Join Date: Nov 2018
Location: Southern California
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Infuriatingly Mysterious Lack of Oomph (Power)
Gentlemen and Ladies, I beseech you, help a poor fool with your collective centuries of Land Rover knowledge. I bought my first Range Rover Classic 3 years ago and love it to death, but I have been trying to sort out an infuriating lack of power from day one and have come up with nothing! She was stock and a bit tired when I got her, but I have methodically replaced thing after thing to no avail. I understand RRC's are absolutely not speed demons, but my father's '94 3.9 disco (bone stock) would run circles around her, so there HAS to be something hinky. Below is a list of the facts, and hopefully my frustration will come to light.
1989 RRC 3.9 (low compression), 136K miles at purchase, 155k currently
Compression test averaged between 148 and 154 for all but one cylinder, which was at 142
Starts easy, idles smoothly and revs nicely, no hiccups or bobbles underway, no smoke out the exhaust, no blow-by out the oil filler cap, doesn't burn a drop of oil, passes smog with flying colors.
Replaced all plugs and wires (magnacors) - 3 years ago
Replaced all fuel injectors with upgraded bosch 4-nozzle ones -1.5 years ago
Replaced distributor (old one had a leaking vacuum advance) and ignition amplifier with new factory one - 1 year ago
Replaced air filter and cleaned MAF with MAF cleaner - multiple times
Checked for dragging brakes (all fine)
Replaced timing gears and chain with Cloyes double roller set - 1 month ago
Replaced cam with custom grind high torque cam from "The Wedge Shop" which specializes in rover v8's, original cam had some lobes worn down almost flat, tremendous lift difference between the old and new - 1 month ago
Timing adjusted per Wedge Shop recommendations for new cam, 8 degrees BTDC at idle, 36 degrees BTDC at 3500rpm.
Verified correct fuel pressure with test kit at pump and at regulator, all good
Replaced original 14CU fuel injection computer with newer 14CUX module from a 1993 3.9 RRC - 2 weeks ago
All this and (much more) has been done, to absolutely no difference (per the butt dyno) whatsoever. She still struggles to climb hills on the freeway, takes absolutely forever to reach freeway speed (merging is a bit tense). I did a 0-60 test, wound her up pretty good, and ended up with the painfully disappointing figure of 19 seconds. I am at a complete loss, and other than dropping in a fresh 4.6 (which I know many will suggest, but I don't have 6-10K to drop on a new motor). The engineer in me is dying to solve this, and at this point I feel like it's got to be something electrical, like a sensor sending bad values that's causing the fuel computer to cut fuel or something of that nature, but I welcome any and all ideas. Please, men and women of the Land Rover community, share your knowledge!!!