I've had a silver 01 cobra for six months. a previous owner put in a fuel cell, oversized fuel filter and line, bored short block (with procharger and more, 525hp), plus an '03 IRS, then put a stock cobra '01 engine back in, replaced fuel cell with '03 tank/pump, added stc chip "for change of gear" (3.55 instead of 3.72) and sold the car. No tune that i'm aware of. the car was sold to the guy i bought the car from, at 4,500 miles. leakdown test was very, very good, plugs still had grease on caps, under the manifold was very clean, however fuel pump was missing the gasket (fuel leaked at fill up) and the evap system was not connected (vacuum lines plugged, cannister connection open). fuel pump gasket was put in at one shop, evap system restored by another, and car runs very smooth now, particularly between 1000 and 2000rpm. Idle is usually steady at 800, acceleration from 3000rpm WOT is close to what i expected. EXCEPT there's slight fuel vapors coming from somewhere at the rear of the car, and there's an occasional stall if in gear. if not in gear, rpm falls off to 400 like it's going to die out, followed by a 'rushing air' sound, engine surges to 1500 then settles back to normal. this happens every 3rd day driving at completely random points: at red light, coasting in 3rd gear, moderate acceleration in 2nd, never at WOT. after a stall i have to wait 10 seconds or so before it will start again, it never starts inside 10 seconds after a stall, but it always starts and always runs fine "until the next time. the shop that restored the evap system said a pressure test "held overnight". So, long story, three - no four - questions: what can i look for to find the fuel vapor source? does the IAC tend toward erratic performance which might explain the above stalling and rushing air sound? should i trust a local ford dealer to look into these two problems? and four, should i buy the expensive helm inc (http://www.helminc.com) shop book before going to the shop (again). many thanks -
i took the car to a local shop, and had a nice surprise: the occasional stall may be due to a bad connection between the ecm and the sct chip. shaking the ecm (which was not tied down) produced the same symptoms so the chip is now out until i can get it re-burned and spend some time on the connector. i don't know if the chip was just badly seated or if the board connector was dirty. fuel vapors are being looked into now.
So what besides the different rear end gears is programmed into that chip? I'd be a little concerned myself until I knew exactly what other parameters may have been tweaked. U.M.
i can only rely on what a previous owner said in an email, just the gear change. in taking the chip out i'm assuming that the stock prom wasn't flashed at some point, which is the same issue over again, so i completely agree with uncle meat, putting down a known map is the right thing to do. at first i was surprised the programming cannot be read back from the prom, by doing some kind of "map dump" of the ecm or the external prom or both. on the other hand, if i had a tuner i wouldn't care what map was on the chip, i'd just load the one i want.
well repairing the fuel vapor problem means replacing the tank: the seat for the fuel pump on the tank is bent (i haven't seen it so that's the best description i have, and how does that happen? i can only guess where it came from) and the unit will not seal to the tank, even with two gaskets, so the tank has to be replaced. not only was the pump gasket originally missing, even the wrong screws were used when the tank/pump was put in, the screws tapped out in the holes. i'm told the '01 GT tank/pump has the same part number as the cobra and there should be a tank/pump available from a salvage yard. the dealer cost is about $800. what do you guys think? salvage yard GT tank or new oem tank? and will an '01 tank mate to an '03 rear differential? (yes it's an '01 cobra with an '03 rear end.)
Don't quote me and I'm sure someone will correct me if I'm wrong.... but I believe the 01 & 03 IRS rear ends are the same except for the gear set (03 came with 3:55's), the halfshafts are larger on the '03 and I believe the rear rotors are larger too. As for the GT/Cobra tank issue... I'd double check on that... I thought the '03 tank was different from a GT because it was set up for dual pumps? U.M.
Solved the mystery behind the bent seat on the tank for the fuel pump: the too long screws came up against the bay over the tank and bent the seat when the tank was strapped in, what a waste. A salvaged tank with pump arrived today, aeroquip fitting tomorrow (after market fuel filter) and maybe i'll be driving this weekend. question came up: if the tank/evap system wasn't holding pressure, why was there no check engine light for codes P0442, P0452? does an external chip block the codes? will i see codes because the knock sensors are disconnected, now that the sct chip has been removed? let's see: "P0325 Knock Sensor circuit fault". should i feel violated now or just stupid? could i have used a Predator as Pro-Hawk suggested on another thread to read the codes before i handed over my wife's savings?
I know that a Predator will allow you to read all ODB codes and clear them too. Whether having that capability sooner would have saved you any money in the long run I don't know... U.M.
Car's Back, runs better, too new tank/pump, no chip, no check engine light, smoother low end response, easier in traffic, and gas fumes f i n a l l y gone. don't know about mileage yet, drove for an hour yesterday at lunch, very nice. idle curiously down to 650/700 from 800 which i thought was programmed. the shop that did the work is great, too: good diagnostics, very thorough, but still very reasonable.
Glad to hear you're getting a handle on those "Bugs". It sucks to get a new car and have problems that prevent you from enjoying it. Keep us posted on the details. U.M.
