Xu9Ja Running Rich On 2 Cylinders?

[djvu205 1]

hi all im really struggling to work this one out and just wondering if anyone has encountered this type of problem before. i have been searching on here for days and only came accross a couple of posts similar but they ended without a diagnosis!

 

basically i have just rebuilt a xu9 8v new rings brgs balanced etc. its std motronic managment, approx 10.6:1 cr and a newmans ph3 cam. all the head was correctly set up by a professional and i dial the cam correctly using the lift at tdc method. i asked the guy that built the head and he set valve clearances at 0.009" inlet and 0.013" exhaust

 

intially the engine started and ran but wouldnt rev past 2000 - 2500 rpm the tacho was going crazy and occasionally the fuel guage would move which it has never done. the spark plugs on cyl #1 and #2 were wet/almost black looking whilst #3 and #4 had very good grey color to them. i swapped some bits around and found the ign module to be the problem of it not reving past 2500 rpm. so problem fixed i thought. no so!

 

it now goes alot better, revs up, idles etc but smelling very rich and a small misfire that comes and goes which is hardly noticable though really. i have managed to take it out the road for a couple of quick 5min spins to run it in keeping the revs up but thats about it. took it into performance engine building place and used there compression tester 186, 188, 192, 196 psi from #1 to #4 respectively and as you can see the rich cyls being slightly lower in compression. i have tried a diffent ecu also and it only seemed to make my fuel guage sort of work (previously it didnt work at all) but when i put revs on the car the guage goes down to empty when i back off guage comes up to full. it has a full tank of 98.

 

the injectors have just been serviced and were flowing at 100 cc/30 at 40 psi. i have tried swaping leads plugs rotor button dizzy cap coil and still it runs rich on those two cylinders only. if you couldnt smell it you probley would think there was anything wrong with the car? it doesnt blow any smoke under normal circumstances only if you blip the throttle, then some very slight grey colored smoke can be seen in rearview. can anyone help me sort this problem before i go completely mad? what other things should i check? bearing in mind that it runs ok but is rich on #1 and #2 cyls only??

[welshpug 1,657]

fuel gauge has nothing at all to do with the engine management so thats a different issue entirely, can't think what else I would check other than wiring and double check the valve clearances.

[djvu205 1]

fuel gauge has nothing at all to do with the engine management so thats a different issue entirely, can't think what else I would check other than wiring and double check the valve clearances.

 

i double checked valve clearances after a 5 min drive up the road, inlets 0.007" - 0.008" and exhaust were 0.015" - 0.016" also tried swaping injector plugs 1+2 to 3+4 visa versa. still no difference in color of plug?

[ljenkins22 0]

i double checked valve clearances after a 5 min drive up the road, inlets 0.007" - 0.008" and exhaust were 0.015" - 0.016" also tried swaping injector plugs 1+2 to 3+4 visa versa. still no difference in color of plug?

is the head ported and polished? possibly inlet gasket leak on 3+4 leaning them off a touch so in effect 1+2 are correct

[Sandy 191]

It sounds as though it's not balanced. Obviously being on a std inlet means that it's not the induction, so I'd turn my attention to valve clearances, cyl pressure check (leak down) at TDC to see if valve leakage is present. It may be that chamber volumes aren't equalised, but that would need to be pretty severe to cause this. Maybe check cam timing at No 1 and no 4, to see if it's the same. Just keep ruling things out.

[djvu205 1]

thanks for the tips everyone will let you know how it goes. i have only used 2nd hand bits to check the electrical side of things so once i have replaced rotor, cap, leads etc with new stuff will double check timing and look for leaks etc.