Engine running rough and shaking badly at idle and at higher rpm too, hot /cold

[alex 1993 525i auto]

Hi there,

My 93 525i was running great all year long before. Saturday night after dinner 50 miles away, started the car to go back home. Obvious rough running and engine making the entire car shaking, but no Check Engine Light (CEL) signal. Once engine hot, no change, while driving it was quite less powerfull and I could hear it and feel it strugle under the gas pedal when accelerating, like if it was missing on some cylinders (but I never experienced that so hard to tell now).

It ran bad like that but I drove it home 50 miles without other problems. On next morning I checked with my Peake tool to see if codes were stored and no codes. I confirmed with the pedal stump test and only code 1444 shows continuously = no codes. Started the engine and it was still shaking badly and running rough. Let it warm up a few minutes and checked by hand that all 6 exhaust ports were as hot one compared to each other, and all 6 were very hot, no difference between any.

I stopped the engine, removed the fan clutch to see if it was the problem and no, same behaviour without the fan clutch. Then I removed both belts, started again the engine and no difference, so it doesn't look like it is something driven by the accessory belts.

I disconnected the MAF socket and started the engine again, the CEL signal appeared right away, but otherwise no difference, still running bad and shaking. Then I repluged the MAF and checked that every vacuum hose was correctly set and everything was where it should be and no worn broken hoses were seen.

In the 4 last years, all vacuum hoses, intake manifold gaskets, throttle body gasket, MAF, O2 senson, coolant temp sensor, idle speed control valve (ICV), spark plugs were replaced. Passed smog test 3 years ago too in California. Also 3 years ago fuel pump with fuel level sender, fuel pressure regulator, fuel pump relay and fuel filter were replaced after fuel level sender failure. This year I replaced the vanos piston seal along with diaphragm spring upgrade on the intake camshaft, valve cover gasket, lower timing chain tensionner, engine doesn't burn any oil and was running great but pinging under load. This summer I also tested compression and each cylinder was at 160 psi, spark plugs were clean. One month ago I decarbonized the combustion chamber to some extent that it doesn't ping anymore, with Seafoam added by the small vacuum hose from the PCV valve. Fumigated the entire neighboorhood by doing that. Battery is 3 year old and seems fine, alternator was rebuilded this summer.

I searched a lot here and on bimmerboard to find insights to what could be wrong now. Most posts say either MAF or ICV or CPS, or fuel related, or coils and spark related. I doubt that MAF, ICV, or fuel related part is wrong because those were replaced recently and with a bad CPS the car should not start at all. Also again, there are no CEL warning.

Next Saturday I'll look at the spark plugs first, maybe test the coils. I read that it is possible that the ICV could block 'mechanically' and that would not be seen by the OBC. I also read a post from a guy that had a broken intake valve and the simptoms were kind of similar to mine. I will see that when I check at the spark plugs I guess it will be obvious on the plug, if not a compression test will tell me.

Any other ideas from the mechanical gurus here?

Thanks, Alex

525i 1993 (built 05), M50TU, auto, 231k miles

[bubba966]

Check part #9 in this diagram
http://www.realoem.com/bmw/showparts.do?model=HD63&mospid=47404&btnr=11_1124&hg=11&fg=40

It's the plastic connector that connects the rubber ICV tube to the intake manifold. The crappy plastic retaining clip on it breaks frequently causing it to back itself out of the intake causing a large vac leak that will cause the engine to run terribly if at all.

Easiest way to check it is to pull the throttle body off the intake and look into the intake through the hole to the throttle body. That connector plugs into the intake right behind the throttle body and is easily seen as it's quite large.

Should be about a $6 part at the dealer. They probably stock it as well do to the frequency of it breaking. I know my local dealer had it in stock...

[alex 1993 525i auto]

I've seen a post very similar to your suggestion (maybe it was you telling that to someone else) and when I look at the vacuum hoses in the intake area I had a look at that particular one, but it is tight on the manifold and ICV. I'll double check anyway Saturday when I'll check at the spark plugs and try to identify the problem again.

If you (or anyone else) have another idea let me know please! Alex

[genphreak]

The pipe to the ICV splits, you really need to check that too. The first pipe to go I think is the fuel pressure regulator vacuum hose, right at the back of the intake manifold. It comes from a connector under the manifold that is reliable. This hose splits and perishes with age...

[Marcusd]

My partners 525i has started behaving in the same way a couple of days ago. This last happened to her E34 a couple of years ago at the same time of year when it got cold outside.

I thought it may have been a cracked block or head gasket problem as it idled really rough, the coolant was a little bit low and it would die if you try to give it any throttle. At the time I put a couple of bottles of K-Seal "miracle cure in a bottle stuff" into the top hose and removed the thermostat. This did not seem to do anything to help at first but when we left the car for a couple of weeks the fault mysterioulsly dissappeared. This was nearly 20,000 miles and 2 years ago. Now the fault has returned.

I have put another couple of bottles of K-Seal in again and it is still running roughly. This always seems to happen when the weather turns cold and we have left the car without using it for a week or two.

Having read your post it sounds exaclty like the problem we have with one of our E34's. I will check the hoses and if I find anything I will post back.

Good luck finding your rough running issue.

Cheers, Marcus

1995 E34 525i 242,000 miles (good)
1995 E34 535i 182,000 miles (running rough at the moment)!

[Marcusd]

Just had a look at mine. The hoses all seem ok with no apparent leaks. I can only get it to rev with this problem by being very gently with the throttle.
I had a look at the fuel pump in the top of the petrol tank, from the panel under the boot (trunk) carpet. It did not seem to make any noise when the engine was running where as our other E34 has a faint humming noise coming from it.

I had a poke around with the connectors and it seems to have brought the pump back into life and cured the problem for now. The connectors were not loose so I am guessing that the drop pump in the tank is on it's way out. Maybe me poking around just freed it for now.

Alex, I know your fuel pump was replaced 3 years ago but is there a quick way you can test your tank pump as your problem sounds very similar to mine? Maybe it could be the relay or wiring to the pump? Once it was going the hoses on the top of the pump felt to have more pressure in them and I can hear the pump now. The car is back to running spot on for now.....

[alex 1993 525i auto]

After reading the last 3 posts:

Thanks Genphreak I'll have a look too at the vacuum hose attached to the FPR.

Hey Marcusd, not so sure about all what your saying... 1st I would avoid over-using that K-seal in the coolant liquid, it might change the properties of the liquid and modify the heat capacity of the coolant and also the micro-ceramic they say will cure leaks might also dirty your thermostat, water pump, radiator and heater core. To verify for a cracked head/block/head-gasket 1st thing is to check the aspect of your oil and coolant. If no oil in coolant (brown droplets on top of coolant) and if no coolant in oil (makes a beige-brown residue on the dipstick) than no cross-contamination occurs. Then the cylinder compression test will tell you if one cylinder (or the valves on that cylinder) is leaking. For your cold start rough idle issue, it could be worn intake manifold gaskets which cause a vacuum leak on cold start, and when the engine gets hotter the heat make them swell and seal as it should when hot. Then you mention that upon playing with the connectors on the fuel pump that it revived your car for now. Below that connector is the fuel level sending (FLS) unit and below that is the fuel pump. In my case it was the FLS witch was worn, testing the resistance on the connector as in the Bentley manual showed this was wrong, not the fuel pump, but I replaced both anyways. If that resistance is not in the good range the current doesn't pass enough to power the fuel pump. Maybe you should check that too. When it happened to me it was intermitent for a few weeks, letting me stranded twice, than restarted after 0.5 - 1 hour. Than it failed for good. Hope it helps. I'll check the my problem is fuel related too once I confirm it is not spark or engine related.

[genphreak]

Yikes! IMHO: If you remove a thermostat on an e34, any e34, or any modern bimmer, and it actually improves the presenting problem/s, you are simply addressing the symptoms of a serious cooling system problem that will sooner, rather than later cause a major 'head'ache... these cars have carefully designed cooling systems designed to maintain engine performance through very carefully considered temperture management in all extremes. As an owner, one has no choice but to maintain it with proper care, especially if the PO did not... and particuallry if they experienced even the most basic of cooling problems.

[Marcusd]

Sorry, forget the K-Seal cracked block thing, this looks like it was just bad diagnosis on my part. When we had this problem before 2 years ago the coolant looked low so even though there was no oil in the water or vice versa, I presumed the block had a crack somewhere. After adding a bottle of K-Seal and leaving the car for a couple of weeks the fault disappeared and the car has been fine for the last 2 years. When the fauly reappeared I presumed that adding another bottle of K-Seal would solve it.
Once I had realised that this problem was something else I looked on the forum and this post was the first post and a near identical problem to mine. I removed the thermostat on this car as it jammed open and could have killed the engine. The thermostat on my engine has been jammed open for years so I have just left it. I know really that I should replace them but with the cars being in the UK, all that really happens is that it takes a little longer to warm up in the morning on cold days, there is no risk of it jamming shut and cooking the engine.

I am going to have another look at the problem today but suspect the fuel pump as my issue has gone for now after fiddling with the pump. As Alex's issue sounds so similar to mine I just wondered if it would be worth him double checking that the fuel pump, relay and regulator are working properly.

[Marcusd]

Thanks for the info Alex, I will dig out my Bentley manual and check the resistance on the FLS.

[alex 1993 525i auto]

I had a look at the small vacuum hose from the FPR and it is fine.

Marcus, 'happy to help you and I hope you find the cullprit.

I did the checks Shayne suggested on bimmerboard. =
-------------------------------------------
Simple test:
Cold car. Open hood. Start car.
Place hand in turn on each header pipe where it attaches to the head. Just keep gently feeling each pipe in turn feeling how hot they are getting. They should heat evenly and consistently.
If one or more is not heating as fast or is remaining cold then you have a problem at that hole.
Replace the plugs and if you still have the issue move the coils. If the problem moves replace ALL of the coils. Use Brembi.
If the problem does not move then you may have a valve or cam issue.
But I can almost guarantee you that the problem is in the high side ignition.

Shayne
525iTA
330iA
-------------

So I started the car and felt the exhaut pipes, notice that the cylinder 6 (the one closer to the windshield) warms slower than the other 5 which were equally warming.

So I removed the plugs on cyl. 1 and 6 and compared. Both looked similar, a little bit of carbon but not terrible, both look quite good after 3 years (40k miles ago; Bosh platinum +4 plugs). I cleaned them with brake cleaner and metal brush, I swapped the plugs to see if the problem would move. No, it was the same cylinder 6 that warmed slower. Then I tested the coil no. 6 and resistance was fine (0.8 Ohm) and voltage at the connecter was 11.6 V. Then I swapped the coils 1 and 6. No change again. Then I started the car to see if the injector was working by listening with a screwdriver and yes, all 6 clicked fine (injectors are clicking but it still could be clugged I guess and causing the cyl 6 to have not enough fuel).

Then I tested the compression on cyl. 6 and it was 0 psi, no pressure at all. I could not believe that then I tested the compression on cylinder 1 and it was at 200 psi after 4-5 strokes and didn't go higher. Then I retested cyl. 6 and I still see 0 psi. Then the battery was drained so I jumped the battery with my wife's car and cranked mine for 10 strokes or so and the needle on the gauge was not shaking a bit. I then reassembled everything... restarted the car with my wife's car still plugged on mine and the car was behaving like before, rough and shaky.

I then unhooked the jumping cables and tested the vacuum with the small vacuum hose on the pcv valve while blocking the pcv's plug where the hose was, vacuum was steady at 20 inches, with the needle vibrating very slightly. It looks ok but I noticed that it was at 22 in. of vacuum when I tested it 1 month ago. I'm not sure if it is related to the fact that my car was hot at that time (after 30 min. highway driving), while now my engine was not warm (0 Celcius or 32 F outside, tested after 3-4 min of idle and the coolant temp still at the coldest mark).

I'd like to know how it is possible that there is no pressure at all in cylinder 6, I could drive 1h on the highway, the exhaust fume is white on cold start (at 0 Celsius) but not blue, doesn't smell oil, just a smell of gasoline (I think it is normal when engine is cold). I didn't lose a bit of oil in the 50 miles trip last week when this began. Is it possible that a valve is stuck open? (I think that would burn oil like crazy) Or that a valve stem on that cylinder is completely shot?

Thanks again for all your suggestion and I'm looking forward for any advice!

[bubba966]

Probably a valve that's not fully closing that's causing your 0 psi in cylinder 6. Broken valve stem will cause the head of the valve to break off doing this.

http://www.bmwpugetsound.com/vbb/showthread.php?t=44476

Have you popped the valve cover off to see what it all looks like from above?

[Tiger]

Tap your fuel injectors to see if that dislodge any gunks that is causing spray pattern. If no difference, then pull your fuel injectors...

[alex 1993 525i auto]

That's something I have to check next w-e, removing the valve cover than crank the engine without fuel pump relay/dme relay and see how the cams and valve lifters behave.

I spoke to a few poeple this weekend after the tests I made and they told me it was probably the exhaust valve seat being toasted because those are working in more extreme temperature, or that the piston is shot, like if a too high temperature would have melted a hole in the piston. Hopefully it is the valve... nice pics of a destroyed engine by the way!

[Tiger]

I doubt it is valve issue as you said engine was working fine before this. Clogged cat will do similar symptom.

[Bob in San Jose]

Explain how a clogged cat causes 0 PSI in only one cylinder.
I think you need to pull the valve cover and confirm the valves are operating.
If they are then it possibly could be a bad injector I guess, but I've never seen one do this. More likely a valve or piston problem.

[Tiger]

Don't see any poist mentioning 0 PSI

[alex 1993 525i auto]

I can't see why a bad injector would cause 0 psi of compression on one cylinder. Like I said the others go at 200 psi after 4 strokes. 'Will see how does it look once valve cover is removed. Even if a valve on that cylinder is stuck open it might look ok from the 'outside' of the combustion chamber as I read. The cam could operate fine, the hydraulic valve lifter too but under the lifter, maybe the valve could not close. Or maybe I will be able to see a lifter not popping up once the cam have relief its pressure, if the spring has failed. I'm not a pro mechanic yet, still learning. I can't see how anyways I can repair that engine without a head job... I'm looking for a cylinder leak-down tester (and a air compressor...) to confirm without any doubt where the problem is exactly also. Saturday I should be able to test a few of those ideas.

[Bob in San Jose]

I don't think you need to bother with a leak down test as you have no compression in the cylinder so there is nothing to leak down.
And i agree it probably is not an injector.
Pull the valve cover and let us know what you find.

[Tiger]

If you got a compressor... hook up that cylinder to the compressor... you can hear if it is the exhaust valve is leaking or intake valve is leaking.

[Dave M]

Just in case, make sure cyl #6 is not 'fuel washed'. Either pull the plug and wait a long while and/or pull the fuel pump relay and turn it over a bunch.

If you get compression back, take a very good look at your plug ceramics as I had similar symptoms and it was a cracked ceramic. I concentrated too much on the business end of the plug and not enough on the boring end. If you want to find a bad cylinder/plug on the M50, try pulling the wire harness from each coil pack listenng for no change in idle. Bentley/forum members probably don't recommend this method, but its worked for me on more than one occasion (just like pulling the plug boot on a single coil ignition system).

Good luck with it, hope it not a serious problem,

Dave

[alex 1993 525i auto]

Thanks all for the infos, here is an update, but the job is not finished yet...

So 1.5 months ago, I had a problem with my car and now I'm in the process of removing the cyl. head to get the valve job done in a machine shop. It is in storage for the winter so I do it myself during weekend when I have time to work on it.

I tried this to test if it is the exhaust valves that are stuck open or broken: I have an issue on the cyl. 6. with no compression at all. After removing the cyl. head cover and fan clutch, I turned the engine to see the cams and hydraulic cam followers and they looked fine. Then I set piston #6 at the highest position with cam lobes pointing up, which close the valves. I added injector cleaner liquid in the spark plug hole with a funnel and I saw the liquid free flowing down. I did the same test with cyl. no. 2 and the liquid was staying inside for a few minutes. I heard the liquid going down the exhaust when pourring it in the cyl. 6. When I remove the intake manifold there was no injector cleaner in there, only a little bit of oil.

Next step will be to remove the exhaust manifold, set the engine at tdc, remove the vanos then cyl. head. and bring it to a shop for the valve job and get the head cleaned. I know I have to buy the gasket set, head bolt set, exhaust manifold bolts and nuts etc. I heard/read that exhaust manifold nuts are very tough to remove, I'll see how hard it is soon. If anyone has tricks and infos please let me know! Thanks

[rockin1978TA]

My 535 was running like that, tracked down a small leak at the intake to head. Used some permatex copper to plug the leak, runs great now.

[alex 1993 525i auto]

Hey! I realized I hadn't followed-up on this one. When removing the exhaust manifold it was an easy find, cyl. 6 exhaust valve had a small hole on the outer side of the valve... for sure this cylinder couldn't have compression... I removed the head, brought it to a machine shop ($500 to get the head refurbished, not bad I tought). Another $400 of gasket set and various other parts and that was it. It took me kind of 40h job alltogether (+ reading time and shoping time) for a first timer, and the car started fine right after reassembly. Thanks to all who post in forums good tricks of all kind (and to the Bentley manual and also I found the Pelican tech info center very useful). The car has been running fine since that repair 2 years ago but just started a little something I'm into checking:

http://www.bimmernut.com/forum/5-series-bmw/44460-low-power-low-rpm-below-2200-rpm-so.html