Ford F150 - 99 F150 Hesitation / Bucking?

99Fordf150lariat · Posted: Fri Mar 14, 2008 8:37 am Post subject: 99 F150 Hesitation / Bucking?

Hi all, lost my old login on system rebuild and had to start over.

I have searched and searched for this answer so I hope someone doesn't say well duhh look two lines down or something.

My 99 F150 Lariat 4X4 5.4 with 30k on it has always had a small hesitation but I thought it was where it sat for weeks on end without driving. Well it has gotten worse, Pulling out I really press the accelerator down so I can get past the stutter (Kind of like having a manual choke on when engine warm) but at cruising speed you feel a bucking? Dont know how to describe but the whole drive train feels like it goes from power to breaking and will just keep doing this at cruise. You can floor it and from 0 to whatever it seems fine, idle barely shutters but it is there. You can leave in neutral and rev to about 1800 and the revs drop from 1800 down to about 1700? (I Believe - Been awhile) according to the dash gauge and you can definitely feel it. Throttle body was caked with carbon so I parked nose down on hill and packed the body with paper towel and used throttle body cleaner to get what I could see. Oh ford service = Useless without time and $$$ (Service mgr really cool though, snuck me info on 3 failing coils). Oreillys AP ODB2 scanner shows nothing, Ford scan shows nothing now. I did disconnect the battery for the TPS replacement and Throttle Body cleaning and upon reconnect / start the baby was smooth till the next mornings start. Which crushed me. I am getting little exhaust leaks throughout the system if this matters.

No Codes at all
Replaced: Plugs, Coils, Fuel Filter, Air filter, PCV, TPS
Cleaned: MAF, Throttle body (no dissassembly)

Next step I guess is to replace the Air Temp Sensor for about 140 on top of the 900 already spent.

Any help would be much appreciated.

chargett · Posted: Fri Mar 14, 2008 9:26 am Post subject:

I think I may have heard of this before...try the EGR...it controls surging and such. Since you say you were 'caked' with carbon, it may have gotten its share too.

onlyford4459 · Posted: Fri Mar 14, 2008 2:02 pm Post subject:

I am actually having the same exact problem. I am so stumped. I changed my #1 c.o.p and #2 with the plugs recently. The others I have changed in recent months. I checked my vaccum lines, and checked my throttle body that seemed clean. I also checked my tps for voltage, I have my 5v reference and when I press the throttle it goes from 1v to 4.5v. I changed my iac also. I changed my fuel filter around 100,000 mi. The truck has over 163,000 now.

Im going out tomorrow to check my fuel pressure and vaccum again. I read somewhere here to check my alternator?! So I did, Im getting 14.5v, and with the truck off I have over 12v on the battery. Im totally stumped.

It starts right up, but drives horrible. It bucks at all speeds. It feels like its trying to correct its self, but doesn't. It feels worse than a misfire. At idle I still feel it too, in park if I rev it stutters at around 1800 rpm as well.

I also checked my cats to see if they are glowing read from being clogged, but they are not. Ill also check the egr as well and clean the throttle body.

What about the maf, maybe fuel pump? Help please, Im dying here!

I'll keep you posted if I find anything.

99Fordf150lariat · Posted: Tue Mar 18, 2008 4:10 am Post subject:

Hey,
Thanks for the posts. I am really thinking about the EGR, I was on call this last weekend and was afraid to tear it down since my wife needed her vehicle. Maybe this weekend I can get a crack at it to knock another thing off the list.

I haven't checked the cats yet, maybe goto harbor freight and pickup a cheap no touch thermometer? Maybe get the back pressure checked in the pipe to be sure.

I have an exhaust leak and the muffler is getting a hole in back of it but the truck has been hesitating seemingly from the beginning.

Stupid warranty ran out a year before I reported the issue; thanks ford for not sending a card to let me know. Wonder why they did that....$$$$

jreiber · Posted: Fri May 16, 2008 10:21 am Post subject: Surge and stumble

I cleaned the EGR and replaced the gasket and everything runs better. I have a 97 F150 with 125,000 miles running the 4.2 v-6.

99Fordf150lariat · Posted: Tue May 20, 2008 11:22 am Post subject:

Hey thats great,
I haven't had the time to tear into the EGR to see if I can clean it and I definitely haven't had the money to waste on a new one.

Thanks for the report, it gives me hope.

Ford

99Fordf150lariat · Posted: Fri Jun 20, 2008 6:31 pm Post subject:

Posted: Fri Jun 20, 2008 9:26 pm Post subject:
Ok,
I finally pulled the EGR and all I saw was some soot; the valve will open with just a hose connected and a slight puff. Put the egr back in and left the stupid vacuum hose off and the truck ran better, no dropping rpm while holding accelerator position, also seems to have more tire spinning power.

1. Shouldnt the lack of vacuum throw some kind of code?
2. Should the EGR function with such low vacuum?
3. Is there just some low level vibration I am not feeling compared to the normal lugging while the EGR is not functioning?

I still wonder if the spring has failed on the EGR and if I shouldnt just replace it, with this test it seems that if something else was failing that it would have shown up now.

Robert

99Fordf150lariat · Posted: Mon Jun 23, 2008 3:56 am Post subject:

Ok, Drove an eighth of a tank through over saturday just enjoying the response without the bucking and with NO code thrown.

Well Monday morning driving to work BAM there is the check engine light.

Please disregard #1 in the last post

Robert