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RPM drop

742 Views 6 Replies 3 Participants Last post by  chuckz28
I have a 2G turbo fwd auto talon stock except for Greddy RS bov. When I accelerate under partial throttle (anything under wot) when the car accelerates up to 3500 rpm it will go back down a couple hundred rpm then go back up to 3500 or so and stay there a little bit before it climbs. The car still accelerates but the rpm drops and you can feel it slow.
Everything seems fine at WOT. any Ideas. Im going to be doing another boost leak check this week to see if that may be the cause.
I havent noticed the problem before The bov install but its may have been there before. My factory 2g pos bov was leaking enough boost that the install of the greddy made a huge difference in the acceleration.
It doesnt seem to be a big deal but I thought id ask. Is this possibly even normal
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No its not normal.
It should accel smooth at part throttle all the way through 5000 rpms.
do you think it could be a boost leak or something else?
chuckz28 said:
do you think it could be a boost leak or something else?
It could be a leak but I'm thinking more as it being something else. I would do the basic maintenance first, (plugs, fuel filter, air filter etc) to see if that helps and of course check for a boost leak or vacuum leak. Usually when it all of a sudden feels slow, its knock causing timing to be pulled way back or running super rich bogging the engine down a bit. Make sure the O2 sensor works as well.

Edit: Also check you BOV install. It could be that its not holding to well since that is the one thing you changed since problem started.
this happened in my buddys maxima it is the clutch I KNOW FOR A FACT it is the clutch his went to 3200 dropped to 2900 went to 3400 and stopped then rose and did it in 1st - 4th
Did another boost leak check and all was good except for a little leak in the intercooler (would make sense with the nice dent in the side of it) Im going to have to be getting a new one soon. Plugs and wires were just changed a week before the problem. I just picked up a fuel filter so we will see how that goes.
firestarter how could it be the clutch when my car is an automatic. I dont see all the clutches in the auto doing the same thing at the same time.
After driving it more and digging around a little more it seems like I am having the bov "breathing" problem that some others have had. Right when its starting to boost it makes a wierd loud sound then the car slows a second and starts to go then the sound and it slows, etc. repetively untill I let off the gas or give it enough gas to downshift then its fine. It only does it up to about 70% throttle or so. No Im not venting and I have tried hard and soft adjustments and it doesnt seem to help much.
Oh and it only does it while driving. If I rev it in park or neutral it doesnt do it because the turbo doesnt boost much.
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Well I installed my boost guage. Come to find out all that extra power I was making and the rpm drop was all due to overboosting. Around 22 psi. Hopefully with a week of driving with that I didnt do too much damage, (stayed out of boost as much as I could). With the BOV that was able to handle the boost the stocker was leaking. I took the bov back off and put the stocker back on. Did a check on the valve with the mityvac. It was leaking vaccum through the top adjuster screw so I put on some teflon tape, but that wasnt the problem. I ran a vaccum line from the compressor housing straight to the wastegate actuator to find out that the BCS was bad. It stoped the rpm problem which was most likely fuel cut. It is still a little high around 14-15 with skipping the bcs so Im going to take a look at the wastegate itself.
I bought the car from a minor accident that I think had to do with the problem because stuff was smashed on the bcs and wastegate actuator arm.
I will keep updated with results from the wastegate inspection.
Now I need to upgrade to be able to make the power Im missing out on. It was nice spinning tires at 20mph half gas on the auto and chirping second. Oh well better safe then sorry. I still have a ways to go to get to that again.
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