I've got a problem I've been trying to work out with my car. After I added my intake mods it started running lean and hot all the time and I can't pass smog with it. The NOx value is too high, all the other measured particulates are well under the allowable limits.

I've got an '88 IROC with an L98 with full bolt ons on the intake and exhaust side. I made a ram air set up, 52 mm throttle body, ported plenum, ported SLP intake runners, ported edelbrock base. On the exhaust I've got 1 5/8'' Hooker headers, hooker 3'' y-pipe, and a flowmaster 3'' cat back exhaust.

The head and cam are stock L98. I haven't changed those yet. I'm still running the stock computer, stock chip and 22 lb/hr injectors.

I set the timing to the factory spec 6 degrees BTDC. I've also got new MSD plug wires, plugs, cap and rotor.

It stays above 240 degrees as well. I've also got a new water pump and new stock radiator as well. What should I do to have it not run lean? Get larger 24 lb/hr injectors and a tune? Or could something else be the problem?

 

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How do you know it's running lean?...are you basing it off smog reading/then internet search?

Suggest a monitoring tool and look at the O2 sensor voltage to start.

 

Smog results and the O2 readings from a live time digital tuner. I'll re-check the 02 sensor voltage as well. What should it be reading?

 

check the ING. timing, it could be to far advanced.

 

I'll re-check the timing as well and make sure it's still at 6 degrees BTDC.

 

High NOx readings is a common issue with even stock engines in CA. Please scan or post your test readings for all 5 gases. This could help with a diagnosis.

I'm assuming you pass visual in that all smog equipment is still present (like the AIR pump)?

Check for vacuum leaks (including the HVAC system) which can cause a lean condition.

Has the EGR system been looked at? If you have an FSM, go through the functional test flow chart that's in the FSM to confirm.

Dirty combustion chambers can make the chambers run hot. Maybe run some Seafoam through the intake.

How old is the cat?

Is the ECM staying in closed loop under test conditions?

Take a look at your 2012 emission test results as see if the state didn't up the passing limits for 2014. This won't help you much but I've noticed this on test limits for my other cars.

There was another CA member here that burned a chip with the just the timing advance table "locked" at 10-degrees and got his car to pass.

Edit: FWIW, Here's the thread regarding the timing table:

https://www.thirdgen.org/forums/tpi/...g-3rd-try.html

 

Thanks for the tips. I live in Modesto so I'm not that far from Tracy. Yeah these stupid smog laws!

Yes I passed everything else for the visual and actual text results except for the high NOx values. Tuning is going to be part of what I have to do as well. I just wish it wouldn't run so hot, maybe the NOx wouldn't be so high and I could pass the test.

I've gone through the EGR system, replaced the valve, the switch, etc.

It goes into closed loop, I've had it on a live time tuner a couple of times.

Vacuum leaks and running seafoam are the next things I'll look for besides a chip and adding bigger injectors.

I had a new cat installed late last year (October-November) and I haven't driven my car 1,000 miles since it got installed so hopefully the cat didn't crap out that fast.

 

Did it fail at both speeds on the dyno?

 

Yes at both speeds on the dyno the NOx was too high.

 

Well you're close enough to me, you're welcome to come over and plug in my Scan tool and see what the ECM is seeing.

I don't recall how to log the data with it, but still have the manuals,,,it's a SnapOn MT2500.

PM me for contact info if you'd like.

 

Thanks. I'll try some other things first and see if I can get it to work.

 

These were the smog results from the last test:

15 mph test: 1,398 rpm

%CO2: measured = 13.5

%O2: measured: 1.8

HC (PPM): measured = 13, average = 48, max = 83

CO (%): measured = 0.00, average = 0.12, max = 0.71

NOx (PPM): measured = 1814, average = 227, max = 537



25 mph test: 1,345 rpm

%CO2: measured = 13.4

%O2: measured: 1.9

HC (PPM): measured = 9, average = 35, max = 83

CO (%): measured = 0.00, average = 0.09, max = 0.40

NOx (PPM): measured = 1645, average = 202, max = 494

 

Did you ever sort out your problem?

 

Not all together. I'm still working on it. I got a Summit Racing aluminum radiator. That took care of the over heating issues. The high operating temperatures was why it was running lean. Now I'm going through the ignition system. The car has a miss in it now and I'm trying to figure out where thats coming from. After that I'll see how it runs and try to smog it.

 

What made you suspect the stock style radiator was a problem even though it was new? What radiator did you go with?

 

Even after I installed the new stock radiator, my car was still running hot - over 240 degrees.

I got a summit aluminum 2-row radiator and it never gets higher than 220 degrees now. The additional coolant capacity the radiator has helps too. I had to have a friend of mine make custom mounts so it would fit. I keep the stock factory dual cooling fans as well.