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86 2.9L "Skips" Upon Acceleration


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Location
Columbus, GA
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9L V6
Transmission
Automatic
Ever since I bought my baby Rusty back in September 2013, I've done everything I can to improve it both cosmetically and mechanically. I've completely redone the interior, I did the K&N air filter swap found in the Tech Articles under "Engine Tech", I've tried my best to keep it up on oil changes and keep all the fluids topped off, and I try to keep it clean as best I can. But it has one problem that no matter what I've tried, I simply cannot seem to shake.

Especially when I first start it up on any given day, regardless of the temperature and how long I allow the motor to warm up, the engine "bogs down" for about a half second when I press the accelerator pedal, then begins to accelerate like normal. I do not have the slightest clue as to what could be causing this problem. My old 2.9 runs about as well as I'd expect a 30 year old engine to run. Here are the only things I know:

-Engine has brand new plugs, wires, and air filter.

-It has a slight oil leak out the driver side valve cover gasket, I have a new set but I've just not gotten around to putting it on.

-My fuel pump shutoff switch or "inertia switch" is somewhat overly sensitive, for example I once slammed on the brakes while pulling a prank on my friend and the truck came to an immediate stop and triggered the switch. However I'm told that this was a common problem on early Rangers.

-Sometimes my fuel pump is a little quieter than normal when I first cut the key on, but other than the skip the truck runs and drives just fine without any issues.

-Zero to 60 is around 10-15 seconds, I've never ACTUALLY timed it but I tried it once just for fun on a straight stretch of road out in the county, I'm not sure what the "norm" is for a 2.9L automatic Ranger, but that just seems a tad slow to me.

-I usually start off driving in D, then shift into OD at about 45 or when I get up to highway speeds. I've been told that driving in OD all the time will mess things up.

-I don't "race" my truck, I've only shown off in it once or twice in the parking lot around my school shop, and the skip existed long before I tried anything funny with it.

The only thing I can possibly think of is perhaps the fuel pump is not as strong as it should be, but I don't want to rule anything else out. Has anyone else ever had or seen this problem, and if so what did you do to get rid of it? I'm going to school to be a Ford tech so I know a wee bit about engine performance, but at this level I'd probably rank myself as "Glorified Part Swapper" lol. Any help is much appreciated!!!
 


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Location
Columbus, GA
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9L V6
Transmission
Automatic

fyre82

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Location
Lake Almanor, Ca.
Vehicle Year
1988/2000
Make / Model
Ford
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2.9/4.0
2WD / 4WD
4WD
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9" on the 2000, 6" on the '88
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265/75/16, 31x10.50x15
My credo
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A suggestion would be to check all of your grounds and connections to be sure they are there and do what they are supposed to do.
Fuel filter change may be in order if with a full tune if you haven't.

Good Luck
Rich
 
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Transmission
Automatic
Okay, I pulled the codes, and I got one for the Throttle Position Sensor, the EGR Pressure Feedback Sensor, and something along the lines of the fuel pump. As luck would have it, my in-line fuel pump went out today, and tomorrow I will be replacing all three parts. I tested the TPS to see if the resistance varied while opening and closing the throttle as it should, and I got no variance in the resistance no matter where it was - I might as well have not had one on there. Also the EGR Pressure Feedback Switch didn't change when vacuum pressure was applied, plus I didn't know how it came out and thus broke it while removing it :icon_rofl:

Also found a plastic vacuum line (the green one) cracked in two, so I fixed that with a small piece of siphon hose. The previous owner of the truck told me that he had gone through and fixed a lot of stuff. I've yet to find any evidence of such activity. :annoyed:
 

Hitchner2009

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1987
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4.0
Transmission
Manual
i have learned when someone you purchase the vehicle from tells you that they have done something. Immediately go in and check it when you are able, chances are they didnt know what the hell they were doing. Better safe then sorry as i always say. Once you fix that TPS and Fuel Pump you should be good to go.

Also, for the valve covers when you get to them. Check and see if your valve covers have the shims that go under the valve cover bolts themselves. If not go to the dealership and get some, there cheap and they help with prevention of future valve cover leaks. Good Luck!
 
Joined
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Messages
85
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Location
Columbus, GA
Vehicle Year
1986
Make / Model
Ford
Engine Size
2.9L V6
Transmission
Automatic
i have learned when someone you purchase the vehicle from tells you that they have done something. Immediately go in and check it when you are able, chances are they didnt know what the hell they were doing. Better safe then sorry as i always say. Once you fix that TPS and Fuel Pump you should be good to go.

Also, for the valve covers when you get to them. Check and see if your valve covers have the shims that go under the valve cover bolts themselves. If not go to the dealership and get some, there cheap and they help with prevention of future valve cover leaks. Good Luck!
I was pretty skeptical at first, but everything seemed legit when I looked it over. I ended up having to replace my in-line fuel pump; it stopped working anytime it got hot and resulted in loss of fuel pressure. I hate having the old OBD I because now my truck is having to "relearn" how to run properly now that everything, to my knowledge, is the way it should be. Sometimes if I've been driving for a while and stop for a bit, like to get gas or something, and I start back down the road, the truck will choke out when I give it gas and I keep having to restart it over and over until finally it works again. I just can't seem to keep this thing going and I don't have the money to keep throwing parts at it, while at the same time I don't really have a choice.
 

Hitchner2009

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Ford
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Transmission
Manual
Have you changed out the Fuel Filter lately? You also have an In-Tank Pump as well, probably wouldn't hurt to replace that either. Sounds like your gummed up somewhere and fuel isnt getting to where it should. You can verify this by doing a simple fuel pressure test at the shrader valve on the fuel rail. Passenger side of the engine at the valley of the upper intake manifold.
 

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