Ford F-150 Guru's !! What's wrong with my Truck??

Bloodyhands

Bloodyhands

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Let me start by saying, I love my truck. Yes, it is a 94' f-150 and yes it has some miles on er, a little over 200k.
It is an extended cab 4x4 dual tank full-sized F-150 and despite some gentle leaks, the miles and a little wear and tear this has been a great truck.

The problem with my truck is that it is not breathing properly. It somewhat revs up and tries to drive forward when in gear, then revs down. It seems to drive relatively normal but does this repeatedly when stopped at light or stopped in general, then it will die and need to be shifted into park and re-started.
Wondering if anyone has any definitive suggestions.
I have replaced the fuel filters and the O2 sensors a while back and that made it a little better for a while but did not fix the problem. I do service the truck regularly.
I desperately would like my truck to run like I know it can.
Thank Ya'll in advance!!
 
Are you able to take upstream 02 sensors out an drive a little ways. Converters can partially clog an cause similar issue. The blockage can change with heat or vibration sometimes. Had this issue with a f150 2002 5.4 litre.
 
I am not. My mechanical confidence is limited with most vehicles and I do not know any mechanic that I would remotely trust in Stanly county currently. It's bad around here, and my truck need help.
 
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Check the onboard diagnostics first. That’s free and it may tell what’s wrong. You can buy a code reader at the parts store or short the contacts with a paper clip. Google how it’s done.
I had a similar issue with a 1988 Chevy s10. Used a paper clip. Got the code for fuel pressure regulator bad. $27part and problem solved.
It pays to figure out what’s wrong before spending money on parts.
 
I had a 94 F150 with the 5.0, my catalytic convertor stopped up and that would choke the engine off, ran like crap, not just at idle Took care of that and all was good. The suggestion about the code reader is a good one.
 
Before buying a code reader you need to know if it is obd1 or obd2. 94 I think is obd1 and the readers are around $20. Read the manual before using and follow the instructions or it will not work correctly. You can check the throttle position sensor with a multimeter pretty easily. I went through a lot of this with a ranger I bought in December. Idled fine but stumbled when you gave it gas. My problem turned out to be bad gas. Hopefully yours is as simple.
 
Best of luck, had somewhat similar issue on an 01 Exploder. Never could figure it out, it would stall rolling through lights. Sold it with the issue disclosed, worried me too much. Interesting, had a conversation recently with a retired mechanic. When I told him about the lights and turning and stuff he mentioned the power steering pump. It can drag the serpentine belt and stall the engine, and he mentioned fords are bad with power steering. Just one more thing to consider, pay attention to if it’s during a turn or not.
 
I'm leaning towards the IAC valve. You might get away with cleaning it....make sure and get the calibration correct if you replace some are a simple key on then off cycle then start.
 
@Mike79 I am inept when it comes to automotive problems.
I am a bit scared to do anything for fear of making the problem worse and can trust NO mechanic I have met in Stanly County.
Already paid too much for nothing twice already, and the first time they made the trucks issues worse.
2nd time, different mechanic, much better by the way and on referral from a forum member, did some stuff and charged a lot but did not fix the issue.
 
Bloodyhands said:
Let me start by saying, I love my truck. Yes, it is a 94' f-150 and yes it has some miles on er, a little over 200k.
It is an extended cab 4x4 dual tank full-sized F-150 and despite some gentle leaks, the miles and a little wear and tear this has been a great truck.

The problem with my truck is that it is not breathing properly. It somewhat revs up and tries to drive forward when in gear, then revs down. It seems to drive relatively normal but does this repeatedly when stopped at light or stopped in general, then it will die and need to be shifted into park and re-started.
Wondering if anyone has any definitive suggestions.
I have replaced the fuel filters and the O2 sensors a while back and that made it a little better for a while but did not fix the problem. I do service the truck regularly.
I desperately would like my truck to run like I know it can.
Thank Ya'll in advance!!
Click to expand...

is it a v8 or the 300 6 cylinder?

fords are bad for IACV issues, and it sounds like your having the issue.

then start looking for vac leaks. easiest way to check for those is spray some carb cleaner around the intake manifold where it bolts up to the head same with the throttle body (be careful doing this and keep a fire extinguisher close by just to be safe) and see if anything changes
 
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Just a quick note, if you use carb cleaner, make sure it’s a type that is flammable. There are nonflammable versions now, yay for safety 🙄. I use starting fluid for stuff like this and just spray in half sec bursts around the intake and all vacuum lines. When you hear the idle change, concentrate on that area, look for a cracked hose or other damage, may hear a hissing sound as well.
 
The on board diagnostics on those are pretty awful, a good manual will provide ohms and/or voltages for the various sensors. Sounds like a vacuum issue, hoses, manifold gaskets, brake booster, and somewhat notorious on those EGR valve. IAC and MAP/MAF could also cause those symptoms but wouldn't be my first suspects.
 
This method saved me big money over the years. Primitive but easy to use vs the modern OBD-2.



obd1.jpgobd1a.jpg
 
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Similar problem with my '99 Taurus, OBD-2, the IAC motor was failing, RPM would hit 2,500 when I put car in neutral or park at drive up windows or ATM,
had to turn car off then restart so I would not slam the transmission at that RPM. Did not get any codes at the time. Another part that will not throw codes is the speed sensor on the transmission, delayed upshifts with high RPM and then slam into second gear. Only once did I get a code for that part, changed over six of them in two cars over 20 years and still drive them. Newer models use the ABS wheel speed sensors now.
 
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Take a look at the multicolored vacuum lines that run all over the engine, the nylon lines will crack over time, easy to replace then with rubber lines.
 
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