RangerM Posted June 16, 2011 Share Posted June 16, 2011 (edited) Over the last couple of months I've noticed what could best be described as "play" in the ignition switch. Rather than the definitive "click" I get when the keyswitch is in On position, the keyswitch can be easily rotated about 15-30 degrees from that normal position up to where the starter would engage. The spring feels a little weak, and I can remove the key without being in Off position (whereas I couldn't before) Starting the truck to come home today, the Check Engine Light (CEL) came on for the first time (ever). Seemed strange, and I turned the truck off. Restarted and CEL came on briefly and then went off as normal. Then on the way home, the truck seemed to lurch (like the key was turned off for a half-second) then the truck continued to run normally. Afterward, the CEL came on for a couple of minutes then went off. This happened a couple more times (with the CEL coming on then going off, NOT blinking) It seems too coincidental for these two symptoms to be unrelated, but would the keyswitch possibly result in the sudden loss of power then CEL, even as the truck ran normally otherwise? Edited June 16, 2011 by RangerM Quote Link to comment Share on other sites More sharing options...
RangerM Posted June 18, 2011 Author Share Posted June 18, 2011 (UPDATE) Thursday morning the CEL never lit on the way to work. Thursday afternoon (when the temperature outside was 20 degrees hotter) the CEL came on and went off periodically, with no real noticeable faults in the way the truck was running. After I got home, I happened to get out of the truck (the CEL was on at the time) while the engine was running. I noticed that the truck was missing (sputtering) a little, like the spark was deficient. Changed the plugs/wires on Friday morning. The truck runs better with no missing however, the CEL was coming on, and staying on. This morning (Saturday) with outdoor temp cooler, I started truck to come to work, and CEL never came on (in 20 mile commute). Not sure if problem solved or not. Will update later. Quote Link to comment Share on other sites More sharing options...
RangerM Posted June 25, 2011 Author Share Posted June 25, 2011 (edited) It seems the problem with the CEL was a faulty mass air flow sensor (according to the shop). Since I don't own a meter, I took it to a shop down the street, where it was diagnosed. They replaced the MAF, and the CEL is off. Sidenote, the shop said the MAF was putting out zero volts and the truck was essentially overfueling (flooding) itself. I'm not sure I understand this. The MAF is a hot-wire anemometer that changes resistance as the flow of air going past it changes. That change in resistance would be measurable as current (amps? milliamps?). How does that jive with putting out zero volts? And how does putting out zero volts (which I'm assuming means a "no air flow" reading) result in the truck flooding itself? Wouldn't the truck cut fuel delivery as air flow goes down to avoid this? Edited June 25, 2011 by RangerM Quote Link to comment Share on other sites More sharing options...
OAC_Sparky Posted June 29, 2011 Share Posted June 29, 2011 Sidenote, the shop said the MAF was putting out zero volts and the truck was essentially overfueling (flooding) itself. I'm not sure I understand this. The MAF is a hot-wire anemometer that changes resistance as the flow of air going past it changes. That change in resistance would be measurable as current (amps? milliamps?). How does that jive with putting out zero volts? And how does putting out zero volts (which I'm assuming means a "no air flow" reading) result in the truck flooding itself? Wouldn't the truck cut fuel delivery as air flow goes down to avoid this? It depends what the tech was referring to, sometimes they're referring to test procedures in the tech manual. In a MAF, the sensor wire is heated to maintain a temperature; as air flows over the wire, it cools it dropping the resistance allowing more current to flow which in turn tells the PCM to increase fuel to the engine. If part of the tech's testing procedure is to look for voltage drop across the sensor wire (checking for open or short) then a zero voltage drop would indicate a short; a shorted MAF sensor would have zero resistance, letting more current flow; just like if a lot of air was flowing through the MAF. Therefore, it would increase the fuel to the engine. Quote Link to comment Share on other sites More sharing options...
OAC_Sparky Posted June 29, 2011 Share Posted June 29, 2011 Like this: Quote Link to comment Share on other sites More sharing options...
RangerM Posted June 29, 2011 Author Share Posted June 29, 2011 (edited) Thanks for info. I'm more familiar with hot-wire anemometers in an industrial setting. I've never seen one that didn't operate on a mA scale. I guess for vehicles a different way works better. Edited June 29, 2011 by RangerM Quote Link to comment Share on other sites More sharing options...
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