2nd (maybe silly) question about Carrera DMEs, O2 and CHT

[Zeke]

Again, the search is not my friend anymore. I can't seem to reduce the bulk of hits no matter what I do.I've given up even using the first box. It returns everything under the sun.

Down to business: You Pelicans are recommending that I replace the O2 sensor and CHT as a matter of course before even attempting smog (that's another issue, it's already failed once and Ijtook the car over on that condition). Are there values and readings I can take off these before just ripping them out?

mean everyone seems to know the Ohm value of a good spark plug wire (I assume it's the same 3K on the Carrera wires), but what about some of the other things? I have some sorting out to do and I know about the unplugging the injector trick. I also know about the older cat, heating it up, replacing it, using Techron, then 87 octane (or not), blah, blah.

I don't have a fuel pressure meter, will that be a necessity? If there was a more complete thread about really comprehensive testing and tuning, I missed it after 2 hours of searching last night.

All my workshop manuals stop at the SC or sooner. I need to get up to speed there.

[Quicksilver]

If it runs ok I wouldn't do anything before trying to smog it. The DME Carreras aren't that old and are very reliable.

The CHT sensor is just one of the first things to check if it does act weird. The replacement is a 3 wire unit instead of 2 wire.

[RickM]

If not experiencing drivabilty or fuel mileage issues I'd say not to bother with testing the sensor. Here are pretty generic testing procedures: http://www.mr2.com/TEXT/O2_Sensor.html

Here's the Bosch manual describing product/installation: http://www.boschautoparts.com/NR/rdonlyres/D90D5AD3-7E41-439E-B271-20A76139E0F7/0/OxygenSensorInstall.pdf

[charleskieffner]

since its already failed emissions, do the following cheap fixes

1 air cleaner

2 cht sensor

3 dme relay

4 02 sensor

5 fuel filter

6 plugs at least look at them

7 plug wires if bad

8 dist cap rotor

9 full tank best gas you can find and some techron

10 drink a beer and get emissions behind you before you add any more goodies which will throw stock out the window.

i will mention one other thing. MAS next to air filter. reason mine was clogged to high hell with 19 yrs of crap from PO. this was the last thing we changed, after numerous problems(dying out under load) unless PO was anal about the above..............just do it. its pretty cheap in the big picture. and you will become one with your new car.

[Zeke]

Pig?? Come on, the debate between the SCWDP and the Carrera owners would have a field day with that!!!

BTW, whatever happened to the SCWDP?? We've got all these new "Gruppes" like the Gruppe B and so on. Did they eclipse the SCWDP boyz? I'm sure the Gruppers B will want to make me an honorary member just for buying a "pig."

I'm not sure what the R Gruppe is gonna do to me. (I won't tell them until I get the backdated bumpers on )

[Zeke]

MAS. Don't these things ever just clean up? I mean the damn dealer sold me a new MAF sensor for the Boxster and I sent it to one of our Pelican mechanics in FL for testing. He said he cleans them all the time but mine worked as is. Another story, obviously, but the point is that it makes me think about just looking the obvious over before yanking parts.

I'll order a Bently form our host right now.

[DW SD]

Post your failed emissions results for some evaluation.

If you are somewhat close, a universal cat could be welded in to replace the aging factory unit and clean things up MASSIVELY!

Doug

[Zeke]

Originally posted by CS119laCoS
As far as emissions, how many miles are on the car, and what part of the emissions did it not pass?

The cat converter does often wear out after 120-150k miles or so. If you have the emission numbers, it would be a good clue as to what the problem is.

Oh yes, I know what it is. Only the HC at 15 mph failed and the reason is the motor is tired. Low compression and oily plugs on 2 cyls. Do I have to tell you how many miles are on this thing?

(A lot, but it runs pretty well. all things considered. A rebuild or motor swap was in the plans from the get go. I just wanna buy myself 2 years.)

I don't want to start a "smog" thread. I read 20 of those. I'm just looking for some testing info I couldn't find using this new search deal. I'm sure it's better, I just got more relevant results with the old one.

[charleskieffner]

if it were the cat, dont weld it in????? why? bolt one in for emissions, and then unbolt it for the other 364 days a year, and slap a GHL by pass in there. get to know elvis here @ 20thstautoparts.com- in phx. for used unrusted unsalted parts. my mas was the last thing we did for poor running symptoms. no one here ever mentioned it as possible cause. the other items were listed as culprits and one by one we narrowed it down. if all the above fail and you still dont pass, pull the MAS off and look for poo poo in it. also there is a gizmo that does wear in there after time. im not trying to scare you but w/out emission readings hard to pin point. also i originally passed emissions here and then it went down hill, as i drove it more. it was a one owner never wrecked, bought new at scottsdale porsche/audi. he was a lawyer, and did have the basics done nothing more thru out its life.

[DW SD]

A new cat would take care of the emissions, unless it is already new.
It is amazing how much cr@p a new cat will burn up.
Just make sure it is nice and warm when it gets put on the machine.
Wires, ignition system and mixture also effect HC (as does compression), however.

Good luck,

Doug

[DW SD]

Milt-
You can make your own cat bypass - Just buy some of the right diameter mandrel bent tubing. You can also buy a cheap cat and copy the rest with the mandrel tubing and some straight tubing. You may re-use the flanges from your current cat.

I would believe that a new cat would not reduce performance in any way. This is my guess and cannot verify with dyno results. A vintage 1988 cat probably would restrict. Though they work the same, they have improved, from what I know and are less restrictive.

Check out summitracing and buy a nice quality generic one built for a camaro or vette and make your own.

I used to work in a foreign car shop as a kid (1992 to 1994) and everytime we had a car on the fence of passing the emissions test and a tune up was done (in other words, the igntion system was in good condition) and the O2 sensor was good, we would change the cat. The emissions would drop by HUGE amounts. And those were cats of 10 years ago. I'm sure they still use the same technology, but I would guess today's are better.

Doug

[Zeke]

I appreciate the comments on the cat, Doug. As you may know, it is a long tubular one and not the ususal generic I would use on my '89 Chey truck. There may not be room for such a replacement. I'll have to check out Summit (I like summit anyway, they have some great race goodies that Pelican doesn't get into).

[DW SD]

I got rid of a low mile 3.2 cat some years ago. I don't remember exactly what it looks like. However, I think there are plenty of designs out there that would be interchangeable. (again, my opinion).

Can you find an SOCG (orange county) brother who would let you borrow the CAT for the purpose of passing smog?

Doug

[DW SD]

A bad (lazy) O2 sensor could be an issue, too. What happens is the O2 sensors become slow to respond, so the engine spends a bit too much time running rich and then lean during its idle. AFR looks like a sine wave if you map vs. time. The sine wave gets S T R E T C H E D O U T when the O2 sensor wears out.
I bought a generic BOSCH one and soldered the Porsche connector onto it. Mine may have come from a Mustang, but is was considerably cheaper at NAPA ~ $35.

Doug

[Carrera3.5L]

If you need to borrow a stock catalyst, let me know. I have my old one with 80K on it tucked away and it works fine...

I also have my stock distributor cap, rotor & plug wires that are all in good working condition if you need to swap those out for the test also...I think I may also have a slightly used CHT sensor as well...just return the parts when you are done...

I just need the cat back before May so I can pass my test...

Ralph

[450knotOffice]

Jeez Doug. Did you sleep at the Holiday Inn Express last night? You've got some seriously deep knowledge of this stuff.

[DW SD]

Originally posted by 450knotOffice
Jeez Doug. Did you sleep at the Holiday Inn Express last night? You've got some seriously deep knowledge of this stuff.

Thanks! No Holiday Inn, but I am GOING TO DISNEYLAND!

Just kidding.......

Yeah, I got to know the 3.2 DME / motronic pretty well - much of it through reading on this site.

Way back, I used to test O2 sensor feedback circuits by tapping into the signal and showing the AFR vs. time on a o-scope. We had a nice BOSCH diagnostic tool which would print, if you wanted it. So we'd print the before and after for the customers, so they understand that their cars were repaired. It was cool and that was 10+ years ago.

Working on cars complemented my engineering school and studies at the time.

Now I'm just a head hunter

CS119laCoS-
I think MAS = mass air sensor (the Aluminum box with the barn door sensor inside).

Doug

[Zeke]

Originally posted by DW SD


Now I'm just a head hunter

Takes a good one to know a good one......

Originally posted by DW SD

CS119laCoS-
I think MAS = mass air sensor (the Aluminum box with the barn door sensor inside).

Doug

And maybe the MAF sensor is the same thing, MAF= mass-air-flow according to the thieves at the dealer. But the Boxster MAF doesn't appear to work on a velocity principle in that something physically moves with the amount of air being let in by the butterfly.

[greglepore]

You don't need a fuel pressure gauge.

If you want to try a cat, look at Summit or Jegs-they have straight thru cylindrical low restriction cats that could be easily adapted with your welding skill.

That said, I suspect that its the crankcase oil that's the culprit.

[Goth]

Hey Milt,

I think Greg is right about the oil increasing HC, but other things can add to it like ignition timing.

Here is a web site with some details on high HC about 1/2 way down the page:

http://www.smogsearch.com/index.php?page=faq

I'm not all that smart, but I do a mean search

Edit:

Another site:
]http://www.visi.com/~rhayman/smog_faq.html#Checking%20Catalyst