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33 1.7 16v running rough/rich low rev's

4K views 22 replies 6 participants last post by  BigAl33 
#1 ·
Hey guys, I have had this issue ever since i brought this car and rebuilt the engine.

It runs really rich and rough on idle and especially under low revs.
There are no vacuum leaks.
I had injectors cleaned and flow tested.
i swapped with a mates oxygen sensor but made no difference
I had the throttle bodies balanced also but no difference.
air flow meter seems ok but dont know for sure

Any help/ideas would be appreciated.
 
#14 ·
If there is no vacuum on the FPR, or the FPR is stuck/damaged, the fuel pressure will be max all the time "3.2 bar" instead of it being at its lowest on idle "2.8 bar".

Take off the vacuum pipe to FPR, block off the pipe, add another pipe onto the FPR and suck on it whilst the engine is at idle, you should hear a slight difference in engine note.
 
#15 ·
hmm... true, but how often would that happen ? Fuel pressure regulators might get stuck - stuck as in not fully closed so pressure gets lost from them. Stuck closed so pressure builds up in the lines ? Its a bit of a long shot mate....

I like the way this conversation is going though :thumbs:

My money is still on the AFM :D
 
#16 ·
:) I had the same thing on mine, I tried all the above and some, eventually tried the fuel pressure to find there was no vacuum acting on the FPR so my fuel pressure was at max on idle. Same thing would happen if the diaphram in the FPR was broken or leaked, max fuel pressure all the time.

Place bets now, CTS / FPR :) or all of the above lol
 
#19 ·
hey guys, thanks for the input!!
i also swapped the CTS a while back but still made no difference.
ill give the FPR vacuum a check today and see how it goes, but ill have to wait to catch up with a friend to swap the AFM.
the car had been sitting round for a couple of years before i bought it so it could be the FPR stuck...
 
#23 · (Edited)
Before buying a new/old one, try taking the top off and cleaning the contacts :) or borrow a known good one.
Also, the correct procedure when changing an AFM or ECU, is to callibrate them to each other.
I know most people don't do this but the correct way is as follows.
Change the fuel type relay for one that is the same ron but without lambda correction.
This will allow adjustment of the idle mix, if you have a dongle that uses lambda correction any adjustments on this screw will be ignored.
You then adjust the idle screw on the AFM until you get a CO2 reading between 0.6 - 1.0 before the cat.
I borrow the correct alfa tool that goes in the 13mm bolt hole by the O2 sensor.
When done replace the correct fuel selector dongle and bobs yr cross dressing aunty.
 
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