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Old 02-04-2003, 07:39 PM
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JimF JimF is offline
'94 S500: only 793 sold!
 
Join Date: Mar 2001
Location: San Diego, CA
Posts: 1,933
Haven't posted this yet . . .

because I'd like to get more data but . . . .

I recently changed my Mass Air Flow (MAF) [stevebfl calls it AMM] sensor. Why?? My gas mileage dropped abit and the dreaded DTC#19 registered in my car (CE light came on). Mileage around 14 mpg.

DTC#19= Bad injector(s) or car's self-adaptation (S/A) is at limit in the LH-SFI module.

This failure is common on most V8s between 92 to 95. It seems to occur around 100K+ miles. Have seen four (4) cars that registered DTC 19 with 90K to 106K miles. Mine came on at 103K.

The S/A is programmed by the eprom that's in the LH-SFI module (N3/1) [check my page, menu #1 and/or 2 for its location). The limits are 0.85 to 1.15 as I understand. When the CE lights, the S/A hits the lower limit of 0.85. The car is still running fine, so there's no problem. But since the mixture is a little rich, the car's lambda starts to drop. The system still corrects properly to maintain the correct air/fuel mixture (as close as possible) but you start to burn more gas in the process.

So I changed my MAF. Immediately lambda changed to the lean side. [Waiting for the S/A to recalculate so that's why I haven't posted this.] For example, the injector duration changed from 3.2 millesecs to 2.8millesecs. That means you using less gas for the same, and in my case, much better power even at low rpms (1500- 2000). My gas mileage has gone up: 16.2 mpg on the last fillup.

So will the IAT do the same thing? Don't know but I think that the MAIN determining element is the MAF and secondarily, the O2 sensor. The IAT would probably not be that important for your '90 300CE as far as gas milage is concerned. My opinion.

BTW, if anybody has the DTC#19 problem, send me email because it can fixed very easily at low cost.
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Last edited by JimF; 02-04-2003 at 07:44 PM.
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