When cruising lightly on the throttle, the AF will spike to 18:1 for a split second and then return to normal, causing the car to buck, kinda like a missfire, but lean. When on full throttle it seems fine till about 6500rpm when it feels like i hit the rev limit and the car backfires really loud, agian showing a lean spike, obviously immediatly let off. I know the tune is good but dont know where to start looking from here. How important are the grounds?? the one on my rocker cover isnt bolted in but i wouldnt think this would be a problem?

Anyone??

 

do you have a wideband or an air fuel guage?

 

Yeah i got a plx wb, ive tuned quiet a few cars and never had this problem, one car is an almost identical setup and he has no issues at all, AFs look great apart from this problem

 

anyone??

 

what are you tuning with? EMS?

 

Uberdata.

The timing maps are fine, the timing was checked at 800rpm and was almost dead on the red pulley mark, the fueling is running slightly richer than stoich cruising and high 11s in boost.

I pulled the spark plugs and put in some colder ones ( 6 ) took it for a gentle drive, still the same. Pulled them back out and they were very white with small black blisters, pointing towards and ignition problem maybe??? Im running MSD 6al, it started to play up a while ago on the old engine, just before i had it swapped, doing the same sort of thing. Anyone think it maybe the MSD?? Likelyhood of it being a fuel/ignition problem?? Any help desparatly needed. thanks

 

sounds very much like closed loop is not disabled. These are the EXACT symptoms

 

it is deffo disabled in the software, and i have used this version on many cars.

 

Will pre ignition cause lean/rich readings?? Im starting to think that it maybe an ignition problem. I had no problems before i changed the injectors and clips though, after the engine install. I take it when fitting the clips it doesnt matter which wire connects to which on the clip/plug???? i have check resistance of the new clips after soldering in, and they are all the same, no short circuits or anything

Anyone help me?? I cant afford to have anymore downtime on the car and need to get this sorted asap.

 

Does it do it consitently at a certain RPM and/or throttle? Check plug gap and what do they look like?

Also, grounds are pretty important to a motor and anything electrical.

 

Denso Iridium plugs originally, I pulled the spark plugs and put in some colder ones ( 6 ) took it for a gentle drive, still the same. Pulled them back out and they were very white with small black blisters, pointing towards and ignition problem maybe??? Im running MSD 6al, it started to play up a while ago on the old engine, just before i had it swapped, doing the same sort of thing. Anyone think it maybe the MSD?? Likelyhood of it being a fuel/ignition problem?? Any help desparatly needed. thanks

 

anyone??

 

what are the plugs gapped at? I would also recommend NGK BKR7E plugs instead of irridium.

 

Changed the fpr, plugs, ecu, map sensor, gonna try different injectors on the weekend, anyone got any other ideas??

 

Does this randomly at any RPM

 

I recently have had the exact same problem (felt like I was hitting the rev limit at 7500)....anways I have the denso iridiums too. Check the gap, they (mine) were gapped at .4! haha Sooo I regapped them to .3 and the problem seems to have gone away.