Hello everyone, I am new to this Forum, and dont usually use forums; so forgive me if this has been discussed before. I am a back yard mechanic and am repairing this for my friend who recently bought this Jag with 150K mi. We had replaced the Fuel pump about 8 months ago when it had a no start condition. After that car ran great and then threw DTC's P0430, and P1388 with acceleration stumble following shortly after. Replaced the O2 sensors already and cleared the codes. The car continued to stumble after going 30 mph and requires feathering the pedal to build up speed. I takes sometime up to two minutes to get to 60mph.

I placed a vacumm guage on it with a steady 22 in hg vac after the TB on the intake. I also placed a fuel guage on the fuel rail with a 33psi at idle and when running at higher RPMS fuel guage decreases 8-10 psi. I then took out the Fuel filter and blew threw it with ease releasing clean fuel in big gobs then freely passing air without restriction. I know this fuel filter was replaced two years ago. I then hooked up my fuel guage before the filter and attahced it to complete the fuel loop and run engine. Fuel pressure is still at 33 psi at idle and decreases with higher RPMS. Driver side CAT was replaced aswell since it no longer had a honey comb in it no more. Need to fix this soon before the new CAT goes bad. Check TB without air duct.TB Plate is responsive with pedal, and cleaned the MAF sensor. Fixed Elbow leak on the driver side intake (near firewall). What else to do? No DTCs present.:icon_confus ed:

 

Please provide the year and model "S" (3.0, 4.0, or 4.2) Fuel pressure should be 50+ psi. Check for vaccume leaks and leaky injectors.

 

Welcome to the forum.

A brief introduction in the New Member Section would be helpful as well as your specific vehicle information as bfgross mentioned above.

I'm guessing you have the 4.0 V8 - P1388 is VVT over retarded (driver's side) the P0430 has to do with the cat converter (driver's side). Changing the O2 sensors is not going to salvage a new cat converter if your issue is related to one or more misfiring coils under load.

As far as P1388 - change the oil to 5W20 and sub 1 of the quarts of oil with Mercon V auto trans fluid (highly detergent) and drive the car - the VVT oil passages are probally clogged. Search "P1388" on the forum for more info.

The un burnt fuel going into the exhaust is what ate through the honey comb material in your cat converter in the first place.

Remember, intermitient misfiring coils will not throw the check engine light and set a code as thresholds are built into the OBD.

Clearly all indicators are pointing towards the coils on the driver's side (bank 2) of the engine - best bet since your DIY - invest in a COP (coil on plug) tester and test coils at idle. You will see which one (or other) coils are working intermitently.

Also, not directly related to your issue (but could be) when were the plugs changed and what brand were used? If the answer to either is "I don't know" might be a good time to invest in new spark plugs as well - stick with NGK double platinum - good for 100K miles.

Also, regarding fuel pressure - I believe pressures should be between 40 - 50 psi - if you have fuel pressure below 40 psi - you have a problem as bfgross points out. Did you replace the fuel pump with new or "used"? If used was the route you went did you at least replace the fuel sock?

I would re-check installation of the pump.

Just my $0.02 - good luck but don't waste too much time as you risk losing that replacement cat converter.

 

Thank you for responding, This Jag is an 01 S-type with a 3.0 v6 engine. The fuel pump was changed before. Also i noticed that on my diagnostic scan tool. The computer indicated 40psi fuel pressure while the fuel disagreed at 32psi. I uncovered the fuel covers under the rear seat and found my fuel restriction. The gas line going to the engine (Driver side) was the culprit. I had placed it under the large 3/4 inch vapor line and it ended up binding in a 90 degree shape. I disconnected the fuel line fished it out and re-routed it above the vapor line.

The hose was comprimazed with a crease line being very appearent. I used channel locks to re-shape it. It look like it handle most of it, but still was delivering less then 40 psi; however the car no longer stumbled and was able to hit 90 mph in a flash. How long did this work... A day , The car began to show the same fuel restrictions after being an hour away from home, but would go away. So I am ordering a new fuel line, which is only 12" long, and may fit with loosening the fuel tank to create a larger gap to remove and install line. The fuel pump was brand new with all new fuel socks, had to purchase additional one since it didnt come with the transfer pump sock. It maybe a week or so for me to get back to the Jag, but i will let you know the outcome.

 

I will work on my member page