Lack of power help!!!

Post Sun Nov 24, 2013 6:42 pm

I have just picked up a 1993 318i Touring for my lad today. Last night the seller rang me to say he was having a running issue. I went to view it today and ended up coming home with it as its incredibly solid underneath. Dispite him putting on a new fuel pump, filter, plugs and rotor arm it still has a problem.

The car starts first time and idles fine, if you rev it up from under the bonnet it gets to 3000 rpm and loses power, let off the throttle and it almost dies then settles back and idles OK. I have just driven it back about 100 miles and at normal speeds it seems fine ish, if you push it up to 3000 rpm it pulls fine till then and dies, back off and it drives OK again.
Couple of things I noticed was
1: When idling if you take oil cap off the engine almost dies, put it back on and revs stable themselves out.
2: When driving at certain speeds if you lightly back off the throttle it sometimes seems to actually accelerate !!!!

Any ideas on possible fault as want to get it sorted before my lad starts using it as I want it to be safe and reliable and I dont want my ex giving me grief!!!!!

As a point of interest the car has done about 100 miles in last year or so, in fact I think i've just done nearly thatto bring it home.

Any advice gratefully received

Post Sun Nov 24, 2013 6:47 pm

Wouldn't surprise me if the Throttle position switch has come lose, or isn't sending a signal at all. Other option may be the air flow meter is unplugged.

Post Sun Nov 24, 2013 7:00 pm

Got to take it for an MOT tomorrow to see if it goes through but will have a look at engine issue during the week. Will check TPS as I know airflow meter is still connected.

Want to get peoples ideas so I've got a checklist to work with.

Post Sun Nov 24, 2013 7:53 pm

Take out a spark plug and tell us the colour of the tip.
On second thoughts, since it's having a MOT test tomorrow, make sure you get the full gas results sheet.

Post Sun Nov 24, 2013 9:02 pm

Will see what it says, only problem is it wont rev up to specified revs will it , AHH !!!!!

Post Mon Nov 25, 2013 9:17 pm

Had a look at the pipework tonight, removed about a whole roll of insulating tape off the air intake pipe and revealed that its split in about EVERY rib of the pipe, me thinks that might not be helping LOL. Gonna get hold of a new one and go from there.

Post Sat Nov 30, 2013 10:47 pm

And all the breather pipes are cracked that come off the air intake, had to order from Germany, another weeks wait then!!!

Post Thu Dec 12, 2013 9:32 pm

Been looking at this on and off in the evenings ( which is fun in the dark LOL), Did find one thing out, when you start from cold the engine revs fine and returns to idle as it should, as it warms up and yoi rev it up it is a bit wooly and the idle almost drops off and stalls??? I have changed plug leads as one was broken at plug boot and I have cleaned out Idle Valve, gonna change temp sensor tomorrow but still open to any advice from you guys.

Post Thu Dec 12, 2013 9:44 pm

Brianmoooore wrote:Take out a spark plug and tell us the colour of the tip.

Post Thu Dec 12, 2013 10:45 pm

Gonna get it back up and running tomorrow night then take it for a run Saturday and see how it goes.I would say fuelling is about right as the cat smells "correct" smell from tailpipe.

Post Thu Dec 26, 2013 9:20 pm

After reading several ( 100's) of posts on this issue a lot are saying Crank Position Sensor, would this cause the fault, I alwauys thought if a crank sensor has gone bad it wouldn't start. Could it be the crank sensor has corroded up as the car had been sat for three years in a lock up. If so thats a pain in the rear as I got one from work but sent it back to supplier as convinced myself it wasnt faulty LOL

Post Thu Dec 26, 2013 9:37 pm

Just to be safe if you have neglected air lines and boots which are not expensive , I would get checking all the fuel and brake lines too.

Post Thu Dec 26, 2013 10:05 pm

Checked and replaced as required.

Post Thu Dec 26, 2013 10:22 pm

The symptoms do not sound like a crank sensor, but sometimes things need to be changed to rule them out.

As Brian has said, a report on plug colour will help diagnosis, its free and takes 2 minutes.

Another line of enquiry would be the coil.

If the car runs ok lower down the rev range, its either lacking fuel, spark, or has air leaks making the mixture too weak.

Post Thu Dec 26, 2013 11:04 pm

Looking back at your list of symptoms, a duff crank sensor wouldn't even figure on my list of suspects (although I don't completely exclude the crank sensor LEAD being savaged by the water pump pulley).
These are extremely simple engines and management systems, especially by today's standards, and are consequentially relatively easy to trouble shoot, but if we're going to be able to do this remotely, then you MUST perform the tests we ask for and post the results.

Post Fri Dec 27, 2013 1:14 pm

Test 1: voltage shut 7.89v
voltage fully open 7.89v
voltage during opening ranging from 7.83 - 7.87 while opening

Test 2: voltage shut 7.93
voltage fully open 7.95

Realise its not showing full 9vollts but sure from what you say that voltage should increase as i open the flap.

Post Wed Jan 01, 2014 12:28 pm

Officially had enough of this car now. Just replaced the airflow meter with new part ( as couldnt get an increasing reading on old one ) and guess what, its the bloody same!!!!!!!

Did have a look at plugs ( in the rain

) and they didnt look too bad considering its only really been run on the drive.

As far as I can see only things left that havent been changed are the TPS and the cat ( assume it isnt blocked as previous owner reckons he took manifold off and run it and was still the same ( starting to think maybe he wasnt telling the truth tho )

Only option open to me is a gallon of fuel and some matches its getting that much of a pain

Post Wed Jan 01, 2014 12:35 pm

One thing I did notice today was that you can build revs up to 3000rpm and it wont rev any further, although you can push pedal down further. If you let pedal off quick it will die and wont return to idle, if you do the same but let pedal off gently it will return to idle without dying.

Post Wed Jan 01, 2014 1:02 pm

Take the rocker cover off and examine the cam lobes.

Bet you can feel the wear with a fingernail!

Apart from swapping the cam,make sure that the oil spay bar is clean.

Post Wed Jan 01, 2014 1:13 pm

Was hoping someone wasnt gonna say that

Post Thu Jan 02, 2014 9:16 am

You should have replaced the TPS a long time ago as per Grrrmachine!

Then check that the TPS switch is "clicking" nicely with a relaxed throttle.

I would check the cam for wear and check the cam-belt tenshion and timing.

Check the connector that goes onto the AFM...the male/female pins need to be clean and the female plugs closed in a bit to make firm contact with the male pins. Pull the rubber boot off of the rear of the connector and look for loose crimps of the wires onto the rear of the pins...I had one bad crimp that I had to solder on!

My 1991 318i four door had an extra length of cable screwed onto the AFM connector...this male/female section of cable is about 18 inches long and is obviously an add-on Engineering change from BMW to fix something up on late-model M40 engines...there is a large "bump" inside this extra harness that has a chip, transistors etc. in line with the AFM signal.
If you have this extra bit of harness...throw it away...I had endless problems with this!

Post Thu Jan 02, 2014 8:02 pm

Thanks will order a TPS switch from work tomorrow ( don't wnat to strip throttle body then find I need a switch ) and will have a look at other connectors on plug. Assumed it was AFM as tetsed as per instructions from Brianmooore and as getting no increase in output as opened flap, took it that it was knacked. Its a pain doing stuff on it as work till 6 each night and the car sits outside so dont get chance when its peeing down

Post Fri Jan 03, 2014 9:43 am

Did you change the fuel pressure regulator vacuum hose.
Had problems with this on our 318i it was leaking at about 3k and dropping the fuel pressure, looked fine but fell apart on removal.

Post Fri Jan 03, 2014 8:49 pm

Yeah did change that as it was a tad brittle ( actually yeah it fell apart ) but wasnt that.

Post Tue Jan 07, 2014 4:43 pm

Had a look at hose today and if I'm honest its a bit of a sloppy fit, might find smaller diameter pipe.
Took car to my mates place last night ( spends his days playing with E30's ) and he stuck code reader on it, only fault coming up was O2 sensor ( bit worrying as its a new one ). He cleared any codes and I then took it for a run ( well my partner drove ), up the A5 you can get it to rev till about 3500 now before it loses power, it sat quite happily at 70mph in fifth but anymore than that and it seems to run out of legs. Checked how much gases are coming out of tailpipe and theres quite a lot, and bloody hot!!!! Other thing I did notice with tailpipe is there is no sooty deposits in it at all, in fact only thing there is a surface rust.

Tempted to still go with TPS even tho it didnt throw a code and check wear on cam !!!!

Post Tue Jan 07, 2014 6:42 pm

A M40 which has developed a rev. limiter at this kind of revs., is usually a M40 with a very badly worn camshaft.

Post Tue Jan 07, 2014 9:38 pm

Time to take rocker cover off me thinks

Post Tue Jan 07, 2014 9:40 pm

Brian if its worn that bad would it rev up to 5000 plus sat on the drive, or is it just that on the road its under load and exagerates fault

Post Sat Jan 11, 2014 9:34 pm

Took cover of today, there is "some " wear on lobes but not as much as i was expecting, admittedly the head was bone dry but is oily now I've fitted a new spray bar. Still rattly tho !!!

Post Sun Jan 12, 2014 2:09 pm

Those lobes do not look worn to me.

I gather you still have not tested/replaced the TPS?

This switch not only makes contact when at idle but also makes a different contact at Wide Open Throttle...to tell the ECU that you need maximum power NOW!

So check that the switch is working by measuring the continuity at the ECU while someone presses the accelerator pedal down (WOT) and then releases it....you can get the ECU pinouts by searching on "pinouts" on the Wiki above.

Noisy tappets are also caused by worn out hydrolic lifters...I had to replace all 8 of mine...or using the wrong oil...I use Castrol 20W50...maybe for your climate you can go for something a bit lighter!

Have you checked the cambelt tention and timing yet?

Post Sun Jan 12, 2014 8:18 pm

Throttle body off is my next job and will check switch for continuity and cleanliness, and no havent dug into the cambelt yet. Other option is to swap engine for a 318iS !!!!!!

Post Wed Jan 15, 2014 8:20 am

skippye36 wrote:Throttle body off is my next job and will check switch for continuity and cleanliness, and no havent dug into the cambelt yet. Other option is to swap engine for a 318iS !!!!!!

Yep this is a conversion I would love to do....probably will not happen though and the M40 serves us well as a reliable, economical runabout to go to the shops and back.

Post Wed Jan 15, 2014 10:21 pm

Or maybe 2.8 LOL

Post Sat Jan 25, 2014 4:44 pm

Right latest update on the Touring:

Parts replaced:
plugs, coil, cap, leads, rotor,airflow meter,fuel filter,all breather pipes, air intake pipe,IAC,coolant sensor,TPS.

Removed and cleaned injectors, throttle body and intake manifold.

Guess what??? STILL THE DAMN SAME.

Officially have NO idea whats causing it now

Post Sun Jan 26, 2014 8:16 am

skippye36 wrote:Right latest update on the Touring:

Parts replaced:
plugs, coil, cap, leads, rotor,airflow meter,fuel filter,all breather pipes, air intake pipe,IAC,coolant sensor,TPS.

Removed and cleaned injectors, throttle body and intake manifold.

Guess what??? STILL THE DAMN SAME.

Officially have NO idea whats causing it now

Have you electrically tested the TPS and Blue Sensor at the ECU connector? Maybe there is a wiring problem!