Have been doing searches for awhile and I’m stuck. I’m failing emissions(results below) and don’t know what to do next. I’m failing nox.
set up–
92 teg GS(manual)(165K)- April 2003-blew timing belt- swapped in new engine from a 93 auto(B18A)(78K) w/ auto intake manifold (w/egr) (egr is closed)
(new O2 sensor and cat 2 years ago (bosch/ aftermarket cat-OEM replacement))
1st time-
w/CRC G2P-
limit/tested result
0.8/0.5 HC Pass
15.00/ 8.99 CO Pass
2.00/ 3.8764 NOx Fail
2nd time-
w/ 1/4 tank 87 octane gas and 3 bottles heet-
limit/ tested result
0.8/ 0.48 HC Pass
15.00/10.59 CO Pass
2.00/ 2.8802 NOx Fail
Tech at emissions station says it’s my cat. Temperature test (I know it’s not definitive of a working cat) showed 280 degrees in front of cat and 400 degrees behind.
Any ideas? I’m thinking of just replacing the cat and getting a manual manifold…kind of at a loss here. I don’t know if getting a cooler thermostat or heat range cooler on the plugs will help but I guess I could do that as well. Any suggestions/comments would help.
put a new cat in and drive the car for 30 minutes on the highway then go get a smog. that should warm it up really good, hondas are notorious for having cats that never reach optimum temp or cool off too fast.
my dad’s bmw 325 had the same problem. His nox was over 2000 ppm. We had to take it to a smog place to fix it. Problem that it had was a leaking vaccuum tube to the fuel pressure regulator (but that only helped a little). The mechanic poured a bunch of cleaner in the gas and cleaned out the combustion chambers. Too much carbon build up will raise the temp of your cylinders. Higher temps equal higher nox. wow, 3 bottles of heet? hehe. Does it run ok with that much heet in it?
It sounds like you did everything else(timing and vaccuum). I agree that it could be your cat.
But he said he got a new cat just 2 years ago. I find it hard to believe…but not impossible… that the cat went that fast unless he has other problems and those other problems will cause the emissions as well. What’s the operating temp of a good cat? Is the numbers he quoted reasonable? I would think they sound a bit low as in maybe his cat was not hot enough to be working properly? But maybe not because the higher temp after the cat shows the cat was working.
This is where my problem is similar to his. I am failing on NOx (30 ppm over the limit) on the 25/15 (first) test and passing on the 25/25 (second) test. I replaced my cat last year. I have done three three-part efi services, replaced plugs, cap, rotor, and replaced my o2 sensor (and tested it with an ohmeter) within the last year. I’m doing fine on HC and CO (not even close to failing on those). I’ve tried retarding my ignition timing, but to no avail. The only thing I can figure is that may cat may not be heating up enough.
Thanks for the comments everyone.
Looks like we’re in the same boat RayB!
I checked my O2 sensor a few minutes ago and looks like it has some carbon build up on it so it might not be responding too well. Also-- a mechanic thinks my HC and CO numbers are too high as well. I ran my cat through a “sun machine” two years ago and it was not doing a good job even though the temp test said it was OK. I’m thinking about doing that again.
Since everything seems to be OK, i’m probably just thinking about getting a new cat and O2 sensor. A little more research and testing though…
The 3 bottles of heet didn’t really affect driving that I could tell. Didn’t get on the throttle much at all though.
I tested vacuum off of my intake breather hose and this seemed really low… 6-8mg Hg.
As for the carbon build up in the cylinders, this may be a problem…I really don’t know. I got this engine with 78K on it and I don’t know what it went through. Although, the engine that blew( always make sure your timing belt is changed at the intervals—my broke sitting at a stop light!!!) seemed to run smoother with 150K on it.
I’m going to have another mechanic look at my graphs to see if he can pinpoint some problem areas.
Also, the first time I went in I drove for 15-20 minutes before going in and the second time was about 10minutes. I’m sure the cat was warmed up but even if it wasn’t, I think there is something wrong here. I’ll keep you posted. Thanks again.
Originally posted by doublepeak Also, the first time I went in I drove for 15-20 minutes before going in and the second time was about 10minutes.
I suggest you take your car out on the freeway before the smog test, to get the cat nice and hot. Driving around for 10-20 minutes isn’t long enough. If you had to wait at all before the smog test your cat would have lost alot heat. I think you should drive on the freeway for atleast an hour. That way you can be sure the cat is hot. Also try to make an appointment with the smog check shop. That way they can test your car right away when you get there. But like you said there may be other causes for your high NOx. Good luck.
Originally posted by jdm91integ I suggest you take your car out on the freeway before the smog test, to get the cat nice and hot. Driving around for 10-20 minutes isn’t long enough. If you had to wait at all before the smog test your cat would have lost alot heat. I think you should drive on the freeway for atleast an hour. That way you can be sure the cat is hot. Also try to make an appointment with the smog check shop. That way they can test your car right away when you get there. But like you said there may be other causes for your high NOx. Good luck.
I actually had a 95 GMC fail simply because the cat was not hot enough. I had been driving for almost a half hour from a cold start on a warm day. Next time I tested it was within 5 min of a 15 min run on the freeway at 65. Passed with no problems. Did nothing between tests. Just made sure the cat was hot.
My igniter and coil went out in addition to this emission problem. anyways, I am going to try a new cat and new plug wires (stock, sumitomo) and see if I pass. This is about the last thing I can do. I’ve checked with three mechanics (ASE certified) and can’t get too much help except that I have some misfiring going on in cylinders 3 and 4. I’ll run the cat for an hour before testing. Wish me luck and I 'll keep you posted.
is your egr hooked up? if not you do not need to hook it up electronically just run a vac. line to it from the int tube b4 the tb. i had the same prob i have a 92 gs 5spd with a auto eng. and the egr was disconnected . reconnect it and make sure it moves and you will be good. i am a ase cert. tech with a insp/ emiss/ and waiver license and i got my L1 cert a year ago.
dattegbol-- timing is at 14 BTDC, cooling fans work(can’t give exact info on this but they turn on/off when engine gets hot/cold)
NO my egr is NOT hooked up. it is closed and sealed to vaccum pressure(i.e- it works). (did a test on it)-- I have a new set of plug wires,igniter and coil, and cat. I was going to test today, but maybe not. I don’t have the picture/ info/car with me to be exact here so bear with me…
for the egr…should I T-connect off of the intake breather hose or the other hose that goes from the intake to the throttle body via the two-way valve( i think this hooks up to the dashpot).
Anytime the engine draws vaccuum, it will open the egr. Is this going to be good and why? ( i know the basics of the egr system- recirculate exhaust into im to cool combustion temps) Will it be bad to have an egr running simply on vacuum from the engine without it being hooked up to the computer. Seems like this needs to be regulated by the computer. Thanks for the replies and any further comments are appreciated.
oh yeah, should heet be used with high or low octane.? I used low octane (87) Xdeep’s post first states high octane but then someone corrects/suggests low octane. Thanks.
whatever works for you. i used 91 since the car was old and could have build up.
i think its the cat too. it looks like your numbers didnt change after adding the HEET. a friend of mine just added some and didnt notice a change either, but he’s running a straight pipe. perhaps your cat isnt functioning as well since everyone else saw drastic results.
Xdeep- what do you think about the egr? SHould I attempt to hook it up? I’ll probably use heet again just to add some help. ANyways, I’ll probably test on monday with:
New igniter
New coil
New plug wires
New Cat
Timing at 14 BTDC
3 Bottles of HEET w/ 1/4 tank 89 (split the difference?) octane
New PCV valve
…possibly an egr valve???
connect the vac. hose to your egr , just make sure its in ported vac and not man. vac. if you have a intake t it into the int. before the t.b. you do not need the electronical part for the egr to work. also if yours was originally a 5 spd car you are missing the contro; box which contains the egr solenoid and conector for the egr anyway. trust me i am a cert. emissions insp. with the exact same prob. to the t as you and my car runs cleaner than ever now.
Originally posted by dattegbol connect the vac. hose to your egr , just make sure its in ported vac and not man. vac. if you have a intake t it into the int. before the t.b. you do not need the electronical part for the egr to work. also if yours was originally a 5 spd car you are missing the contro; box which contains the egr solenoid and conector for the egr anyway. trust me i am a cert. emissions insp. with the exact same prob. to the t as you and my car runs cleaner than ever now.
ya and if the EGR was malfunctioning you would get a code i believe. the ecu does a check on it to make sure the valve is lifting properly and that manifold pressure changes when the valve is opened.
dattegbol, i did the manual conversion and i still have the EGR on the intake manifold, as well as the solenoid box or whatever. i disconncted and plugged up the vacuum line, and disconnected the EGR connector. control box is still hooked up to EGR.
do you think its vital i get it off or swap to a manual intake manifold?
i take it the default position of the EGR is closed right? could it be leaking a little?
the problem is i occasionally get dips and i need to drive again or rev for it to stabilize again. im also experimenting with PGMFI roms (pm6 based) and that one caused the engine to stall upon stepping on the brake pedal, so i cut Q26 off of the board. apparently its one of quite a few circuits that control the EGR and stuff.
