M42club.com - Home of the BMW E30/E36 318i/iS
DISCUSSION => Engine + Driveline => Topic started by: Jimmy Lewis on May 02, 2008, 08:27:31 PM
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Hey guys, I'm in need of a little diagnosis. Well, this last week I slowly tore everything out for my clutch replacement, got that all wrapped up today and I must say it is a world of a difference, but....
Along with the clutch swap I decided to do the TB heater delete as well, deleting the snake of hoses as per tits1's thread regarding it. I'm sure I got all of the major things right, hose running from valve cover to throttle body, manifold to ICV to air boot, and I decided to run a hose running from the coolant junction to the port between cylinders 2 & 3. When I originally started the car to slip the clutch into the driveway where I did the clutch, the car ran like absolute crap, before anything was done to hoses. So, I think the problem already existed before the work was done...
For the last 6 months or so my mileage has been in the absolute pits, averaging 15mpg, sometimes as low as 12mpg, and sometimes up to 20mpg when I do nothing but get on and off the highway. I think my oxygen sensor is bad, as well as my plugs and plug wires. I bought plugs today and some techron to hopefully clean out the injectors from sitting for almost a month. Do you guys have any ideas? One more thing, there is a small diameter hose that comes off a small round thing at the end of the fuel rail that I never ended up anywhere, it looks very worn, any ideas of what it is? And now for the stupid question; there is an arrow on the ICV, should this arrow point towards the intake boot or towards the manifold, I'm sure I have it right, because the car idles better than it does the other way, but who knows. Thanks in advance.
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Sounds like you have a disconnected FPR vacuum hose. Running rich probably.
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Is that what you think the hose is? Where should that hose coming off the fuel rail go to?
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http://www.realoem.com/bmw/showparts.do?model=AF93&mospid=47305&btnr=13_0308&hg=13&fg=15
Hose #11 ?
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Yes sir. It is just laying there not attached to anything, I guess that could be an issue, haha.
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IIRC there is a small hose nipple on the throttle body that it connects to. A b#tch to get at.
This hose basically controls how much fuel pressure goes to the injectors. At full throttle the vacuum drops and allows the regulator to open up and increase the fuel pressure. With zero vacuum at the FPR, like you have, it is maxed out 100% of the time. Plus you have a vacuum leak at the throttle body nipple.
This would cause a rough idle and poor fuel economy.
Somebody correct me if I didn't get this right.
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I will definitely pull the TB and find the nipple you are talking about, it seems that the hose has simply worn so much that it fell apart, that may explain why the fuel economy was so bad and when it finally decided to fall off, made the car run so bad. Thanks, I'll look into it, but any other opinions are welcome as well.
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not to but in but im having similar problems after removing the tb heater but my car just won idle if you give it some gas it runs but as soon as you let off it dies any clue of what may be happining
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The #1 reason these engines do not idle correctly is vacuum leaks. Everyone who owns these high mileage cars should inspect ALL vacuum hoses and the connections. In addition, the intake manifold gaskets leak as well, especially with age.
There is no way to visually inspect ALL of these areas and be 100% certain that they are leak free.
Therefore, as I have stated in several posts : Get a spray can of carb cleaner or similar. Make sure you have the little red nozzle extension attached. And with the engine running, spray a SMALL amount on each hose connection, and all intake gasket areas upper and lower. In addition, check the intake boot and associated connections. When you come across a leak, the engine will immediately increase idle speed and smooth out. It is so easy to do this. The intake manifold fasteners can be tightened a little more if you find leaks there.
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every things tight as for leaks the car wont stay running to check without someone givin it some cas could i have something wrong with my idle control valve im searching into how to cle and inspect this befor i go and buy a new one
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Thanks man, I've done the carb cleaner deal in the past with the cracked mess under the intake, and it works well. The intake boot has worn quite a bit, I'm going to have a new one on the way. Regarding leaks, my only leak is that small hose, the others have very tight connections with hose clamps and I trust that they are sealed. I used new gaskets for the manifolds so I assume that they are sealed well. I'll get it fixed man, thanks for the help.
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Oh the beauty of new spark plugs. My plug on cylinder 3 was badly fouled, probably from the richness of the mixture. Installed new plugs and added some techron injector cleaner and now it purrs like a kitten. Off idle power is better than ever, it pulls smoothly without any sort of hesitation. I never got into it because I'm going to take it easy on the new clutch for a couple days, but from what I see the problem is solved. Thanks Dave for all the help, I'm lucky to have you an Eric in my backyard man, you guys know your stuff.
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Scratch that idea, the new plugs fouled in a matter of driving the car for maybe 20 minutes and now it is running even worse. There are no vacuum leaks and no exhaust leaks, so the only left now is that the oxygen sensor is bad, but would a bad o2 sensor cause the plugs to foul so quickly? What other reasons can you guys give to such a rich fuel mixture? According to the Bentley for the M20 cars, the o2 being faulty shows the exact symptoms I have, poor mileage, poor off idle power, etc. It seems that the car runs relatively ok from around 2000 - 4000 rpm, anything lower or higher, power is nil with chugging. I really need to get my car back on the road, thanks guys.
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O2 sensors are not designed for the life of the car. There is a mileage interval that they are supposed to be changed at. Even if your O2 is not bad, it is probably way past due if it is OEM. $30 gets you a universal Bosch sensor that you splice into your OEM plug. This would eliminate the O2 as a cause for your problem.
Has the car ever run correctly?
There are other problems that could cause this. Have you checked to see if the ECU has thrown any codes?
Your valve timing could be off due to a stretched chain. Even an old chain can be re-timed to get it back to specs. You could have a faulty FPR, I don't know how to check it, I just replace it, $60
Could be your ECU, I have one you can swap to check if yours is bad.
Isn't troubleshooting fun?
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Well man, I'm banking on the FPR as the issue. I've never checked the CEL codes in the car, but the way it is running, it seems to me to be a fueling issue. After driving it some today, it runs very inconsistent and comes in and out of chugging, as if it is getting the proper amount of fuel then is either choked or is getting an excessive amount. The condition of the vacuum hose makes me think maybe having no vacuum to the FPR may have caused it to fail somehow. My question is, wouldn't an issue like bad plug wires or a bad o2 sensor cause the engine to just consistently run bad? The o2 is probably either bad or on its way out but I have read where guys run without one and the car just runs rich rather than the way mine does. With the above said, do you agree the FPR is the most probably cause of the issue?
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Most probable, no. One of several, yes.
Again, you are looking at an item that could be the cause, but you don't really know. The FPR is another part that should not last the life of the car, and at some point it will have to be replaced. Might as well be now, and you will eliminate another possible cause of your problem.
It gets costly to troubleshoot problems like this, and frustrating when there are many possible causes. That's why I replace all of these items when I first get an older car like this. I do ALL fluids, hoses, belts, plugs, brakes, O2, FPR, check the wires, coils, valve timing, check all pan and cover bolts, etc. I must be crazy, as it is expensive to throw money at a used car like this. But I call it establishing a new baseline. You end up knowing exactly what you have and what it needs. It also hopefully eliminates the frustration of trying to figure out what is causing a particular problem down the road. Because you will know what is NOT causing these problems.
Anyway, I have a couple of used FPR's that you're welcome to try if you want to go that way, or a new one is about $60 IIRC.
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Hmm, you are right about this being frustrating. Pelican actually lists the FPR for $50 so I'll likely order a new one just to be safe, as well as get me a Bosch universal o2 sensor to at least eliminate those 2 things as the cause. If only talking about it on the internet would fix my car. Thanks for guidance, I'll get that alignment tool back to you guys tomorrow, would you mind letting me borrow one of your FPRs just for the hell of it?
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Sure, come get it.
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Well, I got the new o2 sensor hooked up and the running has improved but it still chugs under load in the lower revs. The idle has cleaned up a lot and the car runs fine above 3K. I guess I need to keep troubleshooting. From another thread concerning a similar issue it was brought up that a poor running issue in the lower revs, ie under 3K, the AFM is a possible cause. I noticed that when I went to clean it that the door didn't open as smoothly as it did before, getting sort of stuck when completely closed. Who knows, I need to keep messing with this thing. And Dave, I plan to drive the car your way soon to return the tool you lent me. Any more input would greatly appreciated.
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Check your fuel pressure ive been fighting this issue and i finally checked it and im only getting 13 psi out of the pump and i have the same crap happening. it doesnt want to come off the line but it will idle great.
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Hmm, I hope its not pump related. If I can't resolve it with thoroughly cleaning the AFM and swapping out the FPR then I guess I should test the pump. How did you measure fuel pressure at the pump, I'm a troubleshooting noob.
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I unplugged the lower fuel hose that goes under the intake and plugged in the fuel pressure gauge. It took like 5 minutes and it was almost as easy as testing the resistance on the afm
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IIRC there is a small hose nipple on the throttle body that it connects to. A b#tch to get at.
This hose basically controls how much fuel pressure goes to the injectors. At full throttle the vacuum drops and allows the regulator to open up and increase the fuel pressure. With zero vacuum at the FPR, like you have, it is maxed out 100% of the time. Plus you have a vacuum leak at the throttle body nipple.
This would cause a rough idle and poor fuel economy.
Somebody correct me if I didn't get this right.
Yep, correct.
To the OP, I don't think it is the fuel pumps as obviously you are getting plenty of fuel into the cylinders and horrible mileage. I would double check the fuel pressure regulator and its vacuum hose. The fuel pressure regulator looks to be rebuildable or at least removable for cleaning in the parts catalog.
http://www.realoem.com/bmw/diagrams/i/g/236.png
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Yeah, I can't imagine it being a problem with my pump because I get enough fuel for WOT but its just in the low end that it has problems. It really seems like something faulty in the fuel system because it will bog in say 2nd at like 2.5K but if I keep the throttle constant until about about 3K it cleans up completely and pulls great, but as soon as revs drop back down it goes back to chugging. I'll pull the manifolds and try to clean out the FPR. Thanks guys.
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Yeah, I can't imagine it being a problem with my pump because I get enough fuel for WOT but its just in the low end that it has problems. It really seems like something faulty in the fuel system because it will bog in say 2nd at like 2.5K but if I keep the throttle constant until about about 3K it cleans up completely and pulls great, but as soon as revs drop back down it goes back to chugging. I'll pull the manifolds and try to clean out the FPR. Thanks guys.
Well my car does the same with a weak fuel pump. Terrible gas mileage. My car hates to go until about 2k than it stops sputtering so much. I can drive it fine with 1 third the normal fuel pressure. I was just telling you I could have saved alot of time checking the pressure. The autopart store rented it to me for free. You should always get new injectors if your having any running issues on a car with 100k+
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Sounds like a plan, I'll look into it.
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every things tight as for leaks the car wont stay running to check without someone givin it some cas could i have something wrong with my idle control valve im searching into how to cle and inspect this befor i go and buy a new one
pssssst...
http://www.m42club.com/forums/showthread.php?t=5123
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I did not see it mentioned, unless I overloked it while quickly perusing this thread - but when is the last time you changed your fuel filter? A clogged filter can create drivability issues as well and it's a simple, inexpensive fix.
As for testing fuel psi at the pump by the tank, this cannot be done unless you incorporate some kind of fitting into the lines at the tank access hole... and I think by trying to do so would be more than it's worth.
I *think* the fuel pressure should be like 38 psi w/ vacuum line off the FPR and with it connected, fuel psi should be around 30-32psi...? I'd have to check again to be 100%, but I think I'm within range. The proper way to test would be to have a fuel PSI gauge and you need to disconnect the vacuum line going to the FPR - make a note of your reading, then also make a note of your reading once the line is reconnected.
If the car is dumping fuel (saturated) plugs, it could be a bad O2 or bad/leaky injectors. How old is the O2 and/or all injectors (if you know)? O2's control air/fuel ratio. Test the resistance of the O2 sensor w/ a multimeter. If the resistance is higher or lower than what the factory spec should be, replace it. You don't have to buy the $200+ "BMW" O2, as many others have had success buying an O2 used for other vehicles (such as Mustangs) and just spliced in that new O2 (cut off the old O2 connector or plug, splice it into the new O2 wires and install O2). For about $32-$53 (depending on brand - BOSCH, DENSO, Motorcraft), you can pick up an O2 sensor from http://www.rockauto.com (and if you search around by googling, you can find a rockauto 5% discount code - it's not a huge discount, but it helps). Just make sure the O2 you are buying has the same amount of wires (3 wire vs 4 wire).
Also, I would check the resistance of your spark plug wires and see if they are within range if they are old (or you don't know when they were last replaced). Bad wires will not conduct a good spark, thus will not be able to burn the ignited fuel properly.
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its not that hard the guage came with a couple different sizes. I hooked it into the in line just before the fuel rail. It was after the filter but it was new so I knew its not MY filter. Do a fuel filter asap no matter what! Expecially if u run crappy gas :)
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One more thing, there is a small diameter hose that comes off a small round thing at the end of the fuel rail that I never ended up anywhere, it looks very worn, any ideas of what it is? And now for the stupid question; there is an arrow on the ICV, should this arrow point towards the intake boot or towards the manifold, I'm sure I have it right, because the car idles better than it does the other way, but who knows. Thanks in advance.
There is nothing wrong with your fuel pump. You need to re connect the fuel pressure regulator hose. Without it your car will experience the the symptoms you describe. That vacuum hose is critical. It connects to a vacuum port on the back of the throttle body. Best picture I have of it.
(http://farm3.static.flickr.com/2335/2492968369_f31604f765_b.jpg)
The arrow on the idle control valve points in the direction of air flow. It should be pointing to the manifold.
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Old thread I know, but the op is describing symptoms I'm currently having. Did you ever get to the bottom of it?
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Old thread I know, but the op is describing symptoms I'm currently having. Did you ever get to the bottom of it?
as am i