E30 injectors!?!

[e30patalohas]

Hello all,
I recently acquired a good condition 1984 325e, alpine white, automatic, black sports interior, with moderate neglect...:|

The car runs well enough, and handles great on stock suspension with great feel. I have been chasing down a problem with the engine. The exhaust smells gassy and occasional roughness and missing. Milage is okay around town 21-22 and great on the freeway light cruising at 65 gets 32 mpg.

I want to figure out the gassy exhaust before I move on to suspension and other upgrades.

Here's what I have done so far:
-Replaced in tank fuel pump it was dead.
-replaced high pressure pump because it was making noise but due to cavitation from no prime so I think it was already good but oh well.
-replaced fuel filter
-check fuel regulator with know good one no difference.
-checked fuel pressure with gauge per Bentley instructions: 40 psi on relay bypass (spec is 43psi +- .9psi so recommend replacement) when I pinch off return psi goes up to over 43psi. So reg may need replacing.
-new Bosch plat plugs
-wires look good (maybe recently replaced)
-cap and rotor visual insp. and light cleaning looks okay
-checked AFM movement feels okay, cleaned interior was pretty good to start
-vacuum hoses inspected and replaced a couple
-ICV inspected and cleaned and adjusted (was way off)
-adjusted throttle body
-checked TPS
-checked temp sensor resistance ok
-ran a tank with Seafoam
-replaced O2 sensor

Still gassy exhaust!
So figured injectors. Probably original.
Ordered new injectors. Installed and engine runs much smoother, fires up instantly (I think old injectors were leaking into cylinder and depressurizing fuel rail) but still GASSY smell! Milage went down too!!!

Recheck with Bentley Manual - aha!!!

1984 has split injectors based on manufactured date!

Pre 9/84 requires high impedance injectors.
9/84 on requires low impedance injectors.

My car born on 7/84. Had LOW impedance injectors installed when I bought it.
Replacement injectors were also low impedance.

-Could this be the source of the gassy fuel smell from exhaust?!?
Re-ordered high impedance injectors.

Questions:
-running the wrong injectors low imp. = higher current and possibly heat damage to ICM?
-Anyone know if the ICM is different from 9/84-on models vs pre 9/84 models? -Anyway to check which I have in the car? Maybe ICM is specced/swapped for low imp. Injectors already? Not knowing the full history of the car leaves me wondering.
-if I install the high impedance injectors will there be a problem if the ICM is made for low impedance injectors?

Only other item I am thinking of changing is the Catalytic converter. It is probably either burned up or clogged due to all the rich exhaust over who knows how long? Could excessive back pressure be causing any of the symptoms?

Sorry for the long post, but I need expert advice here.

Thanks all!!!

[jlevie]

You have the wrong plugs in the engine. The old style single electrode copper core are what's needed

Having the wrong injectors will have an affect. Having high impedance injectors where low impedance are called for should not harm the DME's control circuits. Even if everything else is working correctly intake leaks can cause partial or complete misfires and result in a smell of gas in the exhaust. Have a shop run a smoke test on the intake & block.

The pressures you saw in the fuel (40/43psi) say that the wrong FPR is installed. Those pressures would be correct for an M20B25 engine (3.0bar regulator). The M20B27 engine that you have calls for a 2.5bar FPR. The excess pressure will result in too much fuel being delivered.

[e30patalohas]

Wow! Okay didn't realze that the FPR should be at that pressure!
I will source a 2.5 bar regulator immediately.
I will also get correct plugs. Installed are Bosch platinum 4037 (not correct?).
Will have running the low impedance injectors while calling for high impedance have done damage to the ICM?

Thanks for your insight! You have been a great help.

[e30patalohas]

I checked my FPR it is the 2.5bar spec. I rechecked the fuel pressure and it reads around to 37-38psi which is close to 36.75psi (2.5 x 14.7) or is my math wrong? I am using the O'riely rental unit, so no guarantee on accuracy.

So still wondering if the low impedance injectors would cause the gassy smell if my 07/84 build calls for high impedance injectors?

Does the copper core plugs make thta much of a difference in spark quality?

I will work on a smoke test when possible. Is there a DIY smoke test that anyone can recommend?

Thanks!

[paperplane94]

DIY smoke test?

Well there are some threads about using a party fog machine.

But this is the one that most interested me...
http://www.youtube.com/watch?v=zMok2y05jNE

[e30patalohas]

Okay so I did more research on injectors...

-Pre-09/84: BMW part 0 280 150 716, WHITE injector plug connection, yellow injector shield and coil resistance of 14.5-17.5 ohms.
-Flow is 140cc at 2.5 bar

-09/84-on: BMW part 0 280 150 126, LIGHT GREY injector plug connection, orange injector shield and resistance of 2.0-3.0 ohms
-Flow is 177cc at 2.5 bar

So 25% more fuel being injected than necessary...?

[e30leigh]

impedance wrong on injectors will result in huge fuelling issues. its a wounder it runs at all in my experience. if you cant find the right high impedance injectors, resistors can be added into the line of the injector trigger pulse wires. but the right ones will be needed. so id highly recommend the right injectors before you try to go down that road.

[e30patalohas]

Roger that! New replacement injectors are OTW, flow will be close to spec. as well as impedance.
Hopefully this will fix the gassy exhaust and low milage.

[jlevie]

DIY smoke test?

Well there are some threads about using a party fog machine.

But this is the one that most interested me...
http://www.youtube.com/watch?v=zMok2y05jNE

That is cute and may work in some cases, but it no substitute for a smoke machine and a properly conducted test.

To smoke test an engine you plug the exhaust and replace the AFM or MAF with an adapter for introduction of smoke. Then you pressurize the engine with 2-4psi of smoke and hold that pressure for a while. I generally hold the pressure of 10-15 minutes to give the smoke time to move through the engine and out the leaks. You'd get nicotine poisoning trying to do that with a cigar.

[e30leigh]

That is cute and may work in some cases, but it no substitute for a smoke machine and a properly conducted test.

To smoke test an engine you plug the exhaust and replace the AFM or MAF with an adapter for introduction of smoke. Then you pressurize the engine with 2-4psi of smoke and hold that pressure for a while. I generally hold the pressure of 10-15 minutes to give the smoke time to move through the engine and out the leaks. You'd get nicotine poisoning trying to do that with a cigar.

LOL!!!!!!!!!!! i second that....

[gp.plus]

Check to see if the black cover on the afm has been removed, po may have messed with the spring in there. This could cause a rich/lean condition. I had a very similar situation to yours and after much frustration this was my problem.

[e30leigh]

Check to see if the black cover on the afm has been removed, po may have messed with the spring in there. This could cause a rich/lean condition. I had a very similar situation to yours and after much frustration this was my problem.

that is possible. some people "adjust" the spring in there as they think itll fix another issue they cant find. where really its just making things worse.

possibly try swaping it out for another one that is known to be untouched and working right off a car that is running right. if the issue is still the same put yours back and keep looking.

[Dirtboy]

How bout the oxygen sensor? Just a thought...

[e30patalohas]

Thanks for the tips fellas...I have replaced the O2 sensor, no diff, so hoping my high impedance injectors come on Monday and they fix the rich exhaust smell. The AFM seems intact so that's a good thing. I will keep u posted after the injectors get changed out.

Still wondering how the DME has held out so long without blowing up running low impedance injectors...If that's the problem...it's been 3 months since I've owned it and I know the PO has been trying to solve a similar issue due to the highlighting in the Bentley's manual that he gave me...?

The reckoning will soon be at hand.

[Thizzelle]

diy smoke test?

Well there are some threads about using a party fog machine.

But this is the one that most interested me...
http://www.youtube.com/watch?v=zmok2y05jne

blow cigar smoke into intake