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Han's Garage
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Discussion Starter #1
I just got this car for free from a friend and trying to see if I can revive it. I've changed out spark plugs and EVAP fuel valve so far and all the codes disappeared. Engine starts fine and idles smoothly. However, when I tap on the pedal to accelerate a little bit it won't go beyond 1500 rpm and resist me from accelerating... Any suggestions?
 

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I just got this car for free from a friend and trying to see if I can revive it. I've changed out spark plugs and EVAP fuel valve so far and all the codes disappeared. Engine starts fine and idles smoothly. However, when I tap on the pedal to accelerate a little bit it won't go beyond 1500 rpm and resist me from accelerating... Any suggestions?


Crazy that you were given this BMW for free. Jealous haha. I’m sorry for the off topic comment.


Sent from my iPhone using Bimmerfest mobile app
 

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Looks like your check engine light is still on so there must be some more codes stored, what are you using to check the codes? You'll need something that reads BMW specific codes such as the Carly app or the BMW software, the software (ISTA) being the better choice as you'll be able to run test plans generated by the faults found in order to narrow the problem down.
A generic code reader won't cut it with these cars I'm afraid, they'll only give you a very basic idea and in many cases won't pick up a lot of the codes these cars generate.

For now though I'd start with the electrical system to make sure it's tip top, measure the voltage at the jump terminals in the engine bay, your looking for over 12v with the ignition and lights on but engine off, with the engine running you want about 14.5v.
Next up make sure all hoses (particularly the intake) are fitted correctly and snugly.
Check the butterfly valve on the throttle body as that can built up quite a bit of crud around it as the years pass but if it does need cleaning only use proper throttle body cleaner.
You might also consider giving the MAF a clean, again using proper MAF cleaner but be real gentle with this as it's very delicate.
I'd also consider measuring the fuel pressure at the rail and giving it a smoke test to look for any un-metered air getting into the system.
The above items are all things that are easy to do or can be done quite cheaply so start with these before throwing too much money at it.
Realistically though it sounds like you might need the software to really tell whats going on unless you get lucky with the above checks.

I'm sure some of the more knowledgeable chaps will be along shortly to add some better ideas as some of them may have dealt with this exact problem :thumbup:.

Can't believe you've been given this car for free, some people have all the luck :rofl:.
 

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Actually having just looked at your YouTube vid for the spark plugs you have an awful lot of corrosion and dirt on that engine, has this car been sitting unused for a long time?
Before measuring your voltages I'd at least give that negative terminal a damn good clean to get the rust off, as you probably know you'll struggle to get an accurate reading with all that on there.
Is that some kind of glue or epoxy resin placed around the electrical connector for bank 2's valvetronic servo motor? If it is then signs like that would suggest to me this car has been maintained on the cheap so assume nothing with this vehicle, I guess you know the person that's given this to you so I'd quiz them on absolutely everything that's been done to it in the past as it might help with your current problem and tell you what maintenance is now needed or due soon.
It also appears as though the vacuum pump either has leaked and not been cleaned up after the repair or is currently leaking judging by the amount of oil around it, if it is then this too will contribute to un-metered air getting in.
Personally I'd give the whole engine a real good clean so you can clearly see what's going on especially where oil leaks are concerned, unfortunately the N62 is prone to them but also in doing this you'll be able to go over the various earth points and get them cleaned up making sure they are all have a good contact. Now that I've seen that vid I'd very strongly advise you get the BMW software if you don't already have it.
You seem like a hands on kind of guy so I'm sure you'll have it up and running in no time and be out there enjoying it but in the mean time I do think you might have a bit of work ahead of you, besides I'd love to hear what that exhaust sounds like once she's running properly :thumbup:.
 

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Disconnect the MAF sensor & see what happens, this will help narrow down the problem, & map the engine in a default mode.. If this helps, I suspect that your problem is with the Vanos solenoids, causing your problems.
 

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Disconnect the MAF sensor & see what happens, this will help narrow down the problem, & map the engine in a default mode.. If this helps, I suspect that your problem is with the Vanos solenoids, causing your problems.
Good call, easy to clean items too, I should have thought of them.
 

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Han's Garage
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Discussion Starter #10
Hsurf! Thank you for all your thoughtful suggestions! So yes, this car has been sitting for about 5 years... I was actually glad that it started right up when I reconnected the battery. I feel like I am SO CLOSE! So the remaining engine check light is the ambient temperature sensor which has nothing to do with the performance of the engine and I actually do have a spare to replace soon. I just want this car to be running so that I can really start restoring it. I don't want to throw money into it knowing that I have to take the engine out and replace all the gaskets... Last night I checked the throttle body and it was working as it should, I even disconnected the MAF sensor and I was able to rev 1500!! But then it started to jerk again so now I'm thinking it is the faulty MAF sensor... I shall clean it tonight and see what happens. THANK YOU ALL!
 

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Han's Garage
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Discussion Starter #11
Disconnect the MAF sensor & see what happens, this will help narrow down the problem, & map the engine in a default mode.. If this helps, I suspect that your problem is with the Vanos solenoids, causing your problems.
map the engine in a default mode? How do I do that? I really hope its not the vanos solenoids... This car only has 90k miles...
 

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Simply running the car with the MAF unplugged will force the DDE to run a default map as it doesn't know what air is coming in so can't alter the fuel/air mixture etc etc.

If the vanos solenoids were dirty when the car was parked up it's probably solidified over the gauze filter given the amount of time it's been sitting around.
 

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Han's Garage
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8 Posts
Discussion Starter #14
Simply running the car with the MAF unplugged will force the DDE to run a default map as it doesn't know what air is coming in so can't alter the fuel/air mixture etc etc.

If the vanos solenoids were dirty when the car was parked up it's probably solidified over the gauze filter given the amount of time it's been sitting around.
So I did run it without the MAF sensor connected last night and it was idling fine. When I accelerated a little bit I was able to go above 1500 rpm and then a couple of times after the same problem occurred where I was not able to go above 1500 rpm. I thought because the MAF is disconnected it wasn't calculated right... So does this mean my vanos solenoids are okay?
 

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The Vanos solenoids do not usually fail, but they do build up with gunk causing them to not set the timing properly. Change the 2 0-rings on each solenoid, & clean them with WD-40, or brake cleaner. I use WD-40, but others use brake cleaner. Make sure to seat the solenoids all of the way back in, or you will have all kind of timing related codes start popping up. I know it sounds strange, but this is what happens. While the wires to the Vanos solenoids are loose, check each wire on the plug to ground. You should get around 3 volts on one side of the plug, & 12.5 volts on the other side of the plug with the key on the second position. If you are not getting the proper voltage, start checking the wires to see if one broke?

It sounds to me like you could have buildup in the fuel injectors, not feeding the fuel to the cylinders properly. Take 2 to 3 bottles of Techron & add it to the fuel tank. Let the engine idle for at least an hour, then take it for a spin. If you are new to the BMW N62 engine, I would suggest purchasing ISTA to do the diagnostics, since a generic code reader really does not help on a BMW.
 
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