89 328 rough idle

No hose goes there (it's "connected" to, and measures the pressure of, the atmosphere). Your '89 euro 328 might be KE3-Jet (something used very late in non-US 328 production -- have you ever decoded your VIN to see what market your 328 was made for? Might be Swiss/CH). KE3-Jet doesn't have a frequency valve -- it uses an EHA instead, but it does have a protection relay (the tall silver box thingy with the 10A fuse on the top) -- check the 10A fuse, and measure the voltage between terminal 87 and terminal 31 when the engine is running = it should be +12V. If the fuse is OK, but you don't get the +12V 87-to-31 = measure the voltage between terminal 30 and terminal 31 -- if that's +12V, buy a new protection relay. If the fuse is OK and the 87-to-31 measures +12V = your problem is elsewhere.

Can you post a picture of your fuel distributor? (It would show the EHA if you have a KE3-Jet system.)

 

PS If the 10A fuse is blown and continues to blow when replaced = your alternator is bad and going overvoltage. The function of the protection relay is to protect the injection ECU from a wacky high alternator voltage -- hence the name.

 

Forgot to ask: Is the rough idle only during cold-running, or during both cold-running and warm-running?

 

Maybe a simple thing and not good visible on the pictures, but is the adjustment hole plugged?
It will give false air as we call it.. unmetered air that will disturb your AFR.


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Yes, that is the KE3-Jet system. The small black box in this picture held on by the two slotted cheese-head screws is the EHA:

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It provides the same function as the frequency valve (changes the lower chamber pressure in the fuel distributor to change the pressure appearing across the slits which adds, or removes, richness for the same size slit opening), but it doesn't vibrate when working so touching it won't tell you if the protection relay system is working or not.

That can be the symptom that the protection relay system isn't working and supplying +12V to run the injection ECU on a KE3-Jet (although there are a lot of other horrible things to go wrong, too ). On KE-Jet, if the protection relay system fails = both cold-running and warm-running are bad (both lean), but on KE3-Jet they made some (clever IMO) changes to how the EHA works so that only cold-running is bad (lean) if the protection relay system fails -- warm-running can still be OKish with the protection relay system not working.

Please do. I will agree with Dré that the "plug" for the mixture screw access hole is not stock (but, if the car was running well before and it wasn't changed, that wouldn't cause a sudden change in behavior if that's what happened -- unless it got loose).

 

It is a Swiss KE3 system like mine is. The idle mixture screw is like mine, it is spring loaded and one can push down with a screw driver to engage the mixture screw.

I note in your second picture with the relay in your hand, there is a fuse in it. That fuse should not be in for normal operation. It is a service procedure to put in a fuse in there to disable the O2 sensor, which is done for eg. setting idle mixture with a gas analyzer. The fuse is removed for normal operation.

So your car is running without the O2 sensor functioning. It might have been done like this to mask some other fuel mixture issue, or a tech forgot to remove it. So just remove the fuse and see if the car starts and idles better.

It is also worth removing one spark plug, post a pic. If the fuel mixture is off for whatever reason, the plug will be black. You could have a plug/wire dist cap issue affecting one cylinder, but a single plug inspection would be a start to some clues.

 

The KE3 idle screw is stock, there are many small features unique to the low volume Swiss cars, this is one. Much more functional and clever than the anti tamper plug sealing of the mixture screw on the typical Ferrari's.

There is a special Ferrari manual available for this Bosch fuel system, unique to some late Swiss market 1988 Mondials and 1989 328's. Same for the Teves Abs brake system which I suspect your car also has.

fyi Many Fchat posts regarding idle and running problems are for the much more common Bosch KE system, and as noted in this post thread there are components like the EHA unit that are only on the KE3 and other items such as the frequency valves unique to the earlier KE's. The KE3 was used on the much higher volume Mercedes of the same vintage, so some of the tips on those enthusiast boards can apply to our units. The KE3 runs at higher fuel pressures, and has different fuel injectors among other things. You need the special Bosch manual for eg. Correct fuel pressures specs. I have the manual, happy to forward extracts if needed, it is on larger than typical page sizes making it difficult to photocopy, I think there may be online copy links out there.

 

Since I was saving these KE3-Jet photos for my reference, I added moysiuan's observation that that fuse shouldn't be present for normal operation (and some other notes):

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I hadn't realized KE3-Jet had that special mixture adjuster (nor how tall it is!), but it's clearly shown in Fig 23 on page 33 of Ferrari's KE3-Jet 539/89 manual:

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A pdf copy of Ferrari's KE3-Jet 539/89 manual can be found here (not all KE3-Jet systems are implemented in the exact same way -- for example, I know the Lancia Thema 8.32 KE3-Jet system is a little different as it has an idle air control valve that is not present in the Ferrari KE3-Jet system):

https://www.dropbox.com/s/95x8kzktl58rbjt/Bosch KE3-Jetronic 539_89 as implemented on late non-US 328 and 3.2 Mondial.pdf?dl=0

 

Before you get too technical, have you checked the basics: i.e. the state of the plugs, checked the extenders for burn through, all the leads for continuity & the condition of the rotors & caps?

 

Nice tidy engine bay, the car has probably been looked after well!

One other easy check item, the Throttle Position Sensor (the black unit on the right side of the throttle body). With the engine off, pull the throttle cable lever a little bit and just off idle position you should hear a faint click from inside the TPS unit. If not, the TPS has two screws, you loosen and rotate the unit slightly to ensure the click occurs just off idle. This is a very fine tune adjustment, and if the TPS is not giving the correct at rest idle signal, this would affect cold idle. That's why the owners manual says when starting the car when cold, you do not press the throttle (I always press and release the pedal before starting to ensure the throttle position is at its idle rest position) and the TPS helps the computer calibrate mixture for a cold start, and on a warm start you press the accelerator slightly while cranking, which negates the TPS rest idle setting and allows for the lesser enrichment required when starting hot (Steve M, I think I have this TPS function correctly described?)