Need Help Solving This

[gmcyukondriver]

Ok, so I'll basically give you all what this thing is doing, any suggestions or tips would be great.
Basically, it starts and drives just fine, but after driving for about 5 minutes, the engine starts running strange. I notice it the most when I hit the brakes to stop, the engine surges a little. After that, it idles at 1000 stopped in Drive, won't shift from first to second until about 3000 RPM. When it does shift, I have to get off the gas and let it roll into 2nd, otherwise it pounds into gear pretty hard. In park, it idles at about 1500. It hasn't died, and if it has time to cool down, it starts the cycle all over again, running fine at first then going bad. I've recently replaced my throttle body gasket and IAC valve, so I'm pretty sure it's not either of those.
Any suggestions would be awesome, I'd rather not have to pay to take it to a mechanic to diagnose.

Also, quick question. I have the K&N FIPK intake, and I was told that I should have a PCV valve in the hose running from the valve covers to the back of the intake above the throttle body, but I didn't see that anywhere in the installation, so do I need it or not?
Thanks guys!

 

[71 cuda man]

sounds like more than one problem the high idle sounds like a vaccum leak get engine to normal operation temp then spray some soapy water around intake & all vac hoses.Look for bubbles ,an old windex spray bottle works great for this,if you don't find any leaks then check the brake boaster.Hope this helps

 

[gmcyukondriver]

I actually just got some carb cleaner, gonna spray that around and see if I get anything. It's most likely one problem. For example, if it's the IAC, then it would cause more air going in, higher idle, and later shifts. I've had that before. One time, it was actually a piece of my K&N CAI intake gasket on top of the throttle body getting sucked into a bleeder hole for the IAC, blocking off air. That was a pain to find. I'll let you guys know when I figure it out.

BTW, if it was the brake booster, wouldn't it only have issues when the brakes are applied, or at least it would have some effect?

 

[gmcyukondriver]

Alright, new piece to the puzzle. I'm getting pretty mad at this stupid thing, so if I can't get it next go round, I'm just gonna take it in. Anyways, still doing all the same stuff, only after warming up though, so after about 5 minutes of driving.
Took my IAC out (which is only a month old), and sprayed out the inside of the throttle body with some carb cleaner, got lots of dirt and crud out. IAC looked fine, but I couldn't watch it move, since I didn't have anyone there to turn on the ignition. However, it was idling funny, then I slammed the hood shut, and it returned to normal. Didn't shut it off, drove it around the block, came back. Idling funny again, got out, popped the hood, slammed it. Same thing, returned to normal for a little bit. Not sure if it's just a coincidence, but it happened 4 or 5 times. Gonna check the IAC movement, intake gasket, and try to get a voltage test on my Throttle Position Sensor, after that, I have no idea, and will just take it in to get fixed.

 

[gmcyukondriver]

Ok, Throttle Position Sensor. Sprayed carb cleaner, checked for vacuum leaks, nothin. Took it in to my mechanic, he popped his computer on there and had it diagnosed within 20 minutes. Sensor was reading 25% when I wasn't on the throttle, so it thought I was 1/4 on the gas when I wasn't. Fun stuff. Anyways, easy fix, should have it back tomorrow. Also, not really somthing you can test without the big fancy computer, at least no way that I know of. Just wanted to let you all know what it was.

 

[gmcyukondriver]

Ok, I know I'm making a thread all by myself, but whatever, this might help someone else later. Mechanic said they replaced the TPS, and still didn't get it. He said it runs on a 5v circuit, and that when not on the throttle, it should read 5v on one side of the sensor, and 0v on the other, then it will shift as the pedal is pushed down. Anyways, it was reading 2v on the side that should read 0v. So it's getting voltage somewhere else. He said they played with the wires and cleaned the grounds, and now it's been running fine for a long time. But if it starts up again, it could be either the computer, or the Coolant Sensor, which is on the same circuit. Or it could be two wires rubbing together. Fun stuff. I hate engine electrical. Oh well, at least it's narrowed down in case it comes back.

 

[71 cuda man]

Ok you slam hood shut & engine smooths out? Check your ground wires there is a loose or corroded connection somewhere.I start at the ground to the hood & work down