E30-1987is idle issues

[Max87IS]

I want to preface by saying that I'm in no way a mechanic, although I've had my '87 for 25 years and it's mostly taken very good care of me.

About a month ago, my 1987 325is suddenly began idling at about 1500rpm. It would idle normally...very smooth purr at 800 rpm... on cold start first thing in the morning, then would be too high after about half hour driving.

Now, it has begun idling very rough, sometimes at that 1500rpm, sometimes lower, say 800-1000rpm. When driving, the car runs as it always does...perfectly smooth, plenty of power, no missing/ hunting/hesitation of the rpm. I had a guy take a look...he says he was not able to get a fault code; he says he cleaned the ICV, but it hasn't helped the issue. The car is still running great apart from this.

He said he suspected that the Idle Control Valve might be malfing, and since this seems to be an easy fix/replacement I was thinking of just putting in a new one; my first question would be with regard to the parts that are available, since they range in price from $45.00 after-market Chinese mfg. to $450.00 OEM Bosch parts. Is there really that much difference in those? Second question (probably should have been first) do these symptoms sound like an ICV issue?

Beyond that, does anyone have a different take on this? The car was tuned up & had timing belt/water pump replaced about 4.5 years ago. In terms of mileage, however, this car probably has about half the number of miles on the clock than one might expect, since I only drive it about 6 months a year. So...while the T-Belt is definitely going to be done soon, it really shouldn't need a tune-up...OR? Could this be something like a cracked plug? I use nothing but NGK plugs in this car (and in the previous 3 Bimmers I've owned) since they always seem to run better than any of the Bosch ones I've tried.

Thanks for any advice!
MaxIMG_7460.JPG

[superj]

not a cracked plug or anything like that. maybe the icv since it only does it at idle. could be a cracked vacuum line or something like that though

[Max87IS]

Thanks for the response. I was thinking cracked vacuum line too, but wouldn't that generate a fault code of some sort? Dude wasn't able to see anything like that. Visual inspection of vacuum lines and nothing obvious, but you know how that goes.

Is there really any difference in quality between an aftermarket cheaper ICV or should I suck it up and spend $450.00 on this (Yikes!).

Thanks again
Max

[82eye]

Is there really any difference in quality between an aftermarket cheaper ICV or should I suck it up and spend $450.00 on this (Yikes!).

Thanks again
Max

light years of difference. try cleaning the original out first. you can use carb cleaner

[OMGE30]

An '87 is likely a Motronic 1.1 DME, which does not store fault codes. That would probably be the reason your dude couldn't pull any.

Pop your VIN into realoem.com, search for DME. Likely will be listed under "Uncoded DME control unit", same as my model. You can verify there. If you have "HARDWARE 1.3" listed, congrats! That means your computer stores codes.

[82eye]

An '87 is likely a Motronic 1.1 ECU, which does not store fault codes. That would likely be the reason your dude couldn't pull any.

when did the coding plug come in ?
there was a guy recent with a $3000 buck machine that pulled codes with the engine running from the under hood code plug. . i don't think either motronic e30 versions store codes though.

edit : i have the later car with the plug.

[OMGE30]

when did the coding plug come in ?
there was a guy recent with a $3000 buck machine that pulled codes with the engine running from the under hood code plug. . i don't think either motronic e30 versions store codes though.

edit : i have the later car with the plug.

Pretty sure I have the same plug, the earlier software just doesn't have the ability. I spent an obnoxious amount of time wondering why the stomp test didn't work, then eventually someone verified that Motronic 1.1 just can't do that.

I remember that dude with the $3K machine, he was kind enough to make that video for my post I bet if we went back, we'd discover he has Motronic 1.3

[Max87IS]

Thanks to all for the responses. One symptom I forgot to include is that the 'check engine' light is on...mostly; it seems intermittent but mostly it stays on. As stated, I'm not a mechanic and have usually relied on one to address problems unless they're butt-simple. Ordinarily, I'd just throw in a new ICV and see what happens, although I'm reluctant to gamble that much money on an OEM one unless I'm sure.

Maybe I'll throw in a cheap one just to see how it affects it and then go from there; if it doesn't help I'll try cleaning the old one again and put it back.

[82eye]

Thanks to all for the responses. One symptom I forgot to include is that the 'check engine' light is on...mostly; it seems intermittent but mostly it stays on. As stated, I'm not a mechanic and have usually relied on one to address problems unless they're butt-simple. Ordinarily, I'd just throw in a new ICV and see what happens, although I'm reluctant to gamble that much money on an OEM one unless I'm sure.

Maybe I'll throw in a cheap one just to see how it affects it and then go from there; if it doesn't help I'll try cleaning the old one again and put it back.

clean the original first. there have been a raft of issues over that part new. and not just the cheap ones. you just spray it out with a bunch of cleaner first and see what that gets you.

[Max87IS]

Thanks...the guy said he already did that...doesn't seem to have helped. Car's still running great apart from this rough idle. It also appears that the part itself is no longer available as OEM Bosch replacement.<br><br>

[superj]

pop the hood and make sure the throttle body arm is fully returning when you move the throttle cable. i wonder if its hanging up sometimes so its not letting the arm seat fully against the stop when letting off the gas each time. sometimes that can happen because the little plastic pieces the cable routes through break and don't keep the right amount of tension on things anymore.

[Elvir]

I had similar problem on my E30 over the last years: In cold start idle is fine but after driving, idle stalling. But in January of this year i solved that. Problem was air leak in hose on brake booster. I put new vacum hose and now idle is perfect in every situation.

[Clio320i]

My 87is does do stomp test codes; you could certainly try that and see what happens. CEL being on always meant there was a code, which may or may not actually be particularly useful.

That said, the idle weirdness you describe to me indicates ICV, or vacuum leak (a small one might *only* be noticeable at idle; I have a similar situation in my E21 M10). What Elvir said about the brake booster lines: I'd check there first. There will be one or two that go from the TB to the booster and the connections at the TB are press fit; they get floppy after some decades. Most of us end up epoxying them back together. IIRC we used JB weld.

[82eye]

I had similar problem on my E30 over the last years: In cold start idle is fine but after driving, idle stalling. But in January of this year i solved that. Problem was air leak in hose on brake booster. I put new vacum hose and now idle is perfect in every situation.

tiny little air leaks add up to issues with these things. at some point it's just an idea to refresh all the rubber under the hood. i know a couple folk solved long running minor annoying issues this way.

[Max87IS]

Thanks again to all for the responses. Took it back to the guy and as it turns out, there is a leaky intake manifold gasket, which he's currently replacing. I don't know if I have the 1.1 or the 1.3 Motronic, but will follow up with him on that score. He says he just got new software that will diagnose my car.