2001 SOHC lean bank 1 but warms and corrects?

[Pat Kunz]

Hello, running across a weird one. Some of you old timers may remember me from kunzkorner and my 2.9 exploits. Anyway far from a novice on these rangers and cologne V6's. Anyway I'll give the back story to my problem. 01 ford ranger 4.0L sohc 175k miles, well maintained, owned for last 100k. Changed oil on Saturday Orielly 5w30 synthetic and wix filter, got done with that. Took to work on Monday, bad snow storm but no issues everything was fine. Worked for 4 hours and started truck, was running kinda rough, rough enough I pulled into a parking lot a 1/4 mile down the road to make sure I didn't have something arcing a wire or something of that nature, check engine light was flashing. Was not in any spot to work on it so continued home, about a half mile down the road it started running fine again and did so the rest of the way home. got home checked codes and had a missfire #2 and pending p0171 lean bank 1. figured probably lean due to missfire. It was about due for plugs so figured I'd throw in a set soon. Next day ran like crap all the way to work and back, same codes. Plugs were pretty smoked so threw in a new set of motorcrafts. Still ran rough on startup but discovered would clear up after engine warmed up and still hade missfire #2 and lean bank 1. Hooked up the smoke machine and let the engine get real cold, pulled back in the shop still running rough. Hooked up smoke machine, and smoked poured out from the bottom of #2 intake runner. Obviously the problem, leaking intake O-ring. Pulled intake manifold, replaced crushed gaskets, took a look at the back of the valves, all looked clean. Put all back together, and started, was still rough but not as bad. Re-smoked engine, in case I screwed something up, no intake manifold leaks, albeit the throttle shaft leaks more then I would like but it would effect both banks. Pending bank 1 lean code but no more #2 missfire. Keep in mind this thing still runs perfect when warmed up. Also issue will start immediately on a cold engine, where it should still be in open loop. One more note on symptoms, does occasionally but not always have a little timing chain noise. Also even if it is running good, if you run in very cold temps the issue returns (eg. long run on the highway), but will run fine again once in traffic. I have two theories at this point, one bank 1's o2 sensor is getting super lazy or heater doesn't work so well when it's cold. Two, for some reason the rear timing chain is getting a lot of slack in it when it's cold, not sure if it runs a hydraulic tensioner or not. This did start just after an oil change. I had an explorer in the shop many many years ago with this engine, that had the rear timing chain jump or broke a tensioner, eg the rear chain was super loose. It ran lean on one bank and rich on the other one, don't remember which was which though. The 02 doesn't make sense to me, since it does it open loop as well. The tensioner one, would just be very strange, maybe I got a bad oil filter, restricting flow. Again as I said this is an odd one, and hopefully somebody has seen this before.

Thanks
Pat Kunz

 

[Brain75]

so you got one issue I have a hunch on and one that needs attention right away.

the attention needed asap... the 4.0 SOHC has a dead giveaway when it is about to become an "exploder" (catastrophic major internal damage) - timing chain noise on startup. The timing chain system was designed by rube goldberg and is a mess. You need to replace the "cassette" - timing chain plus plastic tensioners in a package, one front one back.... the back one flat out requires pulling the motor or the trans.... $150 in parts $$$$$$ in labor.
After all the explorers turned into exploders Ford in their infinite wisdom decided to make the service interval for that every 70k miles... assuming the PO had it done @ 100k, it might be due again, if not and you got to 170k on the original, congrats now change them asap. Ford should have made the tensioners out of metal, and the guy who spec'd it as plastic in the first place should have been shot!

I have a hunch, and this is just a hunch but sounds like #2 injector is partially clogged. When it is cold it is worse, as it heats up it gets better - injectors tend to do that. This is my hunch and would explain misfire and lean, running rough, all of it, but it is just a hunch. Did you let it sit for a 12 month deployment or such a thing and the gas got a little old? Ran any fuel injector cleaner through it recently?

 

[Brain75]

Something just came to mind... when the plastic cassette has really borked up it will throw plastic bits all over and they end up in the oil pan, since you just did an oil change I got to ask, any chunky at all in there (if so don't even turn it over before pulling valve covers and checking timing bits and pieces - interference engine)?

 

[Pat Kunz]

Thanks for the reply Brain75. The #2 missfire code has gone away and it's now every cylinder on bank 2 goes weak. Did a cylinder kill across them and 1,2,3, are all now about the same. Fuel is fresh and did throw some injector cleaner in. It's about 1/2 way through that tank. As a clogged injector was a thought, till I saw how bad the intake gasket on #2 was leaking. I'm well aware of the chain mess that is the sohc, this is my second of this engine 97 explorer sport was the first. This truck is pretty much done if the engine has got to be pulled, it's kinda a big rust bucket at this point (deffinitly can't stand on the foot holds of the step side bed anymore unless you want the fender to come with you). So major surgeries are out of the question. I only use it when I need a truck or I don't want to risk the nicer ones. So it's actual mileage per year anymore are less then 3k. If I can get another year or two out of it would be great.

 

[Pat Kunz]

Something just came to mind... when the plastic cassette has really borked up it will throw plastic bits all over and they end up in the oil pan, since you just did an oil change I got to ask, any chunky at all in there (if so don't even turn it over before pulling valve covers and checking timing bits and pieces - interference engine)?

Nothing unusual was in funnel catch, when I did the oil change.

 

[Pat Kunz]

Update and repair. Well this was a strange one. All my issues turned out in the end turned out to be from #2 cylinder. As stated above, this started as having a #2 cylinder missfire and a lean code on bank1. Found a large vacuum leak on #2 intake gasket which was repaired, that got rid of my missfire code, but continued to run rough when cold and lean code on bank1, which the roughness and lean condition went away once the engine got some heat in it. Well I finally broke down and bought me a scanner and was going to have a look through, before I got into anything drastic, needed one anyway. Well while looking through my PIDS, I noticed the one that said injector #2 malfunction said yes. All other injectors said no. No this was on a cold engine, simply key on looking through the PIDS. Thought this was strange, but lets see what she does when running. The usual started up, running bad as normal. Pulled #2 injector harness, was toggling noid light just fine. Turned engine off varified battery voltage at connector, was good. Started back up and continued to see what was going on as it warmed up. Took a listen to #2 injector vs 1 and 3, and it definitely seemed at least quieter, if it was doing anything at all. Engine started to run a bit better as it built up heat, and noticed the injector fault, was switching between yes and no. Turned engine back off and checked ohms on #2 injector, was 22 ohms, seemed a bit high, as most if I remembered correctly were around 12-14. Hooked injector back up and the PID went back to "no" on the fault and engine ran perfect. Well done with checking at this point as once it's warmed up it does perfect. So order a new injector while at work, check the ohms, 14.2 ohms, that seems about right for what I was thinking. So pulled #2 injector and checked the ohms when it was perfectly cold, it was reading in the K ohms, so way off. Evidently what was occuring was that as it heated up it started to make a better connection till it started to fully work again. In my 30+years of working on cars, I never saw an injector do this before. Put in new injector, and worked just fine. Wanted to give the update, in case anybody runs into something similar, as sometimes a miss can have more then one cause. The part that really boggles me on this, is that the pcm knew there was an injector fault, but not throw an injector fault code of some sort?

 

[cowboycowboy91]

I appreciate you posting the solution to the problem. This sounds suspiciously similar to the problem I just posted about. I am going to check resistance on my injectors now. So, 12-14 ohms is where they should be...right?