e30 has bad idle

RodneyWright · **Posted:** Sun Dec 30, 2012 10:47 pm

Haven't driven the e30 much over the last few months and battery dies on me (yeah, I know, either drive it or buy a battery tender). Did a charge on the battery about 3 weeks ago and went out for the afternoon and the car ran great. Parked the car and battery died on me, so I charged it w/ a 2 amp trickle charge for about 3 hours and then tried to go for a drive. So here's what happens.

> Start the car up when cold w/ no issues.
> Car feels a bit sluggish under acceleration when cold
> Once the car warms up, idle's around ~500rpm and has a slight surge
> Car drives ok when warmed up, but a quick lift off of the accelerator will cause the engine to die, have to ride the gas while braking.

There are no codes on the peak scanner and no billowing black smoke under acceleration. I've done a quick check of the air intake past south of the MAF and can't find any holes or leaks. The interweb suggests either a bad O2 sensor or bad MAF. I find it strange that it ran fine when I parked it and after a battery charge, it won't idle well. Plan on buying some MAF cleaner tomorrow and clean. Any typical places I need to check for broken air lines? Other suggestions?

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

While it's running, pull the dipstick out a few inches. If there is no change, you have a big air leak in the intake tract somewhere. If the engine runs even worse, then I'd keep looking. Maybe suspect the idle air valve.

M20 runs under vacuum unlike other engines. An unmetered air source (aka leak) could cause some of the symptoms you describe.

Something easy to check at least...

steve remchak · **Posted:** Mon Dec 31, 2012 10:17 am

We had similar issues on our LeMons car.

Like Mike said the idle / air system is a likely culprit. Several other things run off that particular system. The cold start valve is notorious for failure also.

I don't think we ever solved the problem. Might be why collectively we race Honda & Nissan these days.............. :wink:

JohnByers · **Posted:** Mon Dec 31, 2012 11:14 am

steve remchak wrote:

We had similar issues on our LeMons car.

Like Mike said the idle / air system is a likely culprit. Several other things run off that particular system. The cold start valve is notorious for failure also.

I don't think we ever solved the problem. Might be why collectively we race Honda & Nissan these days.............. :wink:

All true, it could even be an IM leak.....

RodneyWright · **Posted:** Mon Dec 31, 2012 11:19 am

JohnByers wrote:

All true, it could even be an IM leak.....

IM?

steve remchak · **Posted:** Mon Dec 31, 2012 11:27 am

RodneyWright wrote:

JohnByers wrote:

All true, it could even be an IM leak.....

IM?

Intake Manifold

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

Inquiring minds want to know....did you find the air leak?
Did pulling the dipstick make a significant difference? (I always just cracked the oil filler, but the dipstick seems so much cleaner).
Charlie G
(who just put the "rebuilt engine" back into the '87 BMW) (OK, just new rings and bearings, but it runs oh so much better)

RodneyWright · **Posted:** Mon Jan 07, 2013 11:45 am

Charlie Guthrie wrote:

Inquiring minds want to know....did you find the air leak?
Did pulling the dipstick make a significant difference? (I always just cracked the oil filler, but the dipstick seems so much cleaner).
Charlie G
(who just put the "rebuilt engine" back into the '87 BMW) (OK, just new rings and bearings, but it runs oh so much better)

Haven't touched the car in a week, other projects I'm working on right now. Plan to attack it this weekend...

RodneyWright · **Posted:** Mon Jan 14, 2013 9:59 pm

OK, so here's what I have so far. Pulling the dip stick does induce a worse idle to point where it won't run at all. I've sprayed starter fluid at all of the vent lines I see and nothing. I did spray some at the end of the air intake and it did increase the idle, so the stuff works. Guess it's time to break out the venting schematic and see what runs where.

Other suggestions?

Charlie Guthrie · **Joined:** Thu Aug 28, 2003 8:14 pm **Posts:** 832

The two poor idling issues I have solved on E30s were at the large diameter flex hose between the air box and the manifold. The corrugations can hide cracks, and several vacuum lines come together there.

The starter fluid method would scare the heck out of me. I use a "slightly" less explosive fuel source. I remove the nozzle from my propane torch and attach a 1/4" rubber hose. With a gentle breeze coming out of the hose, I move it methodically around the hose connections and flex hose to find the leak (indicated by an increase in idle speed). With the engine running the fan keeps the amount of fuel from building to the explosive limit. Naturally I wear approved goggles when doing dumb stuff like this. I've lost eyebrows doing explosive stuff for fun...duh.
Charlie G

RodneyWright · **Posted:** Tue Jan 15, 2013 10:57 pm

OK, since no one volunteered to come fix this and my "Hans in a trunk" function is broken, decided to tear into this a little more. Problem found, was a tear in the minor bellows that was the intake point for some of the vent tube routing. Coupled that with 23 year old rubber shrinking and loose connections, I think I'm well on my way on getting this back on the street. Figured while I'm here, might as well get the other crap taken care of, so new valve cover and oil filter block gasket are going in as well.

Good to get my hands dirty and have some grease therapy, work has sucked lately. Anyone looking for a windows server admin that's had experience with hyperv, vmware, ITIL, Service Now, BMC/remedy and project management?

steve remchak · **Posted:** Wed Jan 16, 2013 12:21 am

RodneyWright wrote:

OK, since no one volunteered to come fix this and my "Hans in a trunk" function is broken, decided to tear into this a little more. Problem found, was a tear in the minor bellows that was the intake point for some of the vent tube routing. Coupled that with 23 year old rubber shrinking and loose connections, I think I'm well on my way on getting this back on the street. Figured while I'm here, might as well get the other crap taken care of, so new valve cover and oil filter block gasket are going in as well.

Good to get my hands dirty and have some grease therapy, work has sucked lately. Anyone looking for a windows server admin that's had experience with hyperv, vmware, ITIL, Service Now, BMC/remedy and project management?

Or you could sell rug.................. :wink:

Pete Guthrie · **Posted:** Wed Jan 16, 2013 9:58 pm

are you going to take the e30 to a autocross soon? we have ours going again! If my father knows anything it is older bmws

RodneyWright · **Posted:** Wed Jan 16, 2013 11:36 pm

Pete Guthrie wrote:

are you going to take the e30 to a autocross soon? we have ours going again! If my father knows anything it is older bmws

hummm, autox an e30 slushbox convertible. Don't think it's going to happen Pete.

RodneyWright · **Posted:** Sat Jan 19, 2013 7:14 pm

It Lives!

9 hose clamps, accordion intake, small vent hose along w/ replacing the valve cover gasket and adjusting the valves and it's running fine. Now all I need to do is the oil pan gasket, oil filter housing gasket, guibo, tranny mounts, brakes and radio and I'm done. Don't think I get all of that tomorrow though

Very happy it's running again.

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e30 has bad idle

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