Hi there,

I have somewhere read, that the early throttle bodies on the AJ26 have some common issues... The sensors seem to die or can start dieing and the car will have problems performing.

My 97(!!!) built 3.2L AJ26 has a cold start issue. This means that the engine will always start BUT won't run right for a few minutes. When setting off on a cold engine, you can feel the car loses power, has a few misfires and will then slowly gain power. If you floor it (flooring a cold engine is always a good thing to do) and therefore basically 'flood' the engine with air, it will jump and accelerate great...

Once getting to around 60 kmh (35 mph), the problems go, but if you lift your foot off the gas pedal, the drivetrain bangs one time nastily (kind of like a stall through). This ONLY happens for around 3-4 km (about 2-3 miles).

When the engine has gotten to temperature, it will run like a dream. Full power, no blue smoke, really good and efficient fuel economy (for a V8).

What I noticed a few weeks ago, was that when you turn the throttle body flap by the throttlecable 'lever', the initial move is okay. But about 5 mm in the motion, it gets a little sticky and then moves normally again. Always in the same spot.

Can all these issues be due to a faulty throttle body? The car has NO codes saved and ALL cylinders run. Both lambda sonds are working well. The engine won't run with the MAF disconnected (no idle) and will stall as soon as the MAF plug is removed. Temperature sensors are fine and work well.

Any ideas?

Cheers

Damien

 

This is probably what you are experiencing as I have too. In my opinion if there's no stored codes, don't go chasing sensors or computer inputs/outputs.

https://www.jaguarforums.com/forum/xj-xj8-xjr-x308-27/1998-xjr-throttle-body-concerns-159443/

Forgive my lack of a direct highlighted link.... I'm a link and picture illiterate individual.

 

Okay, I'll be gettong a different TB, of course the right one, to check...

How does the TB actually work? Is there a direct linkage between the throttle cable and the butterfly valve or is it via a sensor, motor and other gubbins?

 

Is this an engine with an idle air bypass valve (see workshop manual, I imagine)? If so, have you checked it's OK?

 

The AJ26 has a direct connection to the butterfly.

 

You mean tge additional air injection system? No. It is a standard model with no additional parts around the TB.

 

Is it then geared or so? I've read that people have fully depressed the gas pedal and it barely opened, even though the linkage was wide open!?

 

The cable attaches to a sheave on the shaft. There is an adjustment at the cable housing mount, but I suppose the cable could stretch to the point that it could not be adjusted. Simple to check by having someone depress the pedal while you look at the butterfly.

 

Mine is fine, but the same writer also stated that later on it would work normally...

 

Ahoi!

Right, so, I'm basically convinced, that my TB is the problrm, but I am still a little confused:

#1 Why is there an electrical motor on the TB if it is a direct ooeration via theottle cable?

#2 How is the idle regulated on these TBs? There is no additional idle regulator, so I assume some form of either bypass or regulation is achieved!?

#3 Can the successor TBs simply be fitted as per plug and play? My car was fitted with LCA1560AJ, LCA1560AA was the successor. Then LCA1560AA1 and now some other number C2A1470... Would any fit with no proble without any kind of niggles or alterations?

Cheers

Damiem

 

The pedal cable is connected to the throttle assy and it ALLOWS the throttle plate to open if the motor is operating correctly with engine running.

The cable/TPS is a SUGGESTION to the throttle assy and the motor has the final say-so.

The motor can close the plate. (like when the Trac Control or DSC demands it)

bob

 

Ah, cheers Bob!

That sounds like my proper culprit then! I know my ASR/TCS works correctly, as it will light up every so often *cough*

That explains a lot then. The TB can be clsed if the engine says 'nope'. That explains then why I lose power and when going off regain it. As I am still on the pedal, it is injecting loads of fuel and that explains why my emissions are currently really bad (very rich mix, lambda regulation is at -15% so nearly at max) and also some of the misfires (no misfiring in the engine but also into the exhaust system)...