Weird EEC problem.

[It's not old it's classic]

EEC-IV Problem

My “89 Ford Ranger” (2wd-4cyl-2.3 liter-manual transmission) runs fine under most driving situations. It does however have an occasional engine issue that I am unable to troubleshoot myself. Through some experimentation, I have noted some symptoms, triggers, and manifestations that I think may help someone reading this to pin-point the vehicles problem. I will try to describe the problem as accurately as possible.

WHAT TRIGGERS IT-
The problem is triggered when I am driving, and I have to make a heavy acceleration (basically when I floor it). Flooring it seems to be the ONLY way to trigger it. If I accelerate normally, then the problem doesn’t happen.

ONCE THE PROBLEM STARTS-
Once I have pushed the gas petal past this “threshold”, the engine begins to run erratically. Any time I take my foot off the gas, (or even simply back off of the gas) the vehicle shakes for about two seconds. (like a misfire shaking). Then the shaking stops, and the engine seems to run smoothly again. Then I may get 4-5 seconds of normal operation (sometime more sometime less) Then it will do the shaking thing again. But it will only do this if I am actively giving it gas. If I take my foot off the gas completely, it will do the two seconds of shaking and then will slowly drop to a normal idle as I slow to a stop. But if I start to give it gas again…. back to the shaking! It will continue to do this until I pull over, turn off the key, and then re-start the engine. It will not clear up no matter how far I drive, or hold long I drive until I do a key off and back on.

SOME OTHER OBSERVATIONS-
This has been happening for quiet some time, so I have taken note of some other particulars. Such as;
A) Once the problem starts, the engine idles noticeable higher when the clutch is engaged, through all gears, and driving speeds (basically when I push the clutch to shift, the engine idle doesn’t want to drop even though I am no longer giving gas as I shift to the next gear) It acctually rises considerable during a shift.

B) After I pull over turn the engine off (Which ALWAYS solves the problem) and back on again, the engine idles noticeably lower. So low in fact that it will sometime stall at the next stop I come too. The low idle seems to come back up to a normal idle after a few miles.

C) I can trigger this weird issue at any time simply by flooring the gas pedal for a few seconds..

WHAT I HAVE TRIED TO SOLVE IT-
My first thought was “Throttle position sensor” must be bad. But I have replaced it TWICE only to have the problem persist.

I run code checks all the time on the EEC, and it reports everything is fine. (Of course everything is NOT fine).

I think the problem MUST be in one of the EEC-IV sensors or actuators since turning off the engine “resets” the problem.

Any help, advice or suggestions would be greatly appreciated.

 

[DJ2.3]

Does it do this at any rpm? Does it do this only after it is warm? Have you changed plugs and wires recently? Another area to check is the fuel system. Is the fuel pressure within spec and is the fuel filter ok? that is just a few thoughts i had. It could be the eec itself but i would check over everything else first.

 

[Earl43P]

Welcome to The Ranger Station!

I like your problem!
A couple things happen when you floor the gas pedal:

TPS triggers the PCM to go into Open Loop (PCM then uses canned values rather than sensor feedback).

Wide Open Throttle relay energizes (this cuts power to the air conditioner compressor clutch coil).

In your situation, the first thing I'd rule out is that WOT relay (just remove it). I'd tell you its location, but I don't have a good reference for your year. I do know that one of its leads will be a Red Wire fed from the PCM relay and one other wire will be the same color as one of the two wires to your compressor clutch coil connector. Those MIGHT be DG/O and BK/Y at the relay and the fourth wire may be the relay coil ground from the PCM (Pin 54) and might be PK/Y.

If you don't have AC, I'm not sure what to tell you.

 

[It's not old it's classic]

To DJ2.3 – Yes any rpm, cold or warm. Plugs have about 7-10k on them. Wires, less than 50k. I checked fuel pressure a few years back, and inspected one injector. Pressure was in the 40s (which I believe is normal. And injector looked surprisingly clean. I changed the huge “lifetime” fuel filter at that time as well. I will check the pressure at the fuel rail again.

To Earl43p – My AC system developed a nasty leak 10+ years ago, and rather than attempting a repair, I simply didn’t use it. I will add that I took the belt off to the compressor about a year ago, thinking that it might help improve gas mileage?? Not sure if either matters in regards to the WOT relay, however seemed worth noting. So to answer your question, I have AC, but it does not function. I am sure that I can locate the WOT relay using the wiring diagrams from my repair manual. I will remove the relay and see what happens. I have the skills to test the relay as well if you think the results may be helpful to a diagnosis.

Thank you gentlemen for the speedy reply's. I appreciate your help.

 

[DJ2.3]

I have seen dirty or worn out Mass air sensors cause similar issues and not throw a code. Most sensors will set off the cel when they are at or very near 0v or 5v (open or short), but simply an inaccurate reading from the MAF can cause the eec to be quite confused. I have seen a vehicle cut out at wot due to a maf sensor issue, yet never throw a code because the eec has a several second delay between the time the sensor voltage is out of range and when it turns the cel on.

 

[It's not old it's classic]

I too had heard that the Mass Air sensors can cause similar symptoms. I believe my year Ranger only has the MAP sensor, and doesn't use a MAF one. I do know that it is the original factory MAP, and I've considered replacing it because of such. I just hate replacing parts blindly because at the age/mileage of my Ranger, every mile is a miracle mile Lol. I may just cough up the $40 bucks for a new one since DJ2.3 has voiced similar concerns regarding MA sensors affects. As an update to the WOT relay, I did a little poking around last night, and I believe I have located the WOT relay inside the left fender between the Battery and the Starter Solenoid. I still have doubts as to whether I am correct or not, so I am going to engage in a little web reserch today and verify it's identity before I start tinkering with the device.

 

[It's not old it's classic]

I feel it necessary to mention that when I do a KOER test with the code reader, it DOES PASS the "punch" test. Or "gun it" test. Or whatever you call it.

 

[It's not old it's classic]

Update: I located the WOT relay and removed it. However it had no effect on my issue. I guess a new MAP sensor is probably my next move. I still have not checked fuel pressure, since I have to borrow the gauge from a friend.

Some FYI for anyone interested.... the WOT, EEC POWER, and FUEL PUMP relays on an 1989 Ranger are located directly under the power distribution box. Removal and installation are pretty obvious once the box cover is removed.

 

[tomw]

I would remove and clean the IAC, Idle Air Control. It is {on my older 2.3} located near the battery atop the air filter box. It can get gummy and respond slowly to idle commands from the ECM. The MAP will give you a crappy idle if it dies, and could, I suppose, get jammed when you floor it, and drop the vacuum in the intake to essentially zero. De-power, and turn it back on, and the MAP could do a reset. You can check its output using a DVOM that has a Hz setting. The Hz will change as the load on the engine varies .. and lead the ECM to order differing fuel injection amounts based on that.
tom

 

[It's not old it's classic]

To Tomw - I will try that. Let me say that during my troubleshooting, I tried to check for a vacuum problem by driving with a vacuum gauge taped to my windshield hooked up to the intake test port. (Please excuse my improvisation, as I am by definition a "shade tree mechanic") I didn't notice any vacuum spikes or dropouts. In fact I observed the vacuum being much more stable than I had expected of a engine under load.

To Earl43 - I know I stated in earlier posts that removing the WOT relay didn't work, however, I drove the vehicle over the weekend, and I was NOT able to trigger the problem. Is it possible that the EEC took some time to update stored values? It's a sign that you may have hit the nail on the head. Although in the past I HAVE HAD days where my Ranger ran fine, they were short lived.

But I am hopeful....

Will keep you posted.

 

[It's not old it's classic]

Bulls eye!

Ok, it's been a week since I removed the WOT relay. Still no sign of the problem!

Wooo whoooo!

also...

It may be that I have just been baby'ing the gas petal for too long, but I swear it feels like I picked up a lot more horse power!

I thank you RS forum members for all your help and advice!!!