Random/Flickering CEL

[WES_393]

I've got an interesting one for you guys. Every once in a blue moon, usually after a good 1st-3rd gear run, my check engine light will kick on. With a few taps of the gas pedal it will flicker and eventually die out. The car doesn't run poorly, A/F ratios are spot-on, oil pressure is normal, everything seems perfect. Since it happens so rarely (maybe 4-5 times total over 4k miles), I'm never taking a log when it happens. But when I do hook up Link, there are never any stored CEL's.

So with those circumstances, I chocked it up to road noise, phantom knock, whatever. Nothing to be concerned about. Until today, the CEL stayed on during startup and flickered every time I hit the gas. It didn't die out for a few minutes this time around. So it's got me worried that something might actually be wrong. Any ideas as to what might cause this? The only thing I can think of is my high oil pressure during WOT pulls starving the lifters and causing them to tick. But even that seems far-fetched...

Any input is appreciated!

 

[greekgodchaos]

What is the condition of your ECU? Sounds like something either in the ECU or MAYBE, there is something funky with your instrument cluster? If you have ECMLink there is that option to turn your CEL into a knock sensor after X RPMS and X speed, hows the condition of your knock sensor? And you mention your high oil pressure at WOT is starving your lifters? Are they the 1mm or 3mm revised?

 

[WES_393]

Yes, my CEL is set to display the knock sensor. Its turned on above 3k rpm and 50% throttle iirc. Knock sensor was replaced a year or so ago, but I honestly dont remember if it was a Mitsu or not. But to my knowledge it has always worked fine. The ECU was socketed, inspected, and caps were replaced by ECM Tuning last year.

I have 3mm lifters, recently installed and very quiet at idle. But I remember reading (quote from Buscher I think) about the stock pressure regulator in the head and how too high of oil pressure can reduce the amount of oil going to the lifters. I have yet to port the OFH as pressure would gradually level out while driving, but after a recent change of oil brand/type I'm seeing way more than normal pressure. Next oil change I planned to go down to 10-40w until I can port the OFH.

I also forgot to mention this has happened with 2 different sets of injectors and 2 different fuel types. Im now on E85 with FIC 1150s (need to update profile). So at this point I'm also wondering if it's something in the dash or wiring. The way it flickers resembles an LED with a shaky connection. But without capturing the issue on Link, it would be pretty hard to find out whats shorting out, or even if that's the problem.

 

[jjw205]

My guess is that it's coolant temperature related. I have ECMLink, and the CEL is set to come on at 2XX degrees. My car was running warm one day after a pull, I came to a stop and the CEL light flickered a little, stayed on for a while (until I started moving again) and then flickered off. Not sure if you have Link or not, but the stock ECU may do this as well when you hit a certain temperature.

 

[WES_393]

My coolant CEL is set around 230*, but I've never seen much above 210*. Also haven't noticed any inconsistencies with the coolant gauge or temp readings in Link. But I can't be certain since I'm never lucky enough to get a log. However, I have had problems with the coolant overflow light. The sensor (bottom of overflow on 95) has had a hard life from previous owner letting it hang and my horrible luck with thermostats. I was under the impression that all the important coolant sensors were in the T-stat housing so I put it farther back on my to-do list.

But it makes perfect sense: A faulty sensor giving a high reading and causing a brief CEL. I'll definitely look into it! Thanks for the suggestion.

 

[95tsiawd0330]

Yes, my CEL is set to display the knock sensor. Its turned on above 3k rpm and 50% throttle iirc. Knock sensor was replaced a year or so ago, but I honestly dont remember if it was a Mitsu or not. But to my knowledge it has always worked fine. The ECU was socketed, inspected, and caps were replaced by ECM Tuning last year.

I have 3mm lifters, recently installed and very quiet at idle. But I remember reading (quote from Buscher I think) about the stock pressure regulator in the head and how too high of oil pressure can reduce the amount of oil going to the lifters. I have yet to port the OFH as pressure would gradually level out while driving, but after a recent change of oil brand/type I'm seeing way more than normal pressure. Next oil change I planned to go down to 10-40w until I can port the OFH.

I also forgot to mention this has happened with 2 different sets of injectors and 2 different fuel types. Im now on E85 with FIC 1150s (need to update profile). So at this point I'm also wondering if it's something in the dash or wiring. The way it flickers resembles an LED with a shaky connection. But without capturing the issue on Link, it would be pretty hard to find out whats shorting out, or even if that's the problem.

My check engine lite does that when i do a pull because the coolant cel was set at 219 and when i was in the pull the temp would be at 218/219 causing the lite to flicker so i raised the coolant cel to 226 and never had that problem.sorry just read post above me i also think its your temp sensor not reading right