C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

1989 strumbling when hot with no code

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Old May 30, 2007 | 08:00 AM
  #1  
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Default 1989 strumbling when hot with no code

Hi,

1st excuse for my bad english

My Vette is a 1989 AT.
When the engine is cold it's ok.
After 40miles my engine strumbles and could stall if I drive slowly.
SES is lighting when it strumbles but there is no code except 12.

As the SES is lighting, the fuel consommation is blocked (dash board indication)

I put these new parts:
-pick up coil
-fuel pump
-fuel filter
-sparks
-cool temp sensor

Thank you for your assistance
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Old May 30, 2007 | 08:45 AM
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Are you 100% sure there is no stored code ??
Do you have access to data logging laptop or scanner.
Is the oxygen sensor working ??
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Old May 30, 2007 | 09:27 AM
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First thing to do is stop replacing good parts, and start testing what youre pulling out before you replace it.

Next thing to do is get the igniton control module tested.

Then check all the wiring to all the sensors. Check the AIR system while youre at it.

This stumble will be probably either fuel or spark, if you can get 40 miles before it occurs id guess at spark and look to ignition control module.
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Old May 30, 2007 | 09:38 AM
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Mine was doing the same thing and 4 of my fuel injectors were shorting out. Check the ohm readings all should be in the 16-17 ohm range. Check cool and then again when warm also. My car was getting to much fuel when in closed loop and running rich. Technically it still as as I haven't replaced the injectors yet.
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Old May 30, 2007 | 09:44 AM
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From: Normandy
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Originally Posted by AGENT 86
Are you 100% sure there is no stored code ??
Do you have access to data logging laptop or scanner.
Is the oxygen sensor working ??
No code stored (A+B connections): That's the problem !

EGR is disable with this:http://cgi.ebay.com/ebaymotors/86-89...spagenameZWDVW
but my engine had the default before I put it.

Thank U
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Old May 30, 2007 | 09:51 AM
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From: Normandy
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Originally Posted by Casethecorvetteman
First thing to do is stop replacing good parts, and start testing what youre pulling out before you replace it.

Next thing to do is get the igniton control module tested.

Then check all the wiring to all the sensors. Check the AIR system while youre at it.

This stumble will be probably either fuel or spark, if you can get 40 miles before it occurs id guess at spark and look to ignition control module.
HEI is new to...
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Old May 30, 2007 | 09:53 AM
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Originally Posted by Cain91
Mine was doing the same thing and 4 of my fuel injectors were shorting out. Check the ohm readings all should be in the 16-17 ohm range. Check cool and then again when warm also. My car was getting to much fuel when in closed loop and running rich. Technically it still as as I haven't replaced the injectors yet.
OK, thank you for all

I keep contact
Philou
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Old May 30, 2007 | 09:56 AM
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Originally Posted by philou
HEI is new to...
Is the ignition control module new? That isnt included with the HEI distributor as far as i know
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Old May 30, 2007 | 10:26 AM
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From: Normandy
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new Distributor Ignition Pickup
new Starter Solenoid
new Control Module
new Distribution Cap and Rotor kit
new Ignition Control Module
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Old May 30, 2007 | 10:38 AM
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Might have to start going through all the wiring and making sure its all nice and firm, sounds like its going to be one of those simple little things that is a ***** to track down.
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Old May 30, 2007 | 10:44 AM
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I'd be doing a fuel pressure test while driving, to see if the pressure dropped when the stumbling occured. Next, as suggested ohm those injectors.
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Old May 30, 2007 | 12:03 PM
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I'd be doing a fuel pressure test while driving, to see if the pressure dropped when the stumbling occured.

I have mounted a LT1 fuel pump because old was bad when hot
cold engine with my old TPi pump at 700rpm: 32 psi
hot engine with my old TPi pump while accelerating : 26 psi

But I have always the bug.
You're right, 1st I must see the presure when stumbling occured.
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Old May 30, 2007 | 12:06 PM
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Might have to start going through all the wiring and making sure its all nice and firm, sounds like its going to be one of those simple little things that is a ***** to track down.

It's the charm of the TPi
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Old May 30, 2007 | 01:49 PM
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Time to test things that will no cause a code. Fuel pressure (especially when the demand on the pump is highest), injectors (ohm hot and cold, also fuel pressure leakdown), ICM and pickup coil, FPR, spark plug check and ohm plug wires, check the connections on all engine function sensors and the above mentioned.

New parts can fail too.
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Old May 31, 2007 | 10:55 AM
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Originally Posted by RRT vette
New parts can fail too.

Oh yes but if one cannot have confidence any more in new parts...
I order to Rockauto: it's more easy from FRANCE.
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Old May 31, 2007 | 11:49 AM
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One cant, one needs to test the parts in question in order to be confident in their function
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Old Jun 1, 2007 | 11:18 AM
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Originally Posted by Casethecorvetteman
One cant, one needs to test the parts in question in order to be confident in their function
You're right
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To 1989 strumbling when hot with no code

Old Jun 1, 2007 | 11:48 AM
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No worries mate
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Old Jun 1, 2007 | 06:25 PM
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I would bet a six pack of good beer that his injectors are starting to crap out due to shorted turns in the coils. This is so easy to check too! Spec is 16.5 +/-.3 ohms. All eight should be very close to the same value.

philou: let us know what you find to be the problem.
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Old Jun 1, 2007 | 07:57 PM
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Originally Posted by Sam Lam
philou: let us know what you find to be the problem.
I wonder why injectors are bad after 30-40miles (or 1 hour) and not at cold engine...

So no problemo, I keep contact with the forum. As soon as I find my bug, I post it

Last edited by philou; Jun 1, 2007 at 08:05 PM.
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