Engine feels less eager & a bit hesitant at constant spe

[minime1275]

My '89 320 has started to feel sluggish the last couple of days. It started when I was pulling away from some lights last week and because my window was down I could hear it misfire a couple of times then it seemed ok.

However, it doesn't feel as torquey or accelerate as quickly as it did a week ago. Also, I've noticed it seems to be a little bit hesitant/jerky when trying to maintain a constant speed in 4th or 5th - it is smooth (if a little slower than usual) if I wind it up towards the top of the rev counter but something just doesnt feel quite right.

I drilled some holes in the airbox (below the filter element and before the air-flow sensor) last week. Because the holes are below the filter and before the air-flow sensor, I reckon its just a coincidence that its not running right. Does anyone think otherwise?

Obviously if people think it has something to do with the holes i drilled for induction noise, I will tape them up again, but surely the air-flow sensor would compensate?!

Could it be to do with the noisy fuel pump? Its not too bad, but a bit whiny when I first start it up.

[Andy_magic]

Sounds like it's leaning out too much to me.

I've drilled the air box on mine (how barry!) and it hasn't changed the running of the engine at any load, it does sound nice though.

You are right to think the AFM will sort out any increased airflow gained.

What I would do is check the AFM to TB hose very carefully asyou may have disturbed it and introduced an air leak, the are under Ԛ£15 to replace. Of course you should check all the hose clips etc for air leaks.

At the time of writing my car is running a bit lean due to a perished AFM to TB hose.

Out of interest, where did you drill the holes. I removed my air box and drilled on the side that faces the inner wing so as to minimise warm air intake.

[minime1275]

Sounds like it's leaning out too much to me.

I've drilled the air box on mine (how barry!) and it hasn't changed the running of the engine at any load, it does sound nice though...

...Out of interest, where did you drill the holes. I removed my air box and drilled on the side that faces the inner wing so as to minimise warm air intake.

Cheers for the advice. It does sound good! Glad I didnt fork out Ԛ£80+ for a K&N!

I drilled the holes on the same side as you and also few on the bottom of the filter box too. I used a 22mm hole-driller thingy and drilled 4 at the side and 4 at the bottom and was amazed at how good it sounded under heavy acceleration yet it sounds standard when cruising!

It crossed my mind that the above problem has occured because crap might have been sucked into the engine via the air-intake, while I was experimenting with the induction noise (because at one point I drove it up the road with no filter whatsoever before realising it could've been sucking in the foam sound proofing on the underside of the bonnet, which is all crumbling and flaking! )

I will double check the hoses as you've suggested, Andy, but Im sure they were all ok when I put the drilled filter box back on. All the jubilee clips were done up tight etc.

[dazleeds]

if you find out what it is let me know cos mine sometimes behaves as you described my airbox hasnt been drilled yet Daz

[vjay]

[color=blue]I had a similar problem with mine (being the 325is) a couple of years ago when I toke it for its first MOT under my ownership. Later on (a couple of months), found out I was losing power and torque, because the exhaust manifold was split. This caused a considerable loss of back pressure needed by the engine (as mine was split between two ports), so essentialy the engine was only running on 4 cylinders instead of six. It may be worth checking. It caused me a whole lot of hassle, and for something so simple.!

[minime1275]

I had a similar problem with mine...Later on found out I was losing power and torque, because the exhaust manifold was split. This caused a considerable loss of back pressure needed by the engine...It caused me a whole lot of hassle, and for something so simple.!

They aint cheap on these cars, are they?

[johnono]

was it expensive/difficult work u had done.. as i may be visiting the whole exhaust manifold department soon

[vjay]

It depends which route you go. A new one ain't cheap (about 450ish), I replaced mine with a second hand one ( does the job for about seventy quid), now looking at going stainless though better air flow from top to bottom. They can be a pain to get off, a couple of the bolts aren't in the most accesible places, but well worth it.

[johnono]

so was the mani actually split/cracked or was it the gasket that was blowing?

ive clunked the underside a few times as shes a bit low, and im thinking ive dine something as i can hear the midbox "paping" under the car

[vjay]

Mine was pretty low at the time too, which also got clunked a few times (to many me thinks). Essentialy it was just a crack but over time she got bigger, eventaully when I came to replace her, it may as well been a two piece manifold, the only thing left holding it was the casting top and bottom. Essentialy in my experince (especially if running a k&n or modified air box) you wouldn't necessarily notice a crack in the manifold, however you should notice any kind of blowing from the underside...... Check it out, got to be worth a look.

[johnono]

nice one vjay its deffinately localised to the midbox region, so i reckon ive done it in, mabey cracked a weld or summin, but im sure the shock cant be good for the manifold, which could prove more serious if i have fcuked it