olderguy

iTrader: (19)

Are the three connectors hanging off the front of the engine still in place? If so open them up and look for corrosion. Water has a way of getting in there and raising hell.

Reverant

iTrader: (10)

What I meant to ask is - are you using the stock coils?

poormxdad

Yes. I've tried three different coil packs. All give the same behavior.

poormxdad

Here's another composite log. I cleaned all the male blades inside all the connectors I could get to easily with contact cleaner and a q-tip. I did not do the water temp sensor at the back of the block. I didn't try to clean the female coil connectors in the harness either. That's next.

Looking back, I did not have these problems before I did the engine swap, but they didn't happen right away. I want to ask again, if the wiring inside the insulation layer of the O2 sensor has been damaged by heat, could shorts there cause the engine problems? My initial feeling is no, since the O2 sensor is just a gauge and not part of the tune, but I'm going to cut away the outer insulation layer and see what I can see. I need to get the car up off the ground.

Thanks much for everybody's help so far. I'm sure this will become a much longer thread.

codrus

I really don't think this is a cam/crank sensor issue, your logs of when the car is running crappy don't show any sync loss. If sensor errors were making it run badly, it would be constantly incrementing the sync loss counter. Composite logs are only useful for debugging cam/crank sensor issues.

When it's running badly, the normal laptop logs show the AFR going very lean, even though the pulse width isn't changing very much. I can think of three possible reasons for this:

1) The wideband is lying. If the car is running closed loop (which it usually is at idle), then a bad wideband sensor will make it run badly, because it'll put in the wrong amount of fuel. OTOH, the pulse width value isn't changing all that much, so I don't think this is likely to be the cause. Also, if the wideband is lying when it says that it's lean, the ECU would be compensating by adding lots of fuel, which it doesn't seem to be in the logs. This would make it rich, and you need to go pretty rich before it will have trouble idling. It's much easier to make it run crappy by going lean.

2) The fuel injectors are not injecting the amount of fuel that's being commanded. This could be caused by bad fuel pressure, by a bad injector, or by bad wiring to the injectors. If you can lay hands on a spare set of injectors, you might try swapping those in. If you stay out of boost, you could even try this with your stock injectors, although you'll need to use the big adjustor to compensate the map (req fuel, I think?). IIRC you checked the fuel pressure while the car was running poorly at idle, right?

3) The engine is misfiring. When this happens, the fuel doesn't burn, which means that the unburned air and fuel are both blown into the exhaust manifold, where the wideband O2 sensor sees the air and indicates lean. Normally I would say this is the most likely, because there are lots of common failures in this system. Poorly gapped plugs, bad plug wires, bad '99 coil packs, all can cause this, but it sounds like you've swapped all of those already. Bad wiring could also cause this.

Bad wiring will make the car run like crap in a bunch of strange and non-predictable ways. If it started when the engine was swapped, then it's theoretically possible that some wire got pinched while installing the engine and partially broken.

--Ian

poormxdad

Ian,

Let's call this an aside.

My understanding has always been the O2 sensor has nothing to do with the way the engine runs--nothing to do with the tune. It's just a sensor and can't actually change anything. If it did change the tune, why would I need a MegaSquirt?

afm

iTrader: (3)

Megasquirt supports EGO correction, where the wideband reading is used in a feedback loop (closed loop fueling) to hit the target AFR. It is an option and may only be on in certain regions; some people do not use it at all as it is off by default with many base maps.

DNMakinson

iTrader: (3)

Depends on if you are running EGO closed loop correction. Ian assumed you are, and stated that it was an assumption. The O2 sensor does not make changes, but the MS certainly can make changes based on the O2 sensor's input. Same with MAP, CLT, etc.

I really hope you solve this.

codrus

The ECU can run in two modes.

1) Open Loop. When running in this mode, the computer looks at the two axis of the fuel table (MAP and RPM, generally), applies trim factors due to other sensors (coolant temperature, battery voltage, etc), computes a fuel amount, and runs the injectors at that level.

2) Closed Loop. When running in this mode, the computer does the same thing as above, except that it also has "feedback". It has a target air fuel ratio and it compares that to the actual AFR as measured by the wideband sensor and calculates an error. That error is then used to modify the fuel computed using the fuel table + trims, either adding or removing fuel to try to move the measured wideband value closer to the target.

So if you "tune" you mean the values that are in the fuel & spark tables, then no, the wideband output does not modify those values directly. It does, however, modify the way in which the computer interprets those values when it calculating how much fuel to actually inject.

There are a bunch of parameters in the megasquirt that enable or disable closed loop under various conditions. Generally speaking, most people set it up to run closed loop at idle or in cruise, but open loop in boost.

--Ian

poormxdad

I understand (or maybe I don't) that when things are bad, the OEM computer makes changes based on O2 sensor inputs. But, I also thought it didn't cause subtle changes to the tune. I also didn't think the O2 sensor was anything more than that with the MegaSquirt. However, this is all magic, smoke and mirrors to me.

poormxdad

Everything was so simple before boost...

My AFR/EGO Control pulldown is set at PID with a bunch of other settings. EGO sensor Type is Wideband,

In the spirit of my initial posts, could any of this be causing my problems?

I bow to everyone's superior intellect on this. I'm just trying to understand.

Thanks,

codrus

'PID' is closed loop. The 'P', 'I', and 'D' values are parameters to tune the way that the AFR error is fed back into the fuel input.

When closed loop is enabled, the ECU is constantly tweaking the looked up value using the error. However, when the measured AFR is close to the target, the error is small, and thus the correction value is also small. If you look at "EGO corr" in TunerStudio or the data log, it will tell you how much this control system is altering the fuel.

As the saying goes, Garbage In, Garbage Out -- if the wideband sensor is bad, then the closed loop will definitely screw up the fuel. You can test this fairly easily though, if you get the car so that it's running poorly at idle, flip it from "PID" to "No Correction" and see if it starts running better.

--Ian

poormxdad

Excellent. I'd like to try as many things as possible before I start taking her apart. It will probably have to wait till the weekend.

Thanks much,

poormxdad

Gents,

I sat with the car while she idled in the driveway, waiting for the rough running so I could engage No EGO Correction. The engine did run differently, but it didn't fix the roughness. I actually saw about a half point richer idle AFR with no correction. I took another log.

I had my non-contact laser thermometer handy. While she was idling, I hit the center of the straight pipe coming out of the flange of the Racing Beat header with the beam. Front to back roughly, 360, 300, 370, 410. The numbers danced around a bit, but I did it several times, measuring at the same part of the header each time and the numbers were consistent. When she started running rough, the numbers went to 370, 330, 410, 380. Does it mean anything?

I'm shooting in the dark, I know, but the next step is to start checking wiring, which means I have to pull the top of the intake manifold and remove the injector harness. I'm willing to put that off as long as possible.

Thanks,

sixshooter

iTrader: (12)

It's interesting you would see a 100*F difference in temps between cylinders. What do your spark plugs look like? Any variations in color between them?

As a diagnostic measure, I would be inclined to switch locations with the number 2 fuel injector and another and see if the low temperature follows that injector.

Have you run a compression or leakdown test on the engine recently?

codrus

IR thermometers don't work very well on polished stainless steel, they can give widely varying results depending on how dirty/clean the surface is, level of polish, etc. So I would be hesitant to draw many conclusions from that data. To get good data you need a thermocouple, ideally an EGT sender in each of the two tubes that you can read simultaneously.

(has to do with something called "emissivity", which the IR thermometer assumes is 1.0, which is a good assumption for most things except bare metals).

--Ian

poormxdad

Ian,

I can't refute your point, but I have to ask... could it give widely varying but consistent results? That first inch or so coming out of the flange is not (or no longer) polished, and the color is pretty much the same for all the cylinders. I measured each cylinder a bunch of times, and the readings were consistently as posted.

Regardless, I pulled the O2 sensor to check the wiring underneath the melted insulation. There is no visible damage to the wiring. I was concerned that maybe the internal wiring was shorting and causing some weirdness in the MS3, and since the problem was getting worse, I thought it could be explained by the wiring touching the header causing a little more damage every outing. That doesn't mean the O2 sensor isn't bad, but I no longer have concerns about that melted spot. I've had the O2 sensor go bad before, and it didn't affect the way the engine ran, only how the gauge displayed. This could be my opportunity to upgrade to the new version of the Bosch sensor, but there's got to be a way to figure this out without replacing everything one piece at a time to see if the problem gets solved.

As to Sixshooter's question, the newer used bottom end produces a noticeable increase in power, along with significantly reduced oil consumption and smoking. I also replaced the valve seals when I swapped my rebuilt head onto the Japan market block. The current configuration is so much better than her former self when she's running right I can't believe there's anything wrong with compression or leak down. Neither of those would be intermittent.

I'm on board with moving the injector from the #2 cylinder. Can I swap in injectors of a smaller size to see if she doesn't run rough at idle without changing the tune? I have some OEM injectors, and a set of unused Deatschwerks 350s that came with the Kraftwerks kit.

Thanks,

codrus

Is the damaged wiring in the wideband O2 sensor or the factory narrowband?

If they were dirty/discolored/etc in exactly the same fashion, then yeah, you should be able to compare numbers between them, but it's possible that they might be sufficiently different to throw off the reading without it being visually apparent. I don't know.

For injectors, if you swap in a known-good set of smaller ones and adjust the big number in TunerStudio (req fuel, I think it is? I don't remember) by the relative amount, and configure the proper dead time for the new injectors, then you should be able to start and idle the car fairly easily.

--Ian

poormxdad

There was no damaged wiring, only melted outer plastic insulation. The asbestos heat shield beneath was still intact, and the individual wire insulation was unharmed. I only have the wideband--no factory narrowband sensor.

sixshooter

iTrader: (12)

I meant to more simply switch locations between the number 2 and the number 1 injectors and see if the cooler temp follows it. Don't get crazy with changing the whole set and introducing other variables.