Any ideas for what's causing extreme acceleration problem in our 1986 ranger? The truck has a great deal of trouble reaching freeway speeds. Even a slight amount of pressure on gas pedal leads to severe bucking, near stalling, and loss of power. Only the lightest feather touch on gas pedal will allow truck to get up to freeway speeds.Sometimes at cruising speed, gas power suddenly is lost and rpms drop off and truck barely recovers.Local good mechanic with no time to see it said it might be acceleration sensor, but sometimes the problem happens at cruise speed while maintianing steady foot pressure. (The main issue is the one of getting up to speed.)...Truck specs:1986 Ranger King Cab Fuel Injection 2.9 liter V6, 5 speed manual transmission... Cruise Control manually disconnected 10 years ago...thanks for any help

 

Is there any smell? Kinda sounds like the cat is plugged.

 

had same issue w/ my 86 2.9l. new throttle position sensor cleared mine up.

 

Does that engine have a MAF sensor-had that problem on my '99-could barely touch the pedal without it choking itself out..dealer replaced MAF, never had that problem again(fingers crossed, LOL), with 80,000 plus on the MAF........

 

You guys are great! Thanks a lot. 2B specific: It sure FEELS like it has a lean-out problem, not a choking problem. No black smoke, for example. Had big choking problem some years back, discovered fuel pressure regulator was way over-pressurizing the fuel feed, replaced it, all was well. Don't know if our vehicle has a MAF sensor...will check.
I would like to replace the throttle position sensor; my Hayne's book gives instructions in the fuel and exhaust systems chapter; you just have to be careful to "align the scribe marks". However, over in the Emissions control systems chapter, it sez, " Don't attempt to replace the TP sensor! Specialized calibration equipment necessary! You'll be so, so, sorry! (my addition)." I hope the special calibration equipment in real life isn't just a scribe punch.
Unfortunately, I need the misbehaving entity for a freeway traveling job that's just come up; and galfriend needs it too, for street level use since the uninsured motorist drove into her car and totaled it. Do I sound like a country song yet?
Once again, thanks, folks: much appreciated. Will gladly accept any more advice.

 

You need to take a couple of minutes to pull the codes.

When my 87 2.9 was pinging & stalling off the line in 1st gear I got a code 53 "TPS signal voltage is too high"

Pulled the connector & checked output voltage & OUCH the TPS was telling the PCM that my foot was on the floor (5 volts when it should have been reading about 2 volts) . No wonder it was pinging & stalling.

Your 86 & my 87 are not equipped with a check engine light, so the only way to know if theres any trouble codes is to hook up your scanner & pull them.

Your 86 has a MAP sensor.

If the MAP is causing your bogging down, you'll get trouble code 22/MAP signal voltage out of spec...

 

codes are hard to pull in a 86-89 SO: under the hood on the passenger side there ought to be a connector near the firewall for OBD. chilton has a good picture. take out the single loose connector and ground it to the battery with the key off. turn key on and look at check engine light for blinks. count number, write result down. Some are spaced a couple of seconds apart; those are different numbers.

there is a list of codes somewhere on this site. have fun. my boy's runs rich until it is warm, no codes, so far replaced everything except pcm. we just let it warm before driving and hope for summer.

BTW MAPS are frequency 96-102 HZ at idle.

 

1986 Ranger 2.9L V6 EFI 5spd. Manual w/ gasp/buck/power drop problem: Searched intensely for my code scanner. Bought another one. Ran tests. (KOEO) Key On/Engine Off/: Got codes #22 & #67…
Fault #22: “MAP or BARO sensor out of range”. Is this a fault diagnosis or testing snafu?… Fault #67: A/C compressor clutch switch fault. Big whoop. A/C went to its maker long ago.
Continuous Memory test result: Fault #63: Throttle Position circuit fault, below minimum voltage. I did an engine running voltage test of TP sensor before I bought the new code reader.
Red wire (Battery voltage?): 4.97 volts
Center wire: 0.02 volts
Top wire: At idle speed: 0.94 volts
At 2200 RPM in neutral: 1.30 volts
At Kick throttle wide open momentarily: Rises up to 4.0 - 5.0 volts at max rev.
I may have middle and top wire readings swapped: am remembering from hours ago.
Replaced MAP sensor some years ago. Still looks clean. Question if MAP sensor fault reading is old memory in computer from previous code scanner reading.
Vehicle gas tank frequently run near empty, especially when CA gas prices were $4.69
A few months ago. Metal appearing fuel filter in frame rail below Brake Master Cylinder
Was replaced between Jan. and May 2007.
Thanks folks for any advice to this wordy post.

 

Hey Fellers, thanks again. I hope all this behavior is not from crud in the tank clogging the in-tank fuel pump, or the inline fuel filter in the area somewhat under the master cylinder. I don't relish trying to bypass the fuel filter to test its quality; nor fooling with the gas tank. My friend in San Francisco has offered to let me use his fuel pressure tester at his warehouse (in-house use only), but I don't think it's safe to take it across the SF/Oakland Bay Bridge. Besides this isn't a problem with truck in neutral; most apparent on incline, accelerating. Gotta do freeway run today regardless, even if it becomes a story about a regettable day. You folks have a great one.

 

your map sensor should be on the passenger side fender with a vacuum line coming off the throttle body over to it (should be a black line) and have an electrical connection. the sensor will be black and about 2x3 inches and 1/2 inch thick, if i remember right. i don't know how to test if it is good or not but its not hard to replace. and just for reference it measures Manifold Absolute Pressure (MAP). The vehicle computer calculates how much fuel to deliver to the engine based on the amount of load being applied to the engine. The computer uses manifold pressure, barometric pressure, engine RPM and throttle angle to determine engine load. Fuel ratio and spark timing are then fine tuned by the computer using additional sensors, this also helps to control fuel economy and emissions.

 

Your truck does not have a MAF sensor.
Throttle position sensor will cause the problem you are having, so will a clogged fuel filter, or weak fuel pump.

The "specialized calibration equipment" you need for the tps is a common voltmeter.jd

 

Thanks, jimdandy and frankenbronco II. I checked out Air filter/throttle body passageways from grill to engine and pretty much determined truck had no MAF sensor. I had replaced MAP sensor years ago, replaced it again yesterday (albeit w/ a clean used replacement, 1 of 2 obtained) with no change in problem. It looks to me that it would be very difficult/hazardous to bypass the frame-mounted fuel filter with a flexible hose fuel line bypass shunt, for a bypass test. Don't know if it's possible to do a fuel pressure test at the fuel rail schrader valve while the truck is doing a uphill driving test run. I say this, because I'm very sure fuel delivery problems won't show up in a static test.
Went 82 miles miles round trip on the freeway yesterday for the very necessary job, and it was sheer, unadulterated hell. Dangerous, too. I enjoyed practicing my patience and my cool.
It couldn't get into 5th gear and maintain speed on return trip; would cruise along in 4th gear at 45 to 60 MPH and then just totally lose power (engine stayed running); I'd pull over, drive along in 1st gear for a few seconds, or sit 5 seconds, or shut down engine for 5 seconds, and then immediately return into diverging traffic to hopefully get back up to 3rd or 4th gear.
Wish it was the time when my uncle Jimmy ran our church's junkyard: we'd just chuck this truck and get another. Will replace TPS today (hopefully) though I'm dubious of results. After I register for our community college's world economic meltdown course.
What do you fellers think about the fuel system test ideas? Would a wesk fuel pump which only shows up at freeway acceleration or high cruise be detectable? Is main fuel pump on frame possibly primary suspect? Or secondary in-tank fuel pump? can debris clog in-tank fuel pump, or not?
This is fun from a very long distanced viewpoint. This truck is NOT going for the 17% grade up Sonora Pass today! Yeehaw!

 

you are describing classic fuel starvation caused by:

fuel line leak and air entrapment
clogged fuel filter
crummy low performance fuel pump
crud in the intank filter.
poor seals at pipe changes
screwed up vent in the fuel cap (oldie)

non fuel leaks:
any vacuum hose connected to the engine

a good jack in the front ought to get you to 25 degrees nose up
look at all the non metal flex lines and see if they have any rubber flaking off. if they do, replace them with new 3/8 oil and gas pressure hose and new hose clamps
blow air back into the tank, I think it is the line that is near the driver's door Take off the fuel cap first.

take valve out of shrader valve on fuel rail , buy a barb fitting and water pressure gauge, couple of feet 3/8 hose hose clamps and hook all this up to check fuel pressure. keep the gauge OUT of the cab, but run it where you can see it while driving. CHECK FOR LEAKS!! fuel fires suck.

I once had a drudge van that only had problems going up this one hill. turned out I had a pinhole air leak at the fuel tank rubber hose.

spray lots of WD40 on all the connections one by one. if you get an engine rpm change, there is your leak

 

Fuel filter maybe! If injected fuel.... injectors clogged! If sensor.. throttle sensor! Like 1 2 3... then it becomes electrical! Second thought would include your lifters are stuttering and causing combustion issues.

 

I would suggest changing the fuel filter on the frame rail. It's kind of a PITA but not that difficult. Run some fuel system/injector cleaner through it like seafoam and see if you don't get better response.

I have changed TPS with no problems before. Just line it up with the throttle body and screw it on. Between the filter and TPS you should get back in the swing.

Of course check those hoses for leaks too, however that would usually lead to a loping or high idle with much of a leak.

Good luck

Rich