Hello everyone. I was driving my old 1987 2.3 5-speed Ranger to work this morning when it started acting up. I had driven about 10 miles at 70 mph and everything was running smooth. Then a car in front of me slowed down and when I took my foot off the accelerator my truck started sputtering noticeably. It did this off and on for a couple minutes then straigtened out again.

Anyone have any ideas what could cause this? The problem seems to mostly occur when the engine is warm and after I let off the pedal to slow down, that's usually when the stumbling starts. I've checked fuel pressure (it's fine) the pressure regulator and scanned for codes. The only code I get is that the system reports trouble maintaining EGR position. That is upsetting because all the EGR components are pretty new.

 

EGR system was my first thought when I read the problem began when you lifted off the acellerator & as I continued reading, it seems the computer thinks so too.

So since the problem comes about during high vacuum times, I'd begin by checking the system's vacuum line connections & the DPFE & VSV, if your early system has those EGR valve feedback & control items.

The DPFE measures the difference between the intake & exhaust manafold pressures & signals the computer when things change. The computer uses this info to decide what it wants to have the VSV to do, in controlling the EGR valve's open or closed position.

So if the DPFE', or it's signal to the computer, or the VSV's vacuum control pulses to the EGR valve are corrupt, the EGR valve will act out.

Let us know what you find.

 

Fuel filter??? Plugs

 

Had a similar problem with my 97. Replaced plugs and wires, added gas treatment, problem solved. BTW, any codes?

 

There is also now a problem at idle. The idle will alternate from perfectly smooth to very rough then smooth again. When it's idling rough there is some black smoke coming out of the tailpipe, which I assume means it's running rich?

The only trouble code is 32, specifiying that EGR position cannot be properly maintained. But this shouldn't cause a problem at idle, should it? I have checked the vacuum lines and they seem fine. Also, all the EGR components are less than a year old. But they could still be defective I guess.

 

Well there are three conditions in which our engines don't have EGR. When it's cold, at WOT (Wide Open Throttle) & when at idle.

SO, maybe you have someting else acting out, who's output is confusing the computer to the point it can't, or thinks it can't properly control the EGR valve & caused it to set the EGR code.

Seeing as how you only have one trouble code clue & the problem has now manifested itself at idle, when the EGR system is out of the suspect loop, we need to look for other suspects that'll mess with the air/fuel ratio & not set another trouble code clue.

The first one that comes to mind is the MAF sensor.
So try pulling it's electrical connector & see if things change somewhat for the better. If so pull the MAF & clean it with a non residual spray formulated for cleaning the MAF sensor & see how things go overall.

If that straightens things out, you need to look up stream & determine WHY the MAF sensor got dirty!!!!!

Look for a damaged, modified, improperly buttoned up air box, or air tube, damaged, or improperly fitting air filter, over oiled foam, or cotton gauze air filter, if your using one of those, or have otherwise modified your air intake system.

Just a thought or two for consideration in your troubleshoot. Let us know how it goes.

 

Its interesting that you mention over oil foam or oil filters can gunk up the MAF, but my K&N filter on my truck gunked up the MAF within 5,000 miles. I try to make sure it is not over oiled, and it still gunks it up. Its a good thing the stuff isn't baking on, because on my truck, the MAF costs nearly double what the Rangers and later B series use.

 

My truck has a MAP rather than MAF sensor. I had the MAP sensor tested and it checked out ok. I also checked the vacuum lines going from the manifold to the sensor and they are ok.

 

I have an 86 with 2.3 and 5speed. I have the exact same problem, same symptoms, same trouble code but it is most noticable when you turn on the AC and headlights together. When both are on the engine sputters and smokes. If one or the other is on, runs fine with no problem. I have changed the EGR valve, position sensor, map sensor and vacuum lines. problem still there. Any and all help welcomed.

 

I have a 1987 2.9 Ranger 4x4 manual and its has a simliar problem, I bought plugs, changed wires(used), cap and rotor not a bit of diffrence, i have to drive in 4th to maintain speed, this all started when i tried pulling a 1990 Jimmy 4x4 with flat tires which was sitting in the field for a couple years. its acts like its has a plug wire off, power seems to be there but its retarted somehow, where is the map sensor?

 

What about the egr solenoid.. maybe it is leaking by allowing the egr to open or not close when decelerating. the computer is not going to know if it is leaking. it uses an inductive signal to tell it when the solenoid is "closed or Open" it is the dpfe sensor's job to tell it. Just my two cents, sorry if this has been mentioned but i have a tendancy to skim over posts.

 

I plugged the hole between the intake manifold and the EGR works alot better but still isnt right, going to get a another EGR and EGR Selenoid and try the TPS again since
thats what the trouble codes said

 

I decided to take my truck to a mechanic for a diagnostic. They told me they ran it, drove it around and it didn't act up for them. They also scanned it for trouble codes and told me a throttle position sensor code came up. Could a faulty TPS cause these symptoms?

 

Well I suppose it could, if it's resistance readings were rough enough & changing enough to corrupt the feedback to the computer & confuse it about the throttles true position.

So with the key & engine OFF, disconnect the TPS electrical connector & measure it's resistance range, with a ohm meter (analog type is best) while you fully & slowly, open & close the throttle. Look for any out of range, unsmooth, jumpy/jittery spots, anywhere between wot & closed throttle position. The resistance readings should change smoothly & be steady, as you slowly open & close the throttle.

Not shure what your year/model TPS resistance range specificarion is, but my manual for 93-99 Rangers calls for higher resistance at closed throttle, 3-4 K ohms & lower resistance at WOT, around 350 ohms.

I'd also check the TPS electrical connectors pins & sockets for damage, or corrosion. If that looks ok, at KOEO check the reference voltage to ground, at the VREF pin, it should be 5.0 volts.

If you can, while your at KOEO, do a back probe operational voltage test, of the TPS, with it's electrical connector in place & the meters + probe on the TP connection & the - probe on the SIG RETURN connection. (Don't forget to change your multimeters setting from Ohms, to DC Volts)
At closed throttle, the voltage should be 0.5-1.0 volts & at WOT 4.0-5.0 volts & it should change smoothly over that range, as you slowly open & close the throttle.

If the readings are out of tolerance, or don't change smoothly, the TPS is suspect.

Let us know what you find.