se7en_

Interesting. I will mess with that tomorrow when my CTS is in. Thanks for taking the time to write all that out.

se7en_

Could I just raise and lower my fuel pressure?

Nikzilla

Yes

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Kingtal0n

how is raising your fuel pressure going to tell you if the maf is working? How will it tell you if the computer is adjusting fueling based on maf inputs?

how will you know if the maf is related to the source of your issue?

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

King. U always blame the MAFs.

MAFs are cute. Stop the hate! Show MAFs some love.

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Nikzilla

I reckon if the hotwire looks clean and the voltages are within spec, it's incredibly unlikely for it to be malfunctioning.

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Kingtal0n

how do you know the computer is even reading the maf? Maybe when he plugs in the maf it doesnt even get a signal from the maf- only noise.'

You cant look at the hot-wire and tell if the computer is reading it.

And it's not like this is a difficult process to test. I am not telling him to rebuild the engine, only loosen a clamp ~ 2 minutes for some critical information.
Instead of just assuming that because it looks clean that it is working.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

He could read the voltage from the ECU harness connector. This is why consult ports are nice.

Also, if it read only noise, the ECU would register a malfunction and go into safety mode. It would ignore the input, wouldn't rev past 2.5k and it would behave exactly as if it was unplugged. The fact that behavior changes with the MAF plugged in rules that out.

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Kingtal0n

voltage does not tell all when it's a Z32 maf on an sr20det, especially through a tuned ECU. What did he compare voltage to? There is no set standard, and a little change as 0.5V can be a big difference on that maf.


I think the problem is a boost leak. Maybe by playing with the couplers he will find one.
Because if there is no boost leak (what psi did you fill the plumbing to?) And all the wiring is good, that only leaves: ECU / sensors malfunction

setting aside the fuel system because it runs with the maf disconnected, and acknowledging good compression.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Nikzilla

A boost leak so large that it stalls the car would be hard miss.

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se7en_

There isn't a boost leak for sure. 10psi easy and smoke tested it as well.

se7en_

I'll check all the things listed and get back to you tonight.

se7en_

Well, I changed the coolant temp sensor for the ecu and now it idles for a few more seconds before it stalls. And it struggles to run right before it quits.

I tried to raise and lower fuel pressure by 5-20psi with not much change, ect it smells super rich when I raise fuel pressure

se7en_

I'm going to try setting the timing with a spark plug white method.

Nikzilla

This is obvious, but check grounds. I mean like religiously check them. Get a guide and find each one individually, and test for continuity between the connector and the chassis/terminal

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se7en_

I went through that already. I even sanded the paint before I bolted the grounds to the body.

se7en_

I have to double check, but I think it runs the same with the iacv unplugged as well.

se7en_

a couple things I'm going to check....

gap plugs to 0.036"
check timing with plug wire
clean iacv
clean maf
double check mechanical timing

se7en_

Ok. update.

I bought new ngk 6 heat range plugs. That helped, but still no idle.
timing was double checked and all good.(mechanical and CAS timing checked with plug wire method)
cleaned maf and iacv

Overall it seems to be better, it'll startup great everytime, then idle high for 5 seconds, then drop to 2-300 rpm and studder there for maybe 5-8 seconds then stall.

I'm sure I'm getting close here.

I turned out my IACV a few turns, but that didn't help.

Could the PROCAMS just be a little too harsh to keep this idling?

Kingtal0n

What cams did you used to have,

and what cams do you have now.

Did you ever try the boost leak idea. That could also temporarily "fix the problem" if it was related to reversion caused by the camshafts.

And I've seen instances where the wrong camshafts (solid lifter type) were sent by accident. Check your part number on the cam itself.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

se7en_

Stock cams before Tomei 260 procams now
I tried the boost leak idea as well as raising and lowering fuel pressure with no luck

Kingtal0n

If the cams are to blame, then adding air and fuel would help the engine idle. The idle might be rough because of the camshafts, have you ever had a set of real cams before?

I am not sure why you chose those camshafts. A much better option would have been S3's. Oh well now. Another possibility is some of the headwork went sour. Did you ever do a compression / leakdown test? I forgot what you had already tried.


In any case, like I just mentioned, adding air and fuel would help idle a rough camshaft. If you crack the throttle open and raise the fuel pressure, and you get a nice rough idle, that is probably how it is supposed to sound. You would then only need to adjust the IACV open more, and add fuel to the tune at idle. This is very common, for camshaft modifications to require additional air and fuel.

Have you tried driving the car? If the problem is related only to the camshafts, then the vehicle will drive pretty normal- it just will not idle without adjusting the fuel at idle (and air).

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Kingtal0n

http://www.youtube.com/watch?v=YUHZBrW7_UE


procams at idle, not sure which, but notice the engine doesn't sound smooth.


Smaller cams than yours
http://www.youtube.com/watch?v=i_nVUxmoY7E


still not smooth

tuning an idle with a rough camshaft can be an art. it depends how you want to drive the car. If you had a power FC i would modify your map real quick and show you what to try.

__________________
5.3/4l80e/turbo 240sx playthrough:
https://tinyurl.com/turbo240

Chaluska

Se7en, im having an identical problem to you, only on a recently installed KA.

have you made any progress? My car starts, and fires up to about 2300 rpms for a few seconds, then stumbles, and proceeds to die.

Throttle has no effect on the engine. i cant free-rev it to any RPM, it just dies.

does yours do this as well?

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se7en_

I can free rev mine. It seems to really try idling at like 200 rpm for quite a while before it quits, but it always stalls.

Chaluska

as a minor update to my situation, i swapped in my OE injectors / MAF and ECU, and the car fired up, and idles and revs fine.. time to dig through the MAF / ECU / injectors problem.

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