4.6 DOHC with hesitation /surge

GA_googleFillSlot("Forums_ROS_300x250_noad"); I have a 1998 lincoln with 100K 4.6DOHC.( I figure this is the same engine as the cobras and might have a better respone here) I am getting severe hesitation /Jerking /Surge on light acceleration. I have replaced

fuel pump and all filters (old pump was running at 22 lbs)
MAF
TPS
Plugs
coils been rotated and checked using a new coil ( changed 1 at a time and test drove)
DPFE
Throttle bottle cleaned with new gasket / EGR as well ( will make a popping sound with vacuum applied)
cleaned injectors and rebuilt with new kit
New Pressure sensor / regulator

car has good gas mileage with no DTC

My STFT are between 4 and -4 for both banks
MY LTFT is now about 20 ( disconnected battery and reset)

If I should punch it out (WOT), the LTFT goes to 0 and my STFT goes to 20 so it basically reverses. Does this indicate a massive air leak? At idle, I am getting a steady reading of about 20 .

My I/M monitors shows the following system as INC ( 3 days after battery reset)

EVAP and CAT MON.INCOMPLETE Are these related to my issue?

The evap could be something to check, vacuum lines from the tank, vent valve, gas cap etc.

Hello, I did drop the gas tank a few times which was cake. I didn't see anything bent or crushed. The first time I dropped the tank, The new fuel pump did not matched. The tank was totally clean and the pump filters were the same. I cleaned it with carb cleaner and it dripped clear. I reinstalled the old pump and moved on to other parts but eventually replaced the pump. I never received any codes for any evap issues. Can the ECU be wacky. All my sensors look good and when the car starts to hesitate 25-40 MPH and some surging at 60, I see the O2 sensors have a negative value so their is gas in the exhaust but the long trims are just about 20 while the short terms are pretty consistant for both banks between -4 and 4 but will spike to + 7 or 8 every now and then. I am expecting the P 171 and 174 codes any time. I did have 2 different tranny guys look at my car because the Ax4n had TB's for hesitation and shudder but they both said they bet it's an engine problem. If I punch it out to WOT the car takes off and shifts well through the gears. I also dont notice any issues in an open loop while cold. This has really been a good issue. I drive the car 70 miles a daywithout worry.Any other iseas? Could the O2 sensors be slow to respond . I see 3 changes in about 2 seconds but can the sensors be out of range and how about the O2 sensor that is downstream that is INC and not reporting??. Without driving the same exact car, its hard to tell. Unless I pretend to interested in buying a car and take it for a test drive *EG*, NA, I rather try to fix it myself. I have this posted in the Lincoln section but I dont think many Lincoln owners fix their own cars *l* and I posted this in the mustang forums since these engines are used in the Cobras.
Thanks
Chuck
Chuck

I'd run it through a few more cycles and then rescan and see what's what. You have to take what the computer gives you, otherwise we are guessing. After a few cycles and starts and stops, it should be set for scanning/inspection with the IM monitors being recalibrated. See what's in the system then and we can go from there. You have replaced alot of parts so, can't be much more.

Ok, I am happy to report that after 4 days of driving and 300 miles of stop and go Atlanta traffic and speeds up to 80 MPH, All my I/M are now good. When I ran my scanner in open loop this morning in 25 degree temps, my LTFT and STFT were all at 20. Once it went into a closed loop state, My STFT went between -4 and 4. When the car hesitates, there is sometimes a small negative value in the exhaust so cant be a lean condition.? Nothing is adding up so if its not logical, it must be the computer *l* Besides how long or how many cycles should it take for the I/M status to all become ready? So can it be a timing issue with the crank sensor allowing for the injector pulse width to start at the wrong time???? Any takers :):eek: punch it out and the tires squeal and at idle it seems to rev higher and lower than the 15 rpms that the scanner is showing. Would the o2 sensors be the next logical step??

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm962.pdf

Ok, I am happy to report that after 4 days of driving and 300 miles of stop and go Atlanta traffic and speeds up to 80 MPH, All my I/M are now good. When I ran my scanner in open loop this morning in 25 degree temps, my LTFT and STFT were all at 20. Once it went into a closed loop state, My STFT went between -4 and 4. When the car hesitates, there is sometimes a small negative value in the exhaust so cant be a lean condition.? Nothing is adding up so if its not logical, it must be the computer *l* Besides how long or how many cycles should it take for the I/M status to all become ready? So can it be a timing issue with the crank sensor allowing for the injector pulse width to start at the wrong time???? Any takers :):eek: punch it out and the tires squeal and at idle it seems to rev higher and lower than the 15 rpms that the scanner is showing. Would the o2 sensors be the next logical step??

http://www.motorcraftservice.com/vdirs/diagnostics/pdf/obdsm962.pdf

Also what is the silver solenoid device that mounts on the throttle body opposite of the EGR valve ?

Also what is the silver solenoid device that mounts on the throttle body opposite of the EGR valve ?I believe it may be the IAC valve but would this be a factor if my car Idles fine? Could it let in unmetered air upon acceleration?

Ok, I spent another 100 bucks and the o2 sensors were replaced. Same results. I reset the battery and my LTFT is 0 and my STFT are in the high teens and this was the same as before. As the LTFT increase the STFT will eventually read correct. Since this doesnt make any sense it must be logicall so the ECU will be replaced within a week. the ECU should fix the issue because there is nothing else to replace

ECU is responsible for electronic engine management and fuel and igntion system control functions

Hello Again,

If I replace the ECU with a used one from anothe vehicle with the sameexact part number, Is there anything else that needs to be done. Can I assume the FW on these boxes can be updated without being in the vehicle if I wanted the latest code?

Chuck

Could you past all the PIDS that are giving you trouble? You seem to be focused on the STFT. These are not what you need to look for. LTFT will give you the indiaction of what your engine is doing. Are the readings positive ot negative when you have the 20 reading. Have you thought of the fuel pressure regulator? We had one thas stayed at +25 and all tests showed within parameters except the LTFT which stayed at +20 at idle. The regulator was hung partially open allowing too rich mixture at idle. If you can post the PIDS that you are looking at, it can help us a little more.We need to find the cause instead of the symptom

Pids as in DTC's? the eis nothing outstanding , pending or in the works. my STFT does not reflect the LTFT and they move in oppsoite directions. I can only assume my ECU has a corrupt A/F table or hardware issue. The pressure sensor/ Fuel pump was replaced with a new one along with many other parts.The car hauls ass in WOT mode and will chirp the tires. my MPH this morning moving at 60 was 28.5 which is dam good.
Thanks

Chuck

http://www.carclinicmagazine.com/ford_common_ecu_failures.html

The Ford EEC IV and the EEC V ECU do have common problems with non starting, emission control issues and misfire/hesitation fuel curve malfunctions

I have replaced my ECU but car wont start. i will need to search for ECU replacment. i will keep you posted

Update..

I disconnected the battery and reset the ECU. my LTFT are now 0 and my STFT are now 18-20 for both banks. I checked for leaks using carb cleaner at idle on the intake but seen no differences. I then tried it again using starting fluid and sure enough, the one bank went down to -2 from 18. I then sprayed the intake on the other bank and that side also went down and the original side went back up to 18-20. I sprayed both banks along the fuel rail and all my STFT went to around 0 and then climbed back up to 18-20. I will replaced the intake gaskets and report back. It appears that both sides of the intake gaskets are leaking. WOW...

Chuck

It appears the I have a shaft leak on my IMRC. Can these be replaced or modified with a delete plate and still have good gas milegae and functionality. What are my options