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Car starts, wont stay running unless moving throttle. by Shonyman32
Started on: 02-28-2013 11:25 AM
Replies: 207 (6294 views)
Last post by: 2.5 on 11-27-2013 11:18 AM
Shonyman32
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Report this Post11-24-2013 10:54 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post
1987 Fiero. I swapped the old 2.8 that spun a bearing for a 3.1 block and crank bored .040 over. I put in a cam that had a lift of .281 - .283 on one of the lobes. (do not know if it was exhaust or intake). The block was decked the heads were gone through by my machine shop, 3 angle valve job, all valves good, all springs in check, new seals. Bottom end completely new. Crank balance and block was line bored with new cam bearings, mains, rods, piston rings. and pistons. Has all new gaskets. Had to make an oil pan gasket and water pump gasket out of RTV because they sent me the wrong gasket set.
Has a new MAP sensor, O2 sensor, CTS, IAT, IAC, TPS was checked on a potentiometer and tested good. I have sprayed propane and acetylene around the engine bay looking for a Vac. leak and didn't find any.

I taped up my entire air filter and the car continued to run but when I taped up the throttle body it didn't. I don't know if having a leak int the filter housing or the black tube is bad but I never noticed the leak with the propane and acetylene just taping everything up.

All my readings look good now on WinALDL except my BLM's to my knowledge. My BLM's are maxed out at 150. This means something is telling the computer it is running lean and to spray more fuel. At high RPM's the car runs fine but at low RPM's it stumbles. It doesn't Idle and it miss fires all the time at lower RPM's. It does run a little better once it gets warm and goes into closed loop but still not like it should by any means.
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Gall757
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Report this Post11-25-2013 09:14 AM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Are you using the original Fiero ECM and 15 lb. injectors?
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Shonyman32
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Report this Post11-25-2013 03:00 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post
I am using the original 87 ecm and 15 pound injectors out of a 91 3.1.
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Gall757
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Report this Post11-25-2013 03:23 PM Click Here to See the Profile for Gall757Send a Private Message to Gall757Edit/Delete MessageReply w/QuoteDirect Link to This Post
Your computer thinks it is feeding a 2.8, and in reality you have a 3.2. I can't say that is a problem, but other forum members should know the limits of the chip and comment.
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Shonyman32
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Report this Post11-25-2013 04:49 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post
Also the FPR is unplugged so it is running at max PSI of fuel pressure.
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Shonyman32
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Report this Post11-25-2013 04:51 PM Click Here to See the Profile for Shonyman32Send a Private Message to Shonyman32Edit/Delete MessageReply w/QuoteDirect Link to This Post

Shonyman32

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Member since Jan 2012
 
quote
Originally posted by Shonyman32:

Also the FPR is unplugged so it is running at max PSI of fuel pressure.

Also when at a lower RPM and I push the gas it acts like the accelerater pump on a carb engine is out and the rpm's fall for a second.

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armos
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Report this Post11-26-2013 12:40 PM Click Here to See the Profile for armosSend a Private Message to armosEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Shonyman32:

Also the FPR is unplugged so it is running at max PSI of fuel pressure.

Doing this will confuse the ECM. The fuel pressure regulator should maintain a constant differential versus the manifold pressure. This is to offset the changes of air pressure in the manifold, so when the ECM commands a certain injector opening, it will actually spray a consistent amount of fuel.
If you're convinced that this behavior isn't working correctly, then that should be fixed. Running at a constant fuel pressure, while manifold pressure varies, will lead to inconsistent fuel delivery.

 
quote
Also when at a lower RPM and I push the gas it acts like the accelerater pump on a carb engine is out and the rpm's fall for a second.

This could be a tuning issue. There is an "acceleration enrichment" factor which acts like the pump shot on a carburetor. When the ECM detects that the throttle has been snapped open, it sprays an amount of extra fuel which is programmed in the ECM. This factor would need to be adjusted for the change in your engine size and cam.

Elevated BLMs would result from the engine constantly needing more fuel than the ECM was programmed to assume.

I've never done a 3.2 + cam upgrade, so I don't know if the extent of your issues can all be blamed on ECM tuning, or not. It's an issue, but I don't know if it's the only one. 17lb injectors would at least crudely compensate, but retuning the ECM would still be desirable.
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2.5
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Report this Post11-27-2013 11:18 AM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Shonyman32:

Also when at a lower RPM and I push the gas it acts like the accelerater pump on a carb engine is out and the rpm's fall for a second.


I'm still wondering about the cam being too much for the rest of it, or the rest needing to be tuned to it.
But its really a guess i dont know cam numbers or requirements specifically.
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