CA Smog diagnostic Help

[cganne]

Took car in to smog on Tuesday, failed on NO(ppm):

1989 325is Manual

Measured

15MPH - 1166 (Max is 767) FAIL
25MPH - 1195 (Max is 706) FAIL

Tech advised it was most likely exhaust leak. Went back through exhaust and found that the exhaust manifold to head was quite loose. Also, was missing one stud/bolt on manifold to downpipe which was fixed.

Took car back today and readings were:

15MPH - 1371 (Max is 767) FAIL
25MPH - 629 (Max is 706) PASS


At this point, should I take in for diagnostic or are there additional steps I can take to remedy on my own?

Engine is bone stock.

[mr.vang]

Most like replacing the cat will help you pass

[cganne]

Cat has less than 3,000 miles on it, aftermarket MagnaFlow.

[oldmann]

Stomp test, get codes, go from there.

Search "failed emissions" lots to read and do. 20 yr old cars need lots of love.

[jlevie]

You don't say whether the car is failing for high HC or high NOX. The difference is important.

[cganne]

HC on first and second passed no problem.

First test they measured at 15 @ 15mph with Max being 108 and 17 @ 25mph with max at 83. On second test, it was 14 @ 15mph and then 9 @ 25mph.

[jlevie]

So it is failing on NOX? That would be caused by the engine running lean or from bad catalytic converters. A lean condition could be from intake leaks, invalid rail pressure, or clogged injectors. A smoke test and a check of fuel rail pressure would be the first things I'd do.

[cganne]

Did the fuel pressure test at the rail, idle was about 40psi (2.6 bars or so), when rev'd would jump to about 3 bars.

Car has approx 300k, I have not done an injector refresh or change fuel filter since I purchased the car, approx 5,000 miles (3 years). Will change out filter today and most likely will send out injectors for refresh through "Cruzin Performance" this week.

When I change out the filter, since I will be down there anyways, will i get a proper reading with the fuel pressure test if I just hook up at filter once replaced?

[Lingurade]

Change fuel filter, use better quality gas? i only use top tier stations such as chevron, 76, shell, and texaco. running premium and as close to a full tank as possible helps. and having 3000 miles on a cat that was ran with arco can make it bad. not accusing you of running bad gas but just a suggestion. best of luck

[jlevie]

Did the fuel pressure test at the rail, idle was about 40psi (2.6 bars or so), when rev'd would jump to about 3 bars.

Those numbers sound right for an M20B25 engine. The pressure at idle should be a bit below 3.0bar and if you disconnect the FPR vacuum line you should see 3.0bar.

It doesn't sound like the engine has a rail pressure issue. Have a shop run a smoke test as the next step.