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Old 07-07-2010, 12:41 AM   #1
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Default Rebuilt .040 over - running like crap

I just rebuilt my motor with .040 over pistons and green NA supra injectors.
The car is running with 20-25lb vacuum.
About 15:1 afr.

Problem is it's running like crap.
It misfires now and then and if it idles long enough it will eventually stall.

Any tips on what I should be looking for?
Is it because the stock ECU can't adjust for the larger pistons and injectors?



Thanks
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Old 07-07-2010, 12:55 AM   #2
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Is it because the stock ECU can't adjust for the larger pistons and injectors?
I'd agree with above. You drive a '94, invest in a MSPNP.
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Old 07-07-2010, 01:03 AM   #3
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yeah put in the stock injectors and get it running
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Old 07-07-2010, 03:01 AM   #4
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yeah put in the stock injectors and get it running
That's what I was planning to do next. Just waiting to get some injectors from my friend's house.

The novice thing to do would be to throw parts at it. Like a MSPNP. I want to find out the reason why it's running bad before I invest money into parts.
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Old 07-07-2010, 03:43 AM   #5
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Well...in all fairness, a novice would punch out an engine, throw larger injectors in, and expect it to run well on the same tune as earlier. Just to be fair. And if you're thinking a MSPNP, and frowning at the $700 price tag, don't forget that building one yourself can be half as much.
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Old 07-07-2010, 04:25 AM   #6
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A stock ECU can handle a motor 40 over no problem.
The injectors are supposedly plug and play.
So why shouldn't I expect it to run well on the same tune?

Not frowning at the price tag. I've seen it go for $4-500 on this site but I already have a emanage.
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Old 07-07-2010, 04:50 AM   #7
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What size are the supra green tops? Are You running the emanage or the stock ecu? If they're bigger and you don't adjust anything, it'll be running super rich. I'm not sure I'd trust the 15:1 number if it won't even run long enough to idle.
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Old 07-07-2010, 05:40 AM   #8
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That 15:1 is from a wideband, right?
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Old 07-07-2010, 05:47 AM   #9
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Are those the 315cc green tops? I don't see why they wouldn't work well enough to at least run. I also don't see the .040 over messing it up much. I say your issue is elsewhere.
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Old 07-07-2010, 08:34 AM   #10
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Quote:
Originally Posted by Halcyon View Post

The novice thing to do would be to throw parts at it. Like a MSPNP.
Not such a novice thing to do when it implies that you'll will be using said part (actually more like a tool) to tune for the changes you've made.

The overbore won't affect much, which means that if these are the only two changes you've made, then the problem lies with your injectors.

If you're still on the stock ECU you are going to have to make some adjustments. Those green tops are squirting ~20% more fuel than your stockers, depending on which stockers you ran.

If you don't want to throw parts at it then you can either get new motor running on stock injectors and stop washing down the cylinder walls, or make the adjustments needed to run those bigger injectors. Are you planning on using an afpr?
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Old 07-07-2010, 11:28 AM   #11
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Get your Injectors cleaned.
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Old 07-07-2010, 02:44 PM   #12
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It's the 7MGE injectors rated at 305. They were cleaned.
It's only 15% bigger but I'll swap the stock ones back on to check.
The car will idle for quite a while but it will misfire and after about 10-15mins of idling it will stall. If I give it gas it runs fine.

Yes, I'm using a wideband.

My plan is to eventually use a mspnp but right now I'm using a bunch of piggybacks.
According to what I've read on this site everything I have on should be plug and play.
Before I jump the gun and get the mspnp I want to make sure everything else is working fine. For example, found one port on the intake manifold not capped off making it run super lean.
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Old 07-12-2010, 11:44 PM   #13
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Quote:
My plan is to eventually use a mspnp but right now I'm using a bunch of piggybacks.
According to what I've read on this site everything I have on should be plug and play.

Plug and play has several definitions.

The one i'm seeing is the one of which the use of plug and play means not having to hack up your wiring and get different connectors

my RX-7 460's are also plug and play, but I still had to change the settings on my MSPNP to run them well
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Old 07-13-2010, 11:41 AM   #14
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Should idle and run fine with those injectors, I ran 370cc's on a stock ecu for alitle bit.
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Old 07-13-2010, 11:50 AM   #15
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Wait, you're complaining about fouled plugs after 10-15 minutes of idling?!? Christ, you've obviously never worked on a carburated engine. That's going to happen with larger injectors and bandaids. When do you need to idle the car for 15 minutes anyways.
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Old 07-13-2010, 12:07 PM   #16
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Probably have a bad injector. Were they cleaned AND flowed?
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Old 08-12-2010, 06:24 PM   #17
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R U sure the timing belt was degree correctly with the cams/crankshaft to TDC?

Have you tried swapping AFM?
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Old 08-12-2010, 07:12 PM   #18
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what is your base timing set at? Have you measured your fuel pressure? I know you have a wideband but do you still have the stock 02?
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Old 08-13-2010, 04:07 AM   #19
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Quote:
Originally Posted by curly View Post
Wait, you're complaining about fouled plugs after 10-15 minutes of idling?!? Christ, you've obviously never worked on a carburated engine. That's going to happen with larger injectors and bandaids. When do you need to idle the car for 15 minutes anyways.
No one really believes carburators existed, right? A world without EFI is just a story made to scare children.

To OP: HAHAHAHAHAHAAHAHAH.

HA. HA.

Anyway. Ha. Anyway. You have crappy fuel management. You have no idea what you're doing. Get a standalone and send the car to someone to tune it, or start taking advice on what you're doing wrong.

Plug and play injectors you don't need to tune for... this could be the funniest thing i've heard all day.
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Old 08-13-2010, 04:20 AM   #20
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Sounds to me like youre reading lean because the engine is missing
probably because you fail at engine diagnostics

I suggest selling the car, buying something stock and taking up stamp collecting
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