8 cylinder front engine iconic vehicle
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By captainOCD
#66843
I've got a set of S300s chips for my blue 86.5 on the way from Ken and I just got my fuel pressure regulator and new plugs from Roger this week. I figured it was a good idea to look over some stuff while I wait for the chips.

I'll preface this with saying that as far as I can tell there isn't anything wrong with the way the car runs. First thing I tested was the MAF. Measuring at the LH plug I got 5.1Ω across the sensor and 396Ω across the CO pot. Again the car runs fine, but should I be worried about the sensor reading?

I haven't checked the AFR by measuring the O2 sensor voltage or anything. Also don't know how old the O2 sensor is.
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By Crumpler
#66910
Hey Captain, I can help with some of this.
The MAF hot wire circuit sounds slightly out of spec (3.6-4.1) traditionally. You could run it through a burn cycle and verify reading. Or verify directly off MAF pins. The ohms for mixture sound pretty spot on. Experts can speak on direct relationships hot wire sensor to performance but I would not assume it would effect your bottom line significantly. Unfortunately, the alternative is another rebuilt MAF. You know the drill there.

I had a wideband when I installed Ken’s chips to adjust AFR, but I know many have done it with narrowband readings.
If you have a smoke machine check for vacuum leaks before you jump in. 18 greater vacuum doesn’t mean they are not there.
Cheers.
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By worf
#66914
Is LH 2.2 adaptive or does Porken add that to his code?

If you have MAS doubts, you can send it to Rich Andrade (https://electronikrepair.com/) and he’ll test it and tell you where it is with respect to spec and ‘needs-rebuild.’
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By captainOCD
#66924
I think I'll test the readings at the maf itself just to be sure there isn't added resistance in the harness.

Maybe a fresh factory O2 or wideband O2 sensor wouldn't be a bad idea to get an idea for how it's running now before I turn the wick up on anything. At least then I'd know if the engine is at least running right and if the MAF is giving the computer reasonable values.

I tested the MAF on the other 86.5 I haven't got on the road yet as well. It measured 4.5 and 383 Ω. If nothing else at least I have a spare to use while one gets sent out.

I did test vacuum back in 2018 but checking it again probably is a good idea. A fresh set of intake seals probably is in order too anyway. Can't hurt to clean out the valley while it's apart either.
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By worf
#66926
captainOCD wrote: Wed Mar 17, 2021 9:30 am I think ...
What is the lineage of this Mass-Air Sensor? Who rebuilt it? When? Was it a core exchange? How many miles/heat-cycles since?
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By captainOCD
#66931
worf wrote: Wed Mar 17, 2021 9:33 am
captainOCD wrote: Wed Mar 17, 2021 9:30 am I think ...
What is the lineage of this Mass-Air Sensor? Who rebuilt it? When? Was it a core exchange? How many miles/heat-cycles since?

I don't have a clue there. It was on the car when I got it in 2018. No paperwork came with it. Looks like a bosch rebuilt based on the sticker on it. I've put about 3500 miles on the car since 2018.
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By worf
#66961
captainOCD wrote: Wed Mar 17, 2021 9:46 am I don't have a clue there. It was on the car when I got it in 2018. No paperwork came with it. Looks like a bosch rebuilt based on the sticker on it. I've put about 3500 miles on the car since 2018.
I learn something new everyday. Never seen one of those. I don't even know where you'd source a Bosch rebuilt. Not sure I've ever asked though. A bettin' man might conclude Porsche dealer was the installer.

Given that you don't really know how many cycles it's seen, if it was *me*, I'd send it to Rich to be sure that it was in-spec. Worst case is $40 two-way shipping and you know it's good.

Case in point: the Zyclomat Rot S4 that I debugged is coming back in a few weeks to completely re-Shark Tune since it was originally tuned the first time with an almost-out-of-spec MAS and the second time - with the SC - with an out-of-spec MAS.

I hate doing shit twice. Even when I didn't do it the first time (or second time) and am getting paid for the rework.
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By captainOCD
#67042
Wish I could tell more about it, but I'm the kind of moron that buys cars with no history. This car had sat for 10 years or so before I got it (advertised as parts).
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By captainOCD
#68188
Ok, so did some more poking around today and found out/fixed a few things. First off I tried my better meter. Neither of these are high accuracy or anything too fancy, but I do trust the grey meter a little more. It was reading lower resistance across its leads as well. Couldn't swap the leads either, they didn't fit in opposite meters. I did measure about the same .3Ω across the yellow meters leads with the other meter.

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Anyway, doing nothing else I was measuring 4.2 ohms across the MAF wire at the MAF itself. Still about 396Ω across the CO pot. I cleaned up the contacts on the MAF and now am measuring 4.0Ω.

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I also inspected the previous MAF harness repair that was done sometime before I got the car.

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The tape job wasn't pretty, but the connections underneath seem fine. Looks like they were soldered and heat shrunk over. I just taped back over with electrical tape, then cloth tape.

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Now I'm measuring 4.2Ω at the LH for the sensor wire (4.0Ω at the MAF). If you discount the .1Ω in the leads that is about 4.1Ω at the LH. I've seen the spec is around that, so perhaps I am ok there. For what it's worth, I measured MAF on my other 86.5 project car and it came in at 4.1Ω at the MAF itself, so seems like both are about the same.



Beyond that I measured the idle vacuum at the EZF as well. It came in right under 19 inches.

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So what do you guys think? The MAF numbers don't seem too bad. The vacuum seems pretty good too.
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By captainOCD
#68678
Cleaning up the contacts on the MAF doesn't seem to have done anything noticeable to the way the car runs (again, nothing seems wrong with it to me to begin with). Even though the intake doesn't seem to have any vacuum leaks, there is oil seeping from some of the vacuum hoses (pcv?) and pooling in the valley. So I might wind up taking the intake off, resealing it, and replacing some of those hoses first.
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By worf
#68686
captainOCD wrote: Wed Mar 24, 2021 1:07 pm Even though the intake doesn't seem to have any vacuum leaks, there is oil seeping from some of the vacuum hoses (pcv?) and pooling in the valley.
Oil filler neck?
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By captainOCD
#68757
Some of it might be coming from the oil filler neck, but I'm not sure that's the largest source. Throttle body is even wet with oil, and there is some oil in the elbow ahead of the intake, so I think some is seeping out of the intake. Seems like most of it is coming from a hose that appears to be coming from the passenger's side valve cover. Hard to follow under that intake though.

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Can't really see it in this photo (or any of the ones I had handy), but it looks like the hose that's leaking the most is right behind the ICV then goes up over the valve cover.

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By Mike-JDSPorsche
#70385
4.1 Ohms is about right for the wire and your idle pot is fine however that is only in circuit on non-cat 84-86 cars. The resistance on the wire is only part of the story, it just shows the electronics are good, it may still be out of calibration but it sounds like your motor is running OK so I wouldn't worry about it.
I checked a few newly calibrated MAFs in stock and they vary between 3.98-4.18 Ohms.

That is oily under there, maybe time to refresh that intake!
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By captainOCD
#70410
I appreciate the numbers. And yes, I think an intake refresh is next on the list. I have a set of (paper) gaskets. Need to call up Roger and figure out what rubber parts need replaced and what is ok.
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