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164 Q4 rough when cold and rpms drop slowly

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164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Fri Aug 15, 2014 8:58 am

I have this problem with my car, that it runs quite rough when cold (it's very jerky until it reaches about 70 degrees).

Recently I have also noticed that the revs started to go down slowly. That is, when I'm accelerating and changing gears, say at 4000 rpm, when I press the clutch the revs stay at 4000 for a second and then drop quite slowly. Also, when blipping the throttle on low revs, for instance to rev-match, there is a big lag (I press the gas pedal quicly 2-3 times and the revs just go up once and they are "lazy").

I remember it was not like that before, the engine was very responsive.

Those two issues can possibly be related (but maybe they are not). I suspect lambda probes or air/vacuum leak.

I would like to connect WIlco's software and look at the data there, I'm waiting for a lighter socket plug with cable from eBay to arrive so I can supply the 12v to the connector nicely.

Do you have any suggestions? What should I look at when monitoring with the diagnostic software? Should I look at cold or warm engine? What values for the probes/other sensors should I expect?
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby alfa east » Fri Aug 15, 2014 1:38 pm

Terribly inexperienced when it comes to technical issues but the problems you described remind me of when my gasoline pressure regulator had to be replaced.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfan » Fri Aug 22, 2014 4:27 pm

Have you tried disconnecting the idle speed regulator?

And how is progress with the diagnostic sw?
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1989 Lancia Thema 8.32 Verde Indy 265.000km
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Mon Aug 25, 2014 12:31 pm

Unfortunately not much time to work on the car in the next 2-3 weeks, so no updates here. I will post back once I get everything connected. In the meantime I am also waiting for some spares to arrive (ABS pump, power steering pump and some extras).
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby wilco » Wed Nov 26, 2014 7:37 pm

best is to read out the lambda's with hot engine. There you can see wether you have a leak or not.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Thu Feb 26, 2015 11:46 pm

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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfamuppet » Fri Feb 27, 2015 8:36 pm

Hi Mike

I recently had the lambda code and the code 33 showing on mine. There are 2 probes, one in the front down pipe and one in the rear. If you run the programme using the live data you can select the lambda voltage - if the lambda when warm show close to 0.9 mV then they are ok. My were 0.2 and 0.498 so I replacedthem both. They are label front and rear on the programme.

My trouble was rough running or stalling when hot.

The phase sensor points to either the crank sensor or a cam sensor I think, and again I had this error on mine and after a few non starts I replaced the crank sensor and the problem was sorted.

Hope this helps
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Fri Feb 27, 2015 10:22 pm

Alfamuppet wrote:They are label front and rear on the programme.


Oh my... It does help, Alfamuppet! Thanks! Something just came to me when I read the above and I launched the program to check it. It turns out I was using wrong sensors list, I completely overlooked the select box on top of the list! Because I selected "standard" 24V M17 instead of Q4 ML37, I had only one lambda sensor and a lambda integrator. I was scratching my head how to read this, since I know there are two probes. Now everything is crystal clear, as I have the correct sensors list. Can't wait for tomorrow to plug it in and check again! :mrgreen:
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Sat Feb 28, 2015 5:26 pm

OK, I've got something. Today I had some time to investigate further.

Current symptoms are:
  • Rough idle and misfiring, intermittent (cold and hot)
  • Sluggish RPM response and RPMs drop slowly (cold and hot)

What has been done so far:
  • New spark plugs
  • Switched the ignition coils (front with back)
  • Unplugged individual injectors from the front bank, always made it worse (no access to the rear)
  • Unplugged the MAF, much worse (waveform RPMs, raising and dropping)
  • Unplugged the ICV, stalled (i.e. much worse)
  • Checked error codes, nothing obvious related to this issue

Now look at the following readings from the Alfa164Diagnostics, the car was already hot:

Image
Image
Image

Does this mean the front lambda is bust? What about the rear one, I would be expecting a bit higher frequency? Could this possibly cause the above symptoms?

Otherwise there is only the ignition system (coils) and injectors to check, or am I missing something?
Last edited by AlfaWhiz on Wed Mar 04, 2015 9:12 pm, edited 1 time in total.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfamuppet » Sat Feb 28, 2015 8:15 pm

Mike, that does point to the front lambda not working correctly.

The rear at low.200 and high at .800mv is good

The front with no variation is not working correctly - see copied statement below

"A good O2 sensor should produce an oscillating waveform at idle that makes voltage transitions from near minimum (0.1 v) to near maximum (0.9v). Making the fuel mixture artificially rich by feeding propane into the intake manifold should cause the sensor to respond almost immediately (within 100 milliseconds) and go to maximum (0.9v) output. Creating a lean mixture by opening a vacuum line should cause the sensor's output to drop to its minimum (0.1v) value. If the sensor doesn't flip-flop back and forth quickly enough, it may indicate a need for replacement"
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfan » Sun Mar 01, 2015 8:31 am

The front lambda probe is worn out, as it is not adjusting anything. Since there are 2 probes on the Q4, it is only one of the cylinder banks being affected, there is doesn't run completely like crap. If there were both like the front one, I am sure driving it would be a lot worse.

I think you should also replace the rear one (while you are at it), as the range it should regulate should be higher - at least compared to what I have seen in my Q4. At least you should try and clean around the connection between the rear probe and the exhaust, as the grounding here is important. I did that on mine, as connection was sometimes good, sometimes around 0.1V (running rich, I think that is), and it has been good since then.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Fri Jul 24, 2015 7:43 am

Resurrecting the subject slowly.

Both lambda probes replaced, the engine still runs a bit uneven. Still sluggish RPM response and RPMs drop slowly (cold and hot).

I've ordered an used MAF, I'll try to replace it and see if it matters.

Any other suggestions? Where to look now?
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfan » Fri Jul 24, 2015 9:59 am

mike.foxtrot wrote:Resurrecting the subject slowly.

Both lambda probes replaced, the engine still runs a bit uneven. Still sluggish RPM response and RPMs drop slowly (cold and hot).

I've ordered an used MAF, I'll try to replace it and see if it matters.

Any other suggestions? Where to look now?


Did you check that both lambda probes are adjusting correctly now? Could be a connection issue...

Browsing quickly through earlier posts, I don't see if you check injectors on the rear bank?

Are you absolutely sure there are no leaks in the exhaust before the lambda probes?
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Sat Jul 25, 2015 8:12 am

Thanks for your reply.

As far as I've seen, both lambdas are working correctly now. I will re-run the test though and post a screenshot once I have a bit of time to plug it in again.

I believe there are no exhaust leaks, it looks very solid, there are no strange noises or black spots anywhere.

Injectors could in fact be an issue. I haven't checked the ones on the rear bank. Well, by checking I mean that I've unplugged the front bank to see if it makes any changes. Is there a better way to do this? I know about the screwdriver method, but it doesn't really give you much more than if the solenoid is working or not.

I would be tempted to remove the injectors and place them one by one in a plastic bottle with the engine running, but this is impossible due to various reasons (fuel rail sitting on top of them being one).

I'm talking to a workshop right now about a diagnosis, but I'd like to know if there is anything I can still do myself.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby munition » Mon Jul 27, 2015 8:54 am

There is a false air leakage. Bad injectors don't keep RPM up, they may be an issue of rough idle.
Spray break cleaner at every possible location and listen carefully.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Mon Jul 27, 2015 5:05 pm

Thanks a lot for your suggestions. I think it makes sense.

At the moment I believe my problem is complex, i.e. there is no single thing broken, but what I'm observing is probably a combination of multiple issues.

I've started another topic on the engine response itself, to compare experiences: http://alfaromeo164register.com/viewtopic.php?f=2&t=1661

As written there, done to date are:
  • New throttle position sensor
  • New air intake hose (accordion)
  • Checked injectors for ticking, all work (I know nothing about the flow)
  • Measured resistance of the ignition coils, all are comparative
  • Checked and replaced when necessary the 6 individual intake rubber connections
  • Swapped the MAF sensor for another used unit with no difference
  • Played with the idle control valve, disconnecting stalls the engine, I've cleaned it and it looks OK
  • Replaced both lambda probes

Still very poor response and somewhat erratic idle, sometimes skips a beat, sometimes changes tone after 10-20 seconds, but shakes a bit every 2-3 seconds (you can feel that on your butt; I think it should be very smooth).
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby munition » Tue Jul 28, 2015 9:29 am

Yes, you may have a few issues at the same time.

Basics are checked, but: False air leakage is my favorite and needs still to be investigated. Take 2-3 bottles of break cleaner and spray it all over the intake stuff.
Fuel evaporation valve could also be an item. Disconnect the hose from the plenum and close the connection to the plenum carefully. If that valve doesn’t work properly, the symptoms should be gone.
Did you check the air inlet temperature sensor and the coolant temp sensor? Resistance values are listed in the manual area.

Further suspect in regard to engine shaking is the cam belt timing. Just do the easy jobs, but if there is no progress, then the cam belt timing is most likely the issue for rough idle.
But: Before you put the timing dies on, check the compression, please…
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Tue Jul 28, 2015 11:12 am

I agree with you fully, at the moment I also suspect that false air is the most probable cause. I took the car for a drive yesterday and listened to the symptoms carefully.

Further suspect in regard to engine shaking is the cam belt timing. Just do the easy jobs, but if there is no progress, then the cam belt timing is most likely the issue for rough idle.
But: Before you put the timing dies on, check the compression, please…


I don't think the timing is wrong as it would be much worse then, I think the error is much more subtle. Also, then the problem would be permanently present, and not in 2-5-10 second intervals (which by the way make me think of the lambda probes adjusting the entire mixture for the false air in part of the engine and on and off, what probably is happening).
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Sun Aug 02, 2015 7:12 pm

Alright. I sprayed a whole bottle of easy startup aerosol around all the seals I can think of when the engine was warming up. Around injectors, idle control valve, everywhere. I did not notice any changes (no big changes to be exact). It's a bit hard to tell though as today the engine is very uneven in general, but there was no surge in RPMs.

I measured the intake air temperature sensor on a hot engine and the reading reads around 600 Ohms. This corresponds to between 50 and 60 deg C if I see it correctly (not sure if the temp reading is right though).

Current symptoms recap:
  • Rough idle when cold AND hot.
  • Shaking cold AND hot.
  • Lazy response cold AND hot.
  • The rhythm of the engine changes (i.e. roughness is not constant, sometimes it goes into "gallop" and sometimes it's as if one/more cylinders were not firing cold AND hot.
  • BUT disconnecting the individual injectors makes no difference.
  • Disconnecting the idle control valve stalls the engine, but when I reconnect it quickly enough, it runs but surges and it's much worse for some time. I have an used spare, I'll give it a shot.

TODO:
  • Do the fuel evaporation valve test munition mentions.
  • Swap idle control valve.
  • Perhaps check fuel pressure (filter is probably very old, maybe it's not getting enough fuel?).

What then, we will see.

Any additional ideas will be greatly welcome.

EDIT: I will repeat the vacuum test with brake cleaner, the stuff I used was in atomized form, so it's possible it wouldn't reach the leak. It's probably better to use brake cleaner to really soak all the suspected places. We'll see.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Mon Aug 03, 2015 9:04 pm

Today I had about half an hour to run a couple of tests. Here's what I found about the misfire/rough idle:
  • Intake air temperature sensor works correctly (around 1100 Ohms or 30 deg when cold and around 600 Ohms or 60 deg when hot).
  • I took off and plugged various vacuum lines around the throttle body, there was no big difference, if at all. This I will redo tomorrow, but as said, there was no miracle.
  • I did a quick test by unplugging individual injectors (again, to be sure). Every one of them caused a noticeable RPM drop and the idle got worse.
  • For a preliminary fuel pressure test, I clamped the fuel return hose from the fuel pressure regulator and it made it worse, the engine would stall had I not removed it in time.

Here's what I think (or believe to be true):
  • Although shutting down injectors renders the whole situation worse, it does not exclude clogged injectors and not sufficient spray. This however is rather unlikely, as it would be present through the entire RPM range.
  • I believe the misfire/rough running to be happening only on idle, and with some throttle it is better (but I think still not as good as it should be for this V6).
  • I have currently NGK Iridium spark plugs installed, which have slightly larger gap than the Platinum ones. This may be important and will be investigated.
  • As said before, the shaking and misfiring are not constant. The engine has 2-3 rhythms, it goes "mmmmmm" then it goes "mmmm-mm-mmmm-m" missing from time to time, then it goes "mam-pam-mam-pam" like running not on all cylinders and then it can go "mampampam-mampampam-mampampam" also not on all cylinders but different sound (excuse me, I don't know if that makes any sense). This is in no particular order. Shaking goes along with those sounds.

:!:

UPDATE: Here's a video: https://youtu.be/y41Ib6HH9Mg. Please excuse the poor sound, it's apparently the best my phone can do.

:!:
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby Alfan » Thu Aug 13, 2015 8:42 pm

One thing I just remembered, there was a tiny hole in the front exhaust manifold on my Q4, see photos. I had both manifolds replaced together with other work and hesitation and misfires went away. This was 3 years ago, so don't remember all the details. If you haven't checked the exhaust manifolds, it might be worth while to do so.
Attachments
IMG_4744-800.jpg
Q4 front exhaust manifold
IMG_4743-800.jpg
Q4 front exhaust manifold
1994 Alfa Romeo 164 Q4 Proteo Rosso 550.000km
1989 Lancia Thema 8.32 Verde Indy 265.000km
2001 Alfa Romeo Spider 3.0 24V Blue Lightning 55.000km
2015 Alfa Romeo 4C Rosso Competizione 80.000km
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Fri Aug 14, 2015 10:29 am

Thanks Alfan. I am at the moment doing a lot around my car to solve this problem. It is not trivial.

I have the entire intake disassembled again. I tested meticulously for vacuum leaks, to no avail. I could not find anything, no difference.

On my list right now is cleaning of the injectors and examining spark plugs again, this should show something. I will do a compression test and also fuel pressure test after I have the injectors clean. I've checked them and electrically they are fine.

I checked my O2 sensor readings and they were fine I think. I will re-check again once she's running, to make sure. But... as far as I understand, if there was an exhaust leak, the lambdas would detect a false lean condition and richen the mixture, so that the voltage they detect is again correct. Therefore it is possible to see correct O2 readings and indeed have a rich condition because of for example an exhaust leak. This is very much possible and one of the suspects.

Another suspect is an electrical gremlin, as the problem is intermittent. The engine is not running perfect in general, but it really worsens noticeably from time to time. I am sorry for the crap quality of the sound in the video I've posted, I'll have to re-do it with a better mic.

I'll go ahead with the injectors, then spark plugs and since I'm here already without the intake I'll do a voltage drop test to the coils and sparks from the ECU.

Next suspect is the aforementioned exhaust leak and possibly faulty fuel pump. With the pump there will be a fuel pressure test and also voltage drop test if the former shows an error. This should also allow me to debug the fuel regulator (but I think it's fine).

We'll see how this saga ends, I hope it will be soon.
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby munition » Fri Aug 14, 2015 2:31 pm

I would check the fuel pressure before removing the injectors, because it is simple to do. If there is your issue, you will save a lot of work.

Further recommendation from my side: Check spark plugs and do the compression test on front bank at first! When the spark plugs are looking good and the compression is equal on these three cylinders, start removing intake runners, plenum, rear bank spark plugs and check them. If they are good, which I cannot believe, remove the valve covers and check the valve timing.

Holes in the manifold should be identified be listening.

May you take some pictures of spark plugs, ignition coils, compression readings and so on.

Have a nice weekend! :wink:


Btw: The rpms don't drop slowly!
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby wilco » Sat Apr 30, 2016 1:51 pm

how are your spark plugs ? new or old ?
Then, did you also use the brakecleaner at the bottom of the intake tubes ? there are 2 seals under there, 1 under the pipe and 1 under the plate between the pipe and intake. and they like to leak there too.
How long is the timingbelt on now ? When it is a few degrees wrong, it tends to pop in the exhaust.
how is the rubber intake hose connected to the air flow meter ?
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Re: 164 Q4 rough when cold and rpms drop slowly

Postby AlfaWhiz » Tue Aug 02, 2016 12:27 am

Hi guys, sorry for my long absence, I had some other things going on as well.

In the meantime, the problem has been solved. One evening just after I replaced the spark plugs and was checking the ignition coils, all of a sudden huge piles of white smoke started coming out of the exhaust. Car was stationary in my garage. Of course a quick check proved the head gasket at cylinder no. 4 was at fault.

Now after some time, having both head gaskets replaced, head and valvetrain refurbished (checked for leaks, items replaced where needed), I've put 3 new coils on the back head where the access is difficult, new timing belt (previous timing belt was done about a year and maybe 5000 km ago), and perhaps most importantly, brand new 6 injectors of the newer type) she is a completely different animal!

Basically both head gaskets were completely busted, with huge holes in them, one of the injectors was leaking and one coil had a visible and audible erratic short in the boot.

Now no more hesitation, no erratic idle, no misfires.

Pro tip: newer Bosch injectors (red) with 4 nozzles for 3.2, GTA, etc. fit nearly out of the box. One modification is required, I had to cut a groove for the retaining clip, as the newer injector has different style of clips and sits deeper in the fuel rail. Besides that overall dimensions (i.e. height, o-ring diameter) and flow rate are identical, the spray pattern is much better. And... I've paid about 100 EUR for all 6 brand new injectors, which is basically what 1 original one would cost. I'll list the details in the alternative parts sections once I find a bit more time.

Last week unfortunately another problem struck, this time with fuel supply, but that's a different topic.

The slight issue with rpms dropping slowly however remains, and is bugging me a little. The engine response is very sharp, but the revs are hanging a bit between gear changes and I have to wait for a second for them to drop.

All gaskets are new, ribbed air intake as well (I've replaced it with a proven unit not long ago), so I'm positive there are no air leaks. A bit puzzled about this one to be honest, maybe it's normal... I don't know how your cars behave guys. :?:
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