Hard start in the cold, then rough idle, then dies?

[redearedslider5]

just bought my first e28 saturday morning. went to start it this morning (about 30 degrees) and it had a bit of trouble. seems like two issues:

1) the first and likely simpler issue is that sometimes, i go to start it and it makes a whirring sound but not much else happens. i assume this is the starter solenoid not engaging with the engine and it's motor is just spinning? replace starter seems like the obvious fix. doesn't happen all the time but i don't want to wait 'til it fails completely.

2) when the car starts, it idles fairly roughly and the engine speed sags and then dies. i can get it to start again and if i pump the accelerator a few times to keep the idle up, it'll 'catch' after a few tries and then idle fine. also smells like fuel when i'm outside after trying to start. previous owner replaced both fuel pumps recently. another small thing is that the "CHECK" light in the center was on consistently until I backed the car out and it went out. is that normal?

from the research i've done here on the forum, it seems like it's likely a fuel issue. i'm not sure i understand that, given that once the car has been given a little running time, it's fine. i would think a fuel issue would be more persistent. here's what the previous owner had to say when i emailed him:

"That sounds like a normal cold-start scenario. The fluctuating idle on cold-start has been like that since I got the car. After 5 to 20 seconds (depending on ambient temperature), it should settle in at a steady 1000 RPM and stay rock steady after that. And when it’s super cold outside, the starter solenoid occasionally misses on the first crank but always catches on second crank. I know you said you don’t have a garage, but is it possible to park the car in a location where it will catch the morning sun? A car cover might also help. Ice-cold winter mornings are hard on it, but once the day warms up and the fluids are flowing, it’s all good. Having a garage really helps. If the car's parked outside in Jan/Feb/March, you’ll need to give it plenty of time to warm up."

thoughts?

[Mike W.]

1. Yep, sounds like the starter. Just cause it's free and much easier, remove, clean the battery terminals and the cables, and reinstall. It's probably not the problem, but it's easy and free and it might be. If you do have to replace it, consider a B35 starter. Stronger and easier to install. Search for details.

2. That's not normal. It should start fairly quickly and stay running. At that temp it might run a little bit rough at first, but not stall. Not even idle slowly. It could be a bunch of things, at the least check and perhaps replace the distributor cap and rotor and the spark plug cables. They do last a very long time but consequently often get ignored. Maybe replace the plugs too, they're cheap, but whatever you do don't use platinums. Bosch silver or copper or NGK. There's a TPS, check it's adjustment, if it isn't telling the ECU it's at idle it could be the problem. Check the FI temp sender, the one with a 2 conductor plug on it, not the one for the gauge.

2.5. Step on the brake. It's a brake light check. And read the owners manual, if you don't have one, read or download it here. http://www.slideshare.net/BahadirALTUN/ ... k-13406646

Yeah, I threw out some terms you probably aren't familiar with, do a little searching.

[tschultz]

Temperature shouldn't be a concern, mine has started up fine for me as a DD the past 8 years in weather below 0 after sitting overnight. Yeah, it cranks slightly longer but not really that much longer. Once it fires, it idles by itself no problem, just like Mike said.
It could be a cold start injector that isn't working, or maybe something else like a throttle position sensor that needs to be calibrated slightly (so that it always tells the ECU that the throttle is in the idle position), or bad coil/wires (Mike beat me to it).
If you smell fuel-- visually verify you aren't leaking any fuel. That could mean a fuel line needs to be replaced.

It certainly sounds like your starter may be going out. I just did this job and you need to use the box-end 17/19mm wrench from the tool kit to get the top bolt. The toughest part of the job is loosening this nut as well as restarting the bolts with the new starter. Good news for you, any M30 starter will work and I think they even used the same starter on some older BMW models. The lighter smaller m30b35 starter might be a good idea though if you have to buy one from somebody, like Mike suggested.

[redearedslider5]

a few questions and pardon my ignorance. why would the tps (throttle position sensor, from what i can figure) be temperature dependent? unless it somehow only gives the wrong reading when it's particularly cold, i wouldn't imagine that'd be the issue. same with the coolant temp sensor (why is it called FI temp sensor? couldn't find that in the search), i would think that checks the coolant temperature to increase the idle speed when necessary to warm the engine up. if that sensor had failed, wouldn't the idle speed never be correct, regardless of temperature? similar w/ ignition systems, doesn't seem like a temperature dependent part and if it was failing it would run rough all the time. the one that makes most sense to me is the cold start injector.

again, no disrespect intended, just trying to understand the logic so i can troubleshoot better in the future. thanks!

oh and quickly, the temperature gauge reads about a third of the way across from the left, slightly left of 12 o'clock. is this normal?

[tschultz]

2/3's is where you want it, so that's good.

For the TPS, it may not be resetting to the idle position. The ECU needs this 'idle position' setting from the TPS to know to enter into closed cloop idle and activate the idle control valve. If the TPS isn't at the idle position, the idle control valve (idle air) will not activate. For a manual car, there are 2 signals sent; ~1V at idle and ~5V at Full throttle. In between, the controller rely's on airflow via the AFM to control fuelling.
Similarly, the Coolant Temp Sensor is what Mike was referring to. It tells the ECU the coolant temperature and then the fuel mixture is adjusted accordingly. If this sensor is bad it may be sending the wrong value and injecting too much (or too little) fuel.

Coil or spark plug wires could be causing a weak spark in the cold weather, making it difficult to start.

[redearedslider5]

awesome, thank you!!

[Mike W.]

All of it is because cold start is one of the hardest things for the Motronic system to adapt to. The oxygen sensor kind of fine tunes it when it's even somewhat warm and corrects for minor out of spec conditions. And the TPS is a switch like Tom said, but only at idle and at WOT, which for the switch is actually about 2/3 of WOT. The car will idle fine without the TPS even being hooked up when it's warm, although it will tend to die coming down to idle, but on cold start the car needs as much good info as it can get.

[redearedslider5]

just watched this video https://www.youtube.com/watch?v=7-_ORQ-Gsmg

the switches and such i understand but tschultz mentions voltages it's sending. looks like a largely passive device, where would one measure the 1V and 5V? also mike, haven't heard mention of an oxygen sensor yet..?

[Mike W.]

Just measure continuity with it disconnected, again, it's an on/off switch, not a variable sensor. I don't know what voltage it works off of, but one terminal is common, one is idle and one is WOT. Whatever voltage is the same on idle and WOT. O2 sensor is often my first suggestion, but it doesn't come into play on cold start, it has to warm up first some, then some condition has to be met for the ECU to start using that signal. I used to know, but it escapes me at the moment. Temp above ? or time or some condition. Then it adjusts things.

[tschultz]

This is where the Bentley is a good thing to have as it describes the pinouts and reference voltage (5V). The switching voltages are 4.5V at WOT and ~1V at idle if I recall.

[Blue Shadow]

oh and quickly, the temperature gauge reads about a third of the way across from the left, slightly left of 12 o'clock. is this normal?

Since I have this copied for another response, I'll throw it up here for you, too. http://www.mye28.com/viewtopic.php?t=104548

You should have an 80°C/176°F thermostat. Temp should be close to that not 20° higher (12:00 on the gauge).

[Mike W.]

This is where the Bentley is a good thing to have as it describes the pinouts and reference voltage (5V). The switching voltages are 4.5V at WOT and ~1V at idle if I recall.

Nope, it's a basic switch with a common. Since you have (I think) MS on your turbo car, you may be thinking of the EH transmission one. But even on it, I think the variable part is just used for the tranny with stock Motronic.

Here's a snapshot of it.

[a]

You have been here since 2012. You are about to experience the 2K$ rule. Or has it inflated to 3K by now.? Most of that money goes for non engine parts . But unless the car is known to have new ignition parts, it is best to start fresh with new stuff. Plugs wires cap etc. maybe belts. and definitely fuel hoses.

[redearedslider5]

safe to say you mean it's 2 or 3k to baseline everything with fresh parts? maybe i should've started a thread with that.

[a]

My first 528e, The Borman6 won worst of show at 5er Fest '03. I'm a function over form guy (slob) . I put 200k on it. I bought the car with 150 K. I maintained it with basic hand tools .12 yrs in all sorts of driving.Best commuter car I ever had. Never once failed to get home on its own. And it was fun for the most part. E 28s are very wrenchable.

[Blue Shadow]

safe to say you mean it's 2 or 3k to baseline everything with fresh parts? maybe i should've started a thread with that.

Baseline is just do a major service on the car, Inspection II plus brake fluid and coolant and you have reset the maintenance clock to zero and can follow a schedule of your own.

The 2 grand rule is the money you need to throw at a used car to make to make it right and safe for regular use. May or may not include Insp II work. We're talking all the worn out rubber front and rear, brake pads, rotors, tires, wipers, clutch, fuel lines, seals and gaskets and all that other crap that is maintenance that needs to be done when stuff wears out as opposed to being specified by a schedule.

Gotta go over the car with a knowledgeable helper and make a list, get a pile of parts (based on budget and safety/reliability need) and start throwing them at the car. Your inspection of the car or recent service receipts can keep a bunch of that expensive stuff off the list, but $2000-$3000 will be on the list when you are done knocking stuff off that is in good shape. If you have someone do the work, at lest double that budget.

[redearedslider5]

got around to checking TPS this morning and it ohms out as it should, according to that video. thursday is looking like it'll be warm, might take the day off and hit the cold start injector. do you guys know if that's an easy to find part locally or will i have to order online? seems pretty damn specific.

[tschultz]

Verify the TPS clicks when the throttle closes. This adjustment is what could be causing your problem.

Don't try replacing the Cold start injector without ruling out easier fixes.

You still haven't stated how the car runs when it gets fully warm. Your problem hasn't been isolated yet...

[redearedslider5]

the tps clicks when the throttle closes. when the car is fully warm it runs great, it's only for the first say.. 30 seconds or less that there's any issue. trouble starting, it dies, and works once i pump the accelerator a bit to keep the idle up long enough for it to 'catch' so to speak. well, it idles at roughly 1k, which i suppose seems a little on the high side.

where's the coolant temperature sensor and what readings are expected from it? can't seem to find this info anywhere.

[tn535i]

Verify the TPS again just to be sure... The middle terminal is ground or common and either side has 5v from the DME. So checking continuity of the switch is OK but it's better to back probe the connector and watch the 5v go to zero when it closes and on the other side 5v goes to 0 at about 3/4 of the way to WOT. I have seen TPS with poor solder connections inside that open and close with temperature changes, actually I've fixed 3-4 out of 5. They are easy enough to pry open and re-solder.

Now I've given this advice many times and there probably should be a sticky on ICV & T/B balance. It sounds like your cold issue could well be due to the current range balance of the ICV and T/B. If for example your T/B has become pretty dirty the ICV cannot open enough to allow the cold idle to be what it should so it struggles. Normally a cold idle is above 1000 rpm but maybe it cannot get there. A simplest of all test after you verify the TPS function is to just unplug it when the engine has warmed up. If idle speed goes up a bit it's probably OK but if it goes down at all ( I suspect yours may) then the T/B is dirty or physically too far closed. In this case cleaning and/or adjustment is necessary. If you don't want to get messy simply adjust the T/B for a warm idle of about 1100-1200 with the TPS unplugged then plug the TPS back in, check for idle signal when closed and adjust if you moved it that far, and then your idle should settle right back down. Now on the cold start the ICV should have enough range above the base T/B position to keep the idle speed up where it belongs.

Ever wonder why on so many newer cars with electronic idle valve that if the idle gets low or struggles the first advice is to clean the T/B ? This is the same thing happening. I may not have read every reply above but I think most were correct but 'missing' the impact of the baseline T/B setting and ICV interaction.

As to the CTS... IF it is old just replace it with a new Bosch Blue top latest part number which has the tightest tolerance. Search and you'll find discussion on this. $20 and you don't have to worry but you could also test the CTS hot and cold with your ohm meter. >2500 cold and more like 300 when warm but I've also seen CTS get flaky with poor internal connections that cannot be fixed and the bounce from OK to wide open causing great havoc with the DME.

[redearedslider5]

hm, any details on how to clean the throttle body? i'm pretty good with electronics but it's the mechanical stuff i'm learning more on. my bentley manual can't get here fast enough.

[tschultz]

Pull off the AFM and air filter box, along with the rubber accordion piece.

Then spray some brake cleaner in there and remove all oil debris from the throttle plate.

This should hold you over in the mean time-- I suggest reading through ALL of it. Read step 14 for cold starting system.
http://www.hiperformancestore.com/motronic.htm

[redearedslider5]

funny, i just came on to post that i found a lot of good info at that exact link. thank you! also seems like the coolant temperature sensor should just be replaced, if it's only 15 bucks.

[tn535i]

I think the hpstore article is great but leaves out what I think is the easiest way to test and adjust the balance of T/B and ICV, especially for a novice. They are right in that the T/B is almost fully closed but too much and your ICV cannot compensate enough. And I did not mentioned it is a good idea to clean the ICV as you would the T/B and then test it for resistance and for full range of operation. The M30 T/B is very easy while the M20 is a pain. And IF you ever get the good pleasure of doing an ITB adjustment/balance on a S38 you will think the M30 is child's play.

Yes, just do replace the CTS. You can test your old one but it's inexpensive and I've had problems with the old white ones and an aftermarket one. Another tip if you like to carry any emergency spare parts is to stash a 400 ohm resistor in there. If the CTS fails a 400 ohm resistor across the wire harness will allow it to run pretty well. Also you may read sometimes dealers added a resistor in the harness when customer complained of rough idle... this added resistance and caused the motor to run a little bit richer at idle making it slightly smoother. I'm not sure the resistance of that, never seen or measured one, but was put in series in the harness so if it broke it went way too rich and simulated a really cold motor. You might make sure you don't have that as a bad connection will come and go, run fine then run very poorly for no apparent reason.

If your car runs now and you do some 'baseline & tune up" to it then the old parts like cap, rotor, plugs/wires, VR, belts, hoses, sensors etc are all known working and can be stashed under the backseat in that huge void just in case you need something one day.

[redearedslider5]

had a chance to play around a bit during lunch. cold on a 40 degree day, the coolant temp sensor reads about 5.2k and once warmed up, it read 300. i pulled the connector while it was still cold and the engine went from a solid 1k and started lugging betwen 500-600 rpm. once it was warm, i pulled it again and the engine slowed down steadily and died. aside from the dying while warm, it seems to read correctly. one oddity is that when i put the meter on the sensor, it reads 0 and then increases. initially i thought it might be a capacitive effect, implying the sensor was bad as thermistors read like resistors, but i think it might just be my cheap meter trying to find the right scale. i'll likely try it again later with a good meter.

[Mike W.]

One more bit, the cold start valve is just that, not a warm up device. As soon as the key is released from the start position, the cold start valve is off.

[travisj]

Have you checked to see if your shift key is functioning?

[redearedslider5]

Have you checked to see if your shift key is functioning?

is that a joke because i don't capitalize or a part i've never heard of?

[travisj]

Kind of a joke... part of your keyboard. Though, I did just notice that I didn't use the key myself when creating my screen name.

[Blue Shadow]

it's only for the first say.. 30 seconds or less that there's any issue.

This is your ICV. Replace it. Nothing works like a new ICV.