92 Q gas smell from exhaust > cold start > cold weather

[greg_atlanta]

At 226K, car runs like a dream.... so I don't think I have an injector problem. Under plenum fuel hoses have been replaced twice and I would recognize that smell (unburned fuel). This problem is minor... I only notice it in cold weather (which is rare these days) on a cold start leaving work at midnight when my car sits at a red light for 2-3 mins. I can see the exhaust -- white from condensation for a few minutes only -- curl over the back of the car and evidently get in the vents. I get a subtle fuel smell from the exhaust and have to crack the windows once the light turns green. (I have smelled the exhaust to verify the gas smell).

Is this normal? Or do I have a problem with the air/fuel mix? When I got the emissions done in Sept one of the measurements was a little high. Forgot which one (can find paperwork later), but when I researched at the time it said "unburned fuel". I have asked Byron at T3 about O2 sensors in the past and he said not to bother. Gas mileage has been normal at around 16-17 city.

Is this something worth troubleshooting? Or should I just turn off the vents until the car warms up?

I saw another thread that says it's normal for Nissans run rich at startup.

[96Qowner]

Mine is doing that too, now. I had a full hose replacement done several thousand miles ago. I'm thinking a clamp or two needs tightening. The hoses (both inside diameter and outside) shrink in cold weather and pull away from the fittings.

[elwesso]

You will get a gas smell when its cold in the exhaust, due to the ECU DUMPING fuel.. It will smell very rich at cold startup. Its especially noticeable with my car with no cats.

[96Qowner]

Thanks, Wes, that's a bit of a load off my mind. I remember the last time my fuel hose leaked (that lil 2 incher) and I had to take a 1400 mile drive to Atlanta. Kinda disconcerting, even if I WAS riding with a fire extinguisher handy.

I'm taking that same trip at the end of the month, heheh. I hope you're right.

[elwesso]

It should be easy to seperate exhuast from the motor... Seeing that the exhaust [outlet] is about as about as far away from the motor as possible!!

I can actually see a little bit of smoke when I drive off without warming up the motor.... Yes, I would have the NERVE to do that!!

are you going to T3?

[96Qowner]

LOL, yeah, ok, I'll sniff the tailpipe next time I fire it up! Wheeeee!

It's almost exclusively my Interstate car, so I rarely drive it in the winter - only drove it recently because of the Holidays - luxo ride time. Didn't want to dig out the flashlight and hunt for a leak, is all. I'll check which end is smelly, thanks.

No, this is just the regular business trip - the Q is running great - no need for T3 this trip.

(Oh, and ... um ... in 385,000 miles, I NEVER have let the Accord warm up - I guess the motor is gonna go any day now, huh ... )

[maxnix]

(Oh, and ... um ... in 385,000 miles, I NEVER have let the Accord warm up - I guess the motor is gonna go any day now, huh ... )

Same reasoning those people use who say "I've smoked for 55 years and it han't killed me yet."

[96Qowner]

Of course, you're right ... and when the motor finally blows, you'll still be right.



More to the point, the little Honda 4-banger isn't as sophisticated and highly tuned as the VH in the Q (even if it doesn't produce gas fumes out of either end).

(And I've been smoking for 37 years so far, with no ill effects - to each his own - quality of life vs quantity, blah, blah)

[greg_atlanta]

Found my last emissions test results. Everything was well below allowable limits except HC ppm.

25/25 testreading: 87allowed: 103

50/15 testreading: 49allowed: 107

http://www.aa1car.com/library/tr1196.htm

"Hydrocarbon failures mean unburned gasoline is passing through the engine and entering the exhaust. The three most common causes include ignition misfire, lean misfire and low compression (typically a burned exhaust valve). Ignition misfire can be caused by worn or fouled spark plugs, bad plug wires or a weak coil. Lean misfire results where there is too much air and not enough fuel, so check for vacuum leaks, dirty injectors or a fuel delivery problem. In addition to these, hydrocarbon failures can also be caused by oil burning due to worn valve guides, valve guide seals and/or rings."

When I got the emissions done, the &%$#*&@ tech turned the car on and off several times and tried to burn up the flywheel, so that could explain some of it. But with new exhaust smell something else is up. Guess the car is getting old......

I'll be at T3 in a month or two and plan to get an injector cleaning. Is there anything else I should have checked? Or just clean the injectors and wait-and-see? Is there a manual adjustment for the air/fuel mix?

Spark plugs are relatively new. Car burns very little oil (use Valvoline Durablend). EGR has never been cleaned manually but I think that gets cleaned via BG intake cleaning process?

[Q45tech]

And I've been smoking for 37 years so far, with no ill effects .

I quit 8 months, 1 day and 4 hours and 23 minutes ago after 40 years ------------- way too late.

[Q45tech]

EGR [only affects Nox] but that is a separate manual cleaning process not connected with BG vapor induction clean service [roto router the system].

The problem is the O2 heaters don't work fast enough to allow closed loop at idle.............. after a few minutes/seconds of rev down to idle the system goes into open loop................then the rpm and injector rely on brand new preprogrammed numbers..................AND the CATs [still hot] to fix the HC numbers.............old cats and old O2 are not a good combo.

Always run the engine at 2,000 rpm while in line for a tail pipe sniff and wait until the last possible moment to go to idle.

[maxnix]

I quit 8 months, 1 day and 4 hours and 23 minutes ago after 40 years ------------- way too late.

Good for you, Dennis. Much better than another year or ten from now.

If anyone needs some incentive, might I suggest volunteering at a care facility where lung cancer patients are treated? It will cause you to quit the next day, guaranteed.

[greg_atlanta]

I checked for exhaust leaks today and found one pinhole on the driver's side behind the 2nd cat. I was about to patch it with some metal tape, but the hole is perfectly centered on a dimple and sits exactly at the bottom of the pipe -- is that there by design? There is nothing to match it on the passenger side.

If anyone has a sec (and a dirty shirt on) can you look under your car and see if you see the same? The exhaust diagram in the service manual is not detailed enough to show that.

Unrelated note: the plastic shield protecting the brake lines was loose in several places. The tabs where the screwholes are had snapped loose (plastic is brittle). The shield in the front passenger wheelwell had twisted all the way under close the the jacking point. Luckily it was an easy fix... I twisted it back in place, unscrewed the other shield in the wheelwell, secured it under the good shield and screwed it back. If I had hit one big rock I could have damaged a brake line. (I was getting a rattling noise from that corner, so I'll find out soon if that was the cause.)

[Q451990]

I seem to remember the dimple and hole, but I'm pretty sure it's not supposed to be leaking...

Heath

[greg_atlanta]

My dad said it might be a drain hole for condensation, which makes sense since it's at the lowest point of the exhaust system. But why on driver's side only?

Has anyone has to replace cats to pass emissions? Is OEM the only way, or are there decent aftermarket options? (Just forecasting future repairs).