1997 Ford Ranger running rough



Hello all, first time post.

I have a 1997 Ford Ranger and I’ll give a brief description of what has brought me to the point of asking this question. My Ranger started running a little rough when in 5th gear and going up the longer hills (it’s a 2.3L 4-cyl so it’s never been a power house). It got progressively worse and bad enough that it would cause the check engine light to come on so I put a bottle of fuel injector cleaner in it. After I put the injector cleaner in it, it ran fine again for a couple of months and then started slowly loosing power on hills. I added another bottle of injector cleaner and it got much worse during that tank of gas. It runs so roughly like a very bad miss. I changed the plugs and plug wires and it didn’t help at all. I should also mention that after I start it you can really smell gas like it’s flooding. Does anyone have an idea what could be wrong or what I could check next?

Thanks for any replies, Charlie


The first thing you should do is get that code read and post it, please

When the check engine light is on, is it flashing?

How many miles?


I had a gas smell that would not go away and it turned out to be a leak in one of the hoses in the engine area. I don’t recall it ran badly but it is 20 years old with 102K miles so it does not get driven much. I did have engine issues but they were related to a clogged fuel line filter.

A mechanic found the leak. I replaced the filter.


Problems when accelerating uphill suggest a problem with insufficient fuel or air delivery, or exhaust restriction. Suggest to focus on those areas, fuel filter, engine air filter, cat backpressure test. If the spark plugs haven’t been replaced in 30k miles or so, worth a try to replace them. 15k if you are using copper plugs. The gaps widen over time and can cause loss of power and often pinging.


Again . . . please have the codes read and post them

might be good information there, which we can work with


Hello DB4690, I will try to get the codes read and post them. Thanks for everyone’s input so far.


Ok, I had my codes read and they say: (typing just as code reader said it)

P0401 EGR(Exhaust Gas Recirculation) System
P0303 Cylinder 3 misfire detected
p0171 System Too Lean Bank 1

Does this help with the diagnosis?

Thanks, Charlie


Out of all those codes, I would concentrate on P0303

Is the check engine light flashing?

Are you able to easily access the injectors?

The ideal thing would be to measure resistance of all and perform an injector balance test

You could also perform a compression test . . . wet and dry . . . to make sure your misfire isn’t somehow related to low compression

How’s your tool situation?

compression gauge?

digital multimeter?

fuel pressure gauge?

the fact that the truck ran better with the injector cleaner makes me wonder if the injector(s) are partially plugged. An injector balance test would pretty much confirm or dispel this idea

It is possible to perform a thorough injector cleaning by using one of these

But it won’t help if an injector has an electrical fault

P0401 . . . egr insufficient flow. Could be a bad egr valve, plugged passages, etc.

P0171 . . . several things could be causing a lean condition, such as low fuel pressure, vacuum leaks, etc.

Do you have a spark tester?

You have 2 plugs per cylinder, correct?

make sure both #3 plug wires are producing a bright blue spark


An EGR malfunction where the valve opened when it shouldn’t, or opened too wide when it should open (like during accelerations and uphills) could cause the misfire and the lean code. Fords have that DPFE gadget that controls the EGR function and sometimes fails and is a pretty common complaint. That’d be my guess for what’s wrong, but it’s only a wild guess. If I had that problem on my Corolla first thing I’d do is apply a vacuum using a hand-held vacuum pump to the EGR valve at idle and make sure that stalled or at least badly stumbled the engine. If it didn’t I’d replace the EGR valve. Suggest to do a little googling on the DPFE gadget though, b/c of the way Ford handles the EGR function.


How do you explain the low flow code?

By your reasoning, OP should have a very different fault code, P0402, I believe


I should have mentioned that it runs with a constant miss. Could a coil pack cause the cylinder miss fire? If so could the miss come from a bad coil pack?


You’re right, too lean wouldn’t be caused by insufficient EGR flow, at least not directly. But missing symptoms might be caused by that, if the cylinder was getting too hot and preventing normally timed combustion. The lean condition could be an offshoot of the missing possibly. Unburned O2 hitting the o2 sensor. Seems a stretch though. Whenever the EGR function is suspect I think it is a good idea to rule out the EGR as a cause early on with misfire symptoms. To avoid going down the wrong path.


Yes, a faulty coil could cause a misfire, and the misfire could cause a lean code. You comment above about the injector involvement is what remains puzzling. Diagnosing misfires is often done by swapping parts between cylinders. If the misfire moves to the other cylinder after a part swap, you know that part is related. Coils and injectors usually.

As a coincidence, I had a misfire problem on my own Ford truck today. Turned out the battery power connection to the coil had a loose connection.


Good morning, if I test for spark on both #3 cylinder plug wires this should either rule out or identify the coil pack correct? I replaced both plugs and wires. Regarding testing the spark, I have a spark tester so I do that with the engine running correct?


Might not catch an intermittent coil problem, but worth a try as a good start. Spark testing is usually done during cranking.


Coil packs are not too much for a pair. Would it be a good idea as a “troubleshooting” method to just replace them both?


It’s worth a try. You run the risk of running out of money before running out of guesses for parts to replace is the downside. Retain possession of the coils you remove. Sometimes I’ve replaced a part on a guess only to discover the new aftermarket part is faulty and all I’ve done is introduce another problem, meanwhile the old oem part was still good.


My gut feeling it’s not a secondary ignition problem


So you don’t think it’s the coil pack? What would be your best guess? I appreciate your input!


My gut feeling is mechanical or fuel

But I could be wrong