535i rough idle at stop. Need help/advice please!

[method0075]

So my e34 1992 535i has been giving me a bit of a problem latley and I need advice. Things I have replaced
-plugs
-wires
-oil
-oil filter
-vacum line to FPR
-All six injectors
So my car runs great when I first start her up even at running temp I can sit in park rev it and not have an idle issue.
I will take it for a spin around the block and with every stop I make, the idle grows worse and worse. Eventually, as I take off after a few stops, the car will sputter/hestitate and then eventually begin firing in time.
I just checked fuel pressure and it is between 38 and 40 psi while running. It shoots up to 50-53 psi as I give it gas in nuetral (like reving it) and psi`s go back down as I take foot off the gas. It`s holding at 40 PSI when shut off as well. If I remove the FPR vacum line it shoots up to almost 55 PSI with no change in the vehicles idle; still rough.
Here is the odd thing the vehicle sounds to have a random miss fire here and there and every once in a while it will even idle smooth as new for a second or two. It will misfire and then get back on rythm. When I`m sitting in idle in park and I tap the gass to rev lightly, it will hesitate and then rev.
Please advise as I have just ordered a new FPR and fuel filter but am beggining to think my problem may be elctrical...

[moroza]

I don't know what the spec fuel pressure is, so someone who does may see an obvious problem.

Fuel filter?

Bit of a stretch from what you describe, but...intake leaks? IACV? When mine has intake leaks, it does what yours does, but it gets better when warmed up.

[method0075]

alot of people point towards intake leaks but I can't find any. I found a few things that Ihave patched up/replaced. There is a valve (not electronic between the intake and valve cover that I want to check. but I know it`s not leaking.

Some say fuel filter but I don;t know the signs of a failing one. Car seems to act up only after driven if I sat in a parking spot and started it after it sat for a while it would idol fine with an occassional hiccup or missfire. Hesitation when I tap the gas to rev. I checked the ecu and it`s not throwing any codes.

[moroza]

If you don't know when your fuel filter was last replaced, do it. The valve you refer to is, I think, the Idle Air Control Valve, which does what it says until it gets too dirty. Pop it out and spray it with carb/MAF cleaner.

[method0075]

I'm going to clean that valve as soon as possible. It is not electric so I'm hoping it`s stuck closed or something since it seems to be manual. With that thing clogged could that be causing the rough idle?

[kipwinger]

How old are your cap and rotor?

[method0075]

It`s funny you asked that I just ordered a new cap and rotor from ebay and expect it here later this week. I don;t know how old these items are. Could they cause this problem? The more I drive it the more the idle and misfiring gets worse but never dies on me?

[kipwinger]

Not sure, but I have always noticed an improvement in idle with a new cap and rotor. I replace them at the same time if not sooner than the plug wires.

[method0075]

I ordered a new cap and rotor, I also ordered a new coil.

I would like to get some feedback from someone in regards to the 3.5L M30 motor and the idle control valve that is not electric. I haven't checked this and am wondering if it`s failure is similar to that of a failed EGR valve in modern cars...

Can someone point me also in the right direction on how to change the cap?

[kipwinger]

It's pretty simple, do you have a Bentley manual? If not there is somewhere that it is available online.

[method0075]

I don't have a manual but I'm concerned about messing up the timing ... That`s why I asked.

[ShapeShifter]

make sure your oil cap (on the cam cover) has a tight seal.

[kipwinger]

I don't have a manual but I'm concerned about messing up the timing ... That`s why I asked.

Just make sure you plug the wires back in the same order that they came off. Or just leave them on the old cap and move it to the side while installing the new parts and swap them directly for less confusion.

[method0075]

I even replaced the oil cap to be sure... So thank you for that advice, anything else you can recomend?

[ShapeShifter]

Try doing one wire at a time.
The firing order is also on your cam cover "zundenfolge" or something like that.

[method0075]

So I just take the old cap off abd put the new one on. I thought there is a pin or connector in there that is to be aligned correctly with the crank?

[moroza]

There's no way to screw up putting a new distributor cap or rotor on - once you crack them open, you'll see that they can't be flipped, so don't worry about your timing.

However, I doubt that's your problem - if it were, you'd have bad idle all the time regardless of warmup or previous driving.

My only vehicle with EGR isn't what you'd call "modern" (carburated 86 Yota truck), so I don't know what its failure feels like. But the IACV is known to get dirty after a while, and is easy to remove and clean. Do that and replace your fuel filter, and check back.