Alfa Romeo Forum banner

1 - 16 of 16 Posts

·
Registered
Joined
·
257 Posts
Discussion Starter #1
I never thought I would be typing these words, but after owning the car for two years (1998 P2 twinny) I have finally sorted my problem and the car is running properly for the first time. (fingers crossed - I hope it holds!)
Symptoms were:
OK start from cold, idle stable.
Once warmed up, erratic idle, especially after dipping the clutch (say while waiting at traffic lights)
Also when driving with 'feathered' revs, it felt like the engine was fighting with itself - surging, 'rising and falling power' feeling.



I had tried and replaced all the usual and the unusual:
  • Airbox - checked many many times for leaks, none found.
  • MAF - replaced with a Bosch new one, overall this improved things a bit, but core problem remained.
  • Oxygen Sensor (Lambda) Only one on my P2, at first a poor trace on ECUDiag, so I replaced it, trace much better, and as with MAF things improved overall but core fault remained.
  • Engine mounts, all checked, found to be ok so left alone
  • Idle control valve - I bought 3x spare throttle bodies on Ebay, with ICV's attached, installed one of those*, still exactly the same.
  • Engine temperature sensor and Thermostat replaced - still the same
  • Exhaust checked for leaks/pinholes - none found
  • Fuel Evaporation solenoid removed and tested - found to be working correctly.
  • ECU changed! - bought a used ECU package on Ebay - swapped out - still the same!
Finally as part of a clutch overahaull, and while I had the throttle body out I decided to replace the ICV again with one of the 3x spares I bought, and BINGO! - car is a different machine. Seems like I must have installed a duff ICV at step * above, or at least one that was exhibiting the same erratic symptoms of my original one.
Now the idle and running is stable with no jiggy, jiggy when driving!
I have a feeling that the ICV, ECU, LAMBDA and MAF were all in a pitch battle against each other to reach their optimum settings, and were each affecting the others adversely, effectively creating a vicious circle of engine management.

It is this type of ICV:
http://www.alfaworkshop.co.uk/images/71713829-685-1-800.jpg
 

·
Registered
Joined
·
257 Posts
Discussion Starter #2
I should add that my quest was helped enormously by the kind and knowledgeable boys in Waterfall Garage in Bridgend, who several times helped me with diag testing and analysing of results, and also tried to source a spare ECU for me (it turned out to be duff but not their fault)
They did all this free of charge as I think the fault was bugging them just as much!
I wouldn't hesitate to recommend them.
 

·
Registered
Joined
·
8,916 Posts
Glad you got it sorted.

Unfortunately this is one of those cases where running on a tight budget has caused you more grief.

Erratic idle, check for air leaks and fit a new idle control valve.

Some second hand parts will always be a gamble, a icv is one of them.

Out off interest, did you try to clean your old valve?
 

·
Registered
Joined
·
257 Posts
Discussion Starter #4
it's not the type that can be cleaned (see my link to the type that it is) but I did take the original one apart (not designed to be!!) just to see how it works.
Effectively it is a two function unit. (1)It provides feedback to the ECU on the position of the throttle, it does this by an electronic emitter/receiver type circular track slider/pickup assy. (2) it opens & closes the flap small amounts at idle by means of a coiled solenoid.
Do not forget that primary control of the throttle flap position on a P2 is via the throttle cable!, but at idle the ICV can open/close the flap small amounts just to control the idle.


I should also point out that I NEVER got the original ICV or the apparently duff one I tried in to pass the diag test in ECUScan, but I could never get a definitive answer if this was just a red herring.

See this thread for more info on the test:
http://www.alfaowner.com/Forum/alfa-gtv-and-916-spider/324607-fiatecu-scan-actuator-tests-idle-valve.html?highlight=
 

·
Registered
Joined
·
2,575 Posts
Nice writeup :thumbs:

I particularly liked the definition of "a vicious cycle of engine management". I'm sure I've dealt with many engines that were having a domestic dispute and getting nowhere...

-Alex
 

·
Registered
Joined
·
8,916 Posts
So no air passes through this valve?

(If that is true it's not really a valve, if it's not true it can be cleaned)

Also, I have just read your other thread, are you saying you didn't believe the diagnostic software?
 

·
Registered
Joined
·
257 Posts
Discussion Starter #7
Correct, no air passes through this valve. It is purely an electronic monitoring/control function.

Correct, I was not able to get anyone else to say if they had seen their ICV valve pass this test. As you will see from that thread, another contributer had same results from the test (fail) but was not convinced it was actually a failing valve rather than a failing 'test' (wrong test condition or parameter, or diag SW bug)
 

·
Registered
Joined
·
8,916 Posts
Right, ok, do does this motor open the throttle air intake butterfly valve slightly then ?

My only experience is with the cf1 and with a 51 plate Ford Fiesta, both of which were a small valve that bypassed the butterfly valve to let air through for idle.
 

·
Registered
Joined
·
257 Posts
Discussion Starter #10
It opens/closes the main butterfly venturi via a stepper motor inside the assembly.
It is coupled to the through centre shaft of the main butterfly.

So as I said earlier in the thread it has TWO distinct functions, control of and monitoring of the butterfly position.
Control at Idle only (I think ) and monitoring at all openings.
At least that is my analysis of its function having taken one apart to see how it works, and then witnessing the havoc a duff one has caused me!
 

·
Registered
Joined
·
6,262 Posts
I am a very interested reader of this as my Phase 2 CF2 twinney exhibits very similar symptons. I have changed the air intake hose which was past it's sell by date and am in the process of renewing the front pipe and lambda as the front pipe has a fracture so if the symptons continue I will be looking to replace the ICV.

A previous owner has installed an induction kit which I think has clouded the issue when technicians have looked at the car in trying to diagnose the problem.
 

·
Registered
Joined
·
6,262 Posts
I am a very interested reader of this as my Phase 2 CF2 twinney exhibits very similar symptons. I have changed the air intake hose which was past it's sell by date and am in the process of renewing the front pipe and lambda as the front pipe has a fracture so if the symptons continue I will be looking to replace the ICV.

A previous owner has installed an induction kit which I think has clouded the issue when technicians have looked at the car in trying to diagnose the problem.
Front pipe and Lambda replaced and then started running as rough as an old dog. MAF changed and now running as sweet as a nut. It's funny that it was ok (ish) with the split in the exhaust but as soon as that was fixed it ran badly and needed a replacement MAF.

When I come to a halt the idle still sticks at about 1100-1200 rpm and then slowly comes down to 750rpm so I would guess that the ICV is ''sticking'' slightly, but otherwise running very well.
 

·
Registered
Joined
·
170 Posts
I never thought I would be typing these words, but after owning the car for two years (1998 P2 twinny) I have finally sorted my problem and the car is running properly for the first time. (fingers crossed - I hope it holds!)
Symptoms were:
OK start from cold, idle stable.
Once warmed up, erratic idle, especially after dipping the clutch (say while waiting at traffic lights)
Also when driving with 'feathered' revs, it felt like the engine was fighting with itself - surging, 'rising and falling power' feeling.
It sounds like I might have the same problem (started only in the last Month or so), my symptoms are slightly different;

From Cold - Engine idle going from nearly cutting out to 1500 revs and up and down and up and down, etc.
Driving to work after going about half a mile it feels like the engine suddenly has extra umph and she does a little bit of a surge.
Once she's warm the Idle behaves itself most of the time.

Two questions.

1. If I disconnect the MAF to see if it's the problem did you find the problem went away? (haven't done it yet but figured that was a good place to start).
2. is the ICV one of those things that works better after a slap of the screwdriver or am I mixing up my problems/solutions?

I had the Air hose from the MAF to the Engine replaced last year as it was more like a colander with the amount of holes it had and I also replaced the MAF then as well as it was well knackered too.

Thanks,

Ned.
 

·
Registered
Joined
·
27 Posts
Just to say what a useful thread this is - thank you Baacow ( excellent ID :) ). I had the same issue with my CF2 and had started going through the same list. I had changed the O2 sensor, changed the top air hose ( which truth to tell was already patched up with glue! ) and cleaned the MAF. After reading this I bought a new Bosch ICV and as you said it could be a totally different car. Very happy!

If you still have the problem Ned, yes, the ICV is black thing screwed to the right ( looking from the front ) of the throttle body that you can whack with a screwdriver. Mine was obviously too far gone to respond to such a subtle technique!

I bought the ICV at the Watford branch of Allparts who were really helpful in tracking down some old stock in the depths of their warehouse. I have found big autofactors ( Allparts in particular ) are a good source of reasonably priced "named" parts - I've had a MAF, crankshaft sensor as well as the ICV from them at more than eBay, but much less than main dealer prices.
 
1 - 16 of 16 Posts
Top