I Hooked my computer today and ran the car and this code came up MALF 16. What it it and how would I check into it?

 

Click the link in my sig for trouble code definitions. Code 16 is for low resolution on the opti. If your engine is now running, the code was intermittent and has gone away, since the engine will not run if the code is active. You can't troubleshoot it if it is not there, but you could at least check the opti harness to see if it is clean and tight on both ends.

 

DTC 16 = Distributor ignition system (low resolution pulse)

Use this LT1=specific code list, courtesy of Shoebox:

http://shbox.com/1/Dtcs.htm

The Optispark distributor has an optical cam position sensor in it. It outputs a "low resolution" pulse signal to tell the PCM where the engine is in it's rotation - e.g. which cylinder is approaching TDC. The PCM uses that data to time the ignition and the sequential fuel injection. If the PCM loses the signal for 2 crank revolutions (there is a high resolution signal as well, that allows the PCM to temporarily estimated rotational position) it sets DTC 16 and shuts down the fuel system. DTC 16 does not turn on the SES light.

If your engine is running, it's a "stored" code. If the engine won't start, it's an "active" code. The code can be caused by a faulty short Opti wiring harness (gray connector on passenger side of intake manifold to the Opti) or a faulty cam position sensor.

If the engine is running, clear the code and see how fast it comes back. Sometimes the code sets when the PCM can't find the signal on startup. If it reappears, or causes the engine to shut down, check the wiring harness for damage. Look carefully at the connector on the Opti end, for damaged or corroded pins. The unvented Opti builds up ozone that causes rust and corrosion. If the harness is OK, then the optical sensor is faulty.

 

Thanks guys. That makes sense cause the engine is very hard to start when its cold. I have to crank it over for a ridicules amount of time every time at first start up till it starts up. It's a daily problem. SO I'll Check and clean the wire harness and if it still gives me a problem then I most likely have to deal with the opti?

 

Hard start when cold could also be due to:

-rapid loss of fuel pressure after pump primes. Check the fuel pressure by turning the key to "run", not "start", and see how high the pressure gets when the pump approaches shuts off, and how fast the pressure drops after the pump shuts off.

-incorrect temp indication from the coolant temp sensor. If the PCM doesn't know the engine is cold, it won't richen the A/F mixture for a cold start. Read this:

4th Gen LT1 F-body Tech Articles

The Opti is not always the problem.

 

Her is my update,I disconnected the battery and reset the trouble code and as soon as I got the car to run the code came back on. So I checked the fuel pressure and visually checked the fuel regulator. Their both good. I checked the water pump temp sensor out of the pump and in a pot of water and used a multi meter and a digital thermostat and matched the readings Temperature vs. Resistance Values. (4th Gen LT1 F-body Tech Articles).
Also tested the temp Sensor harness leads and they are good.
I decided to test the opti harness leads for visual inspection and continuity testing and it was good. I'm guessing its the opti optical cam position sensor. Are there any other things I could check/test?

 

If it's intermittent while starting, it may not be indicating a major problem. If it shuts the engine down, it would be a major problem.

 

I have never had it shut the engine down on me, I know that the colder the engine gets after shutting it down the harder it is to start. I changed out the opti today since I had the whole front apart with another one I had just to see if it made a difference which it didn't.
Could I possibly have a pcm problem, Bad spark plugs, Idle air control valve?.

I did run it again with datamaster and it had the malf16 but cleared it and shut the engine down and started a few time and the code didn't come back on but it was still hard to start since the engine was still cold..

 

I tested the fuel pressure again and it isn't holding pressure. It drops from 44 to near zero. It has a new fuel pump and had the starting problem before the new one.

 

The pressure can drop for several reasons other than the check valve in the fuel pump - although the check valve in pumps like the Walbro seems to be a possible weak point. A pinhole in the flex hose from the pump to the sending unit has been cited as the cause by a couple of people recently. A leak in any line, leaking injectors or a leaking FPR can be the problem.