M52B28 running rich

[e30ftw 410]

My M52B28 is running abit rich at times, especially when engine is cold, can see it is spitting unburnt fuel sometimes and when decelerating it is backfiring when warm.

Had it scanned a while back and it came up with an 02 sensor fault about heating (forgot exactly), But I have since replaced MAF and new bosch O2 sensors, Seems to run alot better now but it is still running a tad rich. Have also replaced the coils but they made no difference, also had new spark plugs when it was put into my e30.

Idle is fine, it never runs rough or stalls.

Probably the M50 Manifold?

I have a new air filter and intake to sort out, since I am using a crappy old setup. But any ideas on what else can cause this? I think I will need to hunt for vacuum leaks but I have all new gaskets / hoses throughout the intake.

Edited March 5, 2014 by e30ftw

[kingkarl 136]

Yeah I'd start with Vac leaks

[twisted 45]

How's the low end power? Could be timing is out/vanos needs attention

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[e30ftw 410]

I've never checked timing, I have new VANOS seals sitting around to be done at some stage however, It is abit down on power in the lower RPM than what I would expect then from 4000+ pulls hard, Probably a combination of M50 manifold + bad VANOS seals.

[BM WORLD 1283]

vac leaks

also check the coolant temp sensor for the ecu plugs , wiring and sensor itself

[e30ftw 410]

I really can't think of any places there would be a vacuum leak, all the hoses seals etc are new.

The only actual difference is I am not running the CCV system the M52 normally has, instead I ran a hose from the crank case into the intake like an m50. One thing I notice, If I take the oil cap of the engine while running, the idle turns really rough (simulates a vacuum leak?),

When I put it back on, it idles perfectly again.

True I actually have a new water temp sensor I never installed. Slipped my mind, But I guess that will make sense if the ecu thinks the engine is still cold and runs it richer.

[yng_750 247]

well the ccv system regulates the vacuum. stops it from sucking to much air and oil out. if you have plumbed the breather hose into the intake it has to go before the throttle body where vac is a few pounds rather than inside the plenum where it can be much greater otherwise it sucks to much air through. most cars run it before the throttle body except for some engine like the m20. in the mean time, vent the crank hose to atmosphere and plug the intake hole. see if it makes a difference.

also coolant sensors.

[e30ftw 410]

It's actually sitting T piped between the Intake boot and ICV line, so kind of inbetween the TB and ICV. So unless the engine is sucking alot of air through the ICV line not sure if it makes much of a difference. I may give it a go though and see how it runs like that.

[e30ftw 410]

OK So now I have done VANOS seals, Cam position sensor (fault coded when I checked it at Andy's), Intake air temp sensor and coolant sensor.

It is still running abit sluggish and has a small miss / hesitation and never really takes off like I know it wants to and has done before.

My guess is it has to be a vacuum leak, the only place will be at the crank case vent, I did block this off at some point and it made no difference to the idle, But possibly under load the flimsy connector to the valve cover could be a vac leak. How is everyone else running their CCV with an M50 manifold on M52? (I haven't blocked it and taken it for a drive however this will be my next step)

I'm looking into the oil separator valve found on M50 engines, Looks like a valve that sits inline with the crank case hose that regulates how much of the crank case it's venting into the intake?

Any suggestions for tracing vacuum leaks under load? My idle is perfect, 900 solid no fluctuations or anything. So I feel if there is a leak which would likely be the cause to my driving issues it must be on throttle under load?

Edited April 1, 2014 by e30ftw

[twisted 45]

Checked your crank sensor? Got a similar issue with mine. Has just started having cold start issues too, so will check with multimeter tomorrow. My 540 had a bad crank sensor with no codes.

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[_ethrty-Andy_ 2132]

you have replaced so muh stuff now im starting to think its how the DME was flashed????

[zero 1162]

Any suggestions for tracing vacuum leaks under load? My idle is perfect, 900 solid no fluctuations or anything. So I feel if there is a leak which would likely be the cause to my driving issues it must be on throttle under load?

Spray brake cleaner on different parts of your inlet manifold etc while the motor is running, and if the engine revs a bit higher when you are a spraying a certain point - there is your leak.

[e30ftw 410]

Yeah thing is it's run fine before and still does, But sometimes (actually most of the time), it is just quite hesitant like it sounds like it's going hard but it's not really. Feels like the cars heavy kind of thing? Hard to explain.

I know that method, But I am meaning if it's only vacuum leaking under engine load in high rpm. How are you able to tell.

[e30ftw 410]

Checked your crank sensor? Got a similar issue with mine. Has just started having cold start issues too, so will check with multimeter tomorrow. My 540 had a bad crank sensor with no codes.

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Yes I have, wish I bought one on my last pelican order but I may do another.. How much does it affect drivability of the car? I assumed it was similar to the m20 one where it's there to sense the engine position for ignition timing, if it were bad the car wouldn't fire type thing. Will look into it though probably the only thing I haven't touched haha.

[_ethrty-Andy_ 2132]

what diff is in it? definately felt a bit slower than my M52 swap. you will get there!! as always, anything i can do to help just let me know etc