Need some help

[uscdiver]

Hello all,

I am having a problem. My Bronco is running great/normal, except when I am lightly touching the gas pedal. The problem is intermittent, but it tends to lag and oscilate 100-200 rpms when I am just cruising and not applying much gas. It seems to get worse when going up a slope. If I step on the gas harder, it rev's right up with no problem. Any suggestions? I am thinking fuel delivery, but don't know where to start. I have replaced recently - fuel filter, plugs, wires, and distributor cap and rotor.

Thanks!!!!! Diver

 

[89Bronco58]

is your check engine light coming on?

 

[kgriffi1]

So many things to check, could be lots of things. From what I've read so far, take the distributor cap off and make sure there is no slop in the distributor. At high rpm's it will be running fine, but at idol it could be flopping around and shorting so that you idol rough. That would also explain the intermittent part. It only does it when it gets out of balance and starts flopping around. That's one possibility. Good Luck

 

[89Bronco58]

where is the timing set as of right now?

 

[uscdiver]

KG,

Thanks for the advice. I'll check it out. When I changed the cap and rotor, I bought them at the Ford dealership, and the cap fit very tight (no slop). The last cap I bought at a Pep Boys or some store like that, was real sloppy, and did not fit snug at all. I will check the rotor, though.

Also, I am not getting a check engine light, and the timing is set dead on at 10 deg. BTDC (as spec'd in the book and under the hood).

Thanks for all the help everyone, and please chime in if anyone else has any ideas.

Diver

 

[miesk5]

I'm guessing...do you think it could be the torque converter engaging/dis-engag.?

Guessing it could be bec. of what you wrote..." If I step on the gas harder, it rev's right up with no problem"

you have a 94 with E4OD? Check fluid level and condition..

Also; even though you do not have a Check Engine Light (CEL) on... Guessing again.. my 96 did not show a CEL even though it was running on 7 cylinder due to corroded FI socket.. then when I went to check out why the CEL did not light up or could not find a DTC with my Code reader (OBD II), I found the cigar lighter fuse blew - it also powers the CEL and diagnostic terminal.

So, when first starting it, does the CEL turn on for a second? If it does not Light up, then check fuse. in my 96 it is #16

From the Owner's Guide.

"The light comes on briefly when you turn the ignition key to ON, but it should turn off when the engine starts. If the light does not come on when you turn the ignition to ON....

If this is the case, then look at the Throttle Position Sensor (TPS) because... of what Xris and other hav wrote...

Xris.."..A number of months ago I discovered that my 86 Ford Full-size would hesitate/buck after about 10-15 minutes when the engine was at operating temperature. It would idle smooth and run fine until it hit 2000-2500 rpms...cruising speed..."

sixlitre (a good pal) "After she's warmed up she's sluggish at all stages of part throttle, like there's not enough gas getting to it, but goes gangbusters at wide open throttle..."

Throttle Position Sensor(TPS) Function & Diagnosis TSB 94-26-4 by Ford for 93-95 Source: by miesk5 (Al M)) at comcast.net

TROUBLESHOOTING THE TPS

The following is a list of vehicle symptoms which have been associated with the TPS, but can also be related to other vehicle components.

Check engine light

Stalls/quits

Hesitation/stumble

Fast idle

-----

Vacuum...

"Almost every vacuum line break I've encountered is where each of the vacuum tree ******* terminate. Most commonly behind the upper intake where the 4 way thermactor valve is or at any of the stops along the way from the air pump back.

A spray can of quick start sprayed at the lines, while the motor runs will usually expose the leak by the idle jumping up with the alcohol."

by Sixlitre

--

Engine Vacuum LeaksBy Larry Carley

__________________

Many other checks here...

And some "NO-CODE" Trouble Shooting by Ryan M

&~ his TPS Article, but I would Not mess with EEC

 

[uscdiver]

Miesk5,

Thanks for all the great info! I really appreciate it. This stuff will definitely give me a few things to check out and cross off the list.

Thanks!!!! Diver

 

[uscdiver]

Hello all,

First, Thanks to all for the help and advice. I learned a lesson last night. I had ignored the TPS sensor as the culprit because I had replaced it in the last year, but it turns out that it was the problem. I went to the local Ford dealership and bought a TPS sensor . . . you know, the kind that is actually made for my truck. It cost $95, and was money well spent. My truck is running better than it ever has!!! The TPS sensor that I bought at a parts store for $35 (Pep Boys, or Kragen, I don't remember) simply was not functioning properly. I had a similar experience with a Dist. Cap that did not fit well, and the one from Ford was perfect.

Bottom line, I will purchase most of my parts from Ford from now on. It is worth the extra $$ to get the correct part that fits properly, and is designed for my truck.

Thanks and I am Stoked!

Diver