2.3L ('83-'97) Rough idle

[martinglen]

I have a 97 Ranger 2.3 with a rough idle and stalling issue. The trouble code is P0303 (cylinder 3 misfire). I have done everything I know to do. I have taken it to 2 shops and can't figure it out. I replaced the fuel injectors and upstream 02 sensor and the cel light is now off but it still runs the same.(Rough idle, sputtering) So far, this is what I've done:
1. Replaced fuel pump
2. Replaced fuel filter
3.Replaced Air filter
4. Replaced entire EGR system
5. Replaced TPS
6. Replaced IAC valve
7. Replaced timing belt
8. Engine temp. sensor.
9. Replaced fuel injectors
10. Replaced upstream 02 sensor
11. Cleaned MAF
12. Cleaned throttle body
13. Replaced plugs and wires
14. Replaced both coil packs

Any help would be appreciated. Thanks in advance.

 

[rumblecloud]

More questions than answers:
It sounds like you replaced almost everything except the engine.
How does it react when driving, accelerating? When does the misfire occur - acceleration or deceleration?
Does it happen when cold or warm or does it matter. Does it ever not run rough?

 

[martinglen]

It has good response. Runs smooth on the highway. The misfire usually happens at low rpm and at deceleration. The cel light flashes at times. It occurs when hot and cold. The only time it doesn't run rough is on the highway at a steady speed. Right now the cel is off. I cleared the code when I replaced the fuel injectors and o2 sensor and so far it hasn't come back on but it still idles rough.

 

[rumblecloud]

I'm hoping one of the resident experts will jump in here with your additional explanation and help out' I was looking for a temperature connection, but now I am not so sure.

Throttle body could be the culprit. Sometimes cleaning doesn't help especially if you're not real careful on how you clean it. Spraying is about all you can do.

Have you checked for any vacuum leaks - smoke test?
Hang in there. I'm sure someone will come along with some solid suggestions.

 

[scotts90ranger]

vacuum leak is a good thought, if the MAF isn't reading the right amount of air things get wonky...

When you pulled the #3 spark plugs, how did they look? If they looked like the other 6 then it's just something wonky. The next possibility is the engine mechanicals... I would start with a compression test since they're easier, next but better test is a leak down test if possible, but reading spark plugs is an easy place to start, if it were me I'd just pull #2 and 3 from the exhaust side and compare...

When you did the timing belt, did you line up the timing marks on the aux pulley or just line it up like it was before?

 

[bobbywalter]

Leakdown

 

[martinglen]

Thanks for responding back. I haven't found any vacuum leaks. I checked it with both a gauge and did the smoke test. I cleaned the throttle body with cdc throttle body cleaner. This has been a real mystery.

 

[martinglen]

vacuum leak is a good thought, if the MAF isn't reading the right amount of air things get wonky...

When you pulled the #3 spark plugs, how did they look? If they looked like the other 6 then it's just something wonky. The next possibility is the engine mechanicals... I would start with a compression test since they're easier, next but better test is a leak down test if possible, but reading spark plugs is an easy place to start, if it were me I'd just pull #2 and 3 from the exhaust side and compare...

When you did the timing belt, did you line up the timing marks on the aux pulley or just line it up like it was before?

I replaced all the plugs about 3 months ago and they all looked pretty much the same. They weren't fouled or burnt. I went ahead and replaced #3 plug when I replaced the fuel injectors a few days ago. I had the timing belt replaced at a shop. Thanks for responding.

 

[scotts90ranger]

Even mechanics screw up, they could have been lazy and not had the aux pulley lined up... I "think" there are two rubber plugs on the timing cover (there were on the '99 2.5L I helped with the other day), they are over the timing marks on the inner timing cover where the marks on the two pulleys line up. Turn the crank until the notch lines up with the 0 on the timing cover, look through the holes, there are triangles and diamond shapes, one on one and one on the other, the inner timing cover has the corresponding shape...

I'd look at my '97 for reference, but I won't be back to it for 16 hours and at that point I'm not going to look at it , maybe tomorrow morning...

 

[corerftech]

you have not replaced the most likely item- the DIS ignition module. The ICM is what drives your coiI. I believe the code is a modern version of what I faced for two months on a 1990.
My coil 3 output died as well.

It’s not cheap but nothing you have done is. It can be tested fundamentally with an LED based 12 probe. My coil 3 driver was so dead that it had zero output and was obvious under test. 1/2/4 all triggered, 3 was flat line.

Unless I misunderstand 1997, it is a DIS engine and not sequential.
The DIS is the culprit I’ll bet.

Worth testing!

 

[martinglen]

So would I need a new ICM?

 

[scotts90ranger]

'97 is DIS but it does not have the module, it's in the computer starting in '96 when they added a cam sensor (only reason for aligning the aux pulley) so it's sequential injection with waste spark so it can still tell if it is misfiring on the #3 cylinder...

 

[martinglen]

Thanks for the info. I swapped that out with one from the salvage yard here while back. But who knows that one could have been bad too. I guess I'll bite the bullet and get a new one.

 

[scotts90ranger]

If you have two computers running the same, it's not the problem, more likely to be a bad connection somewhere but I'm having trouble thinking where that would be, more likely something mechanical...

 

[martinglen]

The only other thing I can think of is either a cam shaft position sensor, Intake temp. sensor or the downstream 02 sensor. Any thoughts about that?