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Discussion Starter · #1 ·
First off... 97 xtra cab zr2 4.3 5 speed.... Started out as my rpms didn't want to drop when I pressed in the clutch to shift gears, was staying around 2000 or so. So I had a ses light anyway so I took into my buddy's shop. He read the codes and got an iac and an o2 code. No problem. Got all 3 o2's and a new iac valve. Installed and did a drive cycle as recommended which was driving at 40 mph for a few miles so the new iac could learn. Since then the rpms have gotten worse... Now it sticks at 3000 plus rpms and won't go down unless I press the brake pedal down to the floor!!! I'm not kidding, that's the only way to get them to drop!!! Hitting the gas just makes it worse!! The bad thing is that it doesn't do it all the time, about 70% of a 7 mile city driving trip( the drive to work). I went out and got a full quality tune up kit... Plugs, wires, cap, and button. Runs better but still no change with the rpm issue. We even went as far as disconnecting the cruise control to see if that had something to do with it, lol!!! My buddy, 2 of his good techs, and myself are out of ideas.... We are gonna do some vacuum testing tomorrow and see what we can come up with but other than that, we are at a wall... Please someone chime in and say you have heard of this problem before, lol!!! This is my daily driver because my srt8 charger is at arrington performance in va getting dyno tuned till god knows when....... HELP!!! Also, I forgot to mention that while driving, if I let off the gas the truck will hold its speed as if the cruise is on but the cruise is not hooked up at the moment.... Kinda unsafe, ya know??
 

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try disconnecting and plugging the vac hose to the brake booster
to see if that has any effect. could be a leak in the booster.
 

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Discussion Starter · #3 ·
Damn. That's what I was scared of.... 10 views and no replies..... I was doin some googlin' and found maybe throttle body gasket, vaccum leak,fuel filter...... Gonna do a carb cleaner spray test and vaccum test tomorrow and see what happens I guess....
 

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Discussion Starter · #4 ·
try disconnecting and plugging the vac hose to the brake booster
to see if that has any effect. could be a leak in the booster.


Actually did that as well and there was no change. When we unplugged the line from the booster it was sucking really strong. I would hit the gas and it would jump to 3000 rpms then mash the brake pedal to the floor and it would go back down to normal. Thumb on and off the line. Confusing the hell out of us. The guys are good I took it too but not great... Backyard country shop. My buddy I'm taking to tomorrow is "The Man'' at a dodge dealership. He was pissed I didn't bring it to him first, lol!!! I will certainly post up what he finds or doesn't find
 

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Discussion Starter · #6 ·
We got the po500 code for a vehicle speed sensor on the tranny... Gonna get one of those tomorrow along with a fuel filter, PVC valve and exchange my new iac I just got for another and prolly change out my throttle blade with another one from the junkyard. I did do the throttle blade mod a few weeks ago but it was doing this before I did that mod. If that stuff don't fix it. It has to be vaccum..... We ran out of time and were not able to check...
 
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