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Hi guys I’ve been trying to adjust the accelerator & cables on my 1997 6cyl 4ltr SC. I’ve followed guidance given by workshop manual (was given in a forum) that went something like.. ”1. Slacken of both cables. 2. screw accelerator cable (long one) till pin on TCA touches the TPS actuator arm. (That part was easy as having removed the plastic cover on the Traction control unit i can see the pin and the “arm” it is to touch against.) 3. screw throttle cable to a 0.25mm gap between the two quadrants.
This raises my first question.. Where does the feeler guage go to measure this gap?
I just carefully tightened the throttle cable (short one) till the slack has been taken out, then backed it back off to make sure its wasn’t Too tight.
my OBD live data reader was showing 0.4% with no pressure on the accelerator pedal and 54% when fully open (pedal to the floor)
i spent a couple of hours adjusting the two cables as I was aiming to see 10-12% resting and 90-95% fully open. But could only achieve 12% resting and 70% open, and this just sends the idle speed to warp 6. (1200-2000RPM) so slacken off to bring the idle down.
My second question is simply, what am I doing wrong?
A similar question just came up in the X305 section. My car reads like that too (even with a different TPS and EMS than the AJ16). Zero at idle and about 75% at wide open. It seems all is well with its running ability! I think there could be a glitch with how some scanners read the data, and/or with the first-gen glitchy OBD these cars have. This theory is supported by your experience of a very high "idle" while your TPS reads only 12%.
If you have a good idle, no slack in the throttle cable, a nice roar and a supercharged pull at WOT, I'd call it good.
True Jesus, I was able to get a little more travel by screwing in the kick-down switch a few turns. Try that Jack. Same switch on the 305.
Generally there are no issues with OBD data as such on x300 so I'd defo try different scanner. At 70% at WOT its basically like a 5 cylinder car at best as fuelling is messed up and at 54% its basically a 4 cylinder car, its a night and day if you compare car that has TPS messed up that badly compared to one that shows 95% at WOT
I've been over this a number of times, yet can never find the last post so here it goes. Your low base TPS voltage at 0.4% seems completely messed up. This is an equivalent to 0.02V which is completely wrong. It should roughly show 0.6V or 10-12% with the foot of the pedal. Check the TPS output directly at the sensor with a multimeter to compare it.
Afterwards its relatively easy. You first check base idle TPS voltage and record it. This is crucial as its stored in ECU and it always has to be set to this with the foot of the pedal. Any adjustments later and that base TPS voltage needs to stay the same, if it wont you'll end up with high idle.
You then start with setting up throttle plate gap. This needs to be set to 0.002" and you set it up with the little screw stop adjuster. Then, you check the TPS voltage and make sure its still the same as first recorded. If it isn't then you adjust it with the TPS bolts. It looks like there isn't any adjustment in the bolts but you can easily get up to 0.1V out there. TPS should show around 10-12% with the throttle closed. Now fully open the throttle by hand and check what's the voltage, this should be as close to 5V or 100% as possible. If it shows 54%, 3V or anywhere below 90% then you have a faulty TPS unit.
If it shows close to 5V or 100% you bolt it to the engine and start adjusting cable. That part should be straight forward but if you cant get full TPS travel and therefore voltage out of it with a confirmed good working TPS then you either have a cable issue or bent pedal(not uncommon!) or some sort of an obstruction in pedal travel.
Sometimes throttle body itself can get sticky but that can usually be fixed with some new springs, cleaning or some sanding of the fuel varnish. I think someone recently even had a bent TB shaft but thats rather extreme.
Also, if your base idle TPS is genuinely below 0.5V or 10% then you'd need a TPS reset or a different ECU. No idea who even has a kit for this in UK, you'd have to call around, maybe KWE or some dealers.
Thank you for a very compressive answer.
I’ll get to work on all that you’ve posted at my first opportunity. 👍🏼
I’m guessing I’ll need to remove the supercharger to gain access to the throttle body and tps?
The throttle is behind the cast elbow where the vacuum line to the brake booster attaches. You might be able to reach under and move the throttle by hand. If not, you can remove just the cast elbow and leave the supercharger in place. The throttle is almost directly above the oil filter.
What I would try is have an assistant hold the throttle to the floor, and then reach in and try and move the throttle by hand and see if it is actually all the way open and the hitting the stop, or if the cable isn't pulling it far enough.
Accessing the throttle body is the main issue on the S/C cars. If you can get the car up in the air, the throttle body can be removed from underneath, which takes long arms and patience, but is in my experience the easiest way. From above, the inlet manifold needs to come off, which also requires patience and perseverance. Both methods are addressed in numerous threads, mainly on the subject of high idle.
I had a guy bring his XJR 6 cylinder to me where the car just had no ***** whatsoever. Hooked up to the PDU and saw the throttle didn’t open fully, just like yours…. The problem was this plastic tube (circled in photo) had snapped in half. It caused a huge amount of slack in cable that simply could not be adjusted out. Fixed it by zip tying a metal rod to the side of it to keep it straight, and that made the throttle open all the way. Good luck!
04-17-2022, 02:03 PM
Throttle not opening beyond 70%
