Do share what you've heard.

I know of one fellow who had an injector harness grounding out causing over-fueling but I think you've already tried different injector harnesses, right?

I'm running out of ideas on this one but, FWIW, I DO think you have overfueling problem causing low vacuum and not the other way 'round.

The fuel trim pot is on the ECU itself. I think I can find some pics.

Cheers
DD

 

Fuel trim adjustment:

Sean's Jaguar Tech Pages - Jaguar EFI ECU Adjustment Tool

Cheers
DD

 

I made a tool this morning using a 4 inch piece of steel fuel line. I had to file the edges down a little to make it thinner and then put a small dent in it for the flat spot. It works great, but didn't change the problem.
I also found a loose ground wire on the harness coming out of the firewall (not the injection harness), but that also didn't change anything. I'm not done yet though, I have a few other things to check.

 

Okay, my eyes are burning from reading, but I have a few other things to add to my list of causes.

At the moment, the exhaust ends at the hollowed out cat-converters. It's possible the nearby O2 sensors are en-training oxygen from the air (not likely, but possible) and causing the ECU to order enriching. So I'll have to finish the exhaust.

There is at least one more ground wire I need to check. When I removed the radiator, I had to disconnect it from the radiator support and it links directly to the harness leading to the ECU. A poor ground here also tells the ECU to run rich.
I'm going to check the harness ground at the ECU, the #1 and 2 pins should be direct to ground. If not, that's another problem I have to locate.

As a side note, the lower vac pressures I was getting are within the normal range for these engines. In fact, there are conditions in which the ECU is programmed not to respond until vac drops below 11.

 

I found several loose ground connections and cleaned and tightened them, but nothing changed. I adjusted the fuel trim all the way in both directions and again, no noticeable change. One thing that seems odd is that if I disconnect the temp sensor, the engine runs slightly better.
It just keeps getting weirder...

 

Well, it's only a trim adjustment....and whatever the problem is, it is overpowering the adjustment range of the fuel trimmer.





Usually the engine will flat-out die with the coolant sensor unplugged. Some say it cuts off the injector pulse entirely; others say it forces a full-lean command. Anyhow, the fact that the engine still runs suggests (to me, at least) that the mixture is very rich and the 'puter doesn't have the range to overcome.




What's your fuel pressure? Excessive fuel pressure will certainly over-fuel the engine. Also, have you checked TPS voltage?

Cheers
DD

 

I haven't checked the fuel pressure, I'll give that a try. What's it supposed to run at?

TPS voltage, where do I check it and what should it be? I'm assuming it's measured off the plug below the linkage assembly in the V?

 

About 36 psi. You have to splice into the hose that runs alongside the the left side of the fuel rail




Probe the red and yellow wires with the harness connected and the key "on". You want about .32-.35v at idle and 4.8-5.0v at full throttle. Slowly open the throttle to make sure the voltage increases smoothly and gradually.

Cheers
DD

 

I'll let you know what I find, thanks!
What would I do without this place?

 

Okay, finally had a few minutes to play with it again. The TPS showed .38v with the key on and engine not running (doubt it makes any difference does it?) The moment I move it it pegs the meter so I'm going under the assumption the TPS is bad. If I unplug it the car actually runs a little better, so again I think you may have hit the nail on the head. Or at least one of them.
So...where is a good place to get a replacement? It looks like mine is the old style if that makes any difference. What about costs?

 

The original "Bournes" TPS is discontinued from Jaguar. Some vendors sell an aftermarket copy---$200 or so, I think. It bolts right in.

Jaguar and other vendors sell a "kit" which uses the later style TPS and includes parts to make it fit to your throttle capstain. $200-$300 ? Not sure.

If your TPS is red it has already been replaced with the newer style.

Or....search for my postings from a few weeks ago about using a $25 Mustang TPS

Cheers
DD

 

Considering all the mods I'm making including switching the engine, I'm not worried about keeping it original. $25 sure sounds better than $200-300!

 

I found it. Reposting it here to help with references.

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 :-)

 

Okay Doug, I've ordered the part and should have it in 5 days or so. I'm hoping you'll be kind enough to help me figure out which what goes where?

 

NO! I won't.

Just kidding. I'm sure I have my old notes somewhere

Cheers
DD

 

From my notes:

A tps voltage red
B sensor ground yellow
C reference voltage green


From this I presume (since I don't actually remember) that the Ford TPS had A-B-C markings corresponding to the 3 pins

As I recall the wire colors change at the connection to the main harness. The colors menioned above should be the colors of the wires coming directly off the sensor.




Cheers
DD

 

According to the tracking code I should get the new TPS on the 12th, and once I have it in my hot little hands I'll have a better idea of what I'm dealing with.
One thing thats been nagging my feeble brain is that at idle my TPS was reading .38V. Is that enough to throw off the enrichment that much?

 

Doubtful

But you mentioned that it pegs the meter whenever it is moved. I assume you mean the voltage shoots way high. That would be a problem. I'd want to replace it for taht reason but you repeat the test with the engine running and see if it stays at .38v

Cheers
DD

 

Update: While waiting for the TPS to arrive, I began checking other things with my Ohm-meter. After checking the injector resistance (all were identical) I took the car down off the jackstands and...it won't start at all now.

Hmmmm...It is flooding itself badly. Now I'm wondering if the ECU is crapped out? We could only get it to run decently by putting 20-22 Hg vacuum to the computer with a pump. From what I've read, normal vac on these engines is 15-17 Hg. Is this correct?

 

Oh...one more thing I want to ask. Where/what is the fuel interface unit and relays? If it is bad, would these symptoms occur?