2000 Dodge Dakota Vacuum System?

SOSCURE

MEMBER
2000 DODGE DAKOTA
6 CYL
2WD
AUTOMATIC
150,000 MILES

I have a number of symptoms, and I think they all started around the same time.
1) Hard starting
2) Occasional drop in RPM for a few seconds at idle
3) Hesitation at low speed and low rpm (20mph 1800 rpm
4) Poor gas mileage
5) Reduced power
6) HVAC is stuck on defrost, wont blow out of dash or by feet

I know a number of these point toward a vacuum leak, but they also could be many other things. So far I have been told: Clogged Cat, upstream O2, Down Stream O2, Mass Air Flow Sensor, Air Charge Sensor, Throttle Position Sensor, Idle Control Valve. I dont have the money or time to just shotgun sensors and parts at this. The check engine light is not on, I dont get any error codes when I try the ignition test, and I had the Autozone guys scan it and they dont get any error codes either.

Any help sure would be appreciated, thanks in advance.

5 Replies

MERLIN2021

MECHANIC
17,250 POSTS

Moer than likley it's a vacuum leak, this is indicated by the HVAC defaulting to defrost, this is by Law and happens in all cars for saftey, trace the vac line from the firewall, to the intake manifold and the check valve to the vauum reaservoir. One of these, or the controller for the A/c has a leak.

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Wednesday, October 13th, 2010 AT 10:44 PM

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Is there somewhere I can get a full diagram of the vacuum system? I am not sure where or what the check valve and vacuum reservoir look like.

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Thursday, October 14th, 2010 AT 7:03 AM

MERLIN2021

MECHANIC
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You have it on the hood already, it's pasted there by the manufacturer. A check valve is a small dic shaped plastic part that is in the vacuum line, it allows air(vac) to flow one way Thus holdin vac in the reservoir until needed during acceleration.

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Thursday, October 14th, 2010 AT 10:28 PM

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The hood on my truck has been replaced and there is no vac system diagram. I checked the disc check valve and it is operating normally. I also checked the main vac line from the engine to the brake booster and it seems to be sucking quite strong as well. My guess is the leak, if there is one, is somewhere up stream of the check valve. I also noted two canisters, one on each side of the engine, that have vac lines to them. Any idea what they are and how they can be checked? My next move will be to inspect the vacuum reservoir under the cowl.

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Friday, October 15th, 2010 AT 7:05 AM

MERLIN2021

MECHANIC
17,250 POSTS

You are looking for a single thin vacuum line from the engine that goes into the firewall, this will be the supply line, check it at the selector knob of the a/c control panel, 15-18 hg of vac should be present at this supply line, If no vac is present the line is broken, if good vacuum is present, hit the gas and raise the RPM's to 2500 or higher, and check it, if the vac drops off upon acceleration, the vacuum resevoir is no good, I will look for a diagram tonight.