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View Full Version : 2 problems: Weird on/off CEL and Harsh idle sometimes/Bogish



alexandermf
10-13-2010, 10:40 AM
hello, I have a 99 2.5gt bd limited, manual.

Miles-110k
Engine Mods-Simplysubie SRI, Flomaster axelback
Recent Tuneups-clutch, clutch master/slave cylinders, fuel filter, plugs/wires, thermostat, radiator, hoses, rad cap, timing belt/water pump, trans/diff flushes, BDK-44 or w/e that super seafoam stuff is,and a few other things I can't think of.... Only thing I haven't done yet is headgaskets which I luckily haven't had to replace yet (but no overheating issues) *and yes all replacements are OEM :)

Problem 1- for the past I'd say 5k miles my cel goes on and off, maybe on for 20 mins-4 hrs and then off anywhere between 20mins-a few days. When we check the code (when its on) it says its the knock sensor malfunction, so I'm wondering if my sensor is bad and I should replace it or if I should relocate it and its not bad? I would think if its bad the CEL would STAY ON, but I'm not sure.
**not sure if this matters but the scoop in my hood is open(took cover under hood off) and it rains/snows here so im not sure if that has an effect on damaging the knock sensor at all (i thought i remembered reading on the forum on someone having similar situation and bad knock sensor) but theirs wasnt going on and off

Problem 2- This has been going on since I can remember (have had the car since late january) and maybe started occuring a month of two after. At first I thought it was doing it when my car started to need an oil change or sometimes when the fuel tank was low, but I have also noticed it after oil changes and when I have a full tank. At idle it will feel like a harsh vibrationish coming from under my feet towards the engine, but you can kinda feel the whole car shudder if ya know what i mean, the needle will drop slightly (not like its about to die, but close) until I start to accelerate. also from start sometimes the engine will be boggish and start off pretty slow (sometimes to the point where it almost feels like its about to die unless I put the clutch in redo the whole starting shift)**(also ive had the notion where it feels like my car got rear ended slightly but there is no car behind me :smt017 , dont know if anyone knows what im talking about but its only happened twice and both when a boggish start was occuring)

**One more note on problem 2 is that sometimes in 4th gear(sometimes 3rd) i notice my car will "pudder/shudder" regardless of low/full tank. My car also grinds slightly into 4th at high rpms so idk if that has to deal with syncros eventually going out or if its connected to the shudder

Sorry for the long information but I tried to be detailed so if anyone can help at all I would really appreciate it, just wanna get it runnin good before winter starts. Also from what I've read so far on forums here maybe fuel injection cleaner will help one of the problems

Huffer
10-13-2010, 11:03 AM
If the knock sensor is triggering it usually means it's on the way out - but if the 2nd issue of extreme vibration is occurring too then that could trigger the knock sensor.

But, I think what is happening is that the knock sensor is faulty and needs replacing, and as a result of being faulty is sending incorrect signals to the ECU because of that, and that is what's causing the bucking issue.

alexandermf
10-13-2010, 11:13 AM
sounds good, seems like im gonna be getting a new sensor then.. ill do this asap here in the next few days and let ya know if that helps the shuddering

one thing is though the shuddering and bogginess has been going on way long before the knock sensor starting freakin out, so should i maybe do some fuel injection cleaner too while Im at it?

Huffer
10-13-2010, 11:47 AM
Well, as the knock sensor was starting to go bad, it could have been retarding the timing of the engine.

alexandermf
10-13-2010, 11:56 AM
ok thank you huffer!

alexandermf
11-19-2010, 12:17 PM
Update: installed new knock sensor and cel is officially off for good! but the bogish idle is still there :( any suggestions?

anothernord
11-19-2010, 01:08 PM
Reset the ECU by pulling the negative battery cable, hitting the brake a couple times, then letting it sit for a while.

alexandermf
11-20-2010, 09:53 AM
^hit the brakes a few times while the negative is off? and sit for how long exactly?

the vibration/boggish idle only happens sometimes... and it doesn't seem to go with how hard the car is being run or the gas level or oil so maybe something in clutch possibly? it seems like when I push the clutch in at idle(when its doing it) it seems to stop... might just be my imagination though wanting to find the source of the problem:)

Huffer
11-20-2010, 10:55 AM
Clean your airflow sensor

anothernord
11-20-2010, 03:20 PM
^hit the brakes a few times while the negative is off? and sit for how long exactly?

the vibration/boggish idle only happens sometimes... and it doesn't seem to go with how hard the car is being run or the gas level or oil so maybe something in clutch possibly? it seems like when I push the clutch in at idle(when its doing it) it seems to stop... might just be my imagination though wanting to find the source of the problem:)

Yeah, just to remove all the charge from the system. It's probably not really necessary, but I always do it. Leave it to sit for ~1 hour. That usually does the trick.

alexandermf
11-22-2010, 10:30 AM
hufffer-great suggestion! sounds reasonable, will do that and also the battery discharge idea...

httrdd
11-22-2010, 10:57 AM
Clean your airflow sensor

Have you had any stalling while this was happening? I know that some times the MAFs solder points become loose. I soldered up my Eg33 MAF and fixed the problem and is running like new.

alexandermf
11-22-2010, 07:52 PM
no stall outs but almost always feel like its about to! anyways Im cleaning the maf and my aftermarket filter as i type so ill be updating ya all soon

alexandermf
11-22-2010, 08:43 PM
everything is cleaned and reassembled... cleaned maf and recharged the k&n filter. the sensor itself wasnt too dirty, in fact it looked pretty clean but the mesh was pretty dirty on both ends so im sure that affected it

all in all i drove around for about 20 miles and 98% no boggish idle/vibrations. I can slightly feel it sometimes at idle but so barley that it feels like nothing compared to how bad it was, I feel like that was the main source of the problem but maybe I should clean the iacv?