hello everyone, i recently bought a '91 civic aaaand it didnt pass smog. so on the inspection report in the test results it says OBD system check-failed. (due to the check engine bulb needing to be replaced, i already replaced it) and the ignition timing-engine speed fail. the guy at the smog place said that my car idles around 1400 rpms when it should be idling around half of tht?. i also noticed that when i am warming up my car the engine revs up and down and up and down and up etc. (idk?) next it says that the catalytic is modified. the smog guy said that there were some numbers on the cat that seemed odd to him (i guess in reference to the year and make of the car) in the emission results he highlighted a few stuff... something with nox and HC? what should i do? i found a muffler place that could replace the cat for around 175. would that completely fix all the problems? including the cars idling and engine timing? sorry for the looong post and id appreciate any help. Thanks JR

 

175 to replace the cat is really cheap. I imagine you are not in California

Some catalytic converters are specific to each state

AND TRY TO KEEP THE CAT IF THEY LET YOU, YOU CAN RECYCLE IT FOR LIKE 70.OO

As for the lopey idle, if he said your timing was okay.
It is a common problem on hondas, pull the iacv off the back of the manifold and clean it with carb cleaner

To adjust the idle, is simply loosening the throttle cable.

 

yes it is cheap because i have known the guy for quite awhile and i am in california. the cat is legal. okay ill try to keep the cat.
and cleaning the iacv and loosening the throttle cable. ill do that as soon as i get home... thanks!

 

as for the iacv and the the throttle cable. where could i locate those? i just want to be 100% sure i know what i am doing! thanks

 

IACV is mounted directly behind the throttle body on the intake manifold, it has a few coolant lines running to it from underneath. It is a bitch to get off because it has two bolts (10mm I think) that attaches it tot he intake manifold.

Throttle cable is attached to a bracket at the front of the intake manifold, and has a few adjustable nuts to tighten or loosen the cable should be easy for you to locate.

I highly doubt cleaning the IACV will help with emissions if you have an erratic idle or rough starts that's another story, warm the car up. The IACV really only is used when the car first fires up to help keep the idle a bit high on startup until t he engine warms up.

 

Okay thanks! I loosened the bolt and it does not idle rough anymore! Hopefully changing the cat would be the reason I didn't pass smog!

 

Post your official numbers so we can help diagnose.

Lopey idle could mean air pockets in your coolant

High Nox is caused by high combustion chamber temperatures

You can see how the two are related.
Might need to bleed the coolant

; On level ground, jak the front end up, start the car and remove the radiator cap, set the temperature **** to HOT
Let it run untill the fan kicks on twice.
Turn the car off and let it cool.
Lower it and top off the coolant. replace radiator cap
repeat at least once.


do it after you clean the iacv since you're going to lose coolant anyways during that time.


It could be the cat, the cat does help with Nox a bit but it's not the main purpose of it.
If you're running lean(not enough fuel in your combustion chamber) it also causes high combustion chamber temperatures. because the fuel helps keep things cool
It might be your o2 sensor.
Might as well buy that too, they're not too expensive at the risk of failing
Check for vacuum leaks and check the bolts are tight on all manifolds
If air is sneaking in after the Mass air flow sensor, that would cause a lean mix as well

 

So I should do all this before I change my catalytic right? I'll post my numbers after work!

 

It's good to change your cat, it's probably gone by now or ready to go

 

here are the numbers... i already got the cat thooo

 

my car (1997 civic) didn't pass smog for the reason of "the vehicle failed the ignition timing check due to engine RPM being out of tolerance". took it to two different shops and couldn't get a straight answer. I got different answers from people like could be the vehicle speed sensor, bad transmission, shift solenoid. Guy who did the smog said RPM's need to be below 1800 while at 15mph and 25mph to pass. My 25mph RPM was slightly above 1800rpm I'm still trying to find a resolution to the problem.