Hi there
I have a 1990 Ford Ranger 2.3L V4, manual, pick up and driving it to the bottom of Argentina (hopefully).. In the start (San Diego, USA) I had an intermittently misfiring engine, it was bad but disappeared after adding multiple bottles of fuel injector cleaner in the gas tank over a period of a month and at the same time new sparkplugs and cables, fuel pump, oil filter, air filter, timing and fan belt were installed.. However after 3 -4 months later (now in Colombia) the same problem has come back at it's becoming worse ( Again I add the fuel injector cleaners but its not working). I took it to a mechanic and he changed the sparkplugs again and gave the air intake system a good clean, which made the engine run better but the misfiring came back.. The engine is running better but the engine is still intermittently misfiring.

The problem happens mainly happens when travelling at slow speeds start/end of journeys, but sometimes still happens on the highway, which is solved immediately by restarting the engine, but can re-occur at any time

I have recently disconnected battery to clear all engine codes and then drove 600miles.
I have now checked the engine codes, for the first time, and this is what I am getting:
Key on engine off:
57 - Octane adjust service pin in use/circuit grounded

CM:
33 - EGR valve opening not detected
41 - HEGO sensor circuit indicates system lean (right side)
88 - Loss of dual plug input control

Key on Engine on:
21 - ECT out of self test range 0.3 - 3.7V
41 - No HEGO switching detected always lean (right side)
33 - EGR valve opening not detected
52 - power steering pressure switch always open or close

After much research, I am thinking of changing O2 sensor, EGR valve and then maybe the fuel injectors to combat the misfiring engine.

Just want to know other peoples thoughts and maybe there is an easier solution.

Thanks in advance
Mick

 

All those codes could cause poor running in terms of fuel efficiency and emissions, and possibly stumbling. If the EGR valve is not closing completely, it can also cause stumbling or stalling.

If the HEGO sensor is original, it probably should be replaced.

Have you checked the throttle body position sensor? It's easy with an analog voltmeter. Check to smoothly changing resistance as you turn it. It's also not very costly to replace.

Are you sure your engine isn't an inline (not V) 4?

 

I found a analog meter, and it seems to be working smoothly.

I just took it to a Ford mechanic and I showed him the codes and told him the story about the adding the fuel injector cleaners. He recommended we clean the gas tank, change fuel filter and clean the fuel injectors... Which is a lot of money!! And he didn't seem to worry about the codes...

My question is would a faulty part in the fuel system cause a the previous codes mentioned??

It is a 4 cylinder engine..

 

The only code that could possibly be generated by faulty fuel system would be 41, but that's more likely to be a faulty HEGO sensor.

Replacing the fuel filter does not seem to be a bad idea for a car that old. I would do that first, and if it clears up the problem for a while, then problems return, then you probably do have crud in the fuel tank. You can keep replacing the fuel filter (it's cheap and easy to do yourself) when the stumbling starts again, to slowly trap all the crud, or you can have the tank cleaned.

You mentioned you had a 2.3L V4 in your Ranger. I don't think Ford has produced a V4 engine since the 60's and definitely not one that big. Are you sure it's not an inline 4? That was very common in the Ranger.

 

So my bad it is a inline 4 engine..

I have had the fuel injectors cleaned, they were all good, changed out the fuel filter and have replaced the Oxygen sensor (which has removed the HEGO codes)
I took it for a drive and the 'stumbling' re-occurred along with remaining codes... I have removed the EGR valve and it seems to be ok, it has no dirt inside and the spring is in good shape...

I will try and find a vacuum tester to test the valve, however could there be problems relating to the EGR valve that could be causing a problem?? Could it also be faulty vacuum solenoid or would that come up as a separate engine code??

I'm struggling to understand... Why does the code say valve not opening... but when the engine stumbles wouldn't that mean the valve is getting stuck open??

 

The EGR valve has a position sensor on it that the EEV looks at to verify operation. That sensor is basically a potentiometer, and is know to cause failure codes even when it's working. You can check the valve itself by pulling and plugging its vacuum line, and use a vacuum pump on the valve. With the engine idling, if you draw a vacuum on the EGR valve, it will open, and should kill an idling engine. To defeat it, you can unbolt it from the EGR plate and cover the holes with a large gasket, and see if the engine still stumbles. That usually indicates a vacuum leak, so I would look for loose or broken vacuum lines or fittings.

There could be other causes of engine stumbling; it's not just the EGR that can.

 

So the EGR valve is fine.. it opens when pressure is applied and holds, when the pressure is released the valve closes... I put the valve back in and took it for another drive and the engine stumbled again, I got out and inspected the valve while the engine was stumbling and the valve was closed!!!! I felt the vacuum hose while revving the engine and felt there was no vacuum against my thumb.. So I am starting to think it might be a faulty solenoid, hence the code 'EGR valve not opening'... I have no done more research and starting to thing it could be a faulty ECT which is mentioned in the codes...
My questions are:
Does and stuck closed valve cause a stumbling engine??
Does the ECT provide data to the computer which control the EGR valve??

EDIT: I just test the solenoid and it is short circuiting.. I'm guessing this will solve my EGR not opening code.. I will buy a new one when the shops re-open in 2 days!!

However it has me more confused as to why the engine is stumbling because the valve has been shut for sometime.....

 

No, a closed EGR valve should not cause engine stumbling. And yes, the ECT does sort of influence when the EGR is activated; the engine has to reach a certain temperature (192F+) before the EEC starts thinkning abut when to activate the EGR. I still think you may have a vacuum leak, or maybe the throttle position sensor may be faulty.

 

ok changed out the solenoid and the same 'egr valve not opening detected' still is occurring along with stumbling engine.. maybe it is the sensor on the valve itself... Is there a way to test if there is a signal being sent to the solenoid??

I tested the throttle sensor with key on engine off, it range from 0.7V to 4.5V with smooth operation in between, even while give the throttle body a whack... the voltage to the sensor and the ground work correctly...

However when the engine is on... I tested it again, it started at 1V and seemed to drop in and out even also when I increased the throttle the voltage increased but just dropped in and out the same... did not increase to full throttle...

I tried finding a vacuum leak with the carb cleaner, couldn't find much but I probably, with my limited knowledge missed a few spots areas..

 

When the the throttle sensor voltage was dropping in and out, did the engine stumble with the voltage changes?

 

sorry when I tested it again, and got the drop in voltage the car was constantly stumbling...

I went back to the original codes and focused on the loss of dual input (88)... I started to play around with the spark plugs and noticed that there was no spark from No.2 on the primary coil and also No.4 on the secondary coil was very very weak... I tested the coils with a multimeter and everything looked fine.. I am starting to believe that the check engine light that comes on while driving and when stumbling is occurring is code 88..
The car starts no problem, does this mean I have a faulty module?? or could it still be the coils?? I am fairly certain that cables and sparkplugs (replaced by mechanic with the last 2 months) and the cables ( replace by mechanic within the last 8 months) are fine..
Or does the throttle sensor also affect the sparks??

 

The symptoms with the throttle sensor voltage changing sounds like an electrical problem, like the power going to the EEC is unstable. Can you check to make sure its power and grounds are strongly connected to where they belong?

The throttle sensor will affect fuel and timing, but the EEC needs stable power to work properly.

 

So I took it to a mechanic and he said just change out both ignition coils, which is what I did and the engine does run much better and all the sparks are nice and strong..

However, the intermittent stumbling is re-occurring, but it is no where near as bad as before I changed the coils.. when it was occurring I jumped out and saw that there was no sparks on any of the towers, on the drivers side coil pack but still had 14V going to the plug.. I swapped it out with the other new coil pack and the problem stayed on the drivers side...

I had reset the computer before I changed the coil pack.. and still getting the same codes, minus the O2 sensor... however when I do Key on Engine on test, it comes up with 73 - TPS sensor did not exceed 25% rotation during dynamic response test... I repeated the test twice and it came up again both times... but I cannot get it to fault when testing it with a multimeter.. and the engine is off...

Also when the engine was warm/hot, I was revving it pretty hard when in neutral and I could not feel the EGR solenoid move.. is that normal??
Its just this and the other problems I mention make me think its the ECC not the Ignition Control Module (I mean at this rate it could also be problem. haha..)

Do you have any tips of testing the computer??

 

The TPS is a cheap part and simple to replace, so you might just try that next.

 

The TPS is not that easy for me to access, it requires removing other parts and one of the bolts is very difficult to access, while I have no dramas that it could be a problem. I am finding it difficult to understand how a faulty TPS can affect the sparks on the coil pack..