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I have a chevy S10 1994 with a vortec engine. Three main problems (that may be related) are high idle, high whistling sound and I feel like I have to stand on the brakes to come to a stop. Plus if its on gravel, the idle is so high that it won’t completely stop, digs in. I’m nervous with snow on the way in PA that it really won’t stop.
Some things I notice are, the whistling will go away when I am on the gas, comes right back as soon as I let off the gas. If the truck is stopped at a light the check engine light will come on. Goes off once you start moving.
The brakes are newer and yes the back? brakes are drums but still shouldn’t have to apply so much weight to stop and to keep it stopped, feels like it wants to jump forward.
These issues may be related with a vacuum leak? If so would the leak be near the brake line?
I’m fairly handy with my way around vehicles, but not sure where to start with this one. I did change the PCV valve and ran some engine cleaner through before changing the oil and it made a noticeable difference in lengthening the time til the check engine light turns on. Plugs and wires were replaced two years ago and only have about 20,000 miles on them. Any thoughts on how to fix would be greatly appreciated!
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Lets brake this down. First the truck is lunging forward
due to the idle being High.I would search for vacuum leaks
also check that your drum brakes are adjusted correctly. what
is the vehicles base idle in park and warmed up? I would also
look at the IAC.only after confirming no vacuum leaks.Try tapping
on the IAC with the handle of a screw driver to see if the idle changes.
if it does change the IAC.Well I guess I’m on the right track since the two videos “college man” posted are the two I watched earlier. I will try to find the leak tomorrow. I also found a diagram of the location of the vacuum hose on the brake booster. Thanks for the information, glad I found this forum!
Just pull the hose off the brake booster and see if it causes a change in the idle. Hold your thumb over the end of the hose to test for the presence of vaccum. Sounds like a problem from the vaccum source for the brake booster and perhaps the booster itself.
Based on your description I would say looking for a vacuum leak at the brake booster is a great place to start. You pretty much describe that problem to a ‘T’. I think either pinching off or holding your finger over the end of the vacuum line going to the brake booster is a great test. If you find that the idle smoothes out then you might want to replace the brake booster. You don’t have to disconnect the brake lines from the master cylinder when you do this. Just leave them connected and move the master cylinder out of the way so that you can replace the booster.
Good luck and keep us posted.
You did not share with us which engine you have – a W, 4.3L, CPI by chance? I would check the vacuum line at the back of the intake plenum, close to the fire wall. Inspect the condition of this vacuum line and work your way back to the vacuum ball (hangs from the hood on your truck I think). Vacuum lines dry rot and deteriorate over time, so being a ’94 this is a good time to inspect all vacuum lines and start replacing them. The plenum hose likes to crack right at the end and you can just snip off 1/2 inch of the hose sometimes.
By chance does your switch from defrost to heat work or is it stuck in the default position – defrost.
The vacuum switch on the transfer case (assuming 4WD) is notorious for failing due to a defect. The transmission fluid from the transfer case will slowly be sucked to the A/C Heater mode control switch. Sometimes you’ll find transmission fluid in the ashtray with this problem. Can you shift into 4WD?
There is also a vacuum line that runs down the passenger side and back to the transfer case. This line can dry rot and fail too. It can easily get too close to the exhaust manifold and melt. You can hear this leak while under the front wheel well on the passenger side.
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