sdeeter19555

Ok, so rising from the dead... I've had this low RPM/idle tick a while now...I have 220k on the clock. Just this week it has gotten louder (or maybe more annoying?). The only thing that changed recently (like last week) is that I went from Mobil 1 5w30 to Mobil full synthetic 5w30...I'm almost wondering if the viscosity is breaking down or just less with the full synthetic than the Mobil 1. I'm going to try getting some Mobil 5w40 (like that European Car oil)...I'd try 5w40 diesel, but I don't want to take a chance of poisoning the cats (although I think Rotella is dual rate CI/SI)... So it's still kicking...doesn't occur a anything about about 1200rpm, it just fades out and a quiet engine.

Ok, they smoked it...no vacuum leaks. They ran some tests and watched the results on their reader/scanner. Everything lead them back to a MAF sensor. There was NO CODE present for the MAF that ever popped. They replaced the MAF and the codes have stayed away for 75 miles now. Before the PO171 code would manifest within a minute and the PO174 would come on after a few miles. So for now, it looks like the problem with the codes may be solved. Hopefully that also solves the AIF problem...time will tell.

I'm completely stock, no tune so kinda hard to disable. That's sort of what I'm finding, one tank of fuel and it goes to some arbitrary %alcohol and never comes back down. I've started another thread about 171/174...

I've searched, nothing hits my symptoms exactly. Truck has 208k, fuel pump replaced as PM around 150k, exhaust bolts and gaskets around 190k, replaced O2 sensors and spark plugs around then also. I bought this truck new... I had my alcohol in fuel (AIF) go wonky on a trip pulling the camper a few years ago, started reading 20% plus AIF even running non-alcohol gas. Running e85 was not possible, it would almost not start. So I assumed the O2 sensors were going bad since they are used to interpret AIF and replaced all four with GM units. No change. A cold start on gasoline was typically bulky and stumbling for about 15 seconds and lopey. I also had a low rpm bucking or surging, but the truck has always had a touch of that since new but this is definitely worse but tolerable. Fast forward to last week, I had the inspection garage run the codes (which I already knew were 171/174 (but no CEL, ever). He check some parameters quickly and the fuel trim and alcohol were all out of whack. He reset that and WOW, nice normal cold starts, truck ran and drove like new, but it (174) would trigger a CEL (171 pops a soft code shortly after reset, 174 may or may not pop a CEL a while later). No other codes are present. A few days later running nothing but e10 93 octane gasoline, and my AIF is back up at 30% and won't come down (it fluctuates slightly, but is around 30%). My cold start stumble and low rpm surging are also back. I took a trip on Wednesday to Annapolis and netted 16 and 17mpg, the truck runs good overall. Still have 171 and 174 as soft codes. Anything particular to look at?

Ok, so following up...I have more issues than O2 sensors. So my alcohol never did settle back down and I've never lost my cold start stumble. I went for inspection and had the local guy hookup his diagnostic deal for a PO171 and PO174, the alcohol was all out of whack and the fuel trim was maxed. He reset just those and WOW the truck started so nice, drove so nice, and the alcohol was back to normal. Fast forward a few days, and running a couple tanks of general e10 premium (93 octane), the alcohol jumped up to 30% and my stumbling is back. PO171 pops up and PO174 will trigger the CEL once in a while (not always). So long story short, the O2 sensors were probably worn but not the underlying issue. For the record, I drove from Harrisburg to Annapolis on Wednesday in Baltimore traffic and got 16 and 17mpg respectively (hand calculated). Not bad for 208k miles and studded snows.

Although there was no indication the harness is bad, the deal finally failed completely. The way it is wired, there is only one way it couldn't have power and that is if the short harness at the headlight was bad. So $50 later, a new harness solved the issues. Hopefully this helps someone down the road.

Update, still chasing it... I did add a relay triggered off the passenger's low beam, which required a diode to prevent it creating a loop (pass headlight turns the relay on, the relay backfeeds the driver's circuit, the relay won't shut off). So after I figured that all out, I thought I had solved the issue. Nope. I have now determined the issue is the passenger's low beam ground...the relay puts reliable power to that headlight, it still dropped out. So I added a ground tonight and pulled the relay as a test for a few days. Anyone tell me where the ground is for the headlights? I pulled, sanded, and put anti-corossion paste on all of them I could find when the truck had nearly zero miles. The truck is oil undercoated so no rust issues. Either I missed it, or I have a wire or connection pulled apart somewhere. Oh, and it is intermittent, so when you pull it apart to start testing, it works and you can't trace it out.

Yeah, when I was doing extended OCIs in my Cummins (some to 45k miles with bypass filters), I ran Wix XPs and Fleetguard synthetic media. For standard OCI, a standard cellulose filter is fine...it's not the life of the filter, it's the capacity of that filter to trap/hold dirt.

Those "synthetic oil" filters are typically a glass fiber and not cellulose. They can trap and hold more dirt, which is good if you do an extended oil change interval. Otherwise, for a normal interval, any good filter will perform fine.

Ok, I now buy that battery comment. It dawned on me yesterday that the computer in these trucks can control each headlamp individually although they are tied to a common relay. Found this out, or more accurately remembered it, doing the TPMS relearn. In the linked thread, I did in fact lose one of the two batteries shortly after this headlight issue. Since I have replaced the batteries, I have not had a single instance of the headlight dropping out. So in conclusion, the truck was likely telling me that I had a failing battery.

I've heard both good and bad with regards to AGM...they don't like overcharging being one bad. My truck occasionally charges at 15.1 or 15.2VDC, I assume it is doing that desulfation cycle but is that considered overcharging? I thought I also remembered someone stating the GMs need the computer told that they have lead acid or AGM batteries for that reason?

I never even gave Amazon a thought. I needed the truck this weekend, so had that urgency on my mind. I guess if you think about it...$400/ten years is really only $40/year. Although I remember buying truck batteries for $25/each!

I could have gotten cheaper, even really cheap, batteries; but I stayed middle of the road. Something decent with a good warranty... The cheap ones were around $100, the expensive ones were around $250.

To add insult to injury, it was the slightly newer by a few months (and I thought better) Deka battery that died...the OE battery is taking a charge (the other battery dragged it down) and load tests perfectly fine! They had multiples of each option (agm, platinum, gold, and silver Diehards) in stock for mine, but I think that 6.0l battery (group 48?) fits a lot of platforms. It just gave me both sticker shock and amazement the OE battery is still kicking.

Well, 2012 to 2022...not bad for factory battery and second Deka battery (I run dual batteries). Just bought two Diehard Golds from Advance, $400!! Not only is gas expensive!