Now for the Cold Starting Problem
Discussion
Upcoming weekend with the wife out of town and the old knee working again...time to play cars:
Yes, there is gas in the tanks, the battery is charged and, thanks to the good input from you'll, the car ('86 280i) starts, drives and stops just fine. (Let’s not discuss the paint, tires and leather, all that is still to come.) With one remaining problem:
It will start immediately but will not run/idle on its own until it warms up enough it reaches operating temperature (or near to it). Last weekend it was 80f (26c) outside and I had to keep the revs above 2K for 3+ minutes to keep it running. It idles smoothly at that very fast idle. But If I let off the gas, it quickly dies; no chugging, the tach just settles to zero RPM over maybe 2 seconds.
However, once it gets warm enough to start moving the temperature gauge up, I can slowly start letting the idle down as the temperature come up. Once it's near mid-gauge (80c), it idles nicely at 950 RPM. Restarts and idles properly, drives fine, etc.
I've studied the manual and the supplements but have not found a good answer. I'd say it's the failure of the widget (and/or the adjustment) that manages the idle (air/fuel) between ambient and operating temperature. Which widget would that be? Also, I must be over-compensating somewhere because it will not idle at a normal cold start (1.2K RPM). Anything below 2K is death and 2.5K is better until it heats up. All input welcome. Grady
Yes, there is gas in the tanks, the battery is charged and, thanks to the good input from you'll, the car ('86 280i) starts, drives and stops just fine. (Let’s not discuss the paint, tires and leather, all that is still to come.) With one remaining problem:
It will start immediately but will not run/idle on its own until it warms up enough it reaches operating temperature (or near to it). Last weekend it was 80f (26c) outside and I had to keep the revs above 2K for 3+ minutes to keep it running. It idles smoothly at that very fast idle. But If I let off the gas, it quickly dies; no chugging, the tach just settles to zero RPM over maybe 2 seconds.
However, once it gets warm enough to start moving the temperature gauge up, I can slowly start letting the idle down as the temperature come up. Once it's near mid-gauge (80c), it idles nicely at 950 RPM. Restarts and idles properly, drives fine, etc.
I've studied the manual and the supplements but have not found a good answer. I'd say it's the failure of the widget (and/or the adjustment) that manages the idle (air/fuel) between ambient and operating temperature. Which widget would that be? Also, I must be over-compensating somewhere because it will not idle at a normal cold start (1.2K RPM). Anything below 2K is death and 2.5K is better until it heats up. All input welcome. Grady
Edited by Grady on Friday 5th February 01:10
Hi Grady...If the temperature was a lot lower i would of said the AAD...Auxiliary Air Device...
You could try unplugging the 7th injector on the plenum to see if that helps..It might be over fuelling....You could check for air leaks...Inspect the air intake hose for any cracks/Splits....
You could try unplugging the 7th injector on the plenum to see if that helps..It might be over fuelling....You could check for air leaks...Inspect the air intake hose for any cracks/Splits....
Possible causes / ideas, things to check.
Idle speed should be faster when cold than when hot. If it's not it could be the auxiliary air valve is seized up
(unit at front with pipe from throttle inlet to aux injector.) it has a vane inside which should close up when hot.
Also it's electrically heated, check the plug and socket, pins are clean (and a dose of WD40 might help)
Aux injector (zig above) should only spray when cranking engine - if it sprays any other time you have a wiring problem, if it drips it needs a clean or replacing.
Pressure control (other thing at the front of the engine) also has an electrical warm up, and it richens mixture when cold or when at full throttle (why it has a vacuum connection). Again, check plug (etc.) is clean.
As USA version, you also have the EGO and its control setup - might be worth unplugging it and see if things get better,
there seem to be a raft of issues with the extra emission control stuff.
If/when you fix something, it may run worse, because they are all interconnected, so you will probably have to reset mixture and idle speed etc etc all over again.....
Idle speed should be faster when cold than when hot. If it's not it could be the auxiliary air valve is seized up
(unit at front with pipe from throttle inlet to aux injector.) it has a vane inside which should close up when hot.
Also it's electrically heated, check the plug and socket, pins are clean (and a dose of WD40 might help)
Aux injector (zig above) should only spray when cranking engine - if it sprays any other time you have a wiring problem, if it drips it needs a clean or replacing.
Pressure control (other thing at the front of the engine) also has an electrical warm up, and it richens mixture when cold or when at full throttle (why it has a vacuum connection). Again, check plug (etc.) is clean.
As USA version, you also have the EGO and its control setup - might be worth unplugging it and see if things get better,
there seem to be a raft of issues with the extra emission control stuff.
If/when you fix something, it may run worse, because they are all interconnected, so you will probably have to reset mixture and idle speed etc etc all over again.....
Here is a supplemental response to the suggestions above. To get the car running, over the last couple of months:
The small air hoses were all replaced, the main air intake was replaced with a silicon hose and the air intake cover was also replaced (those last two about a year ago). With the engine running, I've sprayed (very carefully, Mark) around with starter fluid and gotten no RPM increase so I think the hoses are tight.
All the connectors mention above were unplugged and cleaned as part of the process. They may not be working now but they look OK and tested OK at the time.
The cold start (7th) injector should only work during cranking and it also tested OK. Since the engine starts I don't think that it.
I think I missed out on the "As USA version, you also have the EGO and its control setup". I know some pollution bits are a bit different here (vs. the UK) but I'll have a look at unhooking it. Is it a direct cold start function?
What is the most important component in the fuel/air management during initial warm up? I think that is my problem. Grady
The small air hoses were all replaced, the main air intake was replaced with a silicon hose and the air intake cover was also replaced (those last two about a year ago). With the engine running, I've sprayed (very carefully, Mark) around with starter fluid and gotten no RPM increase so I think the hoses are tight.
All the connectors mention above were unplugged and cleaned as part of the process. They may not be working now but they look OK and tested OK at the time.
The cold start (7th) injector should only work during cranking and it also tested OK. Since the engine starts I don't think that it.
I think I missed out on the "As USA version, you also have the EGO and its control setup". I know some pollution bits are a bit different here (vs. the UK) but I'll have a look at unhooking it. Is it a direct cold start function?
What is the most important component in the fuel/air management during initial warm up? I think that is my problem. Grady
Edited by Grady on Friday 5th February 01:34
I think part of the problem here (and I compare with recent V8 stories too) is that we are all judging the cold running performance against modern standards where the cars drive pretty much the same hot or cold.
In the old days we just used to get in and drive it [and put the choke in] and it warmed up pretty quickly to the point it would idle fine (or whatever symptom went away).
For those that don't remember the "put the choke in" bit, yes we used to be in control of the mixture, so if this part goes wrong (automatic choke/mixture control/leaving handbag hanging from choke knob) it won't run of course.....
In the old days we just used to get in and drive it [and put the choke in] and it warmed up pretty quickly to the point it would idle fine (or whatever symptom went away).
For those that don't remember the "put the choke in" bit, yes we used to be in control of the mixture, so if this part goes wrong (automatic choke/mixture control/leaving handbag hanging from choke knob) it won't run of course.....
What Adam says is true, but a well set up K-jet *SHOULD* be very nearly as good cold as it is hot. The two extra devices at front of the engine effectively provide the old 'auto-choke' function on a carb, one to raise idle speed, one to richen mixture and do the 'extra fuel dump' that a lot of carbs do on full throttle.
Mine runs as well cold as hot.
Grady - Yes, I know you've looked at a lot, I was restating just in case - I should have said that [sorry]
Fuel mix is always under control of main head unit (where the big flap is from air flow) and is fine tuned by the pressure control valve (front of engine) which uses engine temp and vacuum to adjust the pressure. This fine tune affects whole range of throttle.
EGO. This is required for fine emission control. It should be working as soon as sensor reaches its working temp (they don't work cold), but often, faults can show up when it's cold or warm. System should run 'open loop' (= Ignore EGO) until engine exhaust gas heats the sensor. As a safety setup, most systems will happily run open loop if the sensor fails, so one way to check is to unplug it and see if engine runs better. If it does, you may have a faulty or 'gummed up' sensor (sensors can get clogged with carbon etc. it's supposed to burn off, but not always). Also the little computer module can go faulty too, and unplugging sensor stop that doing anything....
So try unplugging EGO, reset idle and mixture (when hot), and then see if it runs properly from cold.....
NB. this info from the later European 'KE" systems which have EGO - I think the USA wedges have an early version of this system.
Info should be right anyhow.
Mine runs as well cold as hot.
Grady - Yes, I know you've looked at a lot, I was restating just in case - I should have said that [sorry]
Fuel mix is always under control of main head unit (where the big flap is from air flow) and is fine tuned by the pressure control valve (front of engine) which uses engine temp and vacuum to adjust the pressure. This fine tune affects whole range of throttle.
EGO. This is required for fine emission control. It should be working as soon as sensor reaches its working temp (they don't work cold), but often, faults can show up when it's cold or warm. System should run 'open loop' (= Ignore EGO) until engine exhaust gas heats the sensor. As a safety setup, most systems will happily run open loop if the sensor fails, so one way to check is to unplug it and see if engine runs better. If it does, you may have a faulty or 'gummed up' sensor (sensors can get clogged with carbon etc. it's supposed to burn off, but not always). Also the little computer module can go faulty too, and unplugging sensor stop that doing anything....
So try unplugging EGO, reset idle and mixture (when hot), and then see if it runs properly from cold.....
NB. this info from the later European 'KE" systems which have EGO - I think the USA wedges have an early version of this system.
Info should be right anyhow.
Edited by RCK974X on Friday 5th February 09:20
My money is on the Aux air device, even though it is 80F it still needs the extra air flow to keep the rpms up.
The fact that it runs ok after warm up does signify that all is probably well with other components, the WUR needs to get to its operating range.
Take the AAD off, soak it in something like Chem 12, blow with compressor.
It should be open....hold over gas ring, not too near, it should close.
As it cools it should open, replace.
After replacing you will probably need to adj by-pass air as your hot idle may/will change, it's the big screw located under butterfly .
The fact that it runs ok after warm up does signify that all is probably well with other components, the WUR needs to get to its operating range.
Take the AAD off, soak it in something like Chem 12, blow with compressor.
It should be open....hold over gas ring, not too near, it should close.
As it cools it should open, replace.
After replacing you will probably need to adj by-pass air as your hot idle may/will change, it's the big screw located under butterfly .
Edited by jeff m2 on Friday 5th February 17:12
This got put off as I bought a "new" (old but rust free) cab for my 78 Warlock pick-up truck.
Pulled the AAD, the gate was open (ambient about 70). Hit it with penetrating oil, waited, put it on the edge of the gas stove on low: at ~212 degrees the gate was completely closed. Put it in the freezer, at about 22 degrees it was maybe 1/3 open (the gate is irregular) but maybe not as open as the illustration on page 17 of the Fuel Injection section of the manual. Reheated it and it closed. Re-chilled it and checked at 70 there was a tiny (pinhole) opening and as it chilled it opened as before.
So I'd say the valve is now moving properly. Also cleaned the contacts and reinstalled.
Started and no joy. Have to force the idle over 2k by throttle.
Pulled the AAD, the gate was open (ambient about 70). Hit it with penetrating oil, waited, put it on the edge of the gas stove on low: at ~212 degrees the gate was completely closed. Put it in the freezer, at about 22 degrees it was maybe 1/3 open (the gate is irregular) but maybe not as open as the illustration on page 17 of the Fuel Injection section of the manual. Reheated it and it closed. Re-chilled it and checked at 70 there was a tiny (pinhole) opening and as it chilled it opened as before.
So I'd say the valve is now moving properly. Also cleaned the contacts and reinstalled.
Started and no joy. Have to force the idle over 2k by throttle.
Hi Grady....I can't help thinking that there may be a lot in what Andy has posted as it kind of sounds like something in the additional relays and emission control devices that were added to the US cars might be causing this issue..I only ever experienced hot start issues with Delilah, She would always start in cold weather and idle high...1200rpm and then settle to around 800rpm..Even without the 7th injector connected...And only running on 5 cylinders.
Out of interest have you touched or tried adjusting the fuel mixture at all at the metering unit?..And is the cold start injector working?...Seems that the air is...You have fuel and a good spark.
Out of interest have you touched or tried adjusting the fuel mixture at all at the metering unit?..And is the cold start injector working?...Seems that the air is...You have fuel and a good spark.
SOLVED - But no real idea why!!!
Studied WUR repairs (looked iffy) and decided to attach my new CIS pressure tester to check control pressure - in the process removed both banjo connections. Put the small one back on, put a tap in distributer side for a pressure test, hit the starter and it started right up at a lovely cold idle. Removed the tap, put the distributer fuel line back on with new copper washers and it idles perfectly. (I hit the mesh filter with some carb cleaner while I had it apart.)
All I can figure was there was a "bubble" or other fuel blockage somewhere in the WUR and breaking the fuel connections resolved it???
Anyway lets hope it holds. Road test! Thanks for all the help. Grady
ETA - Nice short zip around the 'hood. Had to cut it short because one of the mufflers is touching the fiberglass under the seat (bad smell) and she's not street legal and John Law was out in force.
Studied WUR repairs (looked iffy) and decided to attach my new CIS pressure tester to check control pressure - in the process removed both banjo connections. Put the small one back on, put a tap in distributer side for a pressure test, hit the starter and it started right up at a lovely cold idle. Removed the tap, put the distributer fuel line back on with new copper washers and it idles perfectly. (I hit the mesh filter with some carb cleaner while I had it apart.)
All I can figure was there was a "bubble" or other fuel blockage somewhere in the WUR and breaking the fuel connections resolved it???
Anyway lets hope it holds. Road test! Thanks for all the help. Grady
ETA - Nice short zip around the 'hood. Had to cut it short because one of the mufflers is touching the fiberglass under the seat (bad smell) and she's not street legal and John Law was out in force.
Edited by Grady on Sunday 28th February 23:10
The Probst bible says that the WUR has a mesh in one of the ports, and it's not unusual for the mesh to be gummed up with crud ....
Taking it to bits may also have dislodged a [part] blockage....
keep an eye on it and if it happens again, you know where to look !!
Great news.
NB. Mine actually has a MELTED HOLE under the driver's seat where the exhaust box touched it....Scary !
It's on my list to bolt a steel or ally sheet underneath both seats as a safety heat shield.
Taking it to bits may also have dislodged a [part] blockage....
keep an eye on it and if it happens again, you know where to look !!
Great news.
NB. Mine actually has a MELTED HOLE under the driver's seat where the exhaust box touched it....Scary !
It's on my list to bolt a steel or ally sheet underneath both seats as a safety heat shield.
Over the years I've added (to try to pass) and then removed (old age exemption) cats at the rear to try to keep the emission folks happy so now it's the (no doubt blown out and hollow) mufflers under the seats and straight pipes back. Sound way too much like a rice rocket. Need to get some quality back in the sound. Grady
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