1989 325ix Off Idle Engine Hesitation - Video Included

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1989 325ix Off Idle Engine Hesitation - Video Included

Postby c10seth » Wed Dec 11, 2013 2:00 pm

Hello,

I'm new to the BMW world, so I'm learning all the ins and outs of the e30s. I've dabbled in a lot of stuff that includes vintage trucks, 4WD trucks, Hondas, Subies, and sport bikes.

Here's my issue for you seasoned BMW enthusiasts: I have a little hesitation or sputter that happens when I tip into the gas from idle. I have changed the cap/rotor, plugs, wires, oil & filter, and air filter for the engine thus far.

YouTube Link: https://www.youtube.com/watch?v=NPmmh8D4DqM

I've also rebuilt the front axles, have new front lower control arms, and am replacing a rusty front fender. So, lots going on! -grin-

Kindest Regards,

c10seth
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby M20_fever » Wed Dec 11, 2013 2:57 pm

Welcome to e3p! Clean car you got there. The hesitation you hear is totally normal for an m20, not much you can do about it. They put pretty heavy flywheels on these cars, so throttle response off idle isn't great. Even with my lightened flywheel and no accessories or fan my M20 does the same thing. You can adjust the idle up a tiny bit to improve response, but if you do you need to check/adjust your tps to make sure your still hitting the idle circuit or it will run like crap. Some people may recommended adjusting your afm, don't.

As for the squealing, have you tried turning on the AC to see if it goes away? Sounds like a failing compressor clutch to me.

Your fuel pump is louder than any of my e30s have been. You can check fuel pressure at the rail to make sure its up to snuff. If it doesn't cause any drivability issues I would leave it be.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby ten2doyle102 » Wed Dec 11, 2013 3:04 pm

Not on topic.... but that's one of the cleanest IX's I've seen... nicely done. :)
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby Yoshi » Wed Dec 11, 2013 7:26 pm

I don't recall that being normal for an M20... I had that once but I forget what I did to fix it. How are the ignition components?
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby M20_fever » Thu Dec 12, 2013 12:54 am

Dunno, unless there is something in that video I'm missing it sounds exactly like mine.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby c10seth » Thu Dec 12, 2013 1:22 pm

Hey, thank you for all the help ^__^

The car spent 20 years in Windsor and is a little crusty around the edges, but for being 25 years old with about 160,000 miles it's in great shape. The original owner was meticulous!

As for as the ignition system goes I was thinking about replacing the coil. I tried measuring the resistance across the terminals of the coil and my results were rather inconclusive. I've already replaced all the plugs, wires, and cap/rotor along with the air filter and engine oil/filter.

If the M20 is just kind of finicky off idle then that really doesn't bother me. I just wanted to make sure I wasn't missing an adjustment or overlooking a dirty sensor.

I have ran into some driveabilty issues with the car - the last owner was very honest about a "hick-up" or misfire the car had before I came to look at it. When I drove the car it was fine until about 4k rpm where it would then just fall on its face until the revs came down and then it would be fine. Some research that I have done suggests that it may be the fuel pump/filter. It didn't matter what the engine load was either; it would always stop climbing rpm's at about 4k rpm. I can free rev it in my garage just fine though.

Thanks again for all the help, guys. I bought this car to go to Sno*Drift this year and it's going come hell or high water! XD

-c10seth
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby M20_fever » Thu Dec 12, 2013 3:54 pm

OK, we WILL need videos of that thing sliding around! I'm actually trouble shooting a similar issue with not going past 4800rpm under load, and I'm also leaning towards a failing fuel pump. I still need to test the cps and cts but I doubt either are faulty.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby c10seth » Thu Dec 12, 2013 5:18 pm

I'll try to get some action shots when I get her back on all four tires. I'll see if she keeps up the misfire when I finish all the work I'm doing. Then if she is I'll look into a new fuel pump and filter. New fuel pumps are about $200 too -lll._.-

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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby Yoshi » Thu Dec 12, 2013 6:16 pm

eh. I highly doubt it's the fuel pump. If that were the case, you would have driving issues at higher loads. It wouldn't cause hesitations at idle. If it were a fuel pressure issue, I'd point at the regulator. But even then, it should cause regular driving issues.

I believe issues like this are signs of a wearing system, not a dying system. Perhaps too much fuel is getting in due to a vac leak. Or due to a bad O2 sensor.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby c10seth » Thu Dec 12, 2013 6:23 pm

Dang. No I'm kind of really lost on where to start since the car starts fine, free revs to 6k fine, and drives fine below 4k under load. Anyone have any diagrams of the entire fuel system or a shop manual I may download? Thank you.

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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby Yoshi » Thu Dec 12, 2013 11:04 pm

I think Tony is working on it.

I think you're thinking too hard about this. Cars need 3 things. Spark/fuel/air. If any one of these is wrong, things won't happen right but each gives off a specific symptom. Bad ignition usually causes issues on higher load. Which isn't your issue so we can put that on the back burner. That leaves us with fuel/air. Air is very possible. perhaps you have a small vacuum leak. At higher rpms, the little leak doesn't make that big of a difference so it fits in this scenario. Lastly is fuel. Poor fuel pressure causes the injectors to "spit" instead of mist. At higher loads/rpms, the heat and air velocity can still easily combust but down low it might not ignite properly. I would rule out a dead injector but you can easily check that.

I would say the most likely is vac leak. The intake boots tend to rip. the ICVs tend to get stuck open or their hoses weaken due to age (cuz... it's rubber) and can leak. There's a port at the bottom of the M20 throttle body that goes to a charcoal canister. Those almost always crack. There's also the cross over pipe from the throttle body to the valve cover that can leak. There's also the "bitch" tube between the intake manifold and the oil pan where the gasket goes bad and causes a leak. Shit, I think even the oil cap off will cause the car to idle like ass.

Fuel related, I would guess pressure. Get a fuel pressure gauge for $15 (There's a thread with a link to jegs for one) and see if you're at ~35psi at idle.

go go go.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby M20_fever » Fri Dec 13, 2013 4:55 am

Here is the Bentley manual in PDF, but I would still recommend buying the published version.

http://www.e30performance.info/hostedfiles/e30bentley.rar

password is bmw.
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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby 7pilot » Sun Dec 15, 2013 4:47 pm

Welcome. :wink:
1, Your valve clearance may need adjustment as the engine is more tappy than my engine.
2, the stutter at tip in of the throttle is pretty much normal as the intake air charge has mass and it has to accelerate past the barn door of the AFM and then get past the throttle body butterfly valve. The barn door metering flap of the AFM also has mass and has to swing open to admit the intake charge. So there will be a little lag between the instant that the throttle is opened and the intake charge gets the AFM opened, thru the intake elbow, past the TB and getting ignited.
There is also the chance that there is an unmetered air leak around the aluminum elbows of the idle control valve.
3, I think the fuel pump is a little too load for my comfort. I can just hear mine and it is only a couple of years old. Yours sounds like it is cavitating or coping with an old fuel filter.


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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby c10seth » Mon Dec 16, 2013 5:40 pm

Thank you very much guys. I got the car all put back together on Saturday afternoon, took it out, and it was just awesome!! I drove the car from Ann Arbor to Kalamazoo to play in the snow with some friends and the car performed like a champ all weekend. I think I put almost 500 miles on the car ^_^.

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Re: 1989 325ix Off Idle Engine Hesitation - Video Included

Postby M20_fever » Mon Dec 16, 2013 6:51 pm

nice! Looks way better with weaves.
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