My Ranger is Sick

[Hack2ey]

Hi folks. I just bought a 2wd 1990 Ranger with a 2.3 and a Mazda 5 speed manual transmission.

The engine starts and seems to run fine, but I have noticed that there is a pronounced hesitation during acceleration through the gears in the 2500 - 3000 rpm range. It will pull cleanly from just off idle up to about 2500 rpm, and then I notice it start hesitating and almost faltering from there up to about 3000rpm. If I open the throttle almost wide open through this rpm range it seems to help. Once I get to about 3000 rpm, it suddenly begins pulling hard and cleanly again until I shift at 3200 to 3300 rpm.

To give an idea what this hesitation feels like, it's almost like the A/C compressor comes on and stays on until 3000 rpm. It's a very noticeable drag through that rpm range.

I have also noticed that the exhaust smells rich, almost like a vehicle smells when it's running "open loop" before it's fully warm. To confirm my "seat of the pants" judgement that it's running rich, I just checked the fuel mileage after driving it the first 200 miles and it only got 17 mpg.

My Haynes manual isn't here yet, but something is wrong with this otherwise nice little truck. Anybody got ideas what I might look at?

Thanks -Dave

 

[Karbuster]

I don't know much about diagnosing an engine yet but could the Throttle body be sticking?

posted using smoke signals

 

[tomw]

I would check fuel pressure and delivery volume. If there is low or a sticking regulator, it can feel like low power. You might also check the TPS for a 'bad spot' in its arc of motion, but they are pretty reliable. If you have a MAF, it would not hurt to clean the wires, or at least inspect for 'schmutz' which would make their air measurement inaccurate, leading to incorrect fuel-air ratio. Most times they'll show up as hesitation on acceleration.
tom

added... I just re-read your post. Check fuel pressure and see if the regulator responds to the vacuum line being disconnected at idle. The pressure should increase and then drop as the line is re-connected. If not, a sticking regulator might cause fuel pressure to be off, leading to an over-rich condition that is corrected by opening the throttle wide, allowing more air.

 

[scotts90ranger]

See my response to your last post about checking the codes, I'd start there and wouldn't hurt to look at the fuel pressure but don't throw parts at it other than maybe plugs and wires (the drivers side is a pain, the passenger side is the most important side so start there)

 

[Hack2ey]

Update

Thanks to all for good advice. I got the truck fixed by doing a couple of really easy and small things. I thought maybe the info about what solved the driveability problems I had might help others with similar problems, so here's what I did:

- My limited understanding of fuel injection systems told me that the computer uses input from the O2 sensor (among other inputs) to determine how long to fire the fuel injectors. The exhaust from my truck always smelled really rich, and the truck has 100k miles on it, so I figured it couldn't hurt to change the O2 sensor. $40 for a new sensor from NAPA and about 45 minutes getting the old one out, and it was changed.

- Again, with 100k miles I decided to clean the Idle Air Bypass Valve. Got the procedure from this forum and it took 30 minutes.

- Read on another website specializing in Ford 2.3 performance upgrades that the EGR system was a weak design and could cost performance, so I made a blank off plate using a new EGR valve gasket as a template and cutting it out of a stout tin can. 30 minute deal.

These three quick jobs absolutely transformed the way my truck runs! No dead spot or sluggish acceleration. More power throughout the rev range. Rich gassy smelling exhaust gone. Not sure yet, but I'm betting fuel mileage will be much better too, because throttle opening necessary to maintain speed has been reduced. If anyone out there needs to improve the way their truck runs and these things haven't been done, I highly recommend them.

 

[redneck105]

how exactly did you do the egr blank off plate, did you just put inbetween the egr and throttle body like a gasket?

 

[tomw]

Hope you don't start getting pinging now that the EGR is blocked. If you are subject to emissions inspections, you'll likely not pass with a blocked EGR passage. You may get a light on the dash after a while, or not.
EGR is used to decrease peak combustion temperature, reducing NOx formation. Without the un-burnable exhaust gas (already burned...) the temperature will be a bit higher, leading to possible pinging. If you get pings, your mileage will take a hit.
You did too many things to determine the actual cause of the reduced mid-range performance. But it runs well now... which is good.
tom