I am not sure if this is a throttle body issue or not. I can crank the car and it idles fine runs great. If I try to rev the engine up, I hear a sucking air noise like a "swoosh" and the engine shakes and acts like its starved for fuel if i just pump the pedal like I'm "rev-ing". If I drive it down the road and let it just shift out and run it is fine, but I can't like take off real fast or stomp it or it acts like theres not enough gas to get it to go. I have taken the air cleaner off, cleaned it degreased it, new air filter, cleaned the MAF sensors, cleaned the part load and full load breather tubes and put back together. I'm still not any better. I am getting a check engine but this car sat up for awhile and some of these codes won't apply. I have gotten P0332 - knock sensor, P0442 - Evap leak (small) and I fixed a hose i found under the air filter housing that was broken so that is taken care of, P0102 Mass Air Flow sensor and it is clean now so, P0112 - Intake Air temp cirucut??, P1642 - Fuel pump, has been replaced and was the reason the car sat up with previous owner, P0174 and P0171 - upstream oxygen sensors for bank 1 and 2. Would any of these codes make the throttle body do that? I have not cleaned it yet nor the sensor as it runs great at idle, its just under load that it give a fit.

 

What happens if you do it with the gas cap off?

 

Hi coastaljag
Our 2001 XJ8 was giving us P1638 DTC almost every day. It was resolved with new gold tip wiring to the TPS.
Then the P1642 DTC started to appear intermittently. I found out that the Instrument Cluster Module had a bad circuit board and replaced the Module with a used one we found on Ebay.

8 months later we had P1121 and P1122 DTC showing up for a few weeks and we had our throttle body rebuilt to resolve the issue.

No more DTC codes since August 12, 2012.

Jim Lombardi

 

well haven't tried that. I just checked to see that the EVAP is plugged in on top of the fuel tank and it is. New fuel pump and fuel filter. Car runs smooth and purrs at idle. it you ease the gas to it when you are revving the engine up, it will go right on up past 4000 rpm no issues. The issue happens when you fast rev it. It actually dims the lights in the car. My battery is new and cables are tight. I just cleaned the TPS plugs and wiped the already spotlessly clean throttle body. The only code that keeps coming back and will not clear is P0453. I have done hard reset and it will clear out of the scanner.

Live Data at idle as follows:

ST FTRM1 % -3.1 to 4.6 fluctuating
LT % -7.8
ST FTRM2 % -7.8
LT FTRM2 % -8.6

RPM at idle 659

IGN ADV (deg) 4.5
IAT 27
MAF (gm/sec) 6.9 at idle --
ABSLT TPS% 2.3/3.5
02s12 (v) .860 0.7%
02s22 (v) .790 -0.7%


I have no ideas what this means but maybe someone here does. Thanks!

 

Jim, thanks for the response. This car has 105K on the clock, throttle body inside looks like brand new. I'm not getting a code 1638. I did get o2 sensor codes for the upstream banks once, but I haven't driven the car much to get it to code again. I'm thinking maybe this could possibly be an issue?

 

My guess is that you car is in restricted performance allowing it to idle and drive properly until you want the engine to go over 2000rpm then the restricted performance kicks in. I would say you need to look at your battery, MAFS and check the gas cap. You could reset the codes now that you documented them and drive the car until the check engine light comes on and see what real codes you have. Do not jump on the accelerator this may have given you the knock sensor code.

P0332 is correct for knock sensor
P0442 I would say is a bad gas cap
P0102 MAFS or a clogged filter
P0112 Is air intake temp
P1642 is a CAN fault
P0171 & P0174 Bank 1A & B lean mix

Link http://jagrepair.com/images/AutoRepa...ent%201998.pdf

 

The only code I'm getting is P0453. It's not saying Restricted Performance at all. Everything is normal on the dash.

 

I guess it would help if i would read the entire post. See if this helps.


Evaporative Emission System Pressure Sensor/Switch High
What does this mean?
OBD Code P0453refers to
The EVAP (Evaporative Emissions) System allows fuel tank vapors to be purged into the engine and burnt rather than expelled into the atmosphere as harmful emissions. The EVAP system contains a pressure sensor to check the integrity of the system. Periodically, the EVAP system performs a pressure test to check that there are no leaks in the system. It uses this sensor, also known as a fuel tank pressure (FTP) sensor to check for leaks. Basically P0453 means the PCM (Powertrain Control Module) noticed the EVAP Pressure sensor or FTP is indicating a higher than normal pressure (above 4.5 Volts) in the EVAP system. NOTE: On some vehicles the FTP is a part of the fuel pump assembly in the tank.

Symptoms
Possible sumptoms of OBD code P0453
There will likely be no noticeable symptoms along with this code other than the MIL (Malfunction Indicator Lamp), commonly known as Check Engine Light illumination. However, there may be noticeable fuel odors in some cases.

Causes
Possible causes of OBD code P0453
A P0453 DTC trouble code may be caused by one or more of the following: Open on FTP sensor signal wire Short to voltage on FTP sensor signal wire Bad FTP sensor Abnormally high pressure in fuel tank due to blockage in EVAP purge hoses or overfilled tank Loose/damaged FTP sensor connector Loss of ground to the sensor

Possible Solutions
Using an scan tool access FTP sensor value with Key on Engine off (KOEO). Normal value is usually somewhere near 2.5 Volts at atmospheric pressure (may fluctuate some due to altitude). It shouldn't ever be above 4.5 Volts. 1) If it is close to 2.7V with the gas cap off, the problem is likely intermittent. Using a Digital Volt Ohm Meter, measure the voltage on the signal wire while trying to induce the problem by wiggle testing all the wiring at the FTP sensor. If the voltage fluctuates when wiggle testing, check for connector problems; i.e. water in the connector, broken or chafed wiring. 2) If the value shown on the scan tool is above 4.5V, unplug the sensor (if possible) and check for voltage again. If the high voltage is still present when unplugged, inspect wiring harness for a short to voltage on the signal wire. If the high voltage disappears when unplugging the sensor, check for a good ground to the sensor and proper reference voltage. If you have a good ground and 5 Volts reference voltage, replace the FTP sensor since it's likely shorted out.

 

Just out of curiosity, can you hook up the scanner for live data and watch what happens to the tps % as you press the accelerator?

I wonder if there is an issue with the pedal sensor vs throttle body... (I am thinking that when you press the pedal the butterfly does not open but the computer is adding fuel?)
What happens if you try and throttle up by turning the throttle body instead of depressing the pedal?

 

makes some sense there because I was going to clean the throttle body so I had the key off of course and rigged a small pole with one end flooring the gas pedal and then the other against the seat so that it opened the throttle body butterfly like I've seen demostrated. It didn't open it. So where is this pedal sensor?

 

DTC Summaries
V8 A26 Engine Management - 1998

P0453 FAULT DESCRIPTION
FTP (fuel tank pressure) sensor circuit high voltage

MONITORING CONDITIONS (“SERVICE DRIVE CYCLE” For the particular DTC. Operate the vehicle as described to check for a reoccurrence of the DTC.)
Ignition ON > 5 seconds

OBD II
Y (YES – indicates that the DTC is an OBD II DTC)

CK ENG
2 (2 TRIPS – indicates that the CHECK ENGINE MIL is activated by a fault occurring during TWO CONSECUTIVE “TRIPS”.)

OTHER
N (None)

DEFAULT ACTION (ECM default action; Logged – DTC stored in memory buffer; Flagged – DTC stored in memory / CHECK ENGINE MIL activated.)
When CHECK ENGINE MIL is activated DTC flagged; second trip, ECM:
– Inhibits EVAP leak check monitoring

POSSIBLE CAUSES (HIGH VOLTAGE – High voltage can be either EMS sensor supply voltage (5 volt) or B+ voltage.)
FTP sensor to ECM signal ground circuit open circuit
FTP sensor to ECM wiring (supply, sense, signal ground) short circuit to each other
FTP sensor to ECM sense circuit short circuit to high voltage
FTP sensor failure

Here is the JTIS for Fuel Tank Pressure Sensor - SRO (Service Request Order) 19.55.31

Drain Fuel Tank
Remove Fuel Tank
Remove pressure sensor from evaporative loss flange.

Looks like the FTP sensor is on the Fuel Tank and probably cannot be accessed without removing Fuel Tank.

Here are 2 PDF files that I have on my dropbox.com account - 1998 DTC Summaries, 1998 Electrical Guide:
https://www.dropbox.com/s/70vfd5o9zr...nagement.pdf?m

https://www.dropbox.com/s/68e9c6xa9j...wj1998en.pdf?m

These PDF files probably will not be able to be viewed on the dropbox.com webpage, so use the download button, then use the direct download menu option, the choose the open file on the popup.

Jim Lombardi

 

weird that the sensor would go out like that. I just pulled this entire tank with new fuel pump from my other xj8 as the vandenplas came with a gas tank that was full of rusty gas and deposits. I just decided to pull entire good tank with good working components and put it in. Now I'm getting that code! I guess I'll have to live with it. I just need to get this acceleration issue fixed. As long as I just drive it normal and not stomp it or get on it basically, its fine, but if I get on it, it bumps and kicks and acts like its starving for fuel. Weird!!!! Jim what you think?

 

As you say, it seems like the engine is starved for fuel. Try hooking up a fuel pressure gauge, there is a schrader valve on the fuel rail. Someone can correct me on this, but it should be about 40psi. Take it for a drive and stand on it, see what happens.

 

dsnyder586 post# 9 mentions pedal sensor vs throttle body.

I am not sure but I think he is referring to the Pedal demand sensors potentiometers)

Here is an issue posted on 2carpros.com
"when I step on the gas the car does not pick speed it hesitates now if I step on gas little by little no problem"

2carpros.com answer
"Accelerator Pedal Position (APP) sensor is connected to the input shaft within the electronic throttle assembly (throttle body)"

The APP sensor consists of a dual-track potentiometer that provides inputs to the ECM of driver demand at the accelerator pedal.

Here is a weblink to the Electronic Engine Controls forum thread and the post with the link to the PDF file - the Engine Control Module (Accelerator pedal and mechanical guard position sensors; Throttle (blade) position sensor).

Look at page 4 and pages 7-9

https://www.jaguarforums.com/forum/x...77/#post377824

Jim Lombardi

 

I will check out the sensors. Jim if worse case is present I have a working throttle body on a 1998. Can it be used in the 99?

 

Hi Jim- that is what I was referring to, thanks!

 

Sorry to complicate things but those negative STFT and LTFTs point to exhaust back pressure, possibly due to catalytic converter damage.

 

HMM> Hadn't thought of that, but I have had a similar issue. Mercedes wouldn't accelerate but would idle perfectly and drive around 30-40mph without issue- ended up the cat honeycomb had turned sideways and blocked the exhaust.

It's definitely something to put on the list of things to check.

 

Wouldn't I be getting o2 sensor codes if the cat was damaged. I have exhaust coming out and the thrift me body does the same thing if I stand at the hood and manually turn the cable with my hand.

Would a tb from my 98 work?

 

I *think* the TB's are the same- it's only about a 25 minute job to swap so I say go for it.