1993 351W -Code 128

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Sep 11, 2016 | 07:06 PM

E350Bus

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1993 351W -Code 128

Well, fun with the 1993 351. The other day my wife had it stall on her at idle (warmed up). CEL came on and she brought it home (it is the E350). I removed the IAC and cleaned and put back on. It is now high idle and throwing code 128 (KOEO) after the 111 code first. Is this just as simple as a MAP replacement or is there a vacuum issue I should be looking for or ?

Any help appreciated.

Thanks!!

J

Sep 12, 2016 | 10:37 AM

rla2005

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Code 128 (MAP sensor vacuum was not greater than 2 in-Hg (7 kPa) during normal vehicle operation.) is a stored code that happened sometime in the past. You could try clearing the codes then drive the vehicle again to see if it returns.

If there was no high idle before you cleaned the IAC then you may have damaged it or broken a vacuum line during the R & R.

Sep 13, 2016 | 09:07 PM

E350Bus

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Well I pulled negative terminal on battery and then started her up and then rechecked. Code 128 still there. Is there another step in clearing it?

TIA,

James

Sep 15, 2016 | 01:00 PM

rla2005

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Quote:

Originally Posted by E350Bus

Well I pulled negative terminal on battery and then started her up and then rechecked. Code 128 still there. Is there another step in clearing it?

TIA,

James

Removing the battery cable removes the Keep Alive Memory (KAM) supply. That should clear any stored codes. All of my documentation still shows Code 128 is a stored (CM) only code. Odd...

May 3, 2018 | 07:12 AM

Sarah1991

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I have a 1991 F150 4.9 I6 I replaced the IACV, chased all the vacuum lines and found the Map sensor had a leak. I replaced the line and it still throws a 128 and 126 code. Also it will run rough the rpm jumps up and down a few times and then the engine light comes on and it smooths out but idles high. I bought new Maps sensor and it then starts up idles rough and then dies in about 10 seconds everytime. It does this cold hot does not matter runs like junk. Sometimes the engine light will not blink or come on at all when checking codes. Sometimes with old Map it ran ok off and on. I bought a OEM MAP SENSOR and A EEC on its way soon. Hope this will fix it. I read that is could also be coil or distributor causing problems but wouldn't throw other codes as well? Please some one help it is my only car and I need it to run lol.

May 3, 2018 | 08:07 AM

rla2005

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Quote:

Originally Posted by Sarah1991

Best suggestion is to start your own thread. Given your symptoms of the same codes with a new MAP is either a bad connection to the sensor or a bad computer. The latter is more likely the root cause since you state the CEL does not always come on when checking codes.

You could pull out your existing computer then look for signs of leaking capacitors and/or burned components. A very common issue on these old trucks.