Hey... I'm hoping to get to the bottom of this problem. The prominent issue at hand is that I'm having a sluggish acceleration when driving off from a dead stop, pulling out into traffic, and so forth. The problem seems to happen more often when the engine is warmed up and when under 35mph. Once I hit 35, the acceleration picks up as it should and the truck with go. The only thing I've found to get the truck to get up and go when it's being sluggish like this is to push the accelerator to the floor. It will hesitate for a second and then jump forward and go.

Also, I've had a co-occurring intermittent problem with it losing engine power while driving. The RPM's will suddenly drop to zero, almost as if you turned the engine off. It seems to last just for a second and then picks back up when I press the accelerator and then carries on. Pressing the accelerator may not be unrelated and just a coincidence as it seems that's my "first reaction" to a stalling engine! I pulled out into traffic the other day and tried to accelerate to stay out of the way of cars... it was very slow and sluggish at responding. I pushed the accelerator to the floor to get it to "act right" and the loss of power occurred for a moment and then it went.

In attempt to fix the problem, I've changed the following out:
plugs, wires, dist cap
new cats
ACT
ECT
fuel pressure reg
new vacuum lines
IAC
new fuel filter
MAF
cleaned and recharged the K&N filter
cleaned the throttle body (it was filthy)
new ignition module
TPS (and rechecked the new TPS)
fixed a bare wire problem in the PIP wires going into the distributor (the rubber boot around the wires "ate" through the insulation of a couple of wires)

I've done a fuel pressure check after doing all this. The results were as follows:

beginning with the key off, the pressure was at 35psi
at engine idle (around 650rpm), the pressure was 30psi
rpm @ 2500, the pressure was 39-40psi
letting off the accelerator after taking it to 2500 rpm, the pressure fell to 26psi and then back to 30psi

There are two fuel tanks on this truck and the problem occurs with BOTH tanks.

any thoughts??

 

have you pulled codes? this should be done before you begin throwing parts at an unknown issue. it would also be helpful if you could tell us what rig your having this issue with and what year and motor etc..

this problem sounds spark related and since you had wire issues witht he PIP i suspect the dizzy should be replaced.

Its also odd to see the fluctuation in your fuel pressure like that.

 

I had somewhat similar issue that turned out to be because of my truck not liking a parts store TPS. A new Motorcraft one fixed mine up. I personally think that alot of the parts store sensors are often not up to par.

That fuel pressure fluctuation does seem a little odd. Does the vacuum line fit tight on the regulator? If you unplug the line, is gas present?

I wouldn't use KN especially not with MAF.

 

Oh man, i'm sorry... very sorry. I'm working on a 95 F150 with a 302, auto trans, 241k miles. I did check the codes after doing my tune up and then recently right before the fuel filter change (my last thing).

The first pull was at O'Reilly's with their scan tool and I got the following:
KOEO
111 - system pass
but then listed three more codes:
172 - heated O2 sensor fault, lean
211 - ignition pickup circuit fault
212 - loss of ignition diagnostic monitor signal/SPOUT circuit grounded

Neither of us knew what that really meant---if it means that these three codes still exist now and somehow showed up in spite of the truck "passing" the KOEO test or if it means that they used to be present and are still stored in memory.

KOER read as follows:
Cylinder 8
412 - cannot control high rpm during koer
538 - insufficient RPM during dynamic response test; invalid throttle movement during throttle movement test
536 - Brake on/off (BOO) switch not activated during self test
632 - overdrive cancel switch no action during self engine run test

I know that 536 and 632 (and probably 538) were the result of me not pressing the brake, OD switch and reving it high enough during the test at the right time (I was waiting on the guy to tell me to but he didn't till it was kinda too late).

I ran it again and got a 111 pass on both KOEO and KOER tests, using my Innova 3145 scanner.

Oh and I changed the O2 sensor out when I did the cats. The cats, O2 sensor, and tune up were the first things. I had it scanned, changed the TIF and saw some improvement in that it used to buck a lot when I had the sluggish acceleration problem. The engine would sometimes turn over and over and wouldnt start but after changing the ECT and ACT, that went away. I didnt get codes on them but since the truck had so many miles on them and they are the original OEM equipment (and b/c they arent expensive to change), I didnt see where it would hurt.

 

TexasGuy: I've read similar things before and at the same time, I've always had good luck with parts from O'Reilly's. Still, I suppose I could order a Motorcraft TPS and see if that makes a difference. Last night, I did a test on the one I put in and it had a nice smooth sweep as the throttle opened and closed.

And as far as I could tell, the line fit fine. I could buy a smaller diameter rubber hose and try it again. I haven't noticed any gas present on the vacuum line when I pulled it off the old reg. I havent taken it off the new reg to see.

 

The BWD TPS I had had more resistance than the Motorcraft one. This caused a low TPS output problem. The sweep wasnt the problem. My issue was not as bad as yours sounds though. I wouldn't run off and buy a new TPS until we know more. Maybe some others will have more advice.

 

I have a new reman distributor on the seat of the truck. I was thinking of putting it in but have hesitated on it just because if it sounded like something else, I could get my money back for the dist.

I started to put it in one day last week and couldnt get the old one out. That's when I noticed the wire issue.

 

what should the resistance be? and do you have the key on to measure the resistance? when i did mine, i had the key off and it was 2.01 ohms (maybe 2.00, 2.something in that neighborhood).

 

I checked resistance on the bench, so no power was on. I don't remember the actual values off the top of my head. What are yours are idle and wide open throttle? Was that reading at idle?

I guess I missed it. What distributor wire issue?

 

i checked the resistance only with the throttle closed (one probe to the neg term on the bat and one probe to the black wire on the tps). voltage sweep was from 0.80 to 4.80. and i did my test with the engine off.

idk if the wires had a direct link to anything but i cant imagine them being good like they were. if you notice in the first codes, there was a 211 pip code there after receiving the 111 pass code. when i ran it the second time after fixing the wires, i got just the 111 pass code.

 

have you made sure the timing is at 10*btdc with spout connector removed and engine at proper temp? that code 212 makes me think the dizzy isnt advancing the timing properly which will cause it to run like sheet.

 

I have not. I can check that this evening (if i have time) or tomorrow morning. I know that with the spout removed, it runs like crap.

Something else I've seen too that just came to mind are minute fluctuations in the voltage gauge, while the engine is idling. The needle isnt moving much at all, just tiny amounts, and seems to be "in tune" with the engine idle---which is smooth and not missing. I thought I'd mention it just in case it's relevant. The alt was changed with a new one (from OReilly's if that matters) last year.

 

Also, since I have a dist, should I go ahead and put it in? I've been holding off on it hoping that it wouldnt be it and I could get my money back. However, the one that's in there now is the stock one... 17 years old and 241,000 miles on it.

 

swap dizzy, just follow chiltons or haynes manual process.

you might stop buying parts from Oreillys, they bought out schucks and that place sucked. Napa or ford in my opinion.

 

Ok. I'll get on that this weekend. It will be my first time to change a distributor or set timing for that matter (never had a situation to call for it in the past). I have a Haynes manual and this thing called "the internet". I should be able to do it! I'll update everything when done.