engine light coming on for awhile and then going off for awhile. The engine has about 3000 miles on the rebuilt engine. But I keep getting codes P0174, P0171, and P0327. The problem that I am having is that the engine light will come on for awhile and then it will turn itself off for awhile. Can''''t figure out why. My cuz works at Firestone and he ran all the checks ( Smoke test, fuel pressure check). Cause there are no vacuum leaks, fuel pressure 59 to 60 psi.,MAF sensor new, and the O2 sensors were changed last December. Like I said all these problems started after the engine was replaced and the reason it was replaced cause it spun a rear main bearing. Right before the motor went out I was pulling a boat with cruise control on, when I was approaching an overpass the motor raved up like it does with cruise control on, but when I got to the top of the overpass the motor didn''t slow down like it should have so I had to stop it myself. An that''s when the motor spun a rear main bearing. The repair shop said that gas got into my oil and caused the oil to thin out due to the fuel regulator going out. Any ideas??? Will driving with the light on with these codes damage my motor?
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http://www.obd-codes.com/p0174
http://www.obd-codes.com/p0171
and similar to this:
http://www.obd-codes.com/p0325 for P0327 (P0327 Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)

Unless you just got some money...this problem will not be repaired.....


you need a DTC done to test and get reading of the O2 and KS sensors....no money no tests and we cannot direct you as to what is wrong...

I don't want to sound stupid but what in the hell does this mean ( Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)?

well, let's save you "some money" and maybe run driving cycle on your truck and THEN read codes again:

http://www.obd-codes.com/trouble_codes/gm/gm-obd-driving-cycle.php

should the codes stay after that, you know what to do.

I don't want to sound stupid but what in the hell does this mean ( Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)?

your knock sensor mulfunctions and provides lower than normal output to ECM - engine control module. it's fed by 5V i believe from ECM and is supposed to return a specific value back to it for ECM to know how to tune the engine.
i'd start with locating KS, removing contacts, cleaning ALL contacts, both on sensor and on plug, with electrical cleaner, and lubricating with dielectric grease. if it helps - good for you, if not - replace the sucker.

I have also noticed on my truck when I drive around for about 30 mins or so and turn the motor off for about maybe 15 mins. When I start it it idles fine but when I but it into gear it bogs down like now power at all for about 10 secs and then seems ok. Any ideas?

I have also noticed on my truck when I drive around for about 30 mins or so and turn the motor off for about maybe 15 mins. When I start it it idles fine but when I but it into gear it bogs down like now power at all for about 10 secs and then seems ok. Any ideas?

so does my ranger, but only for about a second, then ISCU does its job and adds rpms. and only on cold engine.
laddy, i'd definitely recommend to either do DTC or driving cycle, as recommended. that will let you know what's wrong in general. then fix it. THEN, you will see if it still bogs. as it just sounds that your ECM hesitates on what to do with cooled engine, and you have at least 2 crucial sensors down, so no wonder.
one step at a time, laddy, one step at a time.

That driving cycle will be almost impossible to do. Cause I live in Houston, TX and there is way to much traffic to do it.

Also is it normal for a vehicle with curse control to sound like it is being floored to get back up to the speed you set it at? Cause this weekend around the Canyon Lake area I noticed that my truck was set at 65 mph approaching I slight incline and it would sound like I was flooring it to get up the incline. Is this normal?

Hey guys this is what I found on the autozone site :
spark plug gap fuel pres. idle speed
1999 4.3 W 0.060 ?? 58-64 600625 HYDHYD

4.8 V 0.060 ?? 55-62 ?? HYDHYD
5.0 M 0.060 ?? 60-66 650 ?550 HYDHYD
5.3 T 0.060 ?? 55-62 ?? HYDHYD
5.7 R 0.060 ?? 60-66 660 ?525 HYDHYD
6.0 U 0.060 ?? 55-62 ?? HYDHYD
7.4 J 0.060 ?? 60-66 750 ?675 ? HYDHYD

According to this site my fuel pressure is ok cause I had a 58 to 60 reading and my idle speed is set at 600 to 625. So everything seems to check out.

Ok guys new fuel pump, egr valve, fuel pressure regulator, o2 sensors, distributor cap and rotor, and fuel filter. Cleared codes drove 60 miles and the light came back on again with the same codes as before. Now what do I do?????

Ok guys new fuel pump, egr valve, fuel pressure regulator, o2 sensors, distributor cap and rotor, and fuel filter. Cleared codes drove 60 miles and the light came back on again with the same codes as before. Now what do I do?????

what you should have done to start with:
http://www.obd-codes.com/p0174
http://www.obd-codes.com/p0171
and similar to this:
http://www.obd-codes.com/p0325 for P0327 (P0327 Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)

which clearly told you: MAF and knock sensors. you replaced what?

and speaking of drive cycle: you are jailed in houston or something? get her out in the filed, let engine cool down on one of the back roads, and then do driving cycle. have portable scanner handy. it's totally doable.

MAF sensor is also new and so is knock sensor. Now what?

I have no vacuum or exhaust leaks I am sure about this.

MAF sensor is also new and so is knock sensor. Now what?
well, as the last resort - did you have codes reset after repairs/replacements? as they are stored in the ECM. otherwise, i give up. find a GOOD GM mech, it's electronics, some stupid thing on the tailpipe sensor can screw the whole entire picture somewhere else in the car. i miss g'ol 2 sensor cars.

Yes the codes were cleared and reset.

what you should have done to start with:
http://www.obd-codes.com/p0174
http://www.obd-codes.com/p0171
and similar to this:
http://www.obd-codes.com/p0325 for P0327 (P0327 Knock Sensor 1 Circuit Low Input (Bank I or Single Sensor)

which clearly told you: MAF and knock sensors. you replaced what?

and speaking of drive cycle: you are jailed in houston or something? get her out in the filed, let engine cool down on one of the back roads, and then do driving cycle. have portable scanner handy. it's totally doable.


he has no more money to get diagnostics as you recommended .. I said way back that this is most likely the knock sensor....I would have liked to see diagnostics on that ks signal....with readings to computer...I think its dropping out...loss of communication..

Assuming all the right components were reinstalled and done properly on the engine, the following is recommended, you need 60-66 psi fuel pressure, test it under load, also a new fuel filter just to be sure. If all is ok here, have someone or get a propane hand held torch, unlit, and turn it on low and check for vacuum leaks around the manifold and throttle body, using a scanner the o2 readings should respond to this test if there is a leak somewhere, your are running lean, period, now track it down.

I don't remember the the knock sensor reading. But I don't think the knock sensor would cause excessive oxygen in the exhaust system. The specs on my truck for fuel pressure is 58 to 64 not 60 to 66. And again I have no leaks.

I don't remember the the knock sensor reading. But I don't think the knock sensor would cause excessive oxygen in the exhaust system. The specs on my truck for fuel pressure is 58 to 64 not 60 to 66. And again I have no leaks.



So you have tried the propane method to find leaks....I guess you really have a lot of knowledge with troubleshooting these problems...I thought I was one of the very few that used that trick...



fuel pressure is OK but what about volume??? a fuel filter restricted can give good pressure at idle but not at higher vehicle speeds....


what dtc said there was excessive oxygen in the exhaust ???


I thought this was a low ks signal problem...

Trouble Code: P0174
Fuel Trim System Lean (Bank 2)
Possible Causes:

Air leaks in intake manifold, exhaust pipes or exhaust manifold
Fuel control sensor is out of calibration (ECT, IAT or MAF)
Low fuel pressure (fuel filter clogged, pressure regulator failure)
One or more injectors restricted or pressure regulator has failed
HO2S element is contaminated, deteriorated or has failed
Vacuum hose is disconnected, broken, leaking or looseTrouble Code: P0171
Fuel Trim System Lean (Bank 1)
Possible Causes:

Air leaks in intake manifold, exhaust pipes or exhaust manifold
Fuel control sensor is out of calibration (ECT, IAT or MAF)
Low fuel pressure (fuel filter clogged, pressure regulator failure)
One or more injectors restricted or pressure regulator has failed
HO2S element is contaminated, deteriorated or has failed
Vacuum hose is disconnected, broken, leaking or looseI have also took the truck back to the place I had the motor installed and the found the motor to be sound. I am just lost I've done just all I can do besides buying some C4.