I'm stumped. open loop issue.

[crzycav86]

On my kat, I have 370cc injectors, adjustable fpr, n60(maxima) maf, and I'm using an safc for fuel management with base timing retarded to 16*.

After doing some highway pulls with some friends, the car suddenly lost power, and it would accelerate and decelerate sporadically(at a constant throttle, the car would lose power and regain it). I pulled over. The car would not idle, and it would rev with a lot of difficulty.

That was about 2 months ago. I've only checked on the car twice since then.

My first troubleshoot was to unplug the maf and see how it responded. I turned the fuel pressure down to about 22psi since the safc would not be able to lean out the a/f. After this, the car would be able to idle, free-rev, and hold revs pretty well(considering that the injectors are uncorrected). So I thought it must be a problem with the maf. I bought another n60 maf, and came home a month later to try it out.

Unfortunately, the new maf gave the same problem.... So I switched back to the stock maf - still the same problem.

I tried playing with the safc in/out settings for the n60 maf, I tried adjusting the fuel correction. i did a lot of messing around with the safc, and it didn't help. when I go back home for thanksgiving, i'm going to try reconnecting the maf without having it go through the safc. If that doesn't work, I think it might be a computer problem. If that doesn't work, I will have no more ideas.

One thing I must confess is that I have not checked the spark plugs because I was convinced that it was a maf issue. I will do that next time because spark plugs is pretty much standard procedure.

So to recap, I'm convinced that this is an open loop issue. My question is are there any sensors other than the maf that are not being used under closed loop operation?

Let me know if you guys have any advice on what to check. Remember that the car runs okay with the maf unplugged, so that narrows down the problem down quite a bit, but obviously not enough for me to take care of on my own. I am stumped. Thanks for your help.

[CleanSfourteen]

This is quite a complicated issue...

I see that you said that you put on a N60 MAF sensor, since the N60 is a 5 wire sensor you had to splice into the shielded wire that runs to the ECU...

You hinted that you thought it may be the ECU, so because those wires are shielded, even if you soldered the wires and used shrink tubing on the connection, there is still a possibility that you may be having an ECU malfunction. But before running out an buying one, i would check all of the inputs to the ECU for abnormalities, also soild core spark plug wires could maybe make enough EMI to cause strange problems, and if your motor is anything like my KA24DE then the MAFS wire runs pretty close to the distributor/ignition wires.

I would check spark plugs/ wires also, if the wires have excessive resistance then that would definitely cause the symptoms you're talking about. Normally when ECU's go, they go completely out, i doubt in that cause that unplugging the MAFS would help to correct the idle issue.

Good luck, hope its just your plugs wires...

[KATwo40]

This happened to me twice (DOHC, turbo, blah blah). Both times, it was a dirty IACV.

[crzycav86]

Thanks for your responses.

I don't think it's those issues because the car runs fine with the maf unplugged(closed loop). If it were a problem with the spark plug wires or IACV, the symptoms would be present all the time.

[CleanSfourteen]

Thanks for your responses.

I don't think it's those issues because the car runs fine with the maf unplugged(closed loop). If it were a problem with the spark plug wires or IACV, the symptoms would be present all the time.

Well if it's not electro-magnetic interference then i would assume automaticly that it's a faulty sensor, take a reading from the ECU input to see if it's within acceptable ranges. Beyond that, all you can do is check all the inputs and hope its a sensor and not your ecu...

Any MIL on??? Trouble codes present?

[WDRacing]

What are the sensor reading through the SAFC?

With the MAF unplugged it's in limp mode, which means it shouldn't rev over 2500.

Do you have a wideband?

I twist tied the MAF on my car to test it, worked fine. So I doubt its a shielding issue. I'm thinking its a matter of saving the setting correctly on the SAFC. You have to initialize the SAFC to have it store settings or it reverts back to zero correction. I did this myself for like two days and I was pissed.

Also, is your O2 hooked up, is the connection soldered at all?

WD

[C-Kwik]

Check to make sure no intake connectors came off.

[crzycav86]

What are the sensor reading through the SAFC?

With the MAF unplugged it's in limp mode, which means it shouldn't rev over 2500.

Do you have a wideband?

I twist tied the MAF on my car to test it, worked fine. So I doubt its a shielding issue. I'm thinking its a matter of saving the setting correctly on the SAFC. You have to initialize the SAFC to have it store settings or it reverts back to zero correction. I did this myself for like two days and I was pissed.

Also, is your O2 hooked up, is the connection soldered at all?

WD

i don't remember what the safc was reading. i didn't pay special attention to it aside from messing with the settings.

yeah, the engine was in limp mode w/o the maf. by "rev freely", i meant it wouldn't hesitate like it did with the maf plugged in.

i don't have a wideband anymore. but i will probably have access to one during thanksgiving.

on the safc, i never had to initialize anything after i put the maf on. the maf was working great for the month or two that it was on the car.

the o2 sensor is hooked up and was never cut.

[crzycav86]

Check to make sure no intake connectors came off.

yeah, that is definitely something i forgot to carefully look over because a boost leak would suffer these symptoms to the T.

thanks for the help guys.