ok a list of done items.
1 new rotor with squirt
2 cleaned both fuel tanks and pick ups
3 new fuel filter
4 35 psi of fuel
5 new plugs
6 new top coil
7 new throttle bushings
8 set blades to .002
9 adjusted throttle linkage


so the car idles at 950 ish ok i cab live with that. it does idle smooth. if im sitting in park and apply the fuel rapidly the engine responds very quick. going from 900 to 6000 rpms isnt an issue. holding a steady rpm is the issue. if i press the pedal to try to hold the rpms at 3000 for longer than 2 secounds the engine will respond by giving me a very erractic range of rpms. it will range from 1000 rpms to 3000 rpms within one secound and will continue to do this as long as i hold the pedal steady. the car is not drivable that way. it seems as though it looses spark or fuel to 1/2 of the engine? any thought? thanks

 

crank sensors?

 

I have that problem with mine sometimes. Mechanic says it's a bad tps. Just on the things to do list. The TPS can be responsible for a wide range of throttle problems including but not limited to, surging, irratic throttle response, loss of power, rough acceleration.

 

I agree. It does sound like the TPS.

Here's the bad news:

I believe this is something best left to the DEALER to resolve. I believe that you need some specific Jaguar tool to help calibrate the darn thing.

The part is not cheap, if bought from the dealer either....

 

Have you checked the fuel pressure *while the problem is occuring*? If not it might be something to do.

I had a similar problem on mine...not exactly the same, but similar....and the inlet regulator was faulty. Long story.

But, I agree that the TPS is a likely culprit. These are easily checked with a voltmeter. Post back if you want details.

I used a $23 Mustang TPS on my V12. Worked great but it did take a couple hours of (easy) fiddling about to mount it up.

Cheers
DD

 

Doug more info please

 

Part number for Mustang TPS please.
I rebuilt mine, but it is old and may fail any time.
thanks

 

Your TPS should have green, red, and yellow wires. Probe the red and yellow wires with your volt meter and with the key "on", check the voltage reading. You should see .32-.35 volts at closed throttle and 4.8-5.0 volts at wide open throttle. Most importantly, as you slowly open the throttle the voltage reading should increase gradually without any drop-outs or spikes.

Cheers
DD

 

The AC Delco number is 213-848. You can probably cross that number to another brand. It's a very common Ford TPS. If you need a vehicle application for ordering use "1993 Mustang 2.3L four cylinder"



Here is a partial cut-n-paste from a posting I made elsewhere describing the installation several years ago. The references to "Bournes" go back to the original TPS...manufactured by Bournes.




The drive spindle on the Ford TPS is the "round with two slots" type as
opposed to the Jaguar "round with one flat side" type (as you'd see on a
radio knob, for instance).

Using a sharp utility knife I cut the plastic drive piece off of the Bournes
TPS, leaving me, essentially, with a 3/4" long, hard plastic black tube
which engages the drive on the Jag throttle turntable.

It was then a simple matter to notch the other end to engage the Ford TPS
slotted drive. A couple of trial fits and adjustments for length and the
Ford TPS fit up against the bottom of the throttle turntable almost like it
was "Bourne" there, even has a raised, round area to correspond to a round,
recessed area of the turntable.

When cutting the slots you'll want to observe and be aware of the final
orientation of the TPS....you'll see what I mean.

The Ford TPS has a range of .38 to 4.80 volts. The .38 is a whisker higher
than the ideal closed throttle setting (on an HE) of .32-.36 volts
(depending who you are talking to) but, as far as driving the car goes, it
is great. Whether or not this difference is enough to be worrisome during an
emissions test, I can't say.

I have no detonation, pinging, or outward sign of lean running at WOT,
either, which was a concern since 5.0 volts was not obtainable. If I should
be worried here, somebody please tell me.

Since the "at rest" voltage was .38 there was no point in allowing for
adjustment....it can't go lower and you wouldn't want it any higher....so I
simply screwed it onto the underside of the turntable as is, in a fixed
mounting.

I Googled "Ford TPS" and easily found which pins on the Ford connector would
correspond to the Jaguar wiring. I cut the harness off the Bournes unit and
using (smaller than usual) spade connectors attached it to the Ford TPS. I
used black RTV silicone to fill and seal the rather large connector cavity.
The installation came off nicely, all-in-all. Of course, being hidden,
nobody will ever know :-(

I think I spent a couple hours on the whole shebang. In all honesty I did
this because money is a bit tight right now. Were I a bit more flush I would
have simply bought the later style Jag TPS with the adaptor pieces and be
done with it. <shrug> Bt, Ok, I'll confess it was sorta fun to beat the
system, especially when the end result is quite invisible :-)




Cheers
DD

 

ok did all the above all checks out great. got the tps set works well through the spectrum. still runs like ****..... with the erractic rpms.

heres what i found. the switch that mounts to the rear of the intake. drivers side that attaches to the throttle linkage. with 2 wires onm the micro switch. so heres what i did. i held the switch back like in the idle postion as i worked the throttle and the engine responds perfectly. good idle and good and steady at any rpm. so heres my question. what does the switch do and why would it make it run great when holding the switch as i said before? Doug you are awsome

 

I'm not awesome. I've just been reading, studying, learning, and doing this stuff for a long time. Everything I know I learned from somebody else...and am picking up something new all the time :-). Thanks though.

Since you mentioned early on replacing the "upper coil" I presume you have a Marelli car, right?

If so, does the switch you are describing have two very small gauge wires?

If so (again) that's the "idler switch" which I believes communicates with the Marelli ignition computer. I don't know exactly what happens when it is opened and closed but I presume is alters the timing somehow. It is supposed to actuate as soon as the throttle is opened.....just a silly millimeter of throttle movement.

Cheers
DD

 

Yes marelli. Yes 2 very small wires. Just odd that by bypassing that switch makes it run so sweet. It seems as though it cycles on and off the fuel supply to the injectors at anything over 1500 rpms or do and restores fuel when in drops below 1100 rpms

 

I think he might be talking about switch that makes mixture extra rich at wide open throttle, it sits against the throttle cable...?
Can we get some pictures here?

Doug, thank you for the TPS help!!!

 

Nope... Out at the end of the linkage. On the intakes end

 

Not to resurrect an old thread, but I am having the same issues I think. And will be looking into the TPS Theory.
As for the 2 switches by the throttle turn table, the left (drivers side) I was told was the transmission kick down switch, and the passenger one is a switch for throttle.
This was the actual wording.

The 'sensor' on the throttle cable is the transmission kickdown switch. And just FYI, the switch next to the throttle capstan is a fuel injection enrichment switch.

I only know this now because I asked the same question.


Here's my thread, and my issues. lol

https://www.jaguarforums.com/forum/x...issues-158499/


Cheers.

 

It may be the switch you are speaking of is the "overrun switch". It is supposed to tell the ECU that the throttle is closed. It then compares the intake manifold vacuum and shuts off the fuel. The object is to reduce backfiring and over fueling during coasting. I have this switch on my 92. Earlier models had spring loaded overrun valves that bleed in air during coasting.

 

Yeah the one on the passenger side is the overrun (enrichment control) one. I wonder if mine is bad, and that's why mine is idling all funky and backfires when I press the accelerator. Ever once in a while it runs perfectly fine, like yesterday.

 

mine ran exactly like that 3 months ago after emptying my down pipes.....changed out, amp, coil, ATS, CTS, O2 sensors, ECU and TPS and fuel pressure regulators ( have spares of all on shelf). It ended up being the distributor cap. Car idled funky, backfired, would throttle up fine in park but would bog down in "D" or "R" to check the enrichment switch just push it at idle, if the idle raises its fine, if you think it malfunctioning just pull the leads. I think you'll find it's not your problem

 

This is what it's doing now after I pulled the cap and cleaned the points and looked for moisture and cracks. None. Still an up and down idle with small backfires when trying to press the pedal.

This is at idle. Car ran fine the other day.
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The other day when it was running fine. Out of the few months I have had this car, this is only the 4th time it has ran and idled with no issues. I tinker with it every chance I have gotten for a few months.
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