Alfa Pages

[sf49er]

Friends,

Had to disassemble the intake earlier today in order to free up the distributor. Prior to the "operation" I had a somewhat uneven idle and disastrous emission numbers. Thought I'd start by adjusting the ignition timing but the distributor wouldn't budge. The local garage, who I'd asked to adjust the ignition gave up and told me to free the disty myself before coming back.

Anyway, it meant removing the intake in order to get access to the distributor. Everything went well, the disty was overpowered by sheer stubborness and elbow grease.

Put everything back together and started her up. No problem except that the idle now fluctuates between 1500 and 3000 rpm in an even rythm! Up and down about every two seconds. If you want an audio/visual, albeit in lousy quality, you'll find it here:
http://www.tvc.se/files/33_idle.mp4
Might be best to go to .../files and right click to download.

Anyway, if I disconnect the Throttle Positions Switch it'll calm down but the idle is then at around 3000 rpm. Temperature doesn't seem to matter.

Any suggestions would be gratefully accepted!
_________________
Bo M. Hasselblad
Linkoping, Sweden
Secretary of Club Alfa Romeo Svezia
sekreterare@alfaromeo.org

[paulhide]

Hi, there are probably people on here who can help better than me, but what you've described is termed 'hunting' as the ECU is hunting for the correct settings as something is not working. It could be as simple as one lead or plug not working or a poor earth somewhere or poor signal from the airflow meter. It does seem to be quite a large change in revs. Unfortunately I'm not very familiar with the IE having only had 16vs, P4s and carbed 33s in the past.
Anyone?
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[sf49er]

The work to find a solution has continued but the problem remains! I agree that everything points to a "signal" missing for the CU in order to find the correct idle speed.

Consequently I measured the "static" values fed the CU through the 15-pin connector and everything checked out per spec. I didn't have a chance to check the various values with the engine running since I don't have a break-out connector nor an oscilloscope. However, pins 1, 7 and 12 all carry battery voltage, as they should. Pin 14 (Throttle closed) also has 12+ V with the throttle closed which drops to zero when the throttle is opened. Pin 15 (Full throttle) carries 0 V until the throttle is almost fully open, as expected. Earth on pins 4 and 5 also works.

The Coolant Temperature Sensor, on pin 8, has a resistance of 3.66 kOhm when cold (ambient temp appr 13 Centigrade) dropping to 380 Ohm when warm (80 Centigrade). This also appears to be per spec.

The crankcase vent, which is actually the oil filler neck, has been replaced and the tube and orifice cleaned. The rubber intake "snout" between air flow sensor and throttle body replaced with another which showed no signs of cracking or leaks. I also replaced the air flow sensor, with its built in Control Module, to another unit.

The engine behaviour doesn't change whatsoever if the Lambda-connector is disconnected.

So, I'm kind of running out of ideas

Anyone with a new suggestion?

My thought is that the connection between the distributor and the CU might be at fault. But to check that I assume I'd need an oscilloscope to see what signals the distributor is sending. On the other hand, the CU obviously has an idea what revs the engine is running or it wouldn't cut it out at 2,500 nor engage fuel flow at 1,500 again.

PS: Just for fun I even replaced the intake manifold!
_________________
Bo M. Hasselblad
Linkoping, Sweden
Secretary of Club Alfa Romeo Svezia
sekreterare@alfaromeo.org

[paulhide]

Very weird. Would love to know the answer to this as Alex ('33bits' on here) has just given up on a 156 that is doing exactly the same thing.
Air leak from brake servo pipe, or under throttle body?

Anyone any other ideas?
_________________
Owner's Club 33 Registrar. Now from P4 & S2 1.7 QV
http://www.alfa-pages.co.uk/viewtopic.php?t=5188

[RFlower]

Suggest looking carefully at what you originally disturbed: intake system gaskets and distributor static timing. Personally I'd suspect the gaskets first.
_________________
Dick Flower, Nr. Carcassonne. '94 Trofeo 1.4 ie (F), '93 Imola 1.3/1.4 ie (now for breaking) (F), '91 1.7 ie (GB)(spare car), '86 Sprint 1.5 QV (F). '87 VW Syncro camper (F), '73 NSU Ro80 (F), '99 Fiat Seicento (F)

[sf49er]

I think that's the next logical step!

I know the timing needs to be adjusted and the intake gaskets would be the only items not changed. Also need to make sure the bolts are tightened to the correct torque, which I have as 19 - 24 Nm = 14.0 - 17.7 lb ft. However, I also suspect that two of the pins have been stripped, unless it's the nuts, so also need to replace those.

Will update status once the gaskets are replaced and timing set.
_________________
Bo M. Hasselblad
Linkoping, Sweden
Secretary of Club Alfa Romeo Svezia
sekreterare@alfaromeo.org

[ZeNiTh-PbArM]

Hi,

Be sure to check :
1°) throttle position sensor
2°) idle actuator
which you have removed in order to get the inlet manifold off.
Maybe you just forgot to reconnect one properly?

regards,
zp

[sf49er]

Update:

Finally gave up and handed it over to the local Alfa-guru. He removed and reinstalled the manifold and it is now guaranteed not leaking. He didn't think it was before either. Also set the timing.

As far as I know the LE3-Jetronic on 8V doesn't have an idle actuator or idle control valve. Please correct me if I'm wrong.

However, he then found that the throttle position sensor needs to be adjusted so the "closed position contacts" are not connected. In other words, if adjusted per workshop manual to provide current on pin 14 with the throttle fully closed, it doesn't find the idle and the idle fluctuates. When rotated so it never closes he was able to adjust the idle.

It now idles at the correct 1000 rpm, albeit a little bit rough. Why the TPS shouldn't be adjusted as per spec we have no idea.

Now its on to the next challenge -- the emission values which made it fail the Swedish MOT. But I'll post that in a separate thread!
_________________
Bo M. Hasselblad
Linkoping, Sweden
Secretary of Club Alfa Romeo Svezia
sekreterare@alfaromeo.org

[sf49er]

Since the last post I once again MOT'd it and the emission values were just a out-of-line as before. CO 0,7 (0,5), CO @ 2500 rpm 0,6 (0,3) and HC 218 (100) with limits in brackets. Lambda was the only value within limits at 1,01.

Back to the shop and made sure the intake manifold gaskets didn't leak and checked for exhaust leaks before the lambda. Also adjusted ignition and doublechecked for leaks in the intake flow (which wouldn't have resulted in the high HC anyway). Another test and still the same high CO and HC values.

Checked the plugs, with about 4000 miles on them and they had a nice light brown/greyish coating which indicates proper burning. Replaced air flow meter with integrated CU. Another test and still the same values.

Now sought the assistance of the local Alfa guru and replaced the lambda probe (albeit a used one from another 33 I have sitting) as well as changing back to the original cat. No change in values and a slight feeling of desperation set in

Another change of oil and filter and this time using pure mineral oil with low smoke properties. Back to the gurus garage and again no change. He worked with the throttle position switch and ignition setting and finally got the values into line.

Back to the MOT station after having spent quite some time warming up the oxygen sensor and cat running at least 15 minutes between 5-6k rpm. A 45 minute wait made the exhaust system cool down and the initial measurement gave the same outlandish values. I told the guy doing the testing that the exhaust needed to be warmed up and he said "I'll take for a spin" and I instructed him not to let the revs down under 4500! He went away for about 10 minutes and came back smiling. Plugged the sensor in and we got CO 0,0, CO @ 2500 0,0, HC 001 and Lambda 1,00 -- i.e. perfect values.

So, whats the conclusion from this exercise? I don't except that it extremely important that the exhaust if hot when tested and this takes some extended driving at high revs. Both the lambda sensor and the cat is actually a long way back from the exhaust port and if the lamda only works properly when it's at 600 C then it takes intense driving.

The positives I bring with me is that in order to be friendly to the environment, I need to drive the 33 at high revs in order to keep the system hot

Thanks for the help and assistance, even though the solution was easier the expected.
_________________
Bo M. Hasselblad
Linkoping, Sweden
Secretary of Club Alfa Romeo Svezia
sekreterare@alfaromeo.org

[gritsop]

I agree with you. Since the cat is located almost in the middle of the exhaust system, it is very easy to cool down - thats why modern cars have the cat in engine bay right in front of the engine and right behind the radiator. Surrounding heat sources help the cat run at the desired temp.

Personally I have never managed to obtain legal exhaust values with the engine being relatively cool. Idling at normal temps will not give proper exhaust values - taking the 33 for a good spin will give almost 0 exhaust gases.

Last year during the MOT procedure the technician testing the exhaust gases was seeing normal values (green scale) for oxygen and hydrocarbons but carbon monoxide was above normal. Right away he revved the engine for a few minites and carbon monoxide dropped far below the highest allowable value

Asking him why this happens, his reply was: "these cars need to be warm"

Regards and enjoy your 33
_________________
Thanassis Gritsopoulos
1991 Alfa 33 1.4 IE
2001 Alfa 147 1.6 Distinctive

http://www.alfa-restoration.co.uk
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