I've noticed for the last 2-3 months that under part throttle I'm getting some surging during acceleration. IF I go WOT, seems smooth with no surging. Also, once its over 4k rpm, it smooths out. No codes. Here's the the things I've tried to fix:

1) Air filter Clean
2) MAF spray cleaned
3) Cleaned throttle body

I thought it maybe the TPS, but the symptoms don't quite fit. There is no dead spot in the pedal, it just surges..I can watch the RPMs climb faster then slower during acceleration without changing the position of the throttle. I'm thinking maybe its a clogged fuel filter? Maybe the sock? Don't think that's ever been changed and I'm at 185k.* Perhaps under part throttle the filter is not letting enough fuel through, but once the RPM comes up, the fuel pressure increases?

*Edit- Looks like fuel filters may have been replaced at 90k. Still that's 95k ago.

SOLVED: Changed out the fuel filter, looked somewhat dirty. Test drove... felt a bit better but still has symptoms. Decided to pull intake off to re-clean throttle body and to take a more thorough look. When I pulled the intake assembly out, I noticed the valve breather hose came off quite easy. Further inspection revealed a split in the hose right at the connection. Cut hose a bit shorter, re-installed, and viola...no more surging.

 

I would change the fuel filter. With that many miles, should be clogged already. Restricted fuel causes sudden surges

 

Search for "accelerator pedal position sensor" or "APP sensor". I (and a couple CL'rs) went through a similar ordeal a few years back and the APP sensor replacement fixed it. The ordeal is documented in a thread somewhere in this forum (2GS). The symptoms you describe don't quite match what I was experiencing, but it may be worth a shot to read up on it. I don't think most people realize the APP sensor exists. Good luck!!!

JB

 

I have the same problem, gonna check this out today

 

[QUOTE=JellyBean;6794429]Search for "accelerator pedal position sensor" or "APP sensor". I (and a couple CL'rs) went through a similar ordeal a few years back and the APP sensor replacement fixed it. The ordeal is documented in a thread somewhere in this forum (2GS). The symptoms you describe don't quite match what I was experiencing, but it may be worth a shot to read up on it. I don't think most people realize the APP sensor exists. Good luck!!!


I got 2001 IS 300 same problem, i would like to replace the APPS, is it easy to do this? just like the TPS. and where is is located?

 

i'm guessing on the actual pedal? I'll find out tomorrow...

 

I got it fixed. the APPS was actually at the left hand side of the throttle body. it took me a good 30 minutes to replaced it and everything went well. so far so good. I took it on a long drive last weekend a good 300 miles and still doing well. I think everything improved, it feels like brand new again.

 

dont go by what people say .. youll end up broke swapping out parts.. my car has similar issues.. and i been driving in limp mode for about a month... i swapped the TCM TPS and APS bout 400$ in parts.. i suggest taking it to a good indy shop and getting their opinion and take it from there. after all my problem is the ECM is bad so i have to get a diff one and reprogrammed.

 

When you changed your ecm did your key still work after you reprogrammed the used ecm?

 

Could you take a picture of said hose? I believe I'm having the same issue...

 

I think he is reffering to the fresh air side PCV which is located on the passenger side valve cover