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Hi all

It's my first time here having just bought myself a cracking 155 last week so please take it easy on me!

I'm really pleased with the car but it does not seem to run right on slight throttle. It is fine when the accelerator is at least half pressed but it seems to hesitate and run a bit lumpy when only slight throttle is applied making it difficult to drive round town or fairly slowly. I'm not sure whether this is a common fault or whether anybody has any ideas what might cause this??? I'm not sure I can live with it but hate main dealers even more ! It doesn't really feel like an electrical problem i.e. spark but I could be wrong. Do these suffer from air flow meter problems like my 3.0 GTV ??

Thanks in advance for any suggestions.

Simon
 
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Hello....distinct lack of replies here so I'd best pitch in :D

Yes, they can suffer from AFM problems but are not as bad as the GTVs!!!!

They mainly suffer from water temp sensor and lambda sensor problems, also idle actuator.

wrinx
 
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wrinx said:
Hello....distinct lack of replies here so I'd best pitch in :D

Yes, they can suffer from AFM problems but are not as bad as the GTVs!!!!

They mainly suffer from water temp sensor and lambda sensor problems, also idle actuator.

wrinx
Wrinx

Thanks for your reply and I must admit that, having trawled through the forum a little more last night, I had decided it was probably one of these as well. I'm going to check the lambda fuse later but I don't think it's this as the problem sometimes clears itself and the car runs perfectly (although not that often). The idle is also pretty good and the car doesn't stall. Is there any way of testing the lambda or water temp sensor or is it simply a case of buy a new one and try it?

Cheers
Simon
 

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If the Lambada is knacked, then usually it affects the idle. Best check is to put it on an MOT emissions test rig.


Ralf S.
 

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SimonN said:
Wrinx

... I'm going to check the lambda fuse later but I don't think it's this as the problem sometimes clears itself and the car runs perfectly (although not that often). ........ Is there any way of testing the lambda or water temp sensor or is it simply a case of buy a new one and try it?

Cheers
Simon
That's just what I thought about the fuse - but they can break physically, rather than blow & melt, so you can end up with an intermittent contact that is a ***** to find - simply pop a new one in. Also double-check the heater relay & it's socket as well as the socket terminals can come adrift and get pushed out the bottom.

Testing the lambda is possible - you can at least tell if it's reading somehitng anyway. You need a digital voltmeter. Trace the lambda signal wires (signal and ground) and arrange it so you can connect to them with everything still plugged up (pull back the boot on the loom connector works). Run the motor for a few minutes, let it idle. Meter should read somewhere around 0.5 volt or so (not critical what the actual figure is at this point) but don't expect it to be stable. Blip the throttle - voltage should swing about wildly from around 0 to about 1v and settle back quickly to where it was when you started. If it isn't VERY responsive to the blip then either the heater isn't working or the probe is polluted and dead/dying. Water temp sensor can also be tested with the same DVM, although a thorough test involves taking it out and popping it into water, gradually heated up to boiling, logging the resistance/temperature as you go. Easier to just change as they aren't expensive.

HTH
 
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Chris

A bit of an update.... I have checked the fuse (replaced it) and can confirm it makes no difference. However, I have also discovered that it actually makes no difference whether the fuse is in or not, the car runs exactly the same! This makes me think that, whatever it is supposed to do, it doesn't work. I have just driven the last 100 miles without the fuse in the holder! I have put a DVM on the fuse holder terminals and it reads 14.4v with the engine running. Can you advise me which is the heater relay? The fuse is located under a plastic cover right next to the battery (assuming I have the right one). There are also two relays. Is it one of them??

While I was at it I decided to check the temp sensor. I unplugged it with the engine running. That definately made a difference!! The revs increased dramatically and the cooling fan kicked in immeadiately. Replacing the plug, the revs dropped again and the fan stopped. I think I can safely conclude that this works, I hope you agree!

Thanks
Simon
 

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Simon, on the rear bulkhead just left of centre is the lambda connector, it will have 4 wires on it. If I remember correctly the heater wires are the two grey wires and the others being signal and ground, connect your DVM to these 2 and check as Chris stated.
 
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Eyes Only said:
Simon, on the rear bulkhead just left of centre is the lambda connector, it will have 4 wires on it. If I remember correctly the heater wires are the two grey wires and the others being signal and ground, connect your DVM to these 2 and check as Chris stated.

Eyes Only

I had a look at that earlier. The connector does have 4 wires as you mention but it was dark outside and all 4 looked the same colour to me (light grey) !! I'll look in the morning and try to work it out. I'm guessing if I undo the plug I will effectively be running wth no Lambda sensor? This might tell me whether it is working at all (??)

Thanks for your input, I'll report back in the morning.

Simon
 
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SimonN said:
Eyes Only

I had a look at that earlier. The connector does have 4 wires as you mention but it was dark outside and all 4 looked the same colour to me (light grey) !! I'll look in the morning and try to work it out. I'm guessing if I undo the plug I will effectively be running wth no Lambda sensor? This might tell me whether it is working at all (??)

Thanks for your input, I'll report back in the morning.

Simon
Chris, Eyes Only, Wrinx, Ralf

I had had a bit of a play this morning. I found the Lambda plug on the bulkhead and put my meter on the 4 wires. 2 of them go to ground, one read about 14v and the other must be the Lambda reading. From this I assume the heater supply (fuse/realy) is working (the14v). The 2 grounds would also make sense. However, I'm not convinced on the Lambda readings. At idle the Lambda starts giving about 0.45v but, over the space of a few of seconds this slowly drops to 0.05v. At this stage the engine stutters very slightly and then the Lambda jumps to around 0.7 v before settling at 0.45v again. Then the whole cycle starts again with the voltage slowly dropping to 0.05. Blipping the throttle does make the the voltage change quickly though, jumping to about 0.8v and back to 0.00 (in fact it read a - figure at one point). I know Chris said the reading wouldn't be stable but should the voltage drop like this??

Just for the record, I have used a good quality "Fluke" meter (which I managed to borrow) so I'm fairly confident of the accuracy of the readings.

Any thoughts guys???

Simon
 
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SimonN said:
Is there any way of testing the lambda or water temp sensor or is it simply a case of buy a new one and try it?
You can also test these sensors with an examiner. The Alfa Romeo or FIAT workshops should have this. Its a device that looks a little like a tablet PC. I got my car plugged into this and discovered errors with my lambda sensor and water temp sensor. They can also test many other sensors as well.


SimonN said:
While I was at it I decided to check the temp sensor. I unplugged it with the engine running. That definately made a difference!! The revs increased dramatically and the cooling fan kicked in immeadiately. Replacing the plug, the revs dropped again and the fan stopped. I think I can safely conclude that this works, I hope you agree!
For my case, the water temp sensor was also still working, but the examiner showed that there was a problem with it. We found out that the sensor was not accurate anymore, resulting in the fan kicking in much later at about 100+ °C.
 

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Simon,

It sounds like the lambda probe is working as it should and the problem is elsewhere - the voltages you are seeing suggest the mixture is drifting out of range then being dragged back by a large correction. The fact that it is responsive also suggests that the heater is working as it should. So do your voltage readings - a Fluke DVM is fine for the job.

So, looks like you are searching for a different cause for the problem so now on to the AFM and any air leaks on the inlet after the AFM.

Good hunting!
 
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Fixed it !!

Just a quick update incase anybody is having similar problems to mine... I finally got round to plugging my car in to a friends diagnostic machine (I must admit, I didn't know he had the chip for my car or I would have done this first before asking all the questions I did!). It reported that the air intake sensor wasn't working and was giving a constant reading of 20 degrees. £25 later (inc vat) at a main dealer, 5 minutes labour (mine), and bingo, all is now running sweetly. It's like a different car :D

I hope somebody finds this useful.

Simon
 
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Re: Fixed it !!

Good, glad you got it sorted....and an unusual solution for an older Twinspark :D

wrinx
 
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Re: Fixed it !!

just reading this and I have for the past couple of weeks thought my air intake sensor is gubbed. The car exhibits similair traits, but only really noticeable when cold outside.
 
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Re: Fixed it !!

marlon said:
just reading this and I have for the past couple of weeks thought my air intake sensor is gubbed. The car exhibits similair traits, but only really noticeable when cold outside.
Got to be worth a try for £25 ! Mine was stuck at 20 degrees but I'd guess it could be stuck at any temp (?) Have you tried unplugging it, my car ran the same even without the plug connected?

Good luck
Simon
 
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