kallcium

Ok, just got done fixing my transmission and clutch and also had a code 1441 where I changed the evap canister and solenoid valve due to charcoal chunks in the valve. Code 1441 went away but only about 20 miles or so my check engine light comes on with codes P0171 & P0174 (bank 1 & 2 lean) coming up. About a year ago I got both these codes and it ended up being the fuel pump as the fuel pressure was only 30psi. I checked the fuel pressure and it is about where it should be at 46 psi so the pump (and fuel pressure regulator) should be good.

The factory manual says it could be the IAC, PCV or the MAF sensor among other things such as vacuum hoses and wires. By they way it never listed the fuel pump as a possible cause. I have done a search and while I have not found many posts with both codes, I have found that the EGR valve could be a cause as well. In the past few months I have cleaned the IAC valve to troubleshoot so it seems to be ok.

So can anyone give me tips on how to determine what could be causing this? Any way to check the EGR valve, IAC or MAF sensor without just parts swapping... would like to keep the cost down. Oh and just had the car smogged (cleared the code in the test station parking lot... the SES light came back on only after I drove away)... the technician said the Nitrous Oxide was passing but just under the limit and said I should have my EGR system checked out.

Anyways thanks in advance for the help.

kallcium

Oh yeah, forgot to tell you that it is a 1996 Camaro 3.8L

kallcium

Ok I thought about it and I think if I cut a plate out of sheet metal with the two bolt holes and install it between the egr valve and the surface it sits on, then I should be able to tell if the EGR is bad or not. If the lean codes go away the the EGR valve was the problem, if they dont then it is something else.

What do you guys think?

Also does anyone know how to check the MAF sensor without just swapping it out? I don't have the fancy GM scanner that the factory manual has you use.

kallcium

Ok created a block off plate for the EGR valve, installed it and erased the codes. The lean codes came back shortly after so it is not the EGR valve.

So is there anyone who can help me ... anyone read this V-6 board anymore?

I guess my next step is to go old school and spray ether start all over to check for vacuum leaks.

Does anyone know how to check a MAF sensor without just swapping in a new one?

kallcium

Alright, so now I have cleaned the MAF sensor and also taken readings of the frequency. The output range of the MAF sensor is supposed to be between 2000 and 10,000 Hertz. It read approx 2500 at idle and 8500 at wide open throttle. The hertz rose immeadately and smoothly as I opened the throttle. So the MAF sensor is good. I have also sprayed Ether Start all over and no vacuum leaks were found. EGR valve and fuel pressure have already been previously elimanated.

So now I am down to a PCV valve or IAC valve causing this problem. I will just replace the PCV since its only $5-$10. If that doesn't work I will replace the IAC valve (about $35 new).

Anyone else have any ideas what could be the problem other than what is listed?

kallcium

Alright, its now fixed!

First I changed out the PCV valve... only cost $3 actually. It didn't fix it but was a cheap troubleshooting tool. So then I pulled out the IAC valve. I have pulled this out before and noticed that it wasn't extened as far as I remember. So I cleaned all the carbon build up in the port of the intake that the IAC valve went into and then I played around with the IAC valve to get it to extend farther and reinstalled it. Code never came back.... so I replaced the IAC valve as insurance (cost only $32).... everything works great. I was starting to wonder if the Evap canister I just changed before this code came up could be the cause... (brand new has only fresh air (lean) rather than fuel vapors)

Most of the advice I found when doing a search just has you replace the EGR valve for this problem. My car has 227700 miles.... EGR valve has never been changed.... seems pretty reliable. Also some advice says to pull the MAF sensor plug and if it runs better then the MAF sensor is bad. My MAF sensor is good but when I pulled the plug... it the car will stall at idle.

The EGR valve and MAF sensor is expensive Best I saw was $132 for the EGR and over $150 for the MAF. Seems like there may be many unnecessary replacements out there. If you sit down and think of creative ways to troubleshoot and do it properly you might save a bunch of money!

Didn't get much help here as I am the only one who posted on this thread, but maybe someone will do a search and get some help from this one!

Jeffs1997

I know this thread is old, I have a 97 firebird 3.8 and these codes 174 & 171 plague my car. However mine also has p0300, p1441, and it also had elevated high idle condition P0507 trouble code.

I got the idle to come down to 900rpm which I feel is correct for mine (has a 5 speed) because that code never has come back.

My injectors are new fuel pump holds at about 43psi while running, new everything on the car just like you did. Prior owner grenaded the old 3.8 and this one is a replacement 3.8 that ran great in the 96 firebird it came from. the throttle body is the original from the 97 so I will clean it like you did and see if 171&174 go away.

kallcium

Hey let me know if you got it fixed.

I just broght my car for it biannual california smog test and I had a code for the EVAP P1441 that I knew about so just beofre I got there I erased it (Should have done it in the parking lot aft the engine was shut off as for most codes if wont give an SES light until two starts). What I didn't know was that there was also a lean condition with the same P0171 & P0174 codes as before. They are suppressed by the P1441 EVAP code so when I erased it, in the middle of the Smog test I got the lean codes and failed. Anyways I fixed the P1441 EVAP with a new vacuum switch (strange as this car has been through 2 EVAP solenoids and thre switches since I have bought it, don't know why they keep failing but I have a brand new charcoal canister and all the EVAP lines are holding a vacuum and many are new)

Anyways I went through all the previous trouble shooting and found that EGR valve and MAF sensor are ok. I brought back the IAC valve as it looked dirty and was under warrenty but it still did not fix. I finally got out the ether start and started spraying. The engine bogged down when I sprayed the PCV cover. So I changed the gasket and the lean codes went away but just the P0174 came back. SInce it was related to only Bank two my last two options were a new bank 2 O2 sensor and a passenger side exhaust manifold gasket. I changed the O2 sensor since it has 140,000 miles on it and was probably time anyways and since it was much easier than the exhaust manifold gasket. It has fixed it and I will go get resmogged this week. Oh and I now have just about 290,000 miles!

As for yours, 900 RPMs is correct (mine is also a 5 speed). The code 0507 may be cause by a crank position sensor gone bad, unfortunatly you would have to remove the harmonic balancer to get at it. Also you should fix the P1441 first as that may cause the lean condition if your purge solenoid is stuck.

Jeffs1997

I had both those lean codes as well. The fix there is a metal tube coming from egr valve to the upper intake, mine was cracked. replaced it and the lean codes went away ... hope that helps was a 97 3.8

kallcium

Had this again a few years later ... ended up as one of these two things - fixed at the same time so I was not sure:

- Cleaned the throttle body of all carbon

- Changed the throttle position sensor (no code but I saw a notch in the lever that interfaces with the throttle body and figured it gives it a false throttle position). None of this is in the factory Helms manual ... everything in their troubleshooting was good, had to think out of the box a little.