I think I need help now...: Grassroots Motorsports forum: Grassroots Motorsports Magazine

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Dec. 12, 2008 11:17 p.m. vazbmw New Reader

Think I may need help now with my BMW 530it The problem is I have a miss that starts at 5500rpms Here is what I have done so far. (Some of these things need to be done anyway): -coils -plugs -Swapped MAFs -TPS sensor -Intake air sensor -Coolant sensor -Fuel pump -Fuel filters -Check crank position sensor and wobble of crank pulley (within spec) -checked of vac leaks The only target left on the trouble shooting list that is left are the cats

Any other ideas. I am almost to the point of taking it to a mechanic. Which is a very last resort for the likes of me. Any ideas from you gurus of all things automotive would be greatly appreciated

I can build a car but can't figure this out? what gives mang!
Dec. 13, 2008 5:47 a.m. minimac Dork

If the wires are good, keep it below 5500rpms. What's a station wagon doing buzzing that high?
Dec. 13, 2008 10:34 a.m. vazbmw New Reader

Redline is 7000rpms Dinan software Dual exhaust with h pipe etc. In sport mode it doesn't even shift until 6500rpms This wagon is suppose to rev

Understand, this is a new problem that started a few weeks ago. The car is supposed to function to redline or at least to its shift points

minimac, I didn't expect a give up answer. I won't give up. I just need some others' experiences with engines, not necassarily with BMWs
Dec. 13, 2008 11:15 a.m. minimac Dork

It's funny you mention the cats. I just had a problem with mine on the 733.Mine would "load up" about 3500. Finally it just quit and wouldn't start. Turned out the cat collapsed internally, and plugged up the exhaust. I ended up pulling it off and gutting it, reinstalled it and the car is running great again. But it drove me crazy until I found it.
Dec. 13, 2008 11:33 a.m. Datsun1500 HalfDork

Did the miss start before you started swapping parts, or did you start the swapping to try and get rid of it?

It really sounds like a bad coil, sometimes they are bad out of the box, I would try another one.
Dec. 13, 2008 11:44 a.m. curtis New Reader

i dont think its a clogged cat you probably wouldnt be able to drive the car above 30mph if it was. Is the miss intermittent or does it ALWAYS happen? Cause if it always happens i would supect a sensor or something that activates around that rpm i think a coil would give more of an intermittent miss just based on load alone it wouldnt always happen at 5500rpm. Try a power brake test see if the car starts to miss at other rpms.
Dec. 13, 2008 2:05 p.m. canzus New Reader

How many miles?? I think you're going to be pulling the valve cover off to check the springs...
Dec. 13, 2008 2:08 p.m. 94megotta New Reader

Fuel pressure?? Check the fuel filter, lines and the pump.
Dec. 13, 2008 5:47 p.m. vazbmw New Reader

The items I listed in the post were to repair the problem and to freshen things up at the same time
Dec. 13, 2008 5:47 p.m. vazbmw New Reader

94megotta wrote:

Fuel pressure?? Check the fuel filter, lines and the pump.

Done
Dec. 13, 2008 5:49 p.m. vazbmw New Reader

only miss at 5500 rpms If the car is some what cold there is no miss. Once I run it into the higher rmps the miss is present

curtis wrote:

i dont think its a clogged cat you probably wouldnt be able to drive the car above 30mph if it was. Is the miss intermittent or does it ALWAYS happen? Cause if it always happens i would supect a sensor or something that activates around that rpm i think a coil would give more of an intermittent miss just based on load alone it wouldnt always happen at 5500rpm. Try a power brake test see if the car starts to miss at other rpms.
Dec. 13, 2008 5:50 p.m. vazbmw New Reader

170K

If I push through the 5500rpm miss (it sounds almost like a rev limiter) It will rev to 7000rpms. But you can tell it is not full power

canzus wrote:

How many miles?? I think you're going to be pulling the valve cover off to check the springs...
Dec. 13, 2008 6:05 p.m. ncjay New Reader

If all the electricals are in proper functioning order, my bet is on the valve springs or camshaft. I would take a look at the cats first though, just to be sure.
Dec. 13, 2008 6:56 p.m. curtis New Reader

I would tell you to check timing but i think you have a chain. check the cats cause its another thing you can check but i still think you would barely be able to drive it if it was that. does the whole powerband altogether feel a little underpowered? does anyone know if the chain tensioners go bad on these cars? Maybe it has something to do with variable valve timing,(if that engine even has that im not familiar with older bmws) maybe you got a bad solenoid or actuator or something. Datsun 1500 may be right also i have seen coils bad right out of the box, maybe not completely bad but underperforming.
Dec. 13, 2008 7:22 p.m. vazbmw New Reader

I just bought a infrared therm. from Harbor Freight. I am not a real fan of HF, but for things like this and a 20 percent coupon it is great.

Measure the temps on the cats. One cat is 420 and the other is 380 degrees. So basically I am ruling them out for now. Plus on the way home I pushed the car a bit. I notice that the miss is not constant.

The Vanos (variable valve time) should be the next area to look at

yes I have timing chains

I guess I should test my cam position sensors now.

Those are the only sensors I have not tested

curtis wrote:

I would tell you to check timing but i think you have a chain. check the cats cause its another thing you can check but i still think you would barely be able to drive it if it was that. does the whole powerband altogether feel a little underpowered? does anyone know if the chain tensioners go bad on these cars? Maybe it has something to do with variable valve timing,(if that engine even has that im not familiar with older bmws) maybe you got a bad solenoid or actuator or something. Datsun 1500 may be right also i have seen coils bad right out of the box, maybe not completely bad but underperforming.
Dec. 13, 2008 7:48 p.m. Jerry From LA Reader

Before we get into the more exotic problems, let's look at something simpler. You may have a lean misfire. The clue is you say the misfire is not present when the car is "somewhat cold." The engine is running a little rich at that point because the O2 sensor is not warmed up and you're not on closed loop yet so the engine is running its cold program.

Look at every vacuum line in the car, including the hard plastic ones. Bend the soft lines and check for hose cracking/dryness. Maybe a hose slipped off. Look for oil-soaked hoses. Check the line to your brake booster and your variable fuel pressure regulator if you have one. Check your charcoal canister for proper operation. There may be a hose underneath you can't see. If you have a repair manual, look at all the tests for charcoal canister operation. Those things crack and go bad on European cars.

Also, check EGR valve operation as well.

Good luck.
Dec. 13, 2008 7:56 p.m. curtis New Reader

well yeah definately before you look into timing and such i would have hoped you already looked for simpler problem like a vacuum leak. And you said earlier that you did some of these items as regualr maintenance, im not saying you did. . . but a couple of times i have been workin on the cars and left connectors off and hoses loose. Make sure its not something you caused.
Dec. 13, 2008 8:02 p.m. vazbmw New Reader

JFL That is very good advice I check for vac leaks, but the I will double back on that

Jerry From LA wrote:

Before we get into the more exotic problems, let's look at something simpler. You may have a lean misfire. The clue is you say the misfire is not present when the car is "somewhat cold." The engine is running a little rich at that point because the O2 sensor is not warmed up and you're not on closed loop yet so the engine is running its cold program.

Look at every vacuum line in the car, including the hard plastic ones. Bend the soft lines and check for hose cracking/dryness. Maybe a hose slipped off. Look for oil-soaked hoses. Check the line to your brake booster and your variable fuel pressure regulator if you have one. Check your charcoal canister for proper operation. There may be a hose underneath you can't see. If you have a repair manual, look at all the tests for charcoal canister operation. Those things crack and go bad on European cars.

Also, check EGR valve operation as well.

Good luck.
Dec. 13, 2008 8:03 p.m. vazbmw New Reader

Curtis I have double check that too

curtis wrote:

well yeah definately before you look into timing and such i would have hoped you already looked for simpler problem like a vacuum leak. And you said earlier that you did some of these items as regualr maintenance, im not saying you did. . . but a couple of times i have been workin on the cars and left connectors off and hoses loose. Make sure its not something you caused.