I am experiencing very bad idle surge (the idle will go from ~800 rpm to 200 rpm and back again and so on)--It will occasionally go just above 1000 rpm then back down again, but it does not go above that except when warming up after startup. I can also occasionally hear and feel a vibration/buzzing in the steering wheel/pedals when the idle surge happens, especially if it gets close to ~1000 rpms when it is surging. I don't know what this is.

At first a vacuum leak was suspected, but after receiving a new Cosworth plenum from Cosworth USA, there does not seem to be any vacuum leaks. Also, my tuner noticed that when the wires from the map sensor that connected to the fcon were pulled, it would idle surge; he did some work to the connections to ensure they were not pulling. He also noticed that when the belts were tightened, the idle surge would go away, but after running awile it would come back.

I have a CAMP2 setup that displays various values, including throttle% (i believe this is based on voltage). One thing I noticed was that when I originally had the SC installed (1.5 years ago), throttle performance was great and the % would indicate 100% when the pedal was pressed all the way down (wot). Lighltly pressing the throttle used to give great response and the % seems accurate. Now, however, it will usually only indicate ~93%, and only occasionally 99 or 100% in 1st gear. In later gears, when moving, and I press the pedal down all the way, even for extended period of time, the highest it will read is usually ~70%, it will not go above that at all, it usually gradually goes down even with the pedal still pushed down all the way. Throttle response does not seem good other than in 1st gear. I'm not sure if throttle is supposed to open up 100% in later gears when the pedal is pressed all the way down, but the CAMP2 display shows no where close to that.

I am not throwing any codes and the car has not gone into limp mode. This is what is puzzling me. I am working on the possible belt slip issue by going back to the stock SC pulley, but am thinking there may be something wrong with the throttle body itself? I have read that the throttle body may get dirty from blow by and such and can cause the plate to get "sticky", causing it to not fully close at idle--causing idle surge--maybe it can prevent the plate from opening up 100% as well? I do remember having some blow by issues before I changed the pcv and rerouted my catch can setup.

I do remember that when I had ~6k miles, I threw a tps code. The throttle body was changed/warrantied by the dealer. I now have ~26,000 miles, but am wondering if I am having an issues with the throttle body itself or any of the sensors. Specifically I am wondering if the idle control valve (attached to the throttle body) is going/has gone bad, or there may be a malfunction in the throttle plate. There may also be gunk on the plate or in the body that may be causing some of these issues as well. Again, I am not throwing any codes or going into limp mode, but I'm not sure that means nothing is wrong. Throttle response seems hesitant/slightly muted in higher gears and the throttle% readout seems much lower than it should/used to be.

I am thinking of either:
1. Attempting to clean the throttle body and plate on the car with CRC tb cleaner and cleaning the maf, or
2. Purchasing and swapping in a brand new (remanufactured tb from Infiniti/NIssan for ~$200) to ensure all parts are up to snuff. Obviously option 1 would be cheaper, but it would not ensure that the sensore/idle control valve are fully functioning. I am unsure if I should datalog to see if it shows anything abnormal.

Any thoughts or suggestions would be appreciated.

 

Did you do all the re-learn procedures?

 

^yes, no luck.

 

What EMS? With the Haltech, setting copy through timing for the idle area of the timing map gets rid of the idle hunting issue. I see CAMP2, so I presume FCON. You may want to contact your tuner to see if some adjustments are needed.

There is a throttle position learning procedure, accelerator pedal position learning, and idle air volume learning - all occurs with just a few key on/off I believe but I have not done this in a while - check FSM?

 

fcon vpro and uprev reflash. Tuner says he has done everything on the tuning side to try to correct the issue. Still no luck. He suspects loose belts/belt slip is causing the idle surge.

I still am wondering if it is normal if you punch the gas pedal down in a higher gear like 3rd,4th,5th,6th, if the throttle only reads 60-80% and not 100%?

I've done all the reset procedures. Sometimes the idle is fine, but most of the time it will hunt.

 

Try the pedal relearn to fix the not going to 100% issue. I believe it's the same procedure as doing the gas-pedal ECU reset.

 

Yeah if the re-learn isn't working then you should just try a new TB.

 

The throttle opening is not based on what gear you're in, it's based on mph and rpm. I think it's 40 mph before it goes 100% then it starts to close at 500 below redline.

 

your TPS voltage should always read 100% when its fully floored. there's a problem right there. If its related to your surging ?

 

Yea, that's what I was thinking, as throttle response seems muted in higher gears and tps voltage indicates no where near 100% when fully floored in 3-6th gear, but 1st gear opens up 100%

I'm not sure if a dirty tb or belt slip could cause tps voltage not to read 100% when fully floored, or if such a problem is related to the sensors going out of sync/going bad. I'm just at a loss of why I am not throwing any codes and voltage seems accurate in 1st gear, but not in any other gear...

While cleaning the tb may be the cheapest way to to try to resolve the issue, buying and swapping in a new remanufactued throttle body may be the most timely and accurate way of knowing if my issue is being caused by a bad tb..

The only other thing I can think of is I have in place a Motordyne Copper Throttle Body heater that was installed 4 years ago. Could this somehow go bad or not be good in FI applications (I don't see how it could)?

 

The only other thing I can think of is I have in place a Motordyne Copper Throttle Body heater that was installed 4 years ago. Could this somehow go bad or not be good in FI applications (I don't see how it could)?
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Shouldn't make a bit of difference. It's just a copper plate with a dead end tube for your coolant line.

 

One strange thing that just happened, is I I turned the key to the "on" position without turning the engine on (2 clicks over) and floored the gas pedal, while looking at the CAMP2 throttle readout, it would not indicate any throttle%--it would stay at zero and while in the cabin, I could hear a constant ticking coming from the throttle body area in the engine bay. When I would put the ignition one to left "acc", the throttle% would jump and down, with no pedal input, similar to what is should have done, when I pressed the pedal down in "on". Very weird....

 

That's normal. You cannot start the car with the peddle fully pressed.

 

But the engine was not on. I've done it before and the throtlle % would read, but now it won't and just a clicking/ticking sound from tb area

 

u have to be in gear to see TPS voltage, the noises are normal

 

Ok, that makes sense. I just did that. In every gear when I floor it with the engine off, the Throttle readout shows 99%.

But when driving and romping on the pedal, 1st will show up to 99-100%, but 2nd will see ~80-90% max, 3rd/4th will show ~75-85% max, 5th/6th will show 70% max. Also in the higher gears, when the pedal is still floored and the car is accelerating, the throttle % will decrease, it will not stay open at the max % it initially showed.

Could it be a tuning issue, or a faulty/dirty tb? Or is this normal behaviour?

I'm on the fence whether to buy a new tb or not..

 

i know for sure that in 3rd gear, I saw 100% TPS, becuase I did all my street logs/tuning on my UTEC with 3rd gear pulls.