1985 735i Running Rough - BMW Forum - BimmerWerkz.com
1,6,7,8 - Series and Mini Cooper General Chat related to models that do not fit into particular categories above. Please try to put your discussion in more appropriate sections. This section does cover the 1 Series, MINI Cooper and 8-Series vehicles: BMW 830i, BMW 840Ci, BMW 850i, BMW 850Ci, BMW 850CSi, M8, Alpina B12, BMW CS Concept and others.

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#1 (permalink) Old 05-01-2005, 08:11 PM
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Hi, I recently bought a 735i and it runs a little rough, so I'm looking to get a set of plugs and wires for it, so I was curious what brand you reccomend and where the best price for each would be. Thank you.
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#2 (permalink) Old 05-02-2005, 10:51 AM
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I have a 1986 735i, I put in the Bosch +4 plugs, after the car had sat for almost a year without being turned on. That and a new fuel filter (the origianl one lasted 227+ thousand miles) plus one interstate international battery and the thing was up and running anew. I have since done all the fluids etc, but those plugs helped!

1998 Cosmos M3
1986 Silver 735i
2000 Gold Tahoe Z71
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#3 (permalink) Old 05-02-2005, 03:59 PM
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So Bosch would be a good plug, thats good, thats one of the ones I was looking into. What brand of plug wires you reccomend, Bosch wires as well?
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#4 (permalink) Old 05-02-2005, 07:07 PM
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GO to www.bavauto.com
They have replacement wire kits for most models, a good upgraded set. If you don't want to spend the money on them, stick with Bosch, BMW loves Bosch, they work well together!!!
Good car, enjoy it!

1998 Cosmos M3
1986 Silver 735i
2000 Gold Tahoe Z71
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#5 (permalink) Old 05-03-2005, 02:36 PM
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Thanks, yeah, I just like this model a lot, been looking into it for awhile. Bosch has become my friend .
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#6 (permalink) Old 05-03-2005, 07:06 PM
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What did you put in??? I am curious, this fall I am going to be pulling out the engine and transmission and rebuilding both. Time to restore my old girl to her former glory!

1998 Cosmos M3
1986 Silver 735i
2000 Gold Tahoe Z71
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#7 (permalink) Old 05-05-2005, 07:16 PM
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Well, I was asking about the plugs and wires because i wanted to know what to buy if they looked like they were in bad shape, but it looks like oem plugs and wires are on the car. I took a look at all 6 plugs and wires, and they all look like they're in good shape. So, I'm not quite sure whats causing my problem. When I first start it, it sounds like its running ok. But after about 5 seconds, it starts missing pretty bad and even when I rev it all the way to about 3k rpm's, and it seems to correct itself, or its just the revving covering up the misfire. So, do you think its a plugged injector or something fuel related thats causing the problem, or something else?
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#8 (permalink) Old 05-05-2005, 09:26 PM
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I would change out the plugs anyway, even the wires, if nothing else that would be better for the engine. I am no mechanic, but I know when my engine started running rough I changed the Fuel filter and it started running nice again. When I took it off a year ago the damn thing said on it, Made in WEST GERMANY 1985!!!! That could be the reason, the fuel in the lines past the filter is what is being used to start and then once the filter comes into play it runs rough. When you put pressure on the filter though the fuel is being pulled through with more pressure causing it not to hiccup. I would have to hear how the engine ran, but try that and see what it does. I put the +4s, new wires and a new fuel filter and it was as if the engine was whispering thank you when I started it back up. keep me posted!
Corey

1998 Cosmos M3
1986 Silver 735i
2000 Gold Tahoe Z71
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#9 (permalink) Old 05-11-2005, 09:15 PM
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Well, I replaced the fuel filter, it didn't fix the problem, but I am now certain it is a fuel problem. I clamped the return line after the fuel pressure regulator, not to the point of closing, but I clamped it a little and the car ran much better, it wasn't running properly, but it revved a lot better, and idled better. I haven't gotten to pressure test the fuel system, but I will within the weeks end. So, I am wondering, could the fuel pressure regulator cause this problem, or is it more likely the fuel pump? I hope it isn't the pump, considering thats a minimum of 150 dollars no matter where you go. n:
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#10 (permalink) Old 05-13-2005, 08:21 PM
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Allright, I did the fuel pressure test today, and its right where its supposed to be, 43 starting, and from 33-38 idle, and it was at about 38 at idle. So, I'm curious, are distributor caps known for going bad on this car? What about the throttle switch, are those known for going bad on a 85 735i? Trying to avoid buying extraneous parts. Thanks, any help is appreciated.
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#11 (permalink) Old 05-14-2005, 12:03 AM
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really distributer caps and the rotors are a common part that should be replaced with every new plugs and wire sets on all cars with a cap and rotor. however you said that when you rev up the engine the miss goes away most of the time the iss will get worse as the RPM's increase if it is a cap and rotor issue. you could atlest take the cap off and see what the contacts look like. if you said that when you clamped the return line the car ran a little better. it could be a clogged injector. becasue if the injector was clogged under normal circumstances the cylinder would run lean and possibly casue a miss. but if when the return line was restricted that would force the cylinders to run a little richer becasue the pressure in the fuel rail would be a bit higher because it wouldn't be flowing correctly. does it seem like ony one cylinder is missing out or are more than one?
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#12 (permalink) Old 05-14-2005, 07:31 PM
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I think I found the problem today, I pulled off the distributor cap, and there was some oil in it. Pull off the rotor, and find that the Cam Seal is completely deteriorated and allowing oil to leak into the distributor cap. I went to a local auto place, and they'll have the seal in on monday, until then, I can't do anything. We'll see if cleaning up the cap and such will alleviate the problem.
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#13 (permalink) Old 05-15-2005, 12:37 PM
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I would imagine you found your problem right there, and that is good to know about my car when I start rebuilding the thing. Let us know how that goes once you change that part, I would imagine that is it. The ignitors could be the problem too, but I would be real surprised if that were the case!

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1986 Silver 735i
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#14 (permalink) Old 06-13-2005, 03:33 PM
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Hmm....after replacing the wires, plugs, distributor it helped. Then I checked the fuel system, and such, pulled off a few connections and cleaned them and such. For the first time the car had power that pulled me back in my seat, but it still occasionally misfired. However suddenly a couple days later it starts bucking really badly, wouldn't respond till I was almost full open throttle, and stalled out at one point. Then I pulled off the throttle switch plug and suddenly it was ok, I cleaned the connection and used an electrical compound and that fixed most of the problem. But unfortunately, it still had the occasional misfires when I go mid to full open throttle but then starts pulling again a second later. I can't seem to find the source of this misfire, its not really predictable, but it does cause the car to lurch a bit. Anyone have any ideas why its just randomly misfiring? Any info appreciated.
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#15 (permalink) Old 10-28-2005, 04:32 PM
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Well, sounds like it shouldn't be a plug wire, but with the RF Friendly plug wires, they can look good on an oscilloscope without any load applied. Then begin misfiring under load. Sounds somewhat consistent with your description.
Ralph
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