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Discussion Starter #1
What a Day. Im so F&^% pissed its not funny.

It all started like this. My s38b36 91, Bog Stock 180,000 Kms full service history (in my hands for less that 1 year). I thought i might take it down and dyno it to see what kind of power its making before i apply some very light mods, mainly exhaust (muffler and cat) related. Obviously i will be able to measure the difference then.

It came up with this.





2 Things.

1. The guys could not believe the power this thing makes. 3.6l, stock standard, almost 20 yrs old and 180kms. 186KW at the wheels = 250 rear wheel HP. Remember this car is standard, nothing done to it whatsoever.

2. He could not believe i had not melted a piston given how lean the car was running looking at the air fuel ratio above which should basically be a straight curve, without spikes.

** Ok so i start shi**ng myself.

Get home, let the engine cool and immediately crack open the spart plug cover and pull a plug out. Guess what?

Bosch 5YDDC - 0.8 gap, used on e36 m3.

S38b36 should be running bosch 6YDC with .6m gap.

** This car was came with receipts from a so called specialist bmw place in Sydney, Australia. Im not going to reveal who they were, but you cant imagine what i want to do to them.

Questions i need answered from you guys in the know:

1. First thing tomorrow i getting correct plugs and changing them. Driving the car felt smooth enough, i would never have picked this without the dyno. What is likely to be the noticable difference with the correct plugs?

2. What potential damage could i have done already with the m3 larger gap plugs?

3. Once plugs are correct, im planning to lacate a workshop with a scanner who can read the O2 sensor and Air mass meter numbers and check if they are ok. Does anyone know the best way to test these readings and what they should be. Bentley and other Do not state testing on the s38 engines.

4. Im having the injectors tested and cleaned next week.

5. What are the chances the m3 plugs are causing it to run lean, and nothing else? 99% ?

6. If im still lean, i guess it's time to look at air leaks and etc. What else can be added to the list?

All help much appreciated guys! And i must really stress, my car drove beautifully, i would have never have known this ever! until either going onto the dyno or 2, melthing a piston. I suggest you ALL have yours checked!

Am i overreacting? Thx Again guys
 

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Plugs won't cause the car to run lean. Fuel delivery and mixture is controlled by a combination of the injectors, ECU, MAF and O2 sensor. Start checking your fuel delivery system and the integrity of your vacuum systems. How long has the fuel filter been in there? What about the pressure regulator? Test the flow-rate and static pressure of the fuel pump. A leak in the intake systems will cause a lean mix as well

And put the correct plugs in there, but don't worry too much about the plugs leaning things out.
 

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What color were the plugs when you pulled them?

tan/gray? = really lean (danger Will Robinson!)

light brown? = lean

brown? = Okay

Black? = rich

Black & wet? = problem

You'll probably find more then one weak link in the system, since it usually can compensate for small variances in fuel pressure and air/fuel mixture.
 

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Unfortunately a 20 year old MAF will underperform and need replacing. Clearly the health of everything else also needs establishing for peace of hard-driving mind.
 

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I would also check your throttle position switch. Make sure it is detecting WOT. The PCM will run lambda 1 (14.7AFR) everywhere without seeing the throttle switch at WOT.
 

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Ouch. I'd definitely take a close look at all vacuum lines.

A nice leak in the intake system helped cause the demise of #5 for this one...
 

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Discussion Starter #8 (Edited)
Hi Guys,

Thx alot for your replies. Much appreciated.

Since the post, obviously i corrected the plugs, also after the scan was showing Faulty MAF code, i replaced the o2 sensor (which was original and in shocking condition however not throwing its own code, little PITA as you need to drop the front pipes to get a spanner onto it) and intake air temp sensor located in the air box (only $AUD 35, pn 1362 1725 323) which was reading 90 deg celcius at idle, obviously impossible. After o2 replaced MAF code has not come back.

I will be checking everything on a 5 gas machine shortly to see how its all going before another dyno run.

FYI, i will be completely overhauling the remained of the ignition and fuel systems, and have put some part numbers together should anyone else wish to do the same.

Prices In australia dollars:

Distributor Cap - 1211 1725 070 - $75
Rotor Button - 1211 1734 110 - $22
Thermostat sender unit - 1262 1747 281 - $88
Temp Sensor - 1362 1709 966 - $15
Temp Water Sensor - 1362 1401 945 - $113
6 * Fuel Injector Reco - $120
TPS switch- already have one.

Already have a new thermastat and will flush and bleed system.
I have valves many times, will do again.
Also will do a TB balance check, anyone know of a good DIY on this?
After all that i might bite the bullet and Get a bew MAF, Not RMFD.


I might also change the crank angle sensor, more preventative than anything : 1214 1312 895 - $122

----

Spoke with BMW Aus and they reckon they have never sold a fuel reg to suit s38 or any e34 for that matter. Are these documented to fail or do they fail often? How do you know if once is bad? Alos how an i to test the flow rate and static pressure of the fuel pump?


M540i LE - Mate it would be great if you can recommend an s38 guy in Sydney? Would really appreciate that.

Look forward to hearing back from you guys.
 
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