Lots of HCs in emissions

C

chickeneater

New Member
Aug 18, 2013
35
0
0
Portland
i recently did a partial rebuild of my 7mge and got really terrible HCs in my emissions testing (320-360). before the rebuild, the car got more like 200-300 depending on the day. previously the car burned oil like crazy, so i had always blamed that for throwing off my fuel injection system.

i understand things might need to break in a bit more, but i also know that i occassionally have a check engine light on for the TPS and that the egr temp sensor cable is unplugged (although my car seems to be from CA, a lot has been replaced by the previous owner and i cant locate any egr temp sensor). im wondering if either of these would strongly affect my HCs or if HCs are usually indicative of different problems. for instance, with numbers like that maybe my cat is just worn out. i dont know but that is why im asking! thanks!

EDIT: btw, the car drives great. so nothing ive listed seems to have aversely affected the driving performance of the car. the emissions also smell a bit different from before (smelled cleaner to me), but clearly the emissions tester found out otherwise!
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,816
13
38
Thousand Oaks, CA
TPS doesn't do much for these tests where the throttle is held at a steady value. EGR temp is used to set a code 71 if the EGR appears to not be functioning. Neither should play a role here. Do you have any codes set?

I suspect the Ox sensor is okay, but it needs to be ruled out. You can also remove it and to a bench test if that is easier for you, but the TSRM test checks the sensor and the wiring.

Having slightly elevated HCs are a pain to diagnose. It may be a tired cat, or a saturated charcoal canister, or carbon buildup on the cylinder walls. On your partial rebuild did you clean out the cylinders? As I recall 7MGE's only have one cat, so it may come down to replacing it if all else fails. COuld also be a drippy injector on one cylinder. Did you get them serviced with the rebuild?
 
C

chickeneater

New Member
Aug 18, 2013
35
0
0
Portland
yes i cleaned the head and honed the cylinders so there is absolutely no carbon in there (other than what a few hundred miles would put in there). i had the injectors sonic cleaned by a reputable local shop so i imagine theyre good too.

the only code ive ever gotten on this car is one for the tps. it looks pretty straightforward to test the o2 sensor based on your link to the manual (thanks!), so i can try that. i appreciate your help very much!

btw im actually not sure how the charcoal canister works/where it is. you mean the big canister with a few vacuum lines that sits right above the ac hard lines? that also seems like a low effort thing to check if you wouldnt mind explaining a bit to me.
 
3p141592654

3p141592654

90T
Oct 11, 2005
3,816
13
38
Thousand Oaks, CA
The charcoal canister loads up with fuel evaporating from the tank when the car is sitting. When the car is started and after it warms up the canister is purged and the fuel vapors sucked into the intake manifold. The ECU compensates for the extra fuel by backing off on the injector duty cycle, but until the canister is purged it can still raise HCs slightly, maybe because the vapors don't get evenly divided among all cylinders, I don't really know. If you drive on the freeway for 15 minutes that is usually enough to purge the canister. You might want to consider doing that before the next test.
 
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