Rough idle 5.3

[dwcardfan]

Just finishing up on my 5.3 / 4l60e swap into my 65 GMC. It runs good but has a rough idle. The codes are p0170 and p0174. Bank 1 and 2 are lean. It has new 02 sensors and there are no vacumn leaks. Fuel pressure is 58. Any ideas?

[foamypirate]

Originally Posted by dwcardfan

Just finishing up on my 5.3 / 4l60e swap into my 65 GMC. It runs good but has a rough idle. The codes are p0170 and p0174. Bank 1 and 2 are lean. It has new 02 sensors and there are no vacumn leaks. Fuel pressure is 58. Any ideas?

Has it been sitting long before you fired it up? The injectors are kind of notorious for getting gummed up with varnish if they sit too long.

[dwcardfan]

Well it had been down for 6 months or so.

[GMC-YA68]

Do you have exhaust on it?

[LEEVON]

Very typical to have intake manifold gasket leaks, causing the lean condition. Did you have the intake off?

[dwcardfan]

Originally Posted by LEEVON

Very typical to have intake manifold gasket leaks, causing the lean condition. Did you have the intake off?

Yes the exhaust is done. And yes I did have the intake off when I installed the motor. I will use some carb spray and check for leaks tomorrow. Thank for the replys

[LeesTruk]

If both banks are lean, then the problem may be in the plenum area or MAF sensor/intake tube. Check the little vacuum nipple on the plenum to see if it's still capped or if there's a vacuum tube running from it to a vacuum chamber for HVAC actuators, make sure that system has good vacuum integrity. Check the power brake booster (if you have that) for leaks, and make sure the MAF sensor is clean and unobstructed.

Do you have a scan reader that'll show a live data stream? If so, check your O2 readings and make sure the voltages toggle and don't just sit at around .45vdc indicating inactive sensors

Check your fuel pressure when you shut the truck off. The system/pump should hold pressure for a little while then slowly bleed off. If the pressure drops instantly, then you may have a faulty injector. You may be able to pull your fuel rail with injectors and fuel line intact, turn the ign. key to run(don't go to start) to prime the system and see of you have an injector that's hanging open. Another thing to check is if the injectors are firing. If the truck will idle, Take a long screw driver (if you have one) and put one end one an injector and put your ear on the other. You should hear a sharp clicking sound as each injector turns on/off. If one sounds "fluffy" or soft as compared to others, than that could be a possible bad injector

Did you put a dual exhaust system on the truck? Listen to each pipe and see if the exhaust note is even, side to side. This will give a clue if one bank is more seriously effected than the other

Just some ideas

[shrunken66stroker]

I had a rough idle problem with my 5.3 and it was due to the O2 sensors being in the wrong holes. The sensors closer to the engine are different from the ones further from it. From what I understand the sensors further down the line are heated to get more accurate readings. Check to make sure the sensors are in the right position. Best to check the easy/free stuff first.

[dwcardfan]

Ok guys here is what I found. My original harness was not usable so I had to purchase another one with the wire delete and computer flash from S & S Performance. S & S takes an original harness and removes what is not needed. The old harness O2 plugs were male and the new harness has female plugs so I got 2 new O2 sensors. The wires in the plugs do not match the harness plugs. The purple signal high is plugging into the heater circuit and the other wires are rolled off by 1. I am not sure which O2 sensors I need but for now I am going to cut the plugs off and solder them back in the correct spots.

[dwcardfan]

Top pic is old harness and sensor and bottom is new.

[First c10]

I installed a LC9 5.3/6L80E into my sons 1970 c10. I had the same codes pop up and idle poorly. I changed the intake tubing and exhaust.
I did this and it worked
Try this: unplug your MAF sensor. It will throw a CEL but if it runs better. It sounds like you will need to calibrate the MAF. At the time I did not have HP tuners or EFI Live so I had a fellow forum member help me and we just disconnected the MAF part if the sensor(yellow wire) and turned off its ability to work in the ECM to control fuel trims and throw a code or CEL. The O2 sensors do it all now. Of course I don't understand 100% what was done or maybe I just cant explain it correctly. This was all done after I was 100% certain I did not have a vacuum leak.

I will see if I can find the thread....found it
MAF issues

this is on my LS swap issue http://67-72chevytrucks.com/vboard/s...=625318&page=4


Hope this helps
Scott

[dwcardfan]

Thanks Scott. I will check this out.

[BR3W CITY]

Originally Posted by First c10

I don't understand 100% what was done or maybe I just cant explain it correctly.

Its force failing the MAF and running the truck off of speed density. Some trucks are setup and tuned to run of off speed density normally, due to setups that make MAF's impractical or don't traditionally have access to a MAF with enough resolution (for FI or huge cube).

[First c10]

Originally Posted by BR3W CITY

Its force failing the MAF and running the truck off of speed density. Some trucks are setup and tuned to run of off speed density normally, due to setups that make MAF's impractical or don't traditionally have access to a MAF with enough resolution (for FI or huge cube).

Correct. so I understand it just couldn't explain it!! Any reason this wont work? my sons truck has been running fine since we did it. I do have HP tuners now just really haven't had time to play with it yet.

[BR3W CITY]

Long term there are some changes you'll want to make in the tune itself. Because your taking away the "safety" that the MAF gives (in terms of being another point of feedback in the fuel/air control loop), you want to spend extra time on the VE tables. Its probably the single biggest thing I see when people complain that they ran into a problem with SD.

I'd also make sure that your still getting IAT signal from that harness. If you only clipped the yellow, then the IAT should be fine, but double check. If you clipp'd more than one (or just took the thing out), then you'll need/want to add the wire for IAT or move the IAT to a new location. If your getting a reading of -43c, then its failed even if its connected.

Other than that, SD is great. Its more dependent on the tuner, but you can get really nice power (and weird setups) to work nicely. I've been on SD for about a year, and have been extremely happy with it. I'll take MAF on a daily that see's -10 > 100* in the course of a year (for ease), but on anything else I'll run SD.

[First c10]

Yes I only disconnected the yellow wire which was the MAF only, IAT are sill reading fine. I will need to read up on how to calibrate a MAF.
Sorry to hijack the thread but I think it all applies.

[cr92]

I'm having a similar problem with my ls swap.. idling bad with maf plugged in.. 1 of my 02's are staying right around the .450 mark and the others reading really low like .160... but both aren't moving much..what does inactive o2 mean ? the o2 itself need to be replaced?