[Gmecm] SER# 1227747 ACSU promID Idle Problems
Programmer
lwester
Fri Dec 8 00:38:12 UTC 2006
Diagnose from the latest calibration first...but your "0" IAC count is
definitely indicating unmetered or uncontrolled air.
Lyndon.
----- Original Message -----
From: "Dave Thomas" <Dave.Thomas at us.festo.com>
To: <gmecm at diy-efi.org>
Sent: Thursday, December 07, 2006 8:41 AM
Subject: Re: [Gmecm] SER# 1227747 ACSU promID Idle Problems
> PCV Valve - Brand new from GM
> EGR Valve - Brand new from GM ( I also tried removing the vacuum hose and
> plugging the vac hose to eliminate the switch leaking)
> I plan on checking the fuel pressure, exhaust backpressure and install new
> AMUR prom. I am going to try to reset the min. air at idle, and I have
> diacom that I will try to record some data. I also plan on rechecking the
> MAP sensor and test the vacuum with a pressure gauge to see if there are
> any inconsistencies.
>
> I have not replaced the fuel pressure regulator, but I would expect the
> fuel pressure test should show any problems with it.
>
> Thanks for your suggestions,
>
> David Thomas
> Food & Packaging SBD Engineer
> Festo Corporation
> Phone: (704) 527-1427
> Fax: (704) 527-7935
> email: dave.thomas at us.festo.com
>
>
>
>
>
>
>
> "Programmer" <lwester at lincsat.com>
> 12/07/2006 10:30 AM
>
>
>
>
> Sent by:
>
> gmecm-bounces at diy-efi.org 12/07/2006 10:26 AM
>
> Please respond to
> gmecm at diy-efi.org
>
> |--+------------------------>
> | | |
> |--+------------------------>
>
> >-----------------------------------------------------------------------------------------------------------------------------------------|
> |
> |
> |
> |
> |
> To|
> | <gmecm at diy-efi.org>
> |
> |
> cc|
> |
> |
> |
> Subject|
> | Re: [Gmecm] SER# 1227747 ACSU promID Idle Problems
> |
> |
> |
> |
> |
> |
> |
> |
> |
> |
> |
>
> >-----------------------------------------------------------------------------------------------------------------------------------------|
>
>
>
>
> PCV valve correct ?
> EGR leaking ? (IS this the correct EGR valve from GM ?)
> The updated PROM ACSU to AKAJ to AMUR had several related TSB's ...and
> these
> updates fixed those concerns.
> TSB 88-180-6E AKAJ
> TSB 88-T-109
> TSB 88-T-25
> TSB 88-87-657-109
> TSB 88-88-657-108AMUR
>
> Lyndon.
>
> ----- Original Message -----
> From: "Dave Thomas" <Dave.Thomas at us.festo.com>
> To: <gmecm at diy-efi.org>
> Sent: Tuesday, December 05, 2006 6:34 AM
> Subject: [Gmecm] SER# 1227747 ACSU promID Idle Problems
>
>
>>
>>
>>
>> I have a 1987 GMC V1500 4WD truck with a 700R4 transmission. The Prom ID
>> is ACSU. I have replaced the original engine with a GM Factory Crate
>> Replacement for VIN K engines. All stock except for an Edelbrock
> EDL-3704
>> manifold. I am having some problems with the idling of the engine and
>> stalling when put into gear. I have noticed on a cold start that
>> everything seems to be fine with the exception of BLM of ~154. As the
>> unit
>> warms up to temperature, I notice the engine will start to reduce the
> idle
>> speed trying for a idle speed of ~625 rpm. At this point the IAC counts
>> are hovering around 40 counts. When I put the truck in gear, the IAC
>> counts start reducing along with the rpms until the rpm reaches ~525. At
>> this point, the IAC counts are usually at 0. When the vehicle is shifted
>> back into park or neutral, the idle will raise back up but the IAC counts
>> will remain at 0. When the vehicle is put into gear the second time, the
>> engine will stall and die. I have tried setting the minimum Idle on the
>> throttle body to allow the IAC to remain open, however 3-5 counts is the
>> best I have ever achieved but this did not correct the stalling. Also, I
>> have tried the service procedure for checking minimum idle air at 425
> rpms
>> in gear with the IAC unplugged. I cannot achieve this number without the
>> vehicle stalling. I have sprayed TBI cleaner around the intake manifold,
>> tbi gakset, all vacuum connections and I have not seen the idle raise
>> showing a vacuum leak. Also, after stalling the vehicle is very hard to
>> start and keep running unless you rev the engine up above 1500 rpm and
> let
>> of the throttle very slowly. Also, occasionally the engine will surge up
>> and down (50-100 rpms) but not too extreme.
>>
>> We replaced the rotor, cap, wires, spark plugs, knock sensor, O2 sensor,
>> new EGR valve, PCV valve, cleaned the throttle body, and all new gaskets
>> during the engine swap. The MAP sensor, throttle position sensor,
>> ignition
>> module, coil, EGR switch, are from the old engine. I have also swapped
>> the IAC motor with one that is known to be good with no change. The
>> original engine was gunked up and not allowing the oil to flow back from
>> the head, after some time of running, oil would enter the exhaust valve
>> guides on the number 7 and 8 cylinders causing the spark plugs to foul.
> I
>> haven't checked the back pressure from the exhaust system/ cat but it is
>> suspect. I also plan to check the Fuel pressure to see if the unit is
>> functioning within specifications (9-13 psi). I have ordered an updated
>> prom with the bin file AMUR which seems to be the latest eprom however I
>> don't really expect this will fix the problem.
>>
>> TPS = 0.66 volts at idle
>> Map at idle was in spec.
>>
>> Everything seems to be working fine but obviously something is not.
>>
>> Any information greatly appreciated,
>>
>> David Thomas
>> Food & Packaging SBD Engineer
>> Festo Corporation
>> Phone: (704) 527-1427
>> Fax: (704) 527-7935
>> email: dave.thomas at us.festo.com
>>
>> _______________________________________________
>> Gmecm mailing list
>> Gmecm at diy-efi.org
>> Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
>> Main WWW page: http://www.diy-efi.org/gmecm
>>
>>
>>
>> _______________________________________________
>> Gmecm mailing list
>> Gmecm at diy-efi.org
>> Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
>> Main WWW page: http://www.diy-efi.org/gmecm
>
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
> Main WWW page: http://www.diy-efi.org/gmecm
>
>
>
>
> _______________________________________________
> Gmecm mailing list
> Gmecm at diy-efi.org
> Subscribe: http://lists.diy-efi.org/mailman/listinfo/gmecm
> Main WWW page: http://www.diy-efi.org/gmecm
More information about the Gmecm
mailing list