M20B28 - Pinging/ Smog Questions

[RCM3]

ISSUE RESOLVED! New CPS fixed the issues.

Hello guys,

Ive done a good bit of research on this subject and have received advice from members in the past regarding smog on another M20 but this situation has a few new variables. The car would be a CA gross polluter but I did a pre-test thankfully. The emissions are pretty bad (see pic below...)

Background on the car:

I bought this e30 somewhat recently, this e30 has 128k on it and a fresh and expensive engine rebuild completed about 5 years ago. This e30 also is stroked to 2.8l done by the PO and has some bigger injectors installed (40 lb. Mustang? I think the PO said). I put in a chipped 173 ECU after I bought it. Everything else is OEM.

The car runs great, makes very nice power also. No idle issues or CELs. I just did an extensive update on the M20: timing belt, tensioner, water pump, O2 sensor, AFM, oil, oil filter, air filter, fuel filter, spark plugs, spark plug wires, thermostat, coolant hoses, BMW coolant, intake manifold gaskets, valve cover gasket. I run only 91 octane in it.

I have noticed at WOT (wide open throttle) when pulling a hill I sometimes hear a rattling from the engine. It happens once I put the throttle down and attempt to accelerate. The car shows essentially no changes in performance while accelerating, but makes this rattle sound, marbles in a tin can kind of noise.

Im wondering if this is related? Timing is spot on, maybe carbon build up from running very rich while the PO owned it?

I have stock M20 injectors or M50 injectors I can swap back in. I also have a stock 153 ECU and factory 325iS exhaust with a solid cat that passed my recently totaled 1988. Im going to change those items out, but is this enough to lower my incredibly high emission numbers? Is there a great product out there I can use to break up any carbon build up? Anything else I can look at to make this car pass smog?

The car has a 2012 sticker on it, so this stroker engine at one point passed smog. Local exhaust shops are booked up for weeks in the town my parents live in (where this e30 is currently). They all want to swap on an expensive cat, and while that might help lower the emissions, I dont think it will ultimately solve this issue without correcting a few other things

Thanks for any information guys.

-Ryan

[RCM3]

I just used some SeaFoam, 1/3 into the brake booster vacuum line, 2/3 into the fuel. Is repeating the process of introducing 1/3 pint of SeaFoam to the intake recommended/ effective if I do in fact have heavier carbon build up? The internet offers conflicting info.

I brought the car to one final smog shop and they wanted to do a deep engine clean (tech suspected lots of build-up based on a quick once over and looking at the smog results) and then suggested getting a new catalytic converter. The deep cleaning was expensive for what it was, so I figured Id run a cleaner through myself.

Then again, maybe the engine is still clean since it has seen very few miles since the rebuild? If the smog numbers werent so high I wouldnt be as worried and just replace the cat.

[efficient]

Wow! Nox is sky high. Vacuum leaks raise nox aswell and also a faulty coolant system.
My friends 325 89 was blowing on nox aswell, we haven't figured it out yet but the car passed smog lol

[RCM3]

Ive never had an e30 fail this miserably! Im going to go back through the vacuum system. But since the car runs and idles so well, I dont know if thats the issue. The car also is cooling well, it runs a the 25% mark on the gauge.

My last e30 didnt blow nearly the white smoke this one did when I SeaFoam'd it. This e30 smoked out the little valley my parents live in out in the country. Is the amount of smoke coming from the exhaust correlated with the amount of carbon material being removed? Ill have to research that...

[rommaster2]

I'm assuming the engine has a chip in it? If so do you know what type of tune it is running? Your explanation of what it sounds like when driving under load sounds a lot like pinging, perhaps too much timing in the tune.

For what its worth though you can check the catalytic converter function with a lift and an infrared thermometer. The engine needs to be running and the cat needs to have been warmed up (like 10 to 15 minutes of driving should do). A functioning cat should run between 800-1200 degrees Fahrenheit and the downstream should be 100 degrees hotter then the upstream exhaust pipe temps. If the cat will not heat up or the pipe farther back is colder then the incoming air the cat is not doing its job.

A vacuum leak can cause a lean miss which would also produce those sorts of HC's however I would think knox would be lower.

[RCM3]

I'm assuming the engine has a chip in it? If so do you know what type of tune it is running? Your explanation of what it sounds like when driving under load sounds a lot like pinging, perhaps too much timing in the tune.

For what its worth though you can check the catalytic converter function with a lift and an infrared thermometer. The engine needs to be running and the cat needs to have been warmed up (like 10 to 15 minutes of driving should do). A functioning cat should run between 800-1200 degrees Fahrenheit and the downstream should be 100 degrees hotter then the upstream exhaust pipe temps. If the cat will not heat up or the pipe farther back is colder then the incoming air the cat is not doing its job.

A vacuum leak can cause a lean miss which would also produce those sorts of HC's however I would think knox would be lower.

The engine is chipped. I actually do not know the specifics on the chip nut it will be coming out tomorrow. Now that you mention it, after the install of the new ECU is about when I noticed this sound starting up.

Ill get the car up tomorrow also and get out the infared temp scanner. Hopefully this is the issue. Ill also do another check to find any potential intake leaks however during the tune up I replaced many of them including the intake boot.

Ill report the findings tomorrow. Thanks for the pointers!

[efficient]

When the car is at operating temperature spray some carb cleaner around the intake side and injectors and see if the carb cleaner changes the way the motor acts. If it changes then you got a leak

[DesertBMW]

all numbers are high, this indicate bad converter. Put back stock chip, and stock injectors and new cat converter, should pass then.

[MR 325]

Your description definitely sounds like pinging and this is not good! Stop driving it like this until you fix the issue. I'd have to agree with above. For smog your best chance is with stock injectors and a stock chip. But after that you need to get a proper tune in that thing before something happens.

Theres always the "other" way to pass smog...

[jlevie]

The mish-mash of mods to the engine certainly makes diagnosis difficult. So I'd start by replacing the injectors and chip with stock M20B25 parts and making sure that the AFM and FPR are M20B25 parts. Then I'd run a rail fuel pressure check and a smoke test, repairing as indicated until a repeat test reveals no leaks. I'd also replace the O2 sensor, ignition wires, distributor cap/rotor with a new OE/OEM parts and replace the plugs with a fresh set of NGK ZGR5A's. I'd also run compression and leak down tests, which might indicate a deeper problem that requires correcting. That may be enough, but if HC & NOX are still high I'd try another 173 DME (or more than one). If still off, replace the non-OE catalytic converters with a new OE down tube assembly.

[efficient]

Fixing a car just to pass smog is pricey but then again its nice to have a nice running car.

[RCM3]

Your description definitely sounds like pinging and this is not good! Stop driving it like this until you fix the issue. I'd have to agree with above. For smog your best chance is with stock injectors and a stock chip. But after that you need to get a proper tune in that thing before something happens.

Theres always the "other" way to pass smog...

In the process of doing this now. I just sold my spare 173 ECU the previous day so Ill need to grab a new one. Im going to let it sit in the garage until I source another ECU and some tested injectors.

I know about the "other" ways... but I want to ensure the car is running properly before I go that route.

The mish-mash of mods to the engine certainly makes diagnosis difficult. So I'd start by replacing the injectors and chip with stock M20B25 parts and making sure that the AFM and FPR are M20B25 parts. Then I'd run a rail fuel pressure check and a smoke test, repairing as indicated until a repeat test reveals no leaks. I'd also replace the O2 sensor, ignition wires, distributor cap/rotor with a new OE/OEM parts and replace the plugs with a fresh set of NGK ZGR5A's. I'd also run compression and leak down tests, which might indicate a deeper problem that requires correcting. That may be enough, but if HC & NOX are still high I'd try another 173 DME (or more than one). If still off, replace the non-OE catalytic converters with a new OE down tube assembly.

I know the AFM is from a B25, Ill check on the FPR and swap in the proper unit if it has been swapped out.

I did do the cap and rotor as part of the maintenance overhaul 2 weeks ago. The spark plugs are new Bosch plugs I ordered from Pelican Parts but I will look into sourcing the other plugs also.

Swapping on the BMW OE manifold through cat assembly this weekend also.

Thanks for the advice again jlevie, your advice helped me get the last e30 to pass CA smog.

[henryki]

It's a shame you're in Nor Cal. I have a guy down here that'll "pass" your car for $150

[RCM3]

Hopefully it doesnt come to that!
The neighboring counties by me dont require a dyno smog test, even that would be nice. Im not heading home for at least a week, so once I swap some parts out Ill update the thread with the post-smog outcome.

[mkcman17]

I don't even try to smog e30s anymore. I'll pay for the security of a pass.

Good luck Ryan!