CEL on & off...

[DynastyLCD]

this pertains to Brian's (unistylef) GVR4. it's all stock, short of an aftermarket exhaust manifold, and a different J-pipe

last night, he stopped by asking about a check engine light that keeps coming on and off. when the car starts initially, the CEL will come on, then go off after a few seconds, come back on, and go off, it will do this a few times, then it goes away, all is well.

when you check for codes, KOEO, it comes up with 13, 25, and 41. intake air temp, baro sensor, and injector. i tried a known good 1g maf to see what would happen. low and behold, same thing. ohm'ed out the coolant temp sensor, mind you it was already at temperature, and it came up with .3 k ohms like it should. also did a boost leak test for the hell of it, and fixed the only leak i found.

Brian reported that it would be tough to start in the morning, especially now that its cold. that's what lead me to the temp sensor diag. i guess i didn't properly diagnose the problem though, as we didn't test it dead cold.

i guess my biggest qualm with this, is why the hell would a CEL come on, and go off, and repeat a few times? and why would i get those 3 codes over and over again? i know the injectors are all good, the car clearly runs on all 4 and very smoothly at that. and the MAF houses the IAT and baro from the factory, IIRC. the MAF i used came out of a running car.

im running short on ideas for this. my next move would be to check the wiring, and also to pull apart that larger connector under the MAF, and clean it out. i read something a year or two ago about people having trouble with that connector getting moisture in it.

ideas? suggestions?

 

[toybreaker]

How's the ecu board look?

I seem to remember that the iat and baro both share a common trace on the ecu board.

Looking at/swapping the maf was a good call, as both of those items are located in in the maf housing.





Haven't seen too many injector codes, but I have seen bad/corroded connections on the injectors themselves or a problem at the injector resistor pack on the firewall.


Do you have a mechanics stethoscope?

Might be interesting to listen to them as they operate to see if they all sound the same.

I have had "bad" injectors that would act up cold and then play nice once they had been running for a bit. They made a softer "click" when they fired compared to their neighbors.


As always, good looking out Phil!

You're an asset to the board and all it's members. /ubbthreads/images/graemlins/smile.gif

 

[transparentdsm]

Phil, check the battery terminal. i had an intermittent CEL light that would flash from time to time because the positive was jumping up and down and shacking around... then if that isnt it. i would check the diagnostic codes again, see what the last code to come up is, because the last code in the list can sometimes cause everything else on the list to happen. Also not knowing what his engine bay looks like, i would check the connections on all the wires. I've had the coolant temp sensor wire brake off like 6 inches back under the tape and wire loom in the past and it caused a bunch of codes to throw because it couldn't read correctly without the coolant temp sensor attached.

 

[DynastyLCD]

thanks for the kind words TB! that's one thing i haven't checked yet - the ECU... and i will try listening to the injectors as well!

Shane, the battery terminals are on really good. and when i unplugged the coolant temp sensor, i got the code for it, plugged in i get nothing.

it's just odd, as Brian stated, as it's been getting colder, the problem is more common.

i think next trip Brian makes up here, is going to involve continuity checks to make sure the harness is okay, and also to closely inspect the ECU.

thank you for your feedback guys!!!

 

[Specter]

Also check if the grips to the maf/injectors/coolant temp sensors are in bad shape or the pins are rusted, it can cause the same problem.