hmmm - not sure. i probably just googled it and found something on amazon. might have been for AC systems though, so i might have gotten it at home depot too. it was years ago that i did it.

Wow, I did a vacuum check on the line that comes out of the 1st vacuum tap forward of the throttle body shaft (goes to the FPR and FPD). It's at zero during idle and jumps up to around 8 during acceleration at 3500 RPM. The aft tap (that goes to the temp switch just aft of the ISV, reads 17 in at idle, 20 in at 2000 RPM and 23 in at 3000 RPM. I checked that the vacuum tap on the TB was clear so I'm puzzled by why it didn't fit the expected readings on the previous post.:confused:

I found that I can use the vacuum gauge for an accurate air pressure input. Now I can plug it directly into the throttle body. Tomorrow's project.
http://forums.pelicanparts.com/uploa...1407456909.jpg

the port in front of the throttle plate is ported vacuum. it won't show anything until you crack the throttle

readings sound right.

a check for holding vacuum and you're good to go

Thanks, I'll let you know what I find. So far I haven't found anything that stands out as an "aha" moment. If I am to resort to adjusting mixture with a probe in the tail pipe, what's the best component to adjust for acceleration, mid-range RPM environment?

a laptop. seriously, you would use something like an LM-2 and an interface between your ECU and your computer like an osterich. part throttle tuning is done while driving. really a 2 man job.

the stuff isn't cheap, and you would probably be better off calling josh or somebody like that who already has a leg up on this and could point you in the right direction. if you were here, i could do it, but that isn't the case

to be honest though, i really think there is something wrong with the car if you truly are running lean. it's not like the tuning would be different for one stock car than the next. at this point though, i doubt that you really are.

the easiest way to find out is to go to a dyno. they can tell you right away what your mixture is. since you are looking for diagnostics, and not tuning, you could probably get them to hook you up and get a reading for about $100 or less.

You should have no continuity and infinitely high resistance on the tests above (disconnect O2-sensor from plug 1st). Otherwise, you have a short in your O2-sensor wiring and giving the DME erroneous data.

Plugging the muffler is to make the pressure-testing for leaks work. There's good chance that one of the cylinders will have both intake & exhaust valves slightly open and all that pressure will just rush out the back end of the exhaust.

Have you pulled the spark plugs for a simple visual inspection? It is a dead giveaway when combustion issues are suspected. If not pull them one by one and check the color chart. They should all be a nice golden brown, anything else and there is an issue. If one plugs color is way different from the rest it is likely just that cylinder is causing the issue (or at least one of your issues).

Also, when you replaced the oxygen sensor did you use a universal and solder it in? If so you need to cut solder connection out and use the provided connector. The oxygen sensor literally breaths through the wires and soldering tends to seal the copper strands air tight. The air it 'breaths' is a base reference for all measurements it takes.



http://forums.pelicanparts.com/uploa...1407503744.jpg

When I pulled the plugs after about 1000 miles, they looked like the engine was running a bit lean. They were all uniform in appearance. There has been some discussion that with the new E85 fuels, cars are running leaner. Don't know about the specifics or validity of that approach. I replaced the sensor with a factory Bosch unit that required no modification or adapting.

actually, it's no longer the case. i have not seen a brown plug in years, unless the car was burning oil. they are all pretty grey now that we are burning unleaded fuel.

here's a basic question: what grade of fuel are you running?

When I first got the car I ran premium because I thought the car had higher compression than it did. since I clarified the required fuel grade, I have been running 87 octane (regular).

well, if you have any buildup on the tops of your pistons, you may need to increase the octane, as the compression would go up due to the effectively smaller chamber. this is incredibly common, and has been for as long as we have been burning gasoline. a quick test would be to run a tank of high octane fuel. if you wait until it is almost empty, you could get away with less of the high octane fuel if it doesn't change things for the better.

i agree about the O2 sensor being a likely culprit. those things are touchy. you can't get anything on them (chemicals etc). they can be touchy about the connections too.

again though, if you can get to a dyno, they can tell you where you are.

Well here's an interesting development. I pressurized the throttle body with a few lbs. of air pressure and I could hear air noise coming from deep under the intake manifold. I sprayed some soapy water solution around in there and there were a lot of bubbles coming out of the Idle Stabilization Valve (Idle Control Motor) from the bottom and around the top where the electrical connector plugs in. I guess it never showed up before when I was doing vacuum checks at the intake of the j boot. So I guess that explains the hunting RPM when the O2 sensor was unplugged and a vacuum leak.

I see there's a lot of different ISV's on ebay that supposedly fit the 944 and other cars. Any thing I should know before I replace this thing?

woohoo!!!!

nothing much to it. pain to get to on the 968. no idea about the 944.

It's not too much of a pain since I already have 1/2 of the intake apart, just to do the intake test. Thing is, I just pulled the intake last month. Oh, well. :rolleyes:

it happens. looks like you're on your way though

I see from your personal data that you're in Orange County? I was a pilot for AirCal in Santa Ana. I miss OC.

lol - small world