Since there are many people smarter than me in the world, I thought I'd bounce a problem I've had for several years off you all. My truck is an '87 Ranger, 2.3 5-speed. For the last few years at start-up I've had to let my engine warm up for a few minutes before driving or it will die. If I start it up in the morning and back out of the driveway it will invariably die when I put it in first and try to drive off. It's acts like it doesn't have any power for a second, sometimes if I really gas it it'll pick up and not die. It's like it doesn't seem to recognize that I'm pushing the accelerator, it just dies. I've never been able to figure this problem out. Any ideas?

 

Might be a bad TPS, they wear out where they are used most.

Take a couple of minutes to pull the codes.

 

I'd clean out the throttle body

 

There haven't been any trouble codes related to this problem. I recently (this week) cleaned the throttle body, changed fuel filter, installed new plugs, rotor and distributor cap. No routine maintenance has ever solved this problem. Is the TPS the sensor near the bottom of the throttle body? Would it go bad without sending a trouble code?

 

Check for a vacuum leak. Maybe a cracked, split or disconnected hose.

 

Just saw your other post where you have pulled code 87 "fuel pump relay circuit failure"

The computer controls the ground to the fuel pump relay.

The wiring diagram shows the computer is grounded by 4 or 5 different wires. I'm not sure which off these grounds is passed thru to the relay. Maybe one of the other guys will know and you can check that ground wire for a clean tight connection.

I see in your other post that Ken sent you the pinpoint tests for the code 87. Any luck with that?

 

I think I fixed the code 87 problem. I had a wiring problem from the relay to the inertia switch, I had to run a new patch wire through part of the line. I've driven it about 20 miles or so in the last couple of days and it isn't exhibiting the frequent power loss that it had been. But this start up thing has been around a while. Once the truck warms up a little there aren't any throttle problems, but if I try to take off cold it dies everytime.

 

Interesting, i would'nt think the computer could monitor that part of the circuit. But if the 87 is gone, thats what matters.

Have you checked fuel pressure, since theres no other codes it sounds like low fuel pressure when it's cold.

When my 87 was bogging down & stalling off the line -hot or cold-it was a bad TPS, very simple to figure out since it gave me a TPS trouble code.

Edit, I would think that a bad coolant temp sensor would give you a code, but you might want to check that also.

 

I just tested the TPS with my ohmeter and I got resistance of about 1.8 Ohms on the 20k scale whith the throttle plate closed and about 4.9 with it all the way open. During movement of the plate it fluctuates but mostly increases, there was one spot where at about 1/3 open the resistance dropped, but then it continued to increase. Do these results mean the the TPS is likely ok or not?

 

One lead from your ohm meter needs to be on the center terminal, thats the signal wire. Cant remember which terminal is the ground. But try testing to both of the outer terminals. Right now your resistance is reading reversed.

Edit, after your hooked up correctly, if you still get that dropout at 1/3 throttle, replace the TPS

 

So resistance should go down as the throttle opens and not up then, correct? I'll give it a try tomorrow morning, thanks for the help.

 

Correct, thats how about 1 volt at idle becomes about 5 volts at full throttle.

I like to get my Ranger up to cruising speed ASAP, so it sees a lot of 5 volt accelerations.

Btw, even though you had your VOM connected wrong you still should'nt have gotten that dropout. So it sounds like you have found the problem.

But go ahead & hook it up correctly & see if you still get the dropout.

 

I agree with 87XLT, sounds like a dead spot in the TPS. It should have a smooth resistance reading through out it's travel, otherwise it sends mixed signals to to the computer, thus confusing it, with what you want it to have the engine do.

 

Well, I tested it correctly this time (as always I'm still learning). Resistance went down steadily while opening the throttle plate except at the first crack where it briefly goes up a bit but otherwise resistance moves down steady. So I imagine that the TPS is probably ok, but it might not hurt to replace it. I think I have a vacuum leak between the upper intake manifold and lower so I might pull the upper off and go ahead and replace the TPS. Is the part fairly inexpensive and can I pick one up at a parts store?

 

You're right, that little glitch probably isn't causing it to stall.
But if you do want to replace it i think i paid about $35.00 at Napa for mine a few years ago.

You might want to take a look at the tech info sticky at the top of the forum, i think there is a thread on testing the engine coolant temp sensor. If it's sending a bogus "engine is warm signal" it will lean out the fuel and that might be causing your cold stalling.