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Discussion Starter #1
Hi Folks..
Does anyone with 1.7 16v ei experience have any diagnostic suggestions for the usual causes for rough idle on late 33's?... I replaced the O2 sensor recently thinking this might be the cause and while the engine did seem to run better, albeit very briefly, it soon fouled up and returned to the bad idle. I've have also replaced the intake vacuum hoses as I found a few cracks in them. It sounds to me like it's over fueling but I can't say for sure. Next thing on my agenda is to swap out the airflow meter to test against a vehicle that I now to be good.
Any other suggestions?
Thanks.
 

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Hi

I have a 16V 33 and I had a similar problem where after I cleaned the tracks in the AFM my car over fueled to the extreme and would hardly start, let alone run. For me it turned out that as the car wore and things became dirty the PO's mechanic would adjust the CO2 pot on the side of the AFM to keep everything running ok. When I went through and cleaned everything this setting was now way, way out. I can't for the life of me remember which of the wires out of the AFM to watch but you need to set this CO2 pot to read around 2.5V. Mine was about 4V. You should be able to just back probe the connector til you find the right ones.

After doing this and the usual maintenance I now get 7.6l/100km in heavy stop start highway traffic. Pretty happy with that.

cheers
Scott
 

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Discussion Starter #3
Thanks for the feedback Scott.. I'm hoping to be able to confirm an AFM issue when I swap it with one from another 33 this weekend. I know the black cover has been removed from my AFM prior to my ownership so maybe it could be a similar issue to yours. Can anyone give any further info on how to reset or test voltages?
 

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Discussion Starter #4
I took the top off the AFM today and the contact track seems ok. I also cleaned the track with contact cleaner while it was apart. After putting the AFM back on the car it seemed to idle nicely for maybe 20 seconds and then went back to its rough idle, burping and with the odd intake pop. What I have also noticed is that when I try to set the ignition timing the flywheel mark doesn't seem to move when I turn the distributor.
 

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Hi

On the 16V 33 moving the distributor has no effect until you go too far, then no more spark. Go even further and then you will start sparking on the wrong cylinder. The dizzy in the 16V basically has nothing to do with timing. All aspects of timing are controlled by the ECU. The dizzy simply aligns the rotor to the right plug. The rotor has a rather large contact area on it so that as long as it is pointing roughly in the right direction, it will spark fine.

Moving the dizzy has no effect as the dizzy does not trigger the spark (through points or contacts) it is all done off the hall effect sensor attached to the fly wheel.

You should see a screw on the side of the AFM to the right of the wiring connector. This is the CO adjustment. Try moving it 2 turns in, then two turns out to see if it makes a difference. This is the adjustment I was talking about. If it ever stops raining here I will go out and check which pins to use so you can make sure yours is set at 2.5V.

The other thing is to make sure you have absolutely no air leaks. The Motronic system is very susceptible to air leaks. Just not having the dipstick seated fully can cause a lean mixture and make your engine ping. Weird but true as on the elbow of the intake between the AFM and the plenum is a line that runs to the oil filler. If the dipstick isn't seated you allow more air to flow through than is expected and voila, lean mixture.

cheers
Scott
 

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Discussion Starter #6 (Edited)
Thanks Scott. I'll check that the rotor is roughly in line with cyl # 1 and go back to the AFM adjustment. I don't think this one has ever been adjusted as I can see no marks from the cover plug having being removed. Let me know if you can identify the connectors on the plug for the voltage test. Do you know if there is a suitable pick up on the motor where I can attach a guage to test for vacuum leaks?... I've replaced the small the manifold vacuum hoses just to be sure but there are no doubt other potential leakage spots. Much appreciated.
Cheers
Ron
 

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Discussion Starter #7
Hi Scott.. I tried the CO2 pot adjuster on the AFM and I couldn't get it to make any difference no matter where I set it to. I tried up to 5 turns in and 5 out with little to no variation in the running. How much of a difference should the adjustment make to the idle?.. I wonder if the AFM could be the culprit?
 

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Hi

For me it made a lot of difference. If I recall mine was reading 4(?)Volts and would only just start, but would not run. At 2.5V it runs sweet as a nut.

Of course this is only a supposition that you could have a similar issue. Have you ruled out the other "basics" such as fuel filter, air filter, plugs, leads, air leaks, bad fuel and compression test.

What do your plugs look like? Have you put an Ohm meter across the leads (more than 1k Ohm per inch of lead and I would replace. Have you tested the primary and secondary sides of the coil? Start spraying a WD40 or the like around all possible areas of ingress for air into the system and listen for a change in tone of the engine.

How clean are your injectors? There is a video of cleaning the bosch injectors at home which I have used and it seemed to work great (I didn't get them flow tested afterwards so I can only speculate on seat of the pants feel).

Another thing to try is the fuel quality plug. You should have a plug, yellow or red "relay". Try removing the relay altogether. This is how I run my car now. It gives the most advance and ignores the O2 sensor (speculated see 'craigs place').

At least if you do the basics you have a known good base line to start from.

cheers
Scott
 

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After doing this and the usual maintenance I now get 7.6l/100km in heavy stop start highway traffic. Pretty happy with that.

Scott
:eek::eek::eek:
Hi,
I have a 33 Imola 1.4 also fuel injected, that runs the Weber Marelli system.
No dizzy, no AFM, no CO2 adjustment....nothing....1.4 engine and I never got down to 7.6l/100km:eek::eek::eek: cruising, so forget those numbers in stop and go traffic.

What I get is aprox 8-8.5L/100 when cruising in the highway and not pushing to hard!?!?!
cheers,
Elvis
 

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Discussion Starter #11 (Edited)
Hi Scott and thanks for your reply. I discovered what looks like a couple of small cracks in behind three of the dizzy cap poles. By connecting a timing light and looking at the flash pattern up against the fire wall I could see that number one cylinder is not firing correctly. I took the plug out and it was pretty black. I then put the plug in to a mates 2 stroke motor bike (same reach) and took it for a blast to check if the plug was at fault. It seemed fine and the run also cleaned the plug up nicely. I have also tested the leads and they check out ok. I then double checked the cap and found the suspect cracks. I've swapped caps but now it's running worse, as if the leads are crossed. I've set it up on firing order 1324 and I also tried moving the leads back and forth one pole on the cap just in case I was out on the cap. All to no effect. I need to go back to basics and start again. Even with the original dizzy cap on it now runs worse. I currently have the position of the dizzy housing 'cut out' slot (for the cap) facing towards the plenum of the intake manifold. Does this look about right? . I know it only needs to be close enough on the Motronic equiped cars.

Fuel filter is new. I haven't done a compression test yet as I don't have a compression tester. I have done a cylinder leak down test though and none of the cylinders seemed to be doing anything unusual.

I doubt if it is any way related but can you tell me what symptoms I might expect if the idle position sensor switch was faulty? I know they should make a clicking (switching) noise when the throttle is taken off idle but other than that I don't know how to check if they are faulty.

The fuel quality relay has already been removed and has been bridge wired to give max advance so I'm reasonably satisfied that it is not the culprit.

Are you able to post a link to the fuel injector cleaning video that you mentioned.

I've just found what looks to be some arc traking under the rotor contact leading edge. That could be my problem. I'll chase down another rotor to test and confirm.
Cheers & thanks
 

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The fuel quality relay has already been removed and has been bridge wired to give max advance so I'm reasonably satisfied that it is not the culprit.
Cheers & thanks
Hi!
The fuel quality relay??? what is that???
Does my 33 Imola 1.4 have the same relay or they didn't fit to Weber Marelli IAW system!!!

Best,
Elvis
 

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Alfa33boxer, the fuel quality relay is on Motronic equipped cars only.

Patanga, on my car the cut out on the dizzy is closer to where your rotor is sitting from memory. That picture doesn't tell a lot unless you are at TDC on number 1. Can you rotate the engine to TDC and take the pic again? We can then see if you are maybe too far out of position to get good reliable spark.

The video on cleaning the bosch injectors is found at

They are a simple on/off switch, not like the TPS on most other vehicles. I can't remember if they are on or off when closed. If you check for resistance as you open the throttle as long as it changes state (ie goes from open circuit to closed circuit or vise-versa) you should be ok. I think the TPS just controls the fuel cut at throttle close above 1200rpm. Not sure how else it is used and what other effects it would have.

cheers
Scott
 

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Hey, cool, the video appeared instead of the link.

I mean, I meant that to happen.

cheers
Scott
 

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Discussion Starter #15 (Edited)
Hi Scott.. I'm still mucking around with the 33 on weekends trying to get the running issue sorted. It has now deteriorated to not wanting to start at all. I've got a good spark at the coil. Fuel pump seems to be working. I've swapped dizzy caps, rotor and O2 sensor without improvement, checked the idle air solendoid mechanical operation, plug leads are all in the right order as well 1324. I've got the induction coil trigger unit out at the moment and I'm hoping to learn how to diagnose if it is functioning ok. Can you help?
Cheers
Ron
P.s. I got all excited when I found a small leak at the fuel pump which turned out to be a damaged copper washer. It was wishfull thinking I know but after it was replaced it still made no difference. I also removed and cleaned the earth bus bar above the starter motor as I've learned that they can be a problem as well. I have now removed most of the electrically powered ignition/ motronic components and will be swapping them out one by one with another 33 owned by a local ABB forum member who has kindly offered the use of his Alfa.
 
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