soundlab

Good day everyone!

I'm new to this forum, and I am from the Philippines. i hope to get helpful tips and tricks and even advices from you guys.

I have a 2001 Nissan cefiro (that's what we call it here) which I believe is the counter part of the 4th gen maxima in other countries.

it has a Vq20 6cylinder engine

it's been a month now that my newly purchased used car is giving me this pain the head.

here's the problem:
I got it for a cheap price relying from what the previous owner said that there is a problem with the idling and he was told that it is the MAF that needs attention.

then I have this good friend who has a shop here in the Phil. that deals with nissans and offered to fix the issue.

here's whats going on, I got the car with a dropping Idle while the A/C is ON while on P or N but if you shift to D or R Idle is @ 900 while stepping on the break, which I felt it would still go higher. if A/C is OFF idle is around 800rpm while in P and N. if I shift to D RPM goes higher still.

I left the car to his shop and he said MAF is working IACV is good, when he check using the CONSULT he saw no reading on the TPS, zero reading and the guage I for the Open and Close throttle was erretic.

he said to me at first that It might not the TPS, because we noticed that the entire engine harness(wirings) got already tampered. after 2weeks when I told him that I need to get the car already (because I felt that they cannot fix it) he told me that the problem was the TPS. I got happy because I thought he would able to fix already.

when I got the car, Idle was A-OK! without the A/C I got 800rpm, with A/C ON I got 900 to 1000rpm (which is still kinda high) but when I shifted to D or even R I got surprised that it was a strong kick, I have noticed that even I don't step on the gas pedal the rpm rises till 1500rpm till it shift to 2nd gear with a strong shock( got it like this before bringing to the shop)

I bought a brandnew Nissan OE TPS from him and paid kinda big for the shop but still the problem wasn't solved.

afterwhich, a nearby mechanic helped me, and we had the IACV replaced because he heard mine has a ticking sound already and the idle screw is all busted, we replaced it with those japanese surplus and seems to work fine.

Idle got fix a little but still I was not contented because of the high rpm while on D.

he told me that the TPS needs to be adjusted to compensate with the high idle while on D or R but he got surprised when he moved the TPS or even unplug the 2 sockets the engine did not react.

we were thinking that it might not been the TPS all awhile, it might be the connection that has a problem since the wires got tampered already.
I have read one of the thread about high idle here that dwells with the high idle cam being adjusted, that sounds really similar with my issue but their TPS is working.

now my questions are:
- would the TPS affect the high Idle while I shift to D and R?
- could this also be the culprit of the shock everytime it shifts to 2nd gear?
- what other things should I also check?
- possible airleak issue??

hope to get help from you guys, because the forums here in the Philippines isn't a good source of problem information/


P.S
TB and MAF got cleaned already..

hornepirate

iTrader: (23)

Try another maf if you can get your hands on one one cheap try it. A lot of times when the maf starts to go it can be very difficult to tell if it is the culprit

soundlab

yeah I think I could borrow a good one from a neighbor.

any other thoughts?

njmaxseltd

iTrader: (19)

Clean the throttle body.
Set the default idle speed on the throttle body. Warm the car up to operating temp, at least 15 min of operation turn off the engine, then unplug the TPS. Restart the car, make sure headlights and all accessories are off. Set the throttle body stop screw so the idle speed is ~650 in N or P. Turn the engine off, reconnect the TPS. Start the engine and check idle speed. It should be around 700-750 in neutral. If its out of range, use the idle air bypass screw to set the correct idle speed.