Hey all,

I recently purchased a 1999 D1 from a seller in Washington state and am having trouble passing emissions in Colorado, specifically for high NOx. I don't have the report with me at the moment, but basically the NOx levels were at 8.9 GPM (vs. a legal limit of 1.5) on the first test, and the CO, CO2, and HC levels were all well below the limits. I took it to Roadside Werx in Denver and they recommended starting by changing the fuel injectors, as the previous owner had installed mustang injectors and they said they'd seen instances of that mod leading to overfueling and thus failed emissions. Switched them out for stock injectors and that brought my NOx levels down to ~6 GPM, so better, but still 4x the legal limit.

Their next recommendation is to check whether the timing needs adjustment - from what I've read, advanced ignition timing can push temps in the combustion chamber over that 2500 degree threshold and skyrocket your NOx levels, so that checks out... however they're quoting me $1000 bucks and can't squeeze me in for 3 weeks, so I'm trying to explore alternatives in the meantime. A few notes:

• The previous owner had a 4.6L top hat engine built and installed, along with a crower performance cam, about ~3k miles ago, so it's not fully stock
• Fuel injectors are brand new, stock
• O2 sensors are brand new
• Spark plugs are brand new
• Cats are brand new, carb-compliant
• No check engine light / error codes
• I've only put premium gas in it for the ~1000ish miles I've driven it
• Yes, I'm warming it up before the test (20 miles for the first test, probably 100 miles for the second as I did it immediately after a drive to / from Pueblo)

My questions:

• $1000 seems extremely steep for a timing adjustment - is there something special about the D1 that would complicate this? Mechanic called it an all day job, which surprised me.
• Mechanic told me the ECU needed a couple hundred miles and a couple of restarts before it could recalibrate to the new injectors... I did almost exactly 200 miles and 2 restarts before it dropped from 8.9 to 6.5 GPM - is there any chance it just needs more time to reset adaptive values? I have a free re-test if there's any merit in trying that.
• Any other things y'all would try before dropping another $1000 on this?

Thanks!
Michael

 

Make sure the two wires with identical connectors leading to fuel and coolant temp sensors aren't swapped. Also check for faulty IACV and/or vacuum leaks. I've successfully reset the adaptive values via OBDLinx and Gems Reader android app.

 

Since timing is controlled by the ECU, how timing is changed on a GEMs engine is a mystery to me. Maybe tweaking the position of the CKP or CMP sensors? Or physically tweaking the timing gears? Maybe ask the mechanic for details of how the adjustment is made?

Maybe move up here to Washington so you don't have to get emissions tests?

 

lol, there's a chance I'm moving out of the Denver metro area (the only part of colorado where emissions tests are required) to the western slope later this year, so there's a non-zero chance I just roll the dice on driving on expired temporary tags until I can get real ones in another county. They'd have to issue me like 20 tickets between now and then before it makes more financial sense to take it back to the mechanic ............... sigh.

 

Do you have $715 or more in emissions related repairs within the last 6 months?

https://dmv.colorado.gov/emissions-waivers

Gasoline Vehicle Repair Waiver Requirements

Requirements to apply for 1968 and newer gasoline powered vehicles, if the vehicle displays a regular license plate:

Failed emissions test no older than 6 months, then

• $715 in emissions related repairs within the last 6 months.1, 2, 3
• Second failed emissions test verifying repairs did not bring the vehicle into emissions Compliance

Additional Information:

• After your application has been submitted, an Air Environmental Systems Technician (AEST) will need to review your application for compliance with application requirements.
• A visual verification of the vehicle must be completed by an AEST at either an Air Care Colorado Emissions Testing Facility or a Colorado Department of Public Health and Environment (CDPHE) Emissions Technical Center to verify the above requirements as determined by the AEST prior to waiver approval.4
  • Any individual may bring the vehicle for this visual inspection.
• Waiver is good for ONE emissions cycle with registration still required annually per county.
• Additional repair waivers may be obtained by following the same requirements as stated above. Cost limits and failed emissions tests reset annually.

 

I think Id try seafoaming it, colder range of spark plugs, and reset adaptive values before the next test

since nox forms at higher temps and compression ratios Id seafoam to remove any combustion chamber junk that could be raising comp ratio

then try to cool it down with spark plugs

 

Here are a few ideas to ponder. Seems you are very close to passing, so some small change might make the difference. BG EPR is an additive also effective at removing carbon. Add to oil, rev up the engine for 15 minutes, then change the really black oil.

Does colder spark plug range impact combustion chamber temperature vs just the temperature of the tip and insulator cone of the spark plug? A different style of spark plug might be worth a try, or larger (or smaller) gap? What plugs are installed now? Maybe worth a try to change since easy and cheap.

Changing adaptive values could impact exhaust, but you don't know in which direction. There is an adjustment on the MAF that impacts CO, but not sure if it impacts NOX, and not sure if only at cold start or normal temperature.

Have the Long Term and Short Term fuel trims been monitored and recorded? How do they look? Long Term trims are adaptive values that get reset, but should return to previous values during drive cycles. What is the gas mileage? Maybe try different gas, or a fuel additive.

 

Unfortunately one of the requirements is that it have passed emissions at least once in the life of the vehicle, so cars bought out of state don't qualify for a waiver. Guess their rationale was that they didn't want to add any net-new vehicles with bad emissions to the area... pretty annoying though.

Isn't seafoaming it more of a thing for older engines that would have accumulated carbon buildup over the years? I didn't bother with this approach yet since it's a virtually brand new engine.

Colder spark plugs are an interesting idea... going to look into this!

 

I wouldn't say VERY close I'm still at ~6 GPM vs a legal limit of 1.5. But I'm optimistic it's just one thing and not several...

Re: my post from a minute ago, isn't addressing carbon buildup more of a tactic for older engines? I'm not opposed to giving chemical treatments a try, just didn't think it would move the needle on a newish engine.

Going to look into the spark plug question, that could be a good / easy / cheap approach.

Gas mileage is 15mpg (mostly highway) right now, which doesn't seem particularly off given the steel wheels / 31 inch tires, heavy bumpers, etc. It actually jumped up from ~13.5 to 15 when I replaced the injectors, so that was good news.

I haven't recorded the fuel trim values, but going to drive around today and give them a look.

Regarding resetting adaptive values, all the posts I see on this topic reference the GEMS Reader android app. Any idea if there's an iphone one? I don't have an android phone, and not sure I have any friends nearby with one.

 

No iphone app exists
You will need a fairly specific ODB2 reader for android as well. The generic cheap blue ones wont work.