Idle Issues
#1
I've had a bit of what I would call an inconsistent idle for a bit. Started after efan conversion. I've bumped up to a 165 amp powermaster alternator. Had same guy who did dyno tune set ecm to operate the fans. He had to adjust in gear idle. Initially, it was a bit low. When ac and fans were on it would idle rough at stops. And, voltage would drop. After adjusting it was fine for a bit. Now, voltage drops sometimes at stops. I have cleaned tb, maf, and air filter. I've replaced iac and tps in an effort to eliminate any of these as problems. I need to if there's something else I need to check. Or, contact tuner to discuss. Any info is much appreciated.
#2
Joined: Jan 2006
Posts: 16,282
Likes: 438
From: Huntsville, AL
Did you do the "big 3" wiring upgrade? Larger wires from Battery+ to alt, engine block to frame, and Battery- to frame? That helps a lot with that sort of issue typically.
#3
I did battery to alt, engine to body, and, engine to battery ground. Did not do engine to frame. How important is that one? Every video I watched and photo I could find wasn't very clear on them. So, I went with best guess.
#4
Joined: Nov 2001
Posts: 4,868
Likes: 16
From: Warr Acres, OK
I've had a bit of what I would call an inconsistent idle for a bit. Started after efan conversion. I've bumped up to a 165 amp powermaster alternator. Had same guy who did dyno tune set ecm to operate the fans. He had to adjust in gear idle. Initially, it was a bit low. When ac and fans were on it would idle rough at stops. And, voltage would drop. After adjusting it was fine for a bit. Now, voltage drops sometimes at stops. I have cleaned tb, maf, and air filter. I've replaced iac and tps in an effort to eliminate any of these as problems. I need to if there's something else I need to check. Or, contact tuner to discuss. Any info is much appreciated.
#5
Without seeing the tune file it is impossible to help. Need to see what the idle speed is set at and there are settings for adding idle airflow when the fans come on. You say you replaced the IAC so it must be a 99-02. (nice that you don't give any vehicle information but that is typical when people ask for help) What type of fan harness did you use? 1 PCM trigger and 1 off the AC clutch or two PCM triggers. Does your harness use 3 relays or two? If the first then there is no way for the PCM to know that both fans are running high speed to make adjustments for that. And sadly, not every tuner know all the differences.
#6
Joined: Nov 2001
Posts: 4,868
Likes: 16
From: Warr Acres, OK
I was looking for some good general ideas for places to start. But, if you want the whole novel. Here it is. 2002 GMC Sierra 1500 5.3 4wd long tube headers, offroad y pipe, all 3 inch mandrel bent pipe with borla pro xs muffler, recent new injectors, approx. 12k miles on new long block, stock air box with k&n drop in filter, new replacement air tube from box to intake, new iac, new tps, dual electric fans with nelson performance harness green wire tied to ac compressor switch wire and sungle pin to pin #42 in ecm, new 165 amp powermaster alternator, sort of big 3 upgrade with 2 gauge cables ran from alternator to +battery, 2 gauge from engine to battery, 2 gauge from engine to body, engine and transmission dyno tuned using hp tuners, all new stainless fuel lines and filter. I don't have access to the tune file. However, the tuner has been in business for about 20 years, with a very good reputation. Fans were installed after initial tune. Went back down to have ecm tuned for fan operation. And, he made a minor adjustment to either idle itself or iac settings because rpm and voltage were dropping so low due to fans and ac being on. It ran fine for 2-3 weeks. And, then voltage began to drop at stoplights. However, idle quality did not seem to be affected compared to before. So, I am attempting to eliminate any other possibilities before contacting tuner about it when the issue is something else. Now, does that provide you with enough information to offer useful advice?
#7
The place to start is your tune file. And being a smart *** providing vehicle information, good luck getting anyone to give you useful advice. I've added efans to more vehicles than I can count without adding extra cables other than the fan harness and never had that problem, But then again I know how to tune for them.
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#8
If you go to User CP toward the top of the page you an build a signature that will show up in every one of your posts. Just the basic info on your truck would be helpful.
Your novel above actually was very helpful. I'm suspect of your injector data. If you changed Injectors and have incomplete or inaccurate data, it's possible that the voltage vs flow in the low voltage area could cause improper AFR. So for example, your voltage drops to 10.0 at idle. Maybe your tuner didn't fill in that part of the table because he thought the engine would never be running at that low of a voltage. Now if your fan tuning was correct it would never run at that lower voltage and uncover this problem. If you had factory injectors with factory data, and you had a bad fan tune, the engine might slow down at idle but not run incorrectly. Or the same with good injector date for your current injectors
So first thing would be to bump fan 1 airflow, other than that I'm not very good at tuning and airflow might need to be increased in other areas to compensate for the load but I'm not sure where because you have a 2002. The next step is to make sure you have complete and correct injector data. My experience with incomplete injector data was when my alternator shut off at high rpm due to weak brush springs and the engine went dangerously lean at the lower voltage, I found data missing in that area, again I'm assuming it's because the tuner didn't bother with such low voltages vs flow.
Your novel above actually was very helpful. I'm suspect of your injector data. If you changed Injectors and have incomplete or inaccurate data, it's possible that the voltage vs flow in the low voltage area could cause improper AFR. So for example, your voltage drops to 10.0 at idle. Maybe your tuner didn't fill in that part of the table because he thought the engine would never be running at that low of a voltage. Now if your fan tuning was correct it would never run at that lower voltage and uncover this problem. If you had factory injectors with factory data, and you had a bad fan tune, the engine might slow down at idle but not run incorrectly. Or the same with good injector date for your current injectors
So first thing would be to bump fan 1 airflow, other than that I'm not very good at tuning and airflow might need to be increased in other areas to compensate for the load but I'm not sure where because you have a 2002. The next step is to make sure you have complete and correct injector data. My experience with incomplete injector data was when my alternator shut off at high rpm due to weak brush springs and the engine went dangerously lean at the lower voltage, I found data missing in that area, again I'm assuming it's because the tuner didn't bother with such low voltages vs flow.
#9
If you go to User CP toward the top of the page you an build a signature that will show up in every one of your posts. Just the basic info on your truck would be helpful.
Your novel above actually was very helpful. I'm suspect of your injector data. If you changed Injectors and have incomplete or inaccurate data, it's possible that the voltage vs flow in the low voltage area could cause improper AFR. So for example, your voltage drops to 10.0 at idle. Maybe your tuner didn't fill in that part of the table because he thought the engine would never be running at that low of a voltage. Now if your fan tuning was correct it would never run at that lower voltage and uncover this problem. If you had factory injectors with factory data, and you had a bad fan tune, the engine might slow down at idle but not run incorrectly. Or the same with good injector date for your current injectors
So first thing would be to bump fan 1 airflow, other than that I'm not very good at tuning and airflow might need to be increased in other areas to compensate for the load but I'm not sure where because you have a 2002. The next step is to make sure you have complete and correct injector data. My experience with incomplete injector data was when my alternator shut off at high rpm due to weak brush springs and the engine went dangerously lean at the lower voltage, I found data missing in that area, again I'm assuming it's because the tuner didn't bother with such low voltages vs flow.
Your novel above actually was very helpful. I'm suspect of your injector data. If you changed Injectors and have incomplete or inaccurate data, it's possible that the voltage vs flow in the low voltage area could cause improper AFR. So for example, your voltage drops to 10.0 at idle. Maybe your tuner didn't fill in that part of the table because he thought the engine would never be running at that low of a voltage. Now if your fan tuning was correct it would never run at that lower voltage and uncover this problem. If you had factory injectors with factory data, and you had a bad fan tune, the engine might slow down at idle but not run incorrectly. Or the same with good injector date for your current injectors
So first thing would be to bump fan 1 airflow, other than that I'm not very good at tuning and airflow might need to be increased in other areas to compensate for the load but I'm not sure where because you have a 2002. The next step is to make sure you have complete and correct injector data. My experience with incomplete injector data was when my alternator shut off at high rpm due to weak brush springs and the engine went dangerously lean at the lower voltage, I found data missing in that area, again I'm assuming it's because the tuner didn't bother with such low voltages vs flow.







