SQLGuy

Hi Stan,

If you're talking about the Y connectors in the MAF boot, one of those actually gets removed for the SC install, and its installation point gets plugged. The fitting itself that I took out was in excellent condition, not cracked or brittle at all.

Wouldn't a leak like this have to be after the throttle plate? Since I am seeing pressurized air flow OUT from at least one line, I would think any leak before the throttle plate is only going to lose air and enrich the mixture a bit (due to overmetering)... but the Lambda circuit should be able to compensate for that anyway.

One other thing I don't understand, though, is, if there's is a vacuum leak, shouldn't that cause the high idle to climb as the engine warms up? My idle is 1K within 10 seconds of a cold start, and stays there right through full hot.

Thanks,
Paul

Mrmerlin

OK Paul one other thing to consider I had a high idle on my 88 after replacing a few things such as the cracked plastic connectors on the MAF boot,
I got the MAF rebuilt this cured the hi idle, maybe this is a cause that needs to be investigated

DR

A few years ago a made a "gadget" for those that had problems with the Elbow coming off the MAF (either end) with higher boost levels on a CS SC or Turbo. This caused a lot of high idle and other issues, Pretty sure Tim solved that a while back, so I only made a few for those by request years ago and never publicly released it as a product. Product Code name was "MAF-LOK" :-)

BUT, if you have an older CS system and suffer from the elbow getting loose or even popping off, this may give you a few ideas to fix it for good. These are pics of the first rough prototype, but you will get the idea.

OH, I do still have a stack of the machined MAF adapters seen below, if anyone wants one cheap, hit me up at SITM.

Tampa 928s

Will this work on an 86?

DR

The top part as is for sure, the lower part would need to be changed some.

SQLGuy

Hi Stan,

Are you saying that, coincidentally with your replacing things that were aged but working OK, the MAF went bad? I had perfect idle before, so the MAF was apparently OK before. Judging by the sealant around the plastic, I think this MAF was rebuilt at some time in the past as well.

Do you know what the whole process was with your MAF causing high idle? Was the LH adding air through the ISV to make up for what it thought was too little air through the MAF? The S/C kit includes a little metal donut to alter the air metering through the MAF, but other kit owners have not had problems with this, so I wouldn't expect it to be the cause of my problem.

What's the idle supposed to be like in limp mode? Maybe I'll try with the MAF disconnected to see what happens.

Thanks,
Paul

SQLGuy

Hi David,

On the kit version I have, the upper elbow is aluminum and has a turnbuckle link to hold it down to the DS fuel damper. The other side is held down by a big hose clamp around the inlet tube and the fuel hard line.

There is no O-ring on the upper tube. The machined lip is actually a very close fit, and, I guess the other idea is that any leakage is overpressure blowing clean air out, so it's not a risk for getting dirt into the system. Also, being upstream from the MAF, leakage there would not be metered.

From what I can see, the MAF is held quite flush down into the bottom elbow. The link and clamp are tight enough that the upper elbow can't lift, but not really putting any pressure on the parts below.

Thanks,
Paul

DR

Yes, but due to being so close to the MAF "element" the turbulance caused by any leaks at the entrance to the MAF will/can do funny things to your MAF signals....some have even had to orient(rotate) their MAFs to eliminate similar issues because of the way the inside of the MAF element and it's "support arm" is made and how it reacts to the air coming in from that elbow.

SQLGuy

Well, I added a bunch of wires to the back of the LH connector and brought them out in a bundle to the plug for the SSI-4. Among them I have:

the Idle switch status, which is logging correctly,
the injector signal, which the SSI-4 seems to have a problem with - it's stuck on 100%
several other signals
and the ISV signal

For the ISV, i was surprised to find that I apparently cannot log duty cycle on channels 3 or 4. However, my trusty Fluke read it easily. At idle, it's sticking pretty close to 40%. This sounds to me like the LH is actively maintaining the high idle. Thoughts?

Later, or tomorrow, I'll do a road test and try to log some additional data.

Thanks,
Paul

victor25

Paul
Pinch off the tube/hose that goes from the maf boot on the drivers side that connects to the main vacuum hose that supports the brake booster. Not the hose comming from the side of the intake, but the hose going down to the boot and I'll bet your high idle goes away. On boosted cars there is a lot of air being pushed through that hose to the intake, instead of it trying to be drawn through, the result is extra air and a high idle.

SQLGuy

Hi Victor,

I tried that, but it didn't make any difference. I then changed my logging wiring to pick up RPM, ISV duty cycle, Idle switch state, and MAF voltage. When I went to restart the car, it died, same a second time. I then started it with my foot on the throttle, and when I let off the idle dropped quite a bit. Currently the car is idle hunting, between 580 and 820, rather than sitting high and stead at 1K. Nothing mechanical changed, and the only electronic change was the 20K Ohm load on the MAF and the change in which other signals I was monitoring with the SSI-4.

I am stumped.