RPMs drop and surge when decelerating

Snunicycler

Test Drive
Location
okc
I havethis weird issue that sometimes presents itself (more often in the cold) overthe last few weeks. I'll be accelerating a bit, and then i'll let off the gas to decelerate and my RPMs will drop very quickly, then spike back up for a split second, thencome back down. Sometimes braking will cause it, other times it just does it onit's own. It didn't really do it much over the weekend but this morning (much colder) it was doing it again. [/FONT][FONT=&quot]
After searching around a bit, I found a few possibilities but I'm leaning towards vacuum leak (maybe?). Recently I had my driver's side Valve cover gasketreplaced, new gasket on intake plenum, and the mechanic cleaned my throttlebody because he said it was pretty gunked up. Ever since then I've had a muchhigher idle (1200-1400 in park when engine is warm, ~950 in drive) and fueleconomy has been suffering a bit.

Does vacuum leak sound like what I should be checking for? If so, is theresomething I should be checking that the mechanic may have damaged while workingon and around the throttle and intake plenum?

2004 XE 4x4 3.3 Naturally Aspirated BTW
Thanks!

EDITED TO ADD: also should mention that i do not currently have any SES codes and I guess I should also mention other things I've found while searching. do any of these sound like they could be the problem instead?

1) Idle air control valve?
2) Throttle Position Sensor?
3) Mass Air Flow Sensor? (I cleaned this when I did my resonator delete a few months ago, no problems until now but I could clean it again if you think I need to)
4) Is there a Idle Relearn procedure (either DIY or @ Dealer) I keep seeing mention of it but can't find anything about it on a 1st gen

Any of that sound more plausible? Also, I wouldn't mind replacing some vacuum hoses since the truck is like, 12 years old at this point, but I don't know which ones to replace is there a list or diagram somewhere that shows all the vacuum hoses?

Thanks!
 
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Joey

First Fill-Up (of many)
Location
Indianapolis
Check the rubber air intake hose. They tend to crack on the bottom and the mass air can not get the fuel air right. This sounds like a classic case. When you let off the Throttle the motor position changes a bit and allows air in thur the crack.
 

bm2004x

Test Drive
Location
United States
I also get this once and a while and have cleaned my intake and TB recently (like 3-5 months). I had a higher RPM and bad fuel mileage for a period of time and also had some surges when sitting idle at a red light. I dont have them too often but once in a while it happens when cold. I dont get the RPM surges on deceleration or i think i dont? Would a torque converter be a possibility of that? Locking and unlocking when dropping gears?

Also an 04 3.3 non supercharged 4x4 auto. 166,000 miles approx. No CEL's and no issues besides some vibrations at 25mph which im chasing down.
 

Rreed

Test Drive
I also get this once and a while and have cleaned my intake and TB recently (like 3-5 months). I had a higher RPM and bad fuel mileage for a period of time and also had some surges when sitting idle at a red light. I dont have them too often but once in a while it happens when cold. I dont get the RPM surges on deceleration or i think i dont? Would a torque converter be a possibility of that? Locking and unlocking when dropping gears?

Also an 04 3.3 non supercharged 4x4 auto. 166,000 miles approx. No CEL's and no issues besides some vibrations at 25mph which im chasing down.


Hi I am having this issue as well. Did either of y’all figure something out?
 

Mike.F

Test Drive
Just to share, I can only get 86% of full throttle when I use tourqe to monitor the rpms, so I decided to adjust my tps, and now I have a surge when I let off the gas. Its exactly as you describe. I didn't have it until I adjusted the tps, so maybe starting there would be good. I can put mine back where it was, and have no doubt it will take the surge away... ill post back once I do.
 
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