Author Topic: Poor running issue, please help. (Read 10068 times)

Wise Old Dog · « **Reply #15 on:** May 04, 2008, 09:54:00 PM »

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.

Jimmy Lewis · « **Reply #16 on:** May 04, 2008, 10:03:55 PM »

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?

Wise Old Dog · « **Reply #17 on:** May 04, 2008, 10:29:06 PM »

Sure, come get it.

Jimmy Lewis · « **Reply #18 on:** May 13, 2008, 07:55:43 PM »

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.

EN318isPDX · « **Reply #19 on:** May 13, 2008, 08:12:15 PM »

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.

Jimmy Lewis · « **Reply #20 on:** May 13, 2008, 09:53:39 PM »

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.

EN318isPDX · « **Reply #21 on:** May 14, 2008, 01:24:14 AM »

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

mkodama · « **Reply #22 on:** May 14, 2008, 01:28:48 AM »

Quote from: Wise Old Dog;48473

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

Jimmy Lewis · « **Reply #23 on:** May 14, 2008, 08:23:30 AM »

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.

EN318isPDX · « **Reply #24 on:** May 14, 2008, 11:37:31 AM »

Quote from: Jimmy Lewis;49299

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+

Jimmy Lewis · « **Reply #25 on:** May 14, 2008, 01:43:23 PM »

Sounds like a plan, I'll look into it.

Cobra Jet · « **Reply #26 on:** May 14, 2008, 02:23:41 PM »

Quote from: 250k318is;48490

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

Cobra Jet · « **Reply #27 on:** May 14, 2008, 02:39:12 PM »

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.

EN318isPDX · « **Reply #28 on:** May 14, 2008, 03:58:13 PM »

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

tjts1 · « **Reply #29 on:** May 14, 2008, 07:57:03 PM »

Quote from: Jimmy Lewis;48429

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.

The arrow on the idle control valve points in the direction of air flow. It should be pointing to the manifold.