Strong gas smell when starting

Jhill

How rich are we talking? If it’s constant and high and truly an issue you should have a check engine light by now. You say it’s only from cold start so I would think you may have a slightly leaking injector (if it’s a hard start as well?). This can be checked by doing a residual fuel pressure check and once confirmed you can remove the plugs and check the tops of the pistons for any that are very clean. Other though that comes to mind although I can’t say how it gets effected on Nissan with the vvel but you may clean the throttle bottles and check the air filters. On cold start the ecu opens the throttle more, adds fuel and also retards timing. This is to try and heat the cats quicker so your basically having the air and fuel burn in the exhaust. If you have a restriction on the air inlet (filters/ throttle body) no you have reduced your air to fuel ratio on cold start (you’ll also have a longer warm up time). Again not entirely sure how effected it is with vvel but can be an issue on GM.

Ps scan data won’t show you much if it’s a cold start issue because the AF sensor won’t be accurately reading at that point.

Z_ealot

Long term fuel trims are constantly over -10%, they dont get up to the constant -25% that’s needed to trip the computer, but the long terms are definitely showing a rich condition is going on. Throttle bodies and air filters are definitely clean though as air filters are new and throttle bodies were cleaned less than 5,000 miles ago. Another thing to note is that when cruising with emgine rpm at about 2500 the long term fuel trim finally starts to level back out towards the nominal 0%, but as soon as the car is stopped and idling that number goes back up over -10%

Jhill

Does your baro reading at KOEO match your altitude?

Z_ealot

Yes, have tested that and baro reading matches what the weather station says is the current outside baro reading

Jhill

If you do an ecm reset after warm how quickly and how high (or low I guess) do the short term fuel trim jump? Meaning does it jump to something like -15 and keep pegging there as long term drops.

Z_ealot

It’s been a while since i did that so i woukdnt be sure about the exact behavior it exhibited. What i can tell you about the last time i did that is that i do remember it struggling and having a rough idle after i performed an ecu reset and performed an idle air relearn, it did finally smooth out after a few minutes though.

Z_ealot

I did the best I could getting a chart of what the fuel trims are doing with what tools I have, keep in mind the blue and gray lines are short term fuel trims for banks 1 and 2 and the orange and red are the long terms, this was taken today with ambient outside temps at 92 degrees while driving normally

Jhill

Little hard to read, is this idling or driving? I was more just after seeing the short term % pegged - after a reset to idicate if you have an injector leaking or something else causing a large unaccounted increase in fuel. Unsure on the z but I've rarely actually had leaky injectors (maybe I'm just lucky). Your comment of it having a hard/stumbling start after reset would indicate an issue (especially if it says a hot start after reset). May be time to check fuel pressure (typical they fail low but I have on vary rare occasion had overly high pressures). Can check residual pressure at same time.