Annoying throttle / fuel problem
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Freshman User
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From: The Catskills, NYS
Annoying throttle / fuel problem
Hello everyone,
I now have my '86 F150 XLT in New York State, having lived its entire life in Fort Worth, TX. Quite a change for the old boy.
As in Texas, it has a niggling throttle / fuel issue that I need help on.
When cruising at any speed, if I back off the throttle slightly, or even if I go on the throttle slightly, it dies momentarily. It could be as long as a second. It recovers when I press the throttle forward, or if I back off completely.
I have a new rail fuel pump (it died on arrival in NY - didn't like the sight of snow I guess) and new gas caps (I thought the old ones might be blocked, causing a partial vacuum). The problem occurs on either tank, at any speed.
Any thoughts from the engine gurus most welcome.
THanks.
I now have my '86 F150 XLT in New York State, having lived its entire life in Fort Worth, TX. Quite a change for the old boy.
As in Texas, it has a niggling throttle / fuel issue that I need help on.
When cruising at any speed, if I back off the throttle slightly, or even if I go on the throttle slightly, it dies momentarily. It could be as long as a second. It recovers when I press the throttle forward, or if I back off completely.
I have a new rail fuel pump (it died on arrival in NY - didn't like the sight of snow I guess) and new gas caps (I thought the old ones might be blocked, causing a partial vacuum). The problem occurs on either tank, at any speed.
Any thoughts from the engine gurus most welcome.
THanks.
FTE Legend
Joined: Sep 2003
Posts: 53,990
Likes: 2,398
From: NY and VA
Fuel filter? TPS (throttle position sensor), Idle air control valve. Have you tried to check the codes?
Where in NY ?(I'm N of Ithaca). Check with Neil about joining the NY Chapter if so desired.
Where in NY ?(I'm N of Ithaca). Check with Neil about joining the NY Chapter if so desired.
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Freshman User
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From: The Catskills, NYS
Thank you for these suggestions. I had a new rear tank installed when I bought the truck, and reading various other threads, I think I have to check the fuel filter, and also possibly install pre-filters, since a lot of gunk seems to come out of these old tanks and / or when any work is done on the lines. I have suspected the TPS from the beginning, but I have no idea how to deal with it. It's homework time for me, I guess! When I was having the inspection done, the guy in my local garage told me that it wasn't possible to check codes on a truck this old, otherwise he would do it for me. More homework for me!
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From: Denver Metro Area, CO
Fuel Injection Technical Library » How To Run a Self-Test
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Freshman User
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From: The Catskills, NYS
Hmm. I think he was neither. I think he didn't know, and was bluffing his way out, since I had specifically asked him to check and diagnose the problem for me, alongside the inspection. It's hard to get good help these days...
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From: Denver Metro Area, CO
I only use the count-the-blinkenlights method and am not sure I can trust the aftermarket code readers. The order of the codes appearing is important but it's been suggested that some code readers may rearrange and sort the codes, that could be misleading.
There are three distinct sets of codes you need to pull, and the engine should be at normal operating temperature at the time:
KOEO
CM
KOER
I also edited my initial post and added some commas, I was actually trying to list out three (not two) possible reasons why that guy told you what he did.
There are three distinct sets of codes you need to pull, and the engine should be at normal operating temperature at the time:
KOEO
CM
KOER
I also edited my initial post and added some commas, I was actually trying to list out three (not two) possible reasons why that guy told you what he did.
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FTE Legend
Joined: Sep 2003
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From: NY and VA
Some places can only check codes , "they say" for 96 and up with the OBD II plug ins. Flashing light isn't too bad a way of checking. Son bought a wally world scanner once - save your money. Since then we've got a better - of course more expensive one that is also OBD II compatible. Have to check and see what it is, son's use it, not me.
Edit:
Found out son's scanner is an OTC Genisys model. They also make a Nemisys model
Edit:
Found out son's scanner is an OTC Genisys model. They also make a Nemisys model
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From: The Catskills, NYS
Quick Post Script, which is unrelated to my original question. I notice a post about extra weight in the winter and it reminded me that my truck did something last weekend that it has never done in its life. It did a lovely (controlled) fishtail in the snow as I left my drive.
Quite unexpected, I might add. I kept my foot to the floor (this is no Mustang) and corrected the slide. I drove on with a big smile on my face, knowing that somewhere in its internals my big ol' Texas truck was going WTF just happened to me?
Quite unexpected, I might add. I kept my foot to the floor (this is no Mustang) and corrected the slide. I drove on with a big smile on my face, knowing that somewhere in its internals my big ol' Texas truck was going WTF just happened to me?
Senior User
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From: Windsor Ontario Canada
Possible causes as described in 1986 Volume H Ford Diagnostics Manual
1.EGR valve Malfunction
2.BVT Malfunction
3.EGR Flange leak
4.EGR, VCV, TVS Malfunction
5.Blocked or restricted EGR passage in valve or spacer.
6.Load Control (WOT)Valve malfunction
7.Vacuum leak at EVP sensor
8.Curb Idle speed too high or too low
9.Ignition timing too low
10.Check for PIP circuit Fault
1.EGR valve Malfunction
2.BVT Malfunction
3.EGR Flange leak
4.EGR, VCV, TVS Malfunction
5.Blocked or restricted EGR passage in valve or spacer.
6.Load Control (WOT)Valve malfunction
7.Vacuum leak at EVP sensor
8.Curb Idle speed too high or too low
9.Ignition timing too low
10.Check for PIP circuit Fault
Last edited by dort; Mar 9, 2013 at 02:42 PM. Reason: typo
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From: The Catskills, NYS
Thanks for your input. I posted the results of my test under a different heading, see below.
I got one of those clever little code readers and pulled the codes, as advised by GLR & CTUBUTIS.
And as everyone knows, it's not so much what the test results are, it's how to interpret those results.
The error codes I got were:
KOEO: 63
C: 63
KOER: 23
All pointing to Throttle Position Sensor. I have one on order, so I assume the fix is a simple replacement of the TPS. Another poster said he carried one around as a spare, so I presume this isn't a difficult job.
I got one of those clever little code readers and pulled the codes, as advised by GLR & CTUBUTIS.
And as everyone knows, it's not so much what the test results are, it's how to interpret those results.
The error codes I got were:
KOEO: 63
C: 63
KOER: 23
All pointing to Throttle Position Sensor. I have one on order, so I assume the fix is a simple replacement of the TPS. Another poster said he carried one around as a spare, so I presume this isn't a difficult job.
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From: Windsor Ontario Canada
the repair can be simple however just remember to mark the current position of the tps and be careful not to damage the screws if they've never been disturbed, if you would like more detail on how to properly calibrate your new sensor i'll be happy to print it all out for you .good luck
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From: The Catskills, NYS
That is very kind of you - thank you! I read elsewhere about the weakness of the screws, with the suggestion that they be replaced with hex bolts. If you happen to know the size of replacement bolts, that would be helpful. Otherwise, I will just take it very carefully.
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