I’m purchasing a 1993 240sx (stock KA24DE with 205k) from someone, and we went to get it e-tested today. It failed because teh NOx readings were too high, about triple that of the limit. the HC and CO were fine, and after he did some cleaning on some part (sry he didnt speak english…didnt tell me what he did, the seller told me what he was saying to him) the HC and CO readings went down more.
Then he supposedly replaced the catalytic convertor, which made all the levels go down a bit more, especially the CO level. The HC level was about half that of the limit. The NOx was about triple the limit. He also was fixing the EGR valve, I think that might be the problem.
I’ve been researching all day, the EGR system is what seems to contribute to NOx emissions, if it is malfunctioning. Also I heard something about timing issues. Any idea to why my engine is running shitty, and should I still buy the car if it barely passes (work will continue today because shop had to close last night)?
btw: I will post my results for curb idle and ASM for 1 or 2 runs when I find the pics I took.
retard the timing, it’ll make the car slow as shit but it will pass with flying colours. once you’ve passed the test, advance the timing back to where it was.
I asked the mechanic to change the timing, but he said he needs to keep it within specification (wtf??? i just want my car lol). BTW as I already mentioned, its a stock KA24DE with 205k on it. Another thing, how is timing adjusted, is it easy to do without any tools? (except me of course lol)
Update: They replaced the cat, and an O2 sensor, and they made the EGR valve function, but the NOx levels are still too high to pass. They are gonna either replace the intake manifold or something like that because they believe that the path for the EGR system is blocked, resulting in the high NOx levels, everything else is great, CO and HC wise, just NOx is too high. The dude selling it to me might bail out if he has to spend 500 before he can sell it to me…damn it.
Btw, if the car isnt passing emissions, isn’t that a sign that something is seriously wrong with the engine, especially after replacing the cat, and an O2 sensor and cleaning the EGR valve, etc…? The problem is that the shop will be closed after tomorrow until the 2nd, and the seller is planning on leaving the country in a week or so…I guess God doesn’t want me to be driving a 240 as of yet cries
Who ever is working on you car is a fool and shouldn’t be working on cars or they just want to rip you off. There was nothen wrong with the ca or o2 sensor sensor that was changed. Retarding the timing will not make the car pass.
I kinda agree with you, but if they were such fools, why did the car fail in teh first place? The seller seems to know the mechanic, otherwise I’d never go to him to begin with.
Back to where I started, what should I do now to make it pass and run well?
okay but i can almost guarantee you that it will. All 3 KADE 240s that i have taken for e-test failed with similar readings, everything is good except NOx is through the roof. the timing was advanced to hell on one of them, the other 2 were within spec. retarding the timing made all 3 of them pass with amazing numbers and the tech that did the test couldn’t believe how well they passed.
high NOx is created from burning too hot, retarding the timing makes it burn cooler.
from my experience these engines run a lot better than stock with the timing advanced slightly (as long as you run premium fuel).
the mechanic is playing you for a fool and doing whatever he can to make an easy buck off you, and it’s working.
^^^ Lets see here??? I’ll bet you the the BPT valve isn’t getting vaccum to lift like most nissan of the 90’s. We all no NOx is created from hot combustion temps (2500 degress F). What lowers combustion temps?? The egr. What lifts the egr open?? Vaccum and a solenoid. Which you want to do, fix car the car or butcher it???
NOx is our smog on summer days. We’ll you retard the timing in you garage to pass them. I rather fix the egr, it only takes like 5-10min for fix the vac line. What happens in the line between the BPT and the egr gets brittle and breaks due to hot exhaust gases travelling though it, causing the egr not to work causing high NOx.
take off the egr and clean out everything even if nothing is obviously broken, lots of old cars have clogged egr valves and complain with check engine lights
I completely agree with your view that it is an incompetent mechanic or he is trying to rip the seller off (he has to make the car pass emissions before it can be sold).
I gave him the suggestion of delaying the timing by 3°, and he claimed that they already tried delaying the timing. At the time they were pulling off the exhaust manifold…tugging on it lmao, then they opened that last bolt holding it on the block sigh, why the hell did I listen to the seller when he claimed he knew the mechanic…
Lets say an engine fails emissions after the timing is delayed, the O2 sensor is replaced, the cat is replaced AND the EGR valve is functioning, what could be causing such high NOx level? I’d say that a clogged EGR system…but they seemed to have cleaned it out. What could make an engine with only 205km run so shitty…it drove fine…was far from rev happy, but I guess thats what KA’s are. (once again, its a completely stock KA24DE)
edit: I came across an article that claimed, carbon deposits on high mileage engines, especially abused ones (maintenance wise), cause high combustion temperature, and therefore high smog (NOx) emissions. I was thinking of buying that pennzoil engine flush from crappy tire…but I heard horror stories about chunks of carbon deposits coming off and clogging oil pumps and filters, killing the engine. If it worked successfully, I believe it would really help restore the motor to a better running state. Any suggestions?
man, just retard the timing and take it somewhere else that isn’t out to scam people who don’t know things.
you loosen the 2 bolts on the distributor and turn it, it takes no time at all.
mufflerman has always treated me well and it’s the only place i’ve gone for e-tests. i retarded the timing while it was sitting on the dyno and he was setting things up, he didn’t care at all. as soon as it passed i advanced it before i even left the building.
Thanks a lot for your suggestions The shop is closed until the 2nd, I believe, so we’ll see what happens. I spoke to the seller about the incompetency of the specific shop/mechanic we went to, and he agreed to take it to another place if more “bad news” arose.
I will update you guys on the situation, with as many details as I can provide. It would really be awesome if someone who’s comfortable with working on KA’s could ride along with me on my next visit to that place lol. Once again, thanks for the responses.
