I have a 1999 X 5.0 AWD w/AT that has a slight hesitation/sluggish feeling and rough idle.

The Check Engine light came on a while back, and was diagnosed as a bad #4 spark. Since then I have replaced the IAC, EGR valve, all 8 plugs & wires, fuel pressure regulator, fuel filter, pcv and I have cleaned the MAF. Since the plugs were changed, the Check Engine light went off and has not come back on. I have had the truck diagnosed by Ford twice, and once by two different independent shops. None of these shops could find the problem. (lack of power, hesitation, rough idle). After placing a post here, I was informed to change the EGR, which was done and has cured "MOST" of my lack of power problems. I still am having a rough idle (first 15mins of driving then it's gone) which is accompanied by a slight surge when starting from a stop (only happens until about the 2nd or 3rd stop/start then it all goes away). Lastly, there is a hesitation on acceleration at all times, and does not go away (most common on hills, or when traveling around 35-45mph).


1) The rough idle starts with the engine, and starts to idle fine after about 10-15mins of driving.

2) The surging only occurs for the first 2 or 3 stops signs/lights when I let off the brake and the truck starts to pull/roll forward (Auto Trans). If I press the accelerator, this does not happen. Only if the brake is released and the accelerator is not pressed. Now this is a very slight surge, nothing dramatic. Feels like the truck pulls(1 sec.), then stops pulling(1 sec.), then starts the process over again.

3) The hestitation happens at all times (warm/cold engine). I have noticed this to occur mostly on hills or when traveling between 35-45mph. When this hesitation occurs, the engine & transmission sound as if they are in too high of a gear. This causes a small vibration feeling through the accelerator. Now this is mostly on light acceleration. If I give it a lot of gas/heavy acceleration, this doesn't seem to happen as often or as bad.

I hope these descriptions aren't to vage, but if need be I can always go into further detail. I do want to thank everyone in advance for any suggestions or advice that they may be able to share with me regarding the problems I am experiencing.

 

Well, I guess no one has any suggestions, so I'll let you know about the symptoms that I am still having.

The rough idle still exsists. Only occurs when the engine is warming up. Only idles high (900-1100 RPMS) when warming up, then the engine will idle fine.

It seems like I do not have the surging problem anymore. This only happened 2-3 times after cold starts, but has not happened since my last post.

The hestitation/sluggish feel is still there. Happens when the engine is cold or warm, but seems to get worse as the engine temp increases. When pressing the accelerator, I get a constant but SLOW acceleration. This slow acceleration is felt through all speeds. This is even worse when I'm trying to climb a hill. I am planning on changing the TPS here soon (already have it, just need to replace).



Any suggestions would be helpful, as I'm getting really frustrated Ford can't seem to find the problem. The problem is so bad that I have 4 banger Geo's passing me (5.0 V8) on hills around here in Colorado. HELP!!!!!!!!!!!!!!!!

 

After reading about your problems I printed them out and gave them to my dad who has been a mechanic for Ford for 23 years and is now a Blue Oval certified service manager. Here is what he said:

Take it to you local ford dealer and ask them to reprogram the GEM module for the transfer case engagement parameters, this will get rid of the vibration feeling in the pedal.

For the rough idling he said make sure you are running motorcraft sparkplugs.

He also said that you throttle positioning sensor might not be working correctly. Have your dealer check the PID's for your throttle positioning sensor to see if it is getting the right amount of voltage at idle.

Let me know how it works out and if there is anything else that there might be to help us figure this thing out.

 

Well, here is what I have so far:

I am running Motocraft Double Platinum plugs with Motorcraft 8 gauge wires, so hopefully this isn't causing the rough idle. This was recommended by my local Ford Dealer, and the original plugs were Motorcraft Double Platinums.

My receipt from Ford (when it was in for diagnosis) states that all PID's are within the proper operating range. Now I do not know what PID's they may have checked and which ones they did not. I have already purchased a new TPS and plan to install it this week (hoping this is the cure). The screws for the TPS are torqued really tight, so this has stalled me until I could find new screws.

After the installation of the new TPS, I will follow your recommendation to have the GEM for the transfer case reprogrammed.

Just a thought to throw out:

I noticed the truck has these symtoms (lack of power, hesitation, surging) under 2000 RPM's. After 2000 RPM's, the "majority" (not all) of the power comes back and there seems to be a lot less of a hesitation/surging. Thought this might help.

I'll let everyone know what the outcome is after the new TPS is installed and the GEM for the transfer case is reprogrammed.

Of course, any suggestions between now and then would be greatly appreciated.

Again thanks for everyones help and advice with these problems. I know I'll get it running right here soon.

 

Just wondering how your are doing? Did the TPS fix work? I am having the exact same problems. This seems to be common with the 97-99 V8. Of course, Ford or anyone else can't fix it. Please let me know if you have the cure!!
Thanks

 

Just got the TPS replaced yesterday, and here is what I've noticed so far.

The new TPS is giving a lot better throttle response and acceleration. I do still have a hestitation/flatspot upon accelerating, but doesn't seem as bad as before. This flatspot/hesitation is now most noticable when accelerating from a dead stop. You can tell by the pressure needed to press the gas pedal and the sound of the engine/trans. The truck reacts a lot better when accelerating from a cruising speed, but there is still that slight hestitation/flatspot on the initial reaction.

Question for everyone: Since replacing the TPS, it seems like I have better throttle response, but I have dropped in MPG. Originally I was getting 15 mpg city prior to any problems. After the problem started the mpg dropped to 13-13.5 mpg city. Now with the new TPS, the mpg's have seemed to dip again, dropping to about 12.5mpg's city. Checking the Haynes manual that I have, it states that the TPS is not adjustable. Could I have installed the TPS incorrectly or is there some adjustment that may need to be done to correct this?

I have a new DPFE, so I'm hoping to get at the DPFE and the DPFE tubes this weekend. Hopefully this will correct the hesitation/flat spot. Every part that I have replaced (plugs, wires, EGR, IAC, TPS, O2's (4), fuel filter, pcv & fuel pressure damper), have each given the truck a little more life/power but stills seems to be having the problem.

Any further suggestions would help, since none of the shops I've been to can figure this one out without the CEL coming on. Thanks again everyone for the excellent advice!

 

Well I finally broke down, and went back to Ford for another diagnosis. Only thing is I decided to go to a different dealer this time for the diagnosis. Took the truck in at 7:00am MST, and received a call at 4:30pm MST stating they were not going to be able to get to the truck. This was a little irritating. When I got to the dealer at 5:30pm MST, the service manager informed me that the Tech was looking at the truck. He informed me he could not find any problems with the truck, but he did reclean the MAF/MAS and recalibrated the PCM. I was a little upset with this diagnosis, until I drove the truck. Evidentally either the cleaning of the MAF/MAS or the recalibration of the PCM cured all my problems. The truck actually performs like a V8 again. Hopefully this will be helpful to anyone else experiencing this problem. I had already cleaned the MAF/MAS, so I think the re-calibration is what did the trick. So anyone with a 97-99 X that is having a problem with acceleration/hesitation or lack of power, should check with a dealer to see if they need their PCM recalibrated. Thanks for the help everyone, I do appreciate all the suggestions and advise. I beleive the recalibration is TSB 99-8-7. Thanks again!!!

 

Another problem that I noticed yesterday, that I don't know if it is related to this. When I engage the Cruise Control, the X will pick up speed for a moment, then slows down and stays at the speed I engaged the Cruise Control. This problem is really getting to me!

 

Well, just got word from the Service Manager at the Ford Dealer I took my X to last. He has spoken with a Ford Engineer, who was unable to direct the dealership in any particular direction. So now the Service Manager is going to look for a 5.0 X that is on their lot. "IF" if they do have a 5.0 X, they will perform a side by side comparison of the two X's. If the results are considerably different, they will do some deeper investigation into the problem. Now if they find that they are running almost exactly the same, I'm SOL. Just wanted to keep everone posted.