Hi Everybody. Happy Thanksgiving to you all.

I am still trying to chase down these P0171 & P0174 codes that won't go away. Live data coming off the scanner shows the O2's and MAF to be working within acceptable voltage ranges so I am trying to investigate vacuum issues.

I am/was having surge issues with the cruise control. I have read that sometimes you have to "unlearn" the computer by setting the CC with the gas pedal steady, turn it of, repeat 10X. This might be a joke but I figured it wouldn't hurt.

So I got on the freeway and set it at 70, turned of the master CC switch and repeated 10X. Well it doesn't seem to be surging anymore but now, when I set it at 70, it will gradually lose speed. In about a mile or two at the most, I went from 70 to 55.

Could this be related to a vacuum leak and, if so, where should I be looking? Also, if I were to take it to a shop, how much might it be to have a smoke test done? I swear I'm gonna get this thing right as I can or die trying.

Thanks again everybody and eat a lot.

 

Have you replace all the vacuum hoses including the one at the second brake pedal.

 

No Mike. I'm a total idiot when it comes to vacuum lines...amoung many other things. Is there a diagram on the Rave showing how many and where they are? While I am an idiot, I never give up. I would rather learn this and be a bit smarter than farm it out and remain clueless.

 

Yes, the Rave has all the diagrams. If you still have problems get back to me.

 

I'm on it. Thank you.

 

If you pull the hose off your vac pump and with the engine running suck on the hose a bit, then place your tongue over the end of the hose.

You will hold the vacuum and the revs or, if you have a leak, the revs will drop.
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You may also want to check the diaphram on the cruise control actuator. I had the same symptoms on my '04 and a cable that was rubbing on the diaphram and wore a small hole in it was the culprit! Replaced the unit, rerouted the cable and all was back to normal. JF

 

Would a bad CC diaphram cause an overall vacuum leak issue? Enough to trigger the p0171 and p0174 codes I'm getting? I haven't had time to track down the vacuum leak via any of this great advice yet due to the holidays but any advice on where to look/how to look is greatly appriciated.

 

There is no vacuum hose to the brake pedal on a DII, the brake switch electrically disengages the CC. There is one hose from the CC vacuum pump(this is not engine vacuum) to the diaphragm. Where the hose attaches to the pump is near the hot exhaust manifold, and it tends to get brittle first, so check there. If the hose is good, then as previously stated, check the diaphragm on top of the bracket. These are the only two CC vacuum items that can leak and move the diaphragm\throttle cable.