Azaka

Right now my idle when warm is up around 1350-1400rpm. When the car is cold the idle is around 1000 rpm which seems like an intake leak, but I can't hear or find one. I have an Apex'I PFC but when I put it in the idle jumps even higher (around 3000rpm).

Also if I floor it in 2nd around 5000 rpms the car starts to jerk and hesitate like crazy. I had the stock turbos upgraded recently and sometimes under full throttle they jump to 15psi and often up to 12-13psi.

In the workshop manual the only things that should produce my symptoms should throw codes. But there aren't any codes to read.

Anyone ever heard of anything like this? I am pretty stumped and no one I've talked to really knows what to do.

BoOsTin FD

I had similar problem, It turned out to be PCV valve hose. If you don't know where it's at. Check the hose coming from the oil filler neck to the Upperi intake manifold. It's right next to the pressure chamber. There is a small pcv valve in between. That hose was broken on my car, causing huge leak and idle was at around 3k.

InsaneGideon

I don't have a PFC myself, but doesn't it log knock and A/F ratio?

If so, see if you're hitting a lean spot in that RPM range.

Azaka

I can't keep the PFC in long enough to drive it because my idle problem is even worse with it in. The idle is around 3000 rpms with the PFC in. I'd like to fix the idle problem first because with the PFC I should be able to fix the hesitation problem.

twint78

ur jerking is from a lack of fuel.i know cuz ive been through it with a the rx7,racebikes,and empty gas tanks.

RX7SpiritR

iTrader: (1)

Azaka

I was riding around for a about 15 minutes and the check engine light came on. Came back and checked the code and it was throwing code 17 (Feedback System). Under that there are a lot of things that could be wrong. Air intake leak, fuel leakage at injector, fuel pressure.....


Any thoughts with this new information?

keynote22

my car did the same thing. Turned out to be a hose fell off the vacuum chamber.

Are you loosing boost at the same time? If you are, you need to start checking hoses. If not, then you have a fuel issue.

My PFC cold start idles at 3k as well. Once you have had it in for a while it should begin to idle at 2.5k. Idle is tied into the cold start assist system..hose on the back of the uim manifold elbow. If you have a greddy elbow, the hose is disconnected. Make sure it is plugged.

keynote22

if you havn't had your pfc tuned, it will have to learn your car. This is evident by the reving "warm" idle. I was told by the company that put in my base map not to hammer the car until the revs started to leveled out a bit. Due to my driving style, this took about 1 week or 5 hours of driving. Now the reving "warm" idle only lasts a few seconds and only .5k movement.

The idea is that the pfc does not know "exactly" what it is supposed to be doing until it learns your car and your driving style. So, under full throttle...it's still on the base map which might not be good enough. Depending on who put in your base map, they may have gotten the map close to your mod list...or they might not have. Either way the map will need to be tweeked. This "break in" period for the pfc might be bs, might not. But it makes sense to me and could explain fuel issues under full throttle.

Check the injector duty on your commander to see if you are geting enough fuel.

Azaka

I understand that the PFC will need to learn my car, but why would it idle that high with the stock computer? I have an S-AFC also, and when I increased the fuel the idle lowered but it never went all the way down to normal before the fuel was too much and the car was bogging like crazy and on the brink of shutting off.


^I'm not losing any boost. Are you saying that your car cold start idles at 2.5k now or idles warm at 2.5k?

keynote22

Is your cold start assits line plugged? If it is not hooked back into the uim elbow, it would cause your car to idle high with both the stock ecu and the apexi.

My car idled at 3k cold until I plugged the cold start line. Now it idles at 2.5k cold. It takes a long time to fully warm up and drop the idle down to 1k'ish. Probably around 15 minutes of driving.


My car never idled at 900. I think your idle is in the normal range and you have a vacuum leak messing up your turbo change over. Your duty cycle will tell you if you have a fuel issue.

Azaka

When cold it idles around 3k then warm it drops down so I don't think that it's the cold assist line.

Yesterday I put in the PFC and drove the car around and just riding around with no boost and little throttle the knock sensor was getting activity. When I gave it some gas and let the turbos spool the knock sensor read as high as 50 at less than 5 lbs of boost. That doesn't seem right. At idle the PFC is advancing the timing by 32°. If I blip the gas the PFC retards it by up to -40°. Does it sound like the PFC needs to be reconfigured with a base map?

The guy that built my engine says that my idle is too high. When we were messing with the AFC increasing the fuel by 35-40% made the idle sound right even thought the revs were around 1050. My car has a streetport so I know it's not going to idle at 850 (or whatever normal stock is) but it's definitely too high at 1400 (and it used to idle around 1300 but it keeps getting higher).

Azaka

Got the new o2 sensor in. The idle is down about 200 rpms when warm from what it was (prolly 1200). When cold the idle sounds perfect for a street port and is prolly around 1000rpms. The extreme hesitation is gone under full throttle but there is still a little jerking under full throttle when boosting (I'm thinking because under full throttle the turbos are boosting too high for the stock ecu (11-12 psi)). The computer is still throwing the same code though (at least I think it is because I don't have the reader anymore).

Any new thoughts or ideas?

911GT2

It sounds like very similar symptoms to what I had before I got my PFC tuned. I don't know exactly what Steve did, but after he tuned my car the idle is smooth at around 950 rpms, power delivery is smooth, and knock reading on PFC stays low.

So my thought is: your car needs some tuning.

Azaka

Was your car throwing codes? I want to make sure there is nothing wrong with the car before putting on the PFC since it doesn't throw codes. I can't figure out why it's throwing this code either (17 (Feedback System)).



Also, what AFR did he tune your car to?

blackscorpio

The jerking could be from you running too rich, you may need to adjust your maps.

Azaka

Right now, I'm not even using the PFC, just the stock computer.