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Hey guys, I have a problem, after a maintenance on the intake manifold gasket that was leaking, we had to remove sensors and the distributor, my car is a 98 Vortec 4.3 and it is running full, strong and without fail, but its idle it used to be at 550 rpm now it is at 1000 rpm and it doesn’t go out of it... and the consumption and the smell of gasoline outside the car has never been so great... I realized in the scanner that the ignition advance is at -16º and it stayed a while the -19º at idle... does anyone have any light for me?! thanks!
Last edited by victornetto; 04-24-2020 at 03:41 PM.
the first picture before maintenance, idle and the oil pressure ok, in the second picture the oil pressure is only on that marker and the idle is irregular (I'm currently using 15w30)
One cause of high idle can be unmetered air, or air that is entering after the MAF. This can be a gasket leak, a vacuum line leak, etc. Fuel trims can help you diagnose this. Another cause could be the throttle body being dirty. Another is the TPS. That should get you started, report back and we can go from there.
Hey George, thanks for the reply, well, the throttle body before doing maintenance was really, really dirty, now it’s clean, when I remove the part that goes over the throttle body the rpm of the car is between 500-700 the car is apparently failing cylinder but it doesn’t get to die, I can hear it injecting more gas... when I step on the brake pedal several times and it gets hard at the car´s rpm it gets up to 100 and then it decreases those 100 rpm more, how can I test if it has air coming in after the MAF?! and how can I test the TPS sensor?! Thanks!!
It sounds like you may have a vacuum leak. You can do a few different things:
Look at fuel trims in live data on a scanner and compare the values at idle with the values at 2500rpm. If the values are excessive positive fuel trims at idle that get much better at 2500rpm then you probably have a vacuum leak. You can also use a water spray bottle in the engine compartment around all vacuum hoses, gaskets etc while the engine is running to see if the rpm changes to identify a vacuum leak. You can also use an old school vacuum gauge.
For the throttle position sensor (TPS) you watch the value in live data as you press the accelerator pedal back and forth through the full range of motion with the key on but the engine off to see if the values make sense.
All right, I will do this as soon as possible, thanks for the tips George, they are being very important to me, I appreciate that. I don't know if this is related or not, but when I put the car in drive or reverse the rpm is 800 or even 600!! When i'm driving, without accelerating the car the rpm is at 1000-1200, just when i totally stop the car it goes back to 600-800 rpm, i didn't know where else to look for what could be the problem, thanks again George, my first step will be to check what you told me! As soon as I get results I'll post them here!
Wow thank you, GM was amazing for me at that time, at the same time several models of the same car being manufactured around the world and all models have their respect. Ya I’m trying to fix this problem on my blazer, but I believe that with the help of all of you I’m close to solving this problem!!
04-24-2020 | 03:38 PM
Help with my 4.3 Vortec 98 Idle
