RB25 High idle and cut

[1GayDrifter]

ive spent an hour searching this forum for a solution but couldnt find one so hopefully this thread will help others with the same problem in the future.

ok i got an rb25 s2 in my 98 240, starts up fine each time no problem. only thing is is that the idle is high. its at 2-2.1k another problem is in boost in the 5k rpm range it bogs. i went through all my vaccum lines and ensured there were no leaks. MAF is in good working order and i also made sure nothing was left unplugged. ive messed with the CAS and still nothing and the tps i also messed with but still wont idle right. any ideas? thanks in advance

[nyc240sx]

if your using the q45 tb u need to remove one of the springs thats used for the coolant lines that suppose to run to the tb if your using this tb you need to remove that part from it i had this issue on mine before after i remove that extra spring high idle went away

[1GayDrifter]

if your using the q45 tb u need to remove one of the springs thats used for the coolant lines that suppose to run to the tb if your using this tb you need to remove that part from it i had this issue on mine before after i remove that extra spring high idle went away


i heard something about thatg and u know what i think that may be it. could u be more specific as to which ones? im not sure which tb it is but what u said is prety helpful

[1GayDrifter]

ok idle is fine. but now when i go into boost, i have to eae into the throttle for it to pick up without cutting. could it be a bad tps? im using the q45 tps and tb

[GSXRJJordan]

ok idle is fine. but now when i go into boost, i have to eae into the throttle for it to pick up without cutting. could it be a bad tps? im using the q45 tps and tb

TPS actually doesn't have a lot to do with it, I'd check the MAF wiring and clean the actual MAF element. You could always try unplugging the TPS and running it into boost.

[OBEEWON]

Im having the exact issue except Im using stock throttle body and Z32 MAF. Using an SAFC (bad I know but temporary) The proper setting is 2 in and 4 out but it only
"works" on 2 in and 1 out. On the right setting the more throttle I give it the faster it dies.

[1GayDrifter]

TPS actually doesn't have a lot to do with it, I'd check the MAF wiring and clean the actual MAF element. You could always try unplugging the TPS and running it into boost.

im on it right now. by clean the maf do u mean the wiring or the maf itself?

Im having the exact issue except Im using stock throttle body and Z32 MAF. Using an SAFC (bad I know but temporary) The proper setting is 2 in and 4 out but it only
"works" on 2 in and 1 out. On the right setting the more throttle I give it the faster it dies.


ya get a tune lol

[1GayDrifter]

alright jordan, i did what u said. with the maf unplugged, it just bogged and died down. i drove it with the tps disconnected and it did the same thing still. im sure its not my maf cause its working properly. so it has to be the tps since it did the same thing unplugged right?

[Darius]

Have you pressure tested your charge piping to ensure that you don't have any boost leaks? I'd start there. The leak could be causing the surging idle and bogging upon boost.

[1GayDrifter]

Have you pressure tested your charge piping to ensure that you don't have any boost leaks? I'd start there. The leak could be causing the surging idle and bogging upon boost.


no sir. how do i do this presure test?

[Ghost240]

First off what are you using to judge your RPM?
Secondly, what MAF are you using
Thirdly, what spark plugs are you using and what is the gap?

And as far as the fast idle on the Q45 TB look on RB20 / RB25 / RB26 Forum: Nissan Forums and Infiniti Forums - NICOclub (http://forums.nicoclub.com/zeroforum?id=135) there for how to take care of it or google.

[1GayDrifter]

q45 tps, stock r33 maf and ngk plugs. what are they supposed to be gapped at?

[GSXRJJordan]

When you say "do the same thing" do u mean it idled high but ran Ok with the TPS unhooked or do you mean I acted the same as it did with the MAF disconnected?

Gap heat range 6 plugs to .030".

[1GayDrifter]

When you say "do the same thing" do u mean it idled high but ran Ok with the TPS unhooked or do you mean I acted the same as it did with the MAF disconnected?

Gap heat range 6 plugs to .030".



no sir, the car ran the same. maf was plugged in,. i ran and boosted the car with tps plug on and then with tps plug off and made no difference. so wouldnt that mean something is wrong with the tps? and plugs are gapped to .32

[Ghost240]

no sir, the car ran the same. maf was plugged in,. i ran and boosted the car with tps plug on and then with tps plug off and made no difference. so wouldnt that mean something is wrong with the tps? and plugs are gapped to .32

Alright well the boost issue could be because of the gap. I've had to gap my plugs down to between .022"-.025". And the hunting idle could be due to the MAF sensor. Have you tried cleaning the element? Swapping out MAFs? Check the wiring (grounds)?

[1GayDrifter]

Alright well the boost issue could be because of the gap. I've had to gap my plugs down to between .022"-.025". And the hunting idle could be due to the MAF sensor. Have you tried cleaning the element? Swapping out MAFs? Check the wiring (grounds)?


yup! maf is fine. cleaned and everything. so the gap between .022 and .32 is a big difference? and its .022 not .22?

[GSXRJJordan]

yup! maf is fine. cleaned and everything. so the gap between .022 and .32 is a big difference? and its .022 not .22?

Yes, it's thirty thousanths of an inch, not hundreths.

That gap that you're running (.032") is fine for stock boost. A gap that's too large (without proper spark energy behind it) will be evidenced by 'missing'/sputtering at high boost, not by a messy idle.

What did you clean the MAF element with?

[1GayDrifter]

Yes, it's thirty thousanths of an inch, not hundreths.

That gap that you're running (.032") is fine for stock boost. A gap that's too large (without proper spark energy behind it) will be evidenced by 'missing'/sputtering at high boost, not by a messy idle.

What did you clean the MAF element with?


i just used a cutip and some small pieces of shop towel. didnt want to risk anything. never really cleaned a maf before

[GSXRJJordan]

i just used a cutip and some small pieces of shop towel. didnt want to risk anything. never really cleaned a maf before

So you physically touched the MAF element? That's a no-no, even with something like a Q-tip. You want to use a MAF or electronic parts cleaner that does not leave a residue, and no physical contact.