'88 328 GTS Failed Emissions

My 88 328 failed emissions, an idle test, in Colorado. Failure mode:HC PPM , Actual test result 470.0 ppm, test limit 220 ppm. Who know what to adjust/change?

 

HC is generally caused by raw fuel. How’s it running? Have you tried giving it an Italian tuneup? If that didn’t work, I’d probably try a new set of plugs and fresh tank of gas and retest

 

Does it has the Cat?

 

Might need a new cat converter , tune it up like the fellow said though. You can also try running a tank of 101 or greater octane fuel as well while your trying to get it to pass. Ask Rifle, he knows these cars inside out, and then some. My 89 has never had an issue, so Im sure you can get yours to pass once you dial it in.

G

 

Maybe try also changing the O2 sensor while replacing plugs and air filter

 

So basically high HC means there’s some unburnt fuel so the suggested steps above can definitely help and/or fuel/air mixture is not set properly. What does the CO says.

 

As an example how clean a 328 can run my own could pass California test with no cat. It was under 100 ppm. Unburned fuel is horsepower running out the tail pipe. 220 is far too high for one running correctly even without a cat. At 470 its a mess and should be fixed if for no other reason than to enjoy a good running car.

Probably a combination of things, there is no magic bullet.
For a car running that bad Id start with cam timing, move up to adjustment of valves, go through the ignition system the have a look at the injection.

 

Also I should say knowing any one gas value is not really enough. Knowing the CO and O2 would be a benefit. Gas ratios tells you a lot. a single gas very little.

I bet Co2 is under 10%. Should be north of 14%. If CO is high its too rich, If low its too lean. If O2 is high it has a miss, bad cam timing or dead cylinder(s).

 

Raw fuel is liquid running out of the tail pipe. HC is incompletely burned gas. There is a big difference. If it runs it cant be raw fuel.

 

Fixing cars the old fashioned way.
Throw parts at it.

 

I appreciate the distinction and correction. Thanks!

 

For what it's worth, if one of my old cars fails SMOG, I take it to a professional. Fuel injected cars stay in tune for so long, it doesn't seem worth trying to DIY. Otherwise, I try to do as much of the maintenance on my old cars as possible.

Bosch K-jet was used by a lot of marques. There is a Jaguar/Rolls Royce/Land Rover independent shop near me that has laid hands on my 308 once upon a time.

 

fair enough. I should have said, check, instead of replace.

 

I had this experience in CA with an 87 BMW 535. High HC in the exhaust stream generally means that the computer is trying to feed in too much fuel. Eleven failed smog tests before I figured out the issue.

Possible causes:
- Air leak in the exhaust somewhere between the cylinder head & the O2 sensor. The O2 sensor sees a "lean" condition due to the extra post-engine air and ads more fuel to try to get back to stoich trying to make up for that "unused" air. Engine can't burn it, extra HCs come out of the engine. ECU corrects, etc. etc., but the Smog sensor is just recording the unburned HCs.
- Coolant temp sensor isn't giving the correct info to the ECU and the ECU thinks engine is cold and is adjusting towards a rich mix. Causes could be a bad CTS or a break in the wiring.
- One or more clogged injectors causing a "lean misfire." This is similar to the exhaust leak. The clogged injector isn't feeding enough fuel in and so you basically have air getting pumped out of that cylinder, causing a very lean condition at the O2 sensor, causing the ECU to over-adjust adn dump more fuel in, etc., etc. Smog machine registers the unburned HCs.
- Bad O2 is possible. If the ECU can't make sense of the O2 signal, you're likely to go into open-loop, which is usually defaults to a rich mix.