Help please new truck runs bad

[welderman85]

Hello all. I just bought my old 1995 back and the previous owner was not very much of a mechanic. It will start and sometimes it will idle. It surges and runs it like a vacuum leak but I can't find anything. It has the EGR removed and there's a block off plate in it's place. It also seems low on power. Sometimes it will smooth out and idle around 1000 rpm but as soon as you hit the gas it has a slight hesitation then revs but then drops way down and almost stalls. I'm kinda lost and don't know where to start. Thanks

 

[Denisefwd93]

Welcome aboard! you did not say what engine and transmission you have.

I had a 93 4.0 long bed I now have a 94 supercab manual 4.0.

Of course you're going to check all your vacuum lines? if you have them, the idle air control, throttle position sensor, and the map sensor that's inside the air intake.
Just bringing up these issues because they're very very common problems

Hello all. I just bought my old 1995 back and the previous owner was not very much of a mechanic. It will start and sometimes it will idle. It surges and runs it like a vacuum leak but I can't find anything. It has the EGR removed and there's a block off plate in it's place. It also seems low on power. Sometimes it will smooth out and idle around 1000 rpm but as soon as you hit the gas it has a slight hesitation then revs but then drops way down and almost stalls. I'm kinda lost and don't know where to start. Thanks

 

[welderman85]

It's a 95 reg cab long box 4.0 5 speed. How do I go about testing those senors

 

[RonD]

4.0l EATS spark plugs
Pull them and clean them then regap, .054, or replace them

Make sure spark plug wires are correct on the coil pack
3 4
2 6
1 5
front

the 5 6 4 side gets me every time

Clean MAF sensor, easy to do, should be done once a year on the 4.0l, but doesn't hurt to do it on ANY engine.

THEN and only then can you move on to possible sensor or electronic control issues

And if Check engine light(CEL) is not on then its a long shot on a sensor issue

 

[welderman85]

I did a new set of plugs as soon as I got it home. And no check engine light.it has me stumped. I wish I would have never sold this truck in the first place. I had it for a long time .and took great care of it. This guy was a hack. Could the EGR delete cause these problems. Is there a good vacuum line diagram I could check out anywhere. Thank you

 

[Denisefwd93]

Tons of info here, http://www.therangerstation.com/how-to/

My 93 and 94 4.0 engines do not have EGR there is not even a place for them.

 

[welderman85]

Thank you Ok I'm an idiot I had two of the wires crossed so now it idles better. Still wants to die after you give it gas it will review then drop to almost stalling and bounce to 1000 or so then try to die again the levels out at idle. I was thinking maybe TPS

 

[RonD]

Maybe but probably not TPS, that's not a direct control, it just "informs" computer of what driver wants to do.
When you step on the gas pedal computer gets the "heads up" to inject more fuel before it would see MAF air flow increase.
But you would get a code if MAF sensor and TPS were not in sync.
Computer "knows" it is running a 4 LITER engine, so it knows how much air should be coming in at any given RPM and at 1/4 throttle, 1/2 throttle or WOT(wide open)
MAFs main job is to WEIGH the in coming air, that varies quite a bit, but there is a range that TPS and MAF have/share
Clean the MAF for sure

IAC Valve is more likely candidate for your symptom, stalling
Remove IAC Valve and then plug in its wires
Turn on the key, engine off
IAC Valve should be open all the way with key on, engine off
Unplug its wires and it should close all the way
Repeat this plugin/unplug as much as needed to make sure IAC Valve is not sticking.
These do get dirty so "plunger" doesn't move smoothly, so computer has to change voltage to get desired idle RPM and that cause up and down RPMs if IAC sticks

Good article here with pictures: http://www.explorerforum.com/forums/index.php?threads/iac-valve-cleaning-thread-w-pics.84220/

TPS is easy to test with Volt Meter and a sewing needle