2003 Jaguar S type R, stereo, engine noise

Someone please help with getting rid of my engine noise. Car Jaguar 2003 S type R. Stock Premium system is all Optical, with a Class D amp in the back. The battery is in the trunk in this car. Keeping stock head unit, because it have everything integrated into it, like the nav, AC features, screen menus, etc and it is all touch screen.   Adding extra amps by using Soundgate XR4 Line Output Converters. (LOC) Started with the front speakers. Took out stock front speakers both right and left and replaced with Boston Pro Components.    So this is the setup: Stock Class D amp (located in driver side rear trunk) wires have been cut, I have connected the LOC to the these wires. These wire then go into the class D amp. The other side of these cut wires were the wires going to the stock front and right speakers.    The LOC rca outputs are going directly into the RCA input of my JBL amp.    Speaker wires from the Amp are running directly to the front right/left speakers (Boston Pro Components).    When the car is in the Acc. position everything works great, but if the car is turned on the noise starts. i.e. engine noise gets winner as engine accelerates. Things I have checked: 1. RCA cables that go from the LOC to AMP, I have        tired a few different cables, did not help also tried grounding shield part of RCA cables, did not help. 2.      Have the Gains on my amp all the way down and the gains on the LOC about midway. Did not help, tried playing around with the both amp and loc gains did not help. 3.     Amps Remote turn on, tired hooking up the amps remote turn on directly to the postive did not help. 4.     Tried moving the LOC away from the Class D amp(extending the wires), about 4 ft away, didn’t help. 5.     Ground connection to Amp, have tired to ground amp at other places in vehicle didn’t help. Using 8 Gauge Wire connections is about 1 foot away from amp. Have checked the resistance, it is at .2 ohms (which is pretty good). 6.     Alternator, tired regrounding the case of the alternator, did not work, checked resistance on alternator case it is at .2 Ohms. 7.     Though of getting a Ground loop isolated, However Soundgates Tech supports told me the XR4 LOC are fully isolated and a Ground loop isolator will not help. 8.     Battery, tired using an external battery, not the stock battery in the car.   Hooked up amps (positive, negative, and remote turn on) to external battery, did not help.    Only thing that did semi-work, was a walkman.   When I connected the amp directly up to a walkman, so the walkman became the music source the engine noise was gone.    Thought about using muting plugs. But what will this tell me??, I believe the noise is coming in from the Soundgate LOC. When I hooked up the amp to the walkman there was no noise, which makes me to believe that the amp is not producing the noise.   But when I hooked up the amp to an external battery the noise was still present?    Has anyone out there installed a aftermarket system in a 03 Jaguar S type, How did you do it, did you have engine noise, how did you get rid of the noise.    Is there other stuff I should try to get rid of the noise, any suggestion will be much appreciated.    I figure the system in this car is somewhat similar to the systems coming in the newer BMW and Mercedes. HELP ME.... [B]1.[/B]S type R.

DYohn, thanks, The ground cable is exactly as you stated painted on. I will try to wire brush it, if that doesn't work I will try a new ground cable. I have checked the resisten where the ground cable is bolted to the inside of the wheel-well. At the battery terminal it is zero and at the bolt it is also zero When you state move the loc, the factory Class D amp is in the trunk as is the battery in the wheel-well, I have tried extending the wires of the LOC so the LOC is laying outside of the trunk basically on the floor, this did not help, are you saying to move the LOC as far from the stock amp as possible, or as far from the battery, I mean outside the trunk is basicaly outside of the car. any input will be usefull..:)_S type R.

DYohn has this car pegged.  I would just add that the lead wires connecting the speaker wires to the LOC should be twisted to cancel noise pick-up.  Left and right twist around each other.  If using speaker wire, tear the double wire down the center and twist at one to two twists per inch.  I've done that on sections as short as one foot.Build the box so that it performs well in the worst case scenario and, in return, it will reward you at all times.

Stevdart, thanks for you input I have the wires the connect the LOC to stock amp(lead wires) twisted but they are not twisted as you suggest. They are lightly twisted. Just to reflect: You suggest two twist, first twist the loc wires to the class D wires. then twist them even more, 1 to 2 twist per inch. correct?? Should I twist the right and left wire together, after I have them twisted as I state above? S type R.

OK, I have twisted the wires as Stevdart suggested, I also wire brushed the bolt the connects the negative battery wire to the inside wheel wheel, still no luck, the noise is still there. I am going to try a new negative battery cable, but have a felling this is not going to solve this problem. The engine noise I am experiencing is very low, I have had other cars where the noise was loud and high, but it is fairly low in this car and slightly increase with acceleration, however if the front two speakers are plugged in you can hear it.   Leave alone when I add the back door speakers. I believe the stereo in this car is a bit different then the Lincoln, All the factory speakers I have taken out are manufactured by Alpine. Anymore suggestions? S type R.

anythingS type R.

I am doing my system in my 03 Jag S type R.Stock it came with the Premium stereo.I have only got to the front speakers so far, this is how it looks:Front Right Mid: Yellow/red+ (I think this is positive)                    WHITE/ red- Front Right Tweet: Yellow/red +                   WHITE/ red -Front Left Mid: Yellow/black +                   WHITE/ black -Front Right tweet: yellow/black +                   White black -I think the yellows are the positives, please correct me if I am wrong.Stock front speaker Ohms are:   Mid = 2.5 ohms                             tweet = 4.0 ohmsThese wires run to the trunk where the Class D amp is housed.Will keep you guys updated as to the back speakers.S type R.

Yes I do have factory subs, I will try disconnecting them. The factory subs plug into the same Class D amp as all other stock speaker in the car. The factory head unit does not even have one wire , I have taken it out, it has a optical cable that plugs into it. The unit is made by Denso. Does your jag have Nav.S type R.