G'day people.

I am currently doing my head in trying to sort out my XG ute (is manual just for refrence).
On the weekend i gave the ute a good head job (CMS Stage 2 head and Cam) after a suspected head gasket, valve stem seals and HLA's etc.

Its running but it wouldn't idle, I have got it to by setting the base timing but idles kinda rough but the black smoke and unburnt fuel is shocking on idle. Fine driving it around but idle is just not good.
To me i thought MAP sensor / vacuum leak for sure but i have had no luck finding a vacuum leak.

I physically removed the hoses and inspected and all good, spayed butane around most things accessible and poured water trying to look for leaks.
I fit a new intake manafold gasket when i did the head so it should be allright.
Waiting to borrow a timing light to check the timing but surely that can't be the prob.

I got a frequency meter and tested the MAP sensor and according to the gregory's repair manual:
Ignition On..............manual said 0.155kHz.............mine 0.155kHz
Engine idling............manual said 0.101-0.103kHz.....mine 0.111-0.115kHz
Engine revved.................0.90kHz approx...............0.9ish
Engine idling with A/C
load..............................0.109-0.111kHz...............0.118ish

So map sensor has got something to do with it but not necessarily the problem. as far as i can gather it still can be a vacuum issue. I'm getting a vac gauge soon to see what the vac says. I was assured from CMS that the stage 2 cam isn't aggressive enough to drop vacuum at idle like a stage 3 and above would.
I'm goin to also try borrow a map sensor to see if that's the prob.
Before the head it only blew smoke when i first put my foot down at an intersection and high rpm's would leave a bit of smoke.

Any help or experiences would be great
Cheers

hi beeksy, it sounds just like the map sensor like you said, id try another one or try unpluging it with it running to try and see if it makes a diferance, prosess of elimination, or it could be a stuck injector, but that wouldnt stop it idaling, cars can do your head in thats for sure, and triple check all connections u never know! hmm check the fuel return line might be twisted or kinket ect, hope this helps, good luck

just remembered, sure its blacke smoke? could be getting oil past the rings, horrible thought but possible

Mate i got my head port and polished and reconditioned with a stage 3 cam and it did the same thing. wat ur problem is prob ur computer not any of the above . as there is more air andfuel gettin in the motor with a different cam timing than standard ur stock computer (Which cannot be tuned) hasn't a clue and still tells the motor run basically the standard fuel and air ratio therefore it runs rich. that was until i purchased a Haltech interceptor computer so i could adjust the fuel/air ratio and cam timing and away went the black smoke and now it runs like a dream. the whole setup: Computer, installation and 5 hours dyno time only cost me $1500

Now i got about 220 hp

G'day

Thanks for the replies, I should be getting a map sensor today from the wreckers, fingers crossed.
When i unplugged the map sensor when the car was running it did change the idle to a bit worse with the same amount of smoke



yea it's defiantly black smoke, i changed the head due to blue smoke from bad valve stem seals. I'm somewhat glad to see black smoke rather than the blue. (doing a comp test this arvy just for piece of mind)

If i had motivation i would take a photo of my now black poka-dot driveway from unburnt fuel. lol

I don't really want to get it dyno'd, its just my s**t ute to save me racking klm's on my turbo but might have to go for a J3 chip maybe.

Thanks for the replies and I'll keep the updates goin

hi beeksy, at leist its black smoke, id say my94xr is right, need j3 chip ect, just od cms were you got the head and cam said it would be ok, should have just replaced the gasket and stem seals hahaha. nothin like creating more work for ones self, let us know how you go.

Yea i thought about just replacing the gasket & stems but knowing my luck the head would have been cracked or warped. I've only had it for 2 months and know nothing about its past. I'm glad i got the head cause the one i pulled out wasn't crash hot at all. and well if i was goin to go to the trouble of pulling off the head why no put a cam in as well.

I got my oldies to pick up a map sensor while they were in townsville today but i worked late and didn't get a chance to pick it up so ill test it tomorrow.

there are other issues that need to be sorted out the stage 2 cam dose not & never needed a chip or computor mods for it to run, I've sold these cams for over 3 years now & its always ends up being something else.......you may have to take it to a mechanic get him to check the injectors idling ms & the 02 sensor at the same time do a vacum check at idle see what its pulling we need to start with the basics first then we progress from there, make sure base idle is set corectly, timming & etc........ I've had cars that have had the battery disconected for a few days & the ecu has lost all base settings you may also have to do a check of all of the sensor voltages at the ecu as a bad conection will do the same thing....

Joe

also do all of your testing at the ecu & use the same earth wires that are going to the ecu as puting your test wire on the chassis will always give you a good earth & sometimes will give you misleading resaults......


Joe

update

I've replaced the MAP sensor and it's doin the same. il have a good go this arvy or over the weekend and try crack down on the problem.

cheers joe for the suggestion at the ecu and what earths to test with.

no problems...let me know how you go

Joe

if you dont have a vacuum gauge,
this might sound strange but put a vacuum hose on the map sensor put it in your mouth and suck it hard while its idling.. if the idle comes good you have a manifold vacuum problem.
either a vac leak low compression or possably a cam timing related issue maybe??
what condition was the bottom end in before the head change?
is the compression good??
i had a similar issue with my old engine after fitting a fresh head and cam..
it turned out the new head and cam made the old bottom end supply more go but also made it show its age..

I'm goin to get a vac guave, timing light, compression guage now so hopefully it will shed some light.
As for the bottom end i could only imagine its ok, not super hot but not super bad either.

Ill post some details as i do the tests

I hooked the vac gauge up on the PCV vac hose and it read a steady 16InHg.
On the gauge in that area it has late ignition timing on it. I don't know if that applies to this or it for something else.
Also i bridged out the terminals on the diagnostic port to check the ignition timing however the manual said that the engine would increase idle but mine didn't. I checked the timing and it varied on and about 10mm before the IGN indicator....

im not sure how much vacuum drop there should be with your cam?..
but as an example my engine sits at 20 inhg at 700rpm..
so to me the vacuum is lower than a std healthy engine..
i would look at compression aswell..