Hard to start and rough idle

[kj4yxy]

So my bimmer was originally hard to start. Had to give it a lot of gas and would take allot to start. But now as it continues to do that, it idles real low.

From what I know it could be the coolant temp sensor.
Any thoughts?


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[jalopi]

Mmmmm not gonna say it's impossible, but it's very unlikely. Is this something that only happens in the mornings when it's cold outside or what? Any particular circumstances?

Also, is your throttle body clean? Sometimes it makes a difference.

[kj4yxy]

Its hard to start always and its now becoming low idle always too. Is the throttle body the part that the air intake manifold goes into? Cause if it is then yes it has a lot of carbon build up in them.

Also what type of gas does this take? Like the 87, 89, or 91?

[ELVA164]

These cars are designed to use 87 octane, so stick with that. Another strong possibility is a vacuum leak that is leaning out the startup mixture. Generally pumping the gas on startup isn't as helpful with fuel injection as it might be with a carburetor, but if it only starts with that richer mixture it could be due to extra air getting in. Have you looked at the fuel filter, fuel pump, 02 sensor, or throttle position sensor yet?

[kj4yxy]

These cars are designed to use 87 octane, so stick with that. Another strong possibility is a vacuum leak that is leaning out the startup mixture. Generally pumping the gas on startup isn't as helpful with fuel injection as it might be with a carburetor, but if it only starts with that richer mixture it could be due to extra air getting in. Have you looked at the fuel filter, fuel pump, 02 sensor, or throttle position sensor yet?

Not yet. But I know a guy who has an 85 and he's putting 91. Also I did a full vac swap and tested for any leaks.


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[kj4yxy]

These cars are designed to use 87 octane, so stick with that. Another strong possibility is a vacuum leak that is leaning out the startup mixture. Generally pumping the gas on startup isn't as helpful with fuel injection as it might be with a carburetor, but if it only starts with that richer mixture it could be due to extra air getting in. Have you looked at the fuel filter, fuel pump, 02 sensor, or throttle position sensor yet?

I'm gunna try to check that. Is there an online manual I could find for my car?


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[ELVA164]

You tested for leaks with a smoke test? Your friend is welcome to use 91, but it's not doing anything except costing him more money. I don't know of an online manual offhand, but it would be well worth it to buy a Bentley manual for E30s. It'll come in handy a bunch of times and I personally like having something I can take out to the car with me. If you do want to stay online, you can find the procedure for just about any repair online somewhere, either in a forum, a tech site, or the E30wiki.

[jalopi]

Pull the plastic boot off your intake. Have a can of brake clean and a roll of paper towels on hand. Wet one of the paper towels with brake clean. Scrub around the throttle body area and the throttle plate until everything is nice and shiny again. Make sure you don't let parts of the paper towel brake off and get lost in your intake manifold.

This might help a little bit... maybe more than a little, given your description of the buildup.

[kj4yxy]

Pull the plastic boot off your intake. Have a can of brake clean and a roll of paper towels on hand. Wet one of the paper towels with brake clean. Scrub around the throttle body area and the throttle plate until everything is nice and shiny again. Make sure you don't let parts of the paper towel brake off and get lost in your intake manifold.

This might help a little bit... maybe more than a little, given your description of the buildup.

When I took the air intake manifold with my friend to replace all of the vacuum hoses, there was literally a shit ton of carbon build up in the intake manifolds. Is that a problem?


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[ELVA164]

When I took the air intake manifold with my friend to replace all of the vacuum hoses, there was literally a shit ton of carbon build up in the intake manifolds. Is that a problem?

Yes, not only will it restrict airflow into the engine but it could allow bits of debris into the combustion chamber. Also, that stuff might be caused by the rich condition you mentioned before. Have you looked at your plugs? I'd bet they're pretty fouled by this point.

[kj4yxy]

So I figured out the problem. It turns out that wile I was replacing the vac hoses, the one connecting to the idle control valve did not get put on tight enough so it slowly came off. I put it on right with a hose clamp and it started and idled right.


But it still is hard to start... Probably the coolant temp sensor.


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[jalopi]

Lol...

Also, hard start = probably not the coolant temp sensor. We're going to need a better description of the problem... 'have to give it a lot of gas' isn't going to cut it. Are we talking a slow crank here? Normal speed crank, just takes a while to fire up? Details please.

[kj4yxy]

Lol...

Also, hard start = probably not the coolant temp sensor. We're going to need a better description of the problem... 'have to give it a lot of gas' isn't going to cut it. Are we talking a slow crank here? Normal speed crank, just takes a while to fire up? Details please.

Have a coolant temp sensor coming in mail...
It cranks nice and fast, but I have to floor the gas pedal and wait about 15 seconds until it will kick in and sputter to life. Wait a few seconds and it will then idle correctly.


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