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Kemp
10-31-2013, 12:58 PM
Initial startup is fine just idles down and dies. Unplug maf and it idles better. If I wait til it warms up and plug it back in it runs fine. Engine is in a buggy with no emissions. Manual tranny. 1990 3.8 sc engine basically stock.

From the codes I pulled looks like a few problems..maf cts and tps all low voltage? Also an ircm code. Any thoughts? Can one problem cause all this?


Pulled codes key on engine off
31
51
56
63
66
67
84
85
87
95

archerman0531
10-31-2013, 01:23 PM
I'm wondering if maybe there is a bad connection to the IRCM and causing it to not put out its required voltage, making the ECM to not have its required voltage, making everything else not have its required voltage, therefore giving you the codes of low voltage.

Just a thought.

KMT
10-31-2013, 01:37 PM
How many volts is the battery showing - engine off and on?

figulaz
10-31-2013, 02:10 PM
Ground strap? I had a toyota with a loose strap. I was amazed how it cleaned up idle and performance. Not sure how sensitive eec iv is to ground.

KMT
10-31-2013, 02:18 PM
Ground strap? I had a toyota with a loose strap. I was amazed how it cleaned up idle and performance. Not sure how sensitive eec iv is to ground.

Tons :)

Bad grounds are bad news for these cars....they depend on reliable circuits.

Kemp
10-31-2013, 03:34 PM
Grounds are good, battery voltage is almost 13 and 13.8-14 while charging. IRCM was my first thought. I'll check voltage from ircm output, it should be 5.5v to sensors correct?

decipha
11-02-2013, 03:37 PM
posting the code numbers without the definition is useless how are we gonna know what the codes mean?

if the tps and maf fail then the isc is clipped to its default value

thats probably causing your issues

you should delete the imrc if you think your having issues with it

KMT
11-02-2013, 03:57 PM
posting the code numbers without the definition is useless how are we gonna know what the codes mean?


See:
http://www.njtacc.com/tech/eec_codes.html

...those are mostly low volts/signal, and since there are so many, they collectively point to something more than just those individual components, I think.

That generally leaves bad grounds, low battery, damaged harnesses, failed EEC(?). Grounds are tricky if you're not aware of all of them. Battery should be straightforward to check, and you can always try another if not sure. Harnesses can suffer from both visual damage and hidden issues. Of course there is always the X factor where the history of the vehicle is unknown and/or work has been done that went awry for any number of reasons.

I'd guess with all those codes, the root issue(s) wouldn't be able to hide for long, but that may rely on being familiar with these cars :)

decipha
11-03-2013, 06:32 PM
that's more work than I'm willing to do considering I'm not the one in need of assistance

taking the few moments to post the code meanings go a long ways when someone is trying to help you, just makes sense

even though it has all them codes they may be nothing, perhaps if we knew what they were for we can give a better response

KMT
11-03-2013, 07:13 PM
31 O,C,R EGR Valve Position (EVP) sensor out of range (low)
51 O,C Coolant Temperature Sensor (CTS) circuit open
56 O,C Mass Air Flow (MAF) sensor out of range (high)
63 O,C Throttle Position Sensor (TPS) circuit out of range (low)
66 C Mass Air Flow (MAF) sensor circuit out of range (low)
67 C Clutch Switch circuit failed (3.8L SC only)
84 O EGR Vacuum Regulator (EVR) circuit failure
85 O Canister Purge circuit failure
87 O,C Primary Fuel Pump circuit failure
95 O,C Fuel Pump circuit open, ECA to motor

Courtesy http://www.njtacc.com/tech/eec_codes.html

decipha
11-03-2013, 07:22 PM
sounds like you lost the 5v ref or the Sig ret

ground pin 46 at the ecu and hope for the best

Kemp
11-04-2013, 12:28 AM
Had my multimeter out and checked everything that I could with it.. Battery is a new optima. (Full charge) Grounds and voltages checked out good. Checked resistance in suspect wires in harness and found nothing wrong. I'll keep you updated as to what I find. Maybe a loose connection and EEC popped the low volt codes??

C'mon I figured you gurus would know the codes ;)
Sorry I didn't define code definitions. The codes were either emissions related (which items I removed and stated) or low voltage which I stated was the problems I was having.

KMT
11-04-2013, 12:46 AM
Engine is in a buggy with no emissions.

Is this a new issue where it was ok before - has this project vehicle ever not thrown these codes?

Did you paint the accessory bracket the DIS sits on?

Kemp
11-04-2013, 11:06 AM
Is this a new issue where it was ok before - has this project vehicle ever not thrown these codes?

Did you paint the accessory bracket the DIS sits on?

Yes this is a new issue, it did throw emissions codes which I expected. I'm going to reset EEC and see if the codes come back for low voltage. I trying to find another ECM so if anyone in ohio has one for a 90 let me know;) As far as dis I didn't paint bracket. I did have old dis tested and it was bad so I replaced it. It does start a lot easier. Acted as if timing was too far advanced before and would turn over slow.

Scott Long
11-04-2013, 12:14 PM
where did you get the DIS from? The early cars had different part numbers for some of the years if I recall.

KMT
11-04-2013, 12:33 PM
Yes this is a new issue, it did throw emissions codes which I expected.

Did this occur after you did some welding on it somewhere?

I think an EEC swap is a good check...

Kemp
11-04-2013, 04:55 PM
Yes actually.. I tig welded so brackets on bumper. and I tried pulling codes after a reset. It started to show codes and suddenly went to a solid light and beep?? After checking harness and voltage I also suspect EEC. I will keep you posted on what I find. So off to the wanted section

Kemp
11-04-2013, 04:58 PM
DIS was from AZ.