New thread for my low speed RPM issues

[camelman]

I have another thread that I started with timing belt questions and moved on to engine operation questions, but figured I should switch to an engine-specific thread to make it easier to follow and search. So...

I replaced my timing belt, spark plugs and plug wires on a 1997 5-speed 2.3 with 175,000 miles on it a couple weeks ago. After doing that, my low RPM performance got bad. I must carry higher revs than before to keep the engine running smooth or else it bucks. I do not have a tach, but this happens if I dip below 10MPH in second, 20 MPH in third or 30 MPH in fourth. I remember the engine pulling smoothly from 0MPH in second, and 10 MPH in third before, so something is up. I did the following to fix it:

1) Replace the IAC
2) Clean the MAF
3) Replace the valve cover gasket and clean the area
4) I checked all electrical connections, and everything seems to be in good shape

~ Replacing the IAC made the engine run more smoothly, but did not fix the bucking at low RPM. The old IAC plunger would stick, so I know it was not working well.
~ Cleaning the MAF seemed to make no difference.
~ I replaced the valve cover gasket because it was so leaky I thought it could be bad for the wires... and it was dripping oil all over the engine.

The engine pulls smoothly and with plenty of power once it is above the "bucking" RPM. Fuel mileage is in the mid 20s, and I have not noticed any pinging. I plan on doing the following:
1) Measure resistance across the TPS to see if it is smooth throughout operation range
2) Clean the EGR
3) Look for leaks in the intake tubing
4) Look for any vacuum leaks
5) ???????What should I check on the DPFE???????

Any other thoughts? Has anyone had success in fixing an issue like this? My check engine light is not flashing, so I have not checked for trouble codes...nor do I have the equipment to check for trouble codes.

Thanks,
Camelman

 

[Earl43P]

SNIP
"I replaced my timing belt.....After doing that, my low RPM performance got bad."


See what I did there^?

I think you are off one tooth on your timing belt.

 

[camelman]

LOL, nice. I'll check that too... plus put a timing light on it. I did rotate the engine a few times before buttoning it back up, but you've a damned good point.

 

[tomw]

I agree, and don't think you could have possibly broken all the stuff you replaced in that short period of time ... unless you are extremely skilled... heh.
Once you check the valve timing, make sure whatever triggers the ignition is correct also. FoMoCo has too many ignition styles for me to remember ... I'm old, and that doesn't help.
I think that some use a sensor placed where the distributor was in the originals, so the aux sprocket may have to be timed also. I just won't memorize who has what...
tom

 

[camelman]

I checked the timing, and it is correct.

Here's more info on my situation. The engine runs great with only a slight hiccup at idle. It pulls well, gets over 25 MPG and doesn't make any strange sounds. The only issue is at low RPM when I push the pedal. It will buck hard with increasing force as I push the throttle further (I figure this rules out the TPS). I have 3.73 gearing (2WD), and at 25MPH in 4th, it bucks around like a wild thing! It did not do this before the new TB, plugs and wires. The plugs might have been original, so I wonder if this is just normal engine operation at low RPM?!

I checked the fuel filter today, and it looks ancient, so I'll change it as soon as the rain stop. When I do that, I'll also pull the MAF sensor connector to see if the engine runs better. Any other thoughts? Could a dirty intake cause this? A dirty EGR valve? It seems isolated to low RPM, and I got the truck up to 85 with no trouble a couple days ago.

Camelman

 

[martin]

25 mph is too slow to be in fourth gear.

 

[tomw]

When you installed the new plugs did you check the gap? If the gap is a bit wider than spec, the engine will have more tendency to buck or surge, a slight bump if you will, when it is subjected to a higher load, such as climbing a hill or... driving at low rpm in a higher gear. You will notice the problem more at slow speeds than at high.
tom

 

[camelman]

Good point on the gap, I'll check them too.

Regarding 25MPH being too low for 4th, I agree. However, the "bucking" wasn't there before, and I also feel the "bucking" in lower gears. I even feel it sometimes when I start off in first gear before the RPMs climb. I don't have a tach, so I can't pinpoint the RPM range this happens in.

 

[XLTsplash]

What brand spark plugs did you use ? It's almost sound like you are lugging the engine. If you are going 25 mph in 4th gear the RPMs are too low to accelerate. You my want to think about adding a tach to your Ranger. I added a aftermarket tach to my Ranger, it's a nice gauge to have with a 5 manual trans. It was easy to install and didn't cost much. Or you can even add a factory tach cluster. Could you be feeling clutch chatter ? With the valve cover leaking maybe oil got down to the clutch ?

 

[camelman]

I bought motorcraft plugs and wires, although the wires didn't come with the plastic handles for installation and removal. I wonder if I got short changed on the wires...

I've experimented with the "chugging", and it has become apparent that it is due to a miss. I gave the 25MPH in 4th gear example to correlate to RPM, but this issue is not related to running the RPMS too low. The engine is definitely missing at low RPM.

I am investigating vacuum leaks in the system, and think there might be a leak in my power brake system since bumping the brake booster vacuum hose/housing will turn on my ABS light... and my brakes don't keep any power assist in "reserve" after the engine is off. I'll try to look into the vacuum leaks this weekend.

Good question about the clutch getting oily, but luckily oil hasn't reached it.

 

[XLTsplash]

It's strange that the ABS light comes on when you move the hose to the booster. I would check for ABS codes. To see if a leaking booster is causing you bucking problem you can unplug the hose to the booster and put a vacuum cap on the port. Then go for a short test drive without power brakes to see if your engine runs any better. The Motorcraft plugs are a great choice, That's what I put in my Ranger. It's to bad your new wires didn't come with the plastic handles. It make the wires much easier to remove and install. I used the blue Belden wires from Napa Auto parts. They have the plastic handles for the wires under the intake. If you check your fuel trim during the misfire and it's 0-12% then the misfire is ignition related and if the fuel trim is above 20% then the misfire is fuel related.

 

[camelman]

XLTSplash, thanks for the fuel trim info. I don't have an OBDII cable yet, but will buy one if I can't figure this out this weekend. I swapped wire ends (old to new) so I could reuse the plastic handles. Would have been impossible to install the plug wires otherwise.

I tested a couple things today, and replaced/checked a few things over the weekend. First, the tests:
1) I tested the intake vacuum at the brake booster line. Vacuum held steady at 19.5, dipped to around 2 when I blipped the throttle with a brief surge to 25 before settling back to... 21. It would hold at 21 for about a minute before slowly falling back to 19.5. Any ideas what that could be? It seems sensor related to me, so I'm going to pull the EGR to clean it as well as clean the intake. I noticed the intake was dirty when I replaced the IAC.

2) I put a timing light on each of the four intake-side spark plug wires. 1 & 4 showed the most inconsistent readings with misfires after every 3-8 flashes. Cylinders 2 & 3 showed more consistent readings with misfires every 6-8 flashes. There were no backfires, and only slight engine stumble during each misfire. I think this is fuel mixture related.

3) I tested the coil packs and each coil read 0.6-0.7 Ohms across the low tension leads, and were consistent across the high tension leads from1-4 and 2-3 (I can't remember the HT reading right now).

4) I sprayed every inch of the engine intake and vacuum system down with MAF cleaner, and found no change in idle.

I replaced the fuel filter and PCV valve on Wednesday. The PCV valve got a new vacuum line too, and the engine definitely ran more smoothly with the new valve and line with much better idle. The fuel filter didn't change engine operation, but it was definitely old. Also, my MPGs are lower than I thought. They're around 20 on the highway, which has me thinking EGR.

I am going to replace the valvecover-to-intake recirc line today before cleaning the EGR and intake. It is old and not sealing well at the valve cover, so I'm sure it contributes some unmetered air after the MAF.

Any thoughts on that strange engine vacuum issue? I have a feeling it is a sticky EGR. Also, I have not changed the oil since I bought the truck, and I'm sure it is due. The oil looks VERY dark and cloudy.

Camelman

 

[camelman]

HELP!! This ranger is going to be the death of me!

I tested the EGR today and it leaked when closed, so I replaced it. I also cleaned out the throttle body, replaced the vacuum line that goes from the bottom of the throttle body to the EVAP control, changed the oil and filter, changed the breather tube from the valve cover and checked everything for vacuum leaks. The engine ran even worse after this. So, I bought a brand new primary coil pack for it and installed it, and no difference! I had to rev the engine so much while parking on a slight hill that I could smell the clutch overheating.

The upside of the EGR and vacuum lines replacement is that the vacuum measurement improved, and floats between 20.5 and 21 without dipping to 19 anymore. The vacuum varies depending on how much the engine misses. I can follow the misfires when using my timing gun. They show about twice as often for cylinders 1 & 4 as for 2 & 3. 1 & 4 are smooth for 8 cycles, misfire once, smooth for 3 cycles, misfire once, and repeat. Cylinders 2 & 3 misfire about every 8 cycles. The repetition isn't exact, but is pretty close. The exhaust-side plugs don't fire at all when idling.

I think this is a rotating sensor issue like the crank position sensor. Can anyone weigh in? The idle stumbling and low RPM missing issue is just getting worse with everything I do.


So far I've replaced:
plugs (8 motocraft)
wires (motocraft)
intake-side coil
EGR valve and gasket
IAT and gasket
PCV valve and vacuum hose
inlet-to-valve cover hose
throttle body lower vacuum hose (and cleaned it out)
air filter
fuel filter
timing belt
coolant
oil (it looked more like molasses than oil... OLD!!!!!)
oil filter

Thanks,
Cameraman

 

[camelman]

Just found a page about the ignition control module. This might just be the issue!

http://easyautodiagnostics.com/ford/2.3L/icm-and-crank-sensor-tests-1

 

[tomw]

Have I mentioned that the intake side spark plugs do not fire all the time. They are enabled only in certain conditions.
The engine runs on the exhaust side plugs, leaving the intake side for extra emissions control duty.
If the exhaust side are firing steadily, they are not the cause of the miss, IMO.
tom