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

[paulthehutt]

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.

[alfa33alfio]

hi paul nice 33 iv seen your from sa im from nsw

get your mechanic or whoever to do a compression test on th cyclinders maybe that could be why its running rough

[paulthehutt]

the thing is i did a full engine rebuild only 5-6000 kms ago, with all new rings, bearings ect
so thought that wouldnt be the issue, but who knows.
it runs great when powering through gears, but just under slight acceleration it runs super rich

[paulthehutt]

i havent replaced the spark plug leads yet maybe thats causing issue???? or fuel filter??

[paulthehutt]

it puts out slight amount black smoke and spits carbon on the ground when idling/revving

[alfa33alfio]

yes could be spark plugs need changing
is it caburator?

[paulthehutt]

its fuel injected

[alfa33alfio]

hmmm clogged up exhaust maifold?

[Supercharged16v]

Mate, its your A/F meter.

It should be the BOSCH system with the adjustor screw on the side (which usually doesnt work anyway).

First thing I would do, is swap the air flow meter with another and check how it goes.

I'm 99% sure thats whats wrong with your engine

[LoneWolf33]

Besides the AFM it might be a defective / coolant temperature sensor as well.

[Supercharged16v]

that too, but the a/f meters are usually the first to go. Temp sensors are rarely faulty, but will give pretty much the same results

[BigAl33]

Also check fuel pressure.

[Supercharged16v]

Originally Posted by BigAl33

Also check fuel pressure.

What ? Fuel pressure going UP on a 33 ?

Thats more like wishful thinking mate

[BigAl33]

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.

[Supercharged16v]

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

My money is still on the AFM

[BigAl33]

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

[Supercharged16v]

Originally Posted by BigAl33

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

Is that why you had me take a video of my vacuum while running ?
FPR VACUM.MPG - YouTube

I thought you just wanted to see how much suction it had

[BigAl33]

yup, that was why , I was about to mention that lol

[paulthehutt]

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...

[deggy]

i have this very same problem. is the AFM on a 16v the box that attaches to the air box? or the sensor on the inside of the throttle body? i changed the latter one to no avail.

[BigAl33]

The AFM is between the plenum chamber and Air filter box.
The CTS is on the inside right TB

[deggy]

cheers, glad this thread came up as i was about to post the same this week. so new afm it is?

[BigAl33]

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.