Ok, so I bought the truck for 800 bucks and I know it has high mileage. But, the darn thing seems to run so good once the RPM's are over 1000ish (no tach). It's a 97 2.3 liter. I've replaced all the vacuum lines that I could find that were bad. I also replaced the upstream o2 sensor. I replaced the intake, exhaust, valve cover, IAC, and throttle body gaskets. I cleaned the MAF sensor. I replaced the catalytic converter. I also replaced the fuel pump assembly because the gas guage didn't work. I also replaced the fuel filter, spark plugs, and wires and I replaced the PCV valve. The only thing I haven't replaced that I think could do this (unless it simply lacks compression, but I doubt it) is the EGR valve or the ignition control module. It seems to be worse when the engine is warm. What happens is, if I don't keep the RPM's up in first, it will get real sluggish, and if i'm not careful, it will sputter. After I start rolling above 5 mph, I don't have a problem. All of the above things that I've done have helped a lot. But it is still there but much better than when I started, so I'm wondering what my next course of action is. Also, high octane gas seems to lessens the problem even more. When I took the intake off, I did notice that the ports on cylinders 1 and 4 had more carbon buildup than 2 and 3. I figured maybe those valves weren't seating as well. But like I said, if it was lack of compression, wouldn't it be a dog through the entire power band?

 

Also, will the downstream o2 sensor affect performance if it is bad? Replacing the upstream seemed to do the most good out of all the 'fixes' so far.

 

Is it throwing any codes? Does it sound like its pinging at all? I don't know about the 2.3L, but my 3.0L acted sorta like that. It was throwing an EGR Valve code, but it turned out to be the sensor for the EGR valve, the DPFE sensor.

 

the only code it is throwing is p0172 system too rich.. I just pulled it this afternoon. It's the latest code since I replaced all the stuff. I pulled the vacuum line off the fuel pressure regulator tonight and didn't see any gas, but oddly enough the truck seemed to run much better tonight than usual, but it's about 10-15 degrees cooler outside than it was this afternoon, so I don't know if that plays a part or not. I'm leaning toward the regulator or injectors, but I'm hardly mechanically inclined enough to test the system.. I can just replace parts and do some voltmeter testing lol. All of the other stuff was pretty much routine maintenance stuff that needed to be done since I had no prior knowledge of the trucks history. Would the downstream o2 sensor affect fuel delivery? It is not new. I only replaced the upstream. The EGR is also oldish looking.. but when i plugged the vacuum line and fitting, it didn't change anything. Oh I checked the TPS too, can't remember if i listed that. It did what it's supposed to voltage wise.

 

sorry I have two user names....

 

anyone have any advice?

 

I had a 93 with a 2.3 that had the same symtems, Seemed to miss at low rpms with no guts, but above 1000 rps ran fine. On mine the compression was only 70lbs on #2 cyl, It would'nt fire on that cyl at idle or low rpm's but would at higher rpm's, Burnt exhaust valve! after replaceing head, smooth as silk.

Take a compression Check.

 

did it cause it to run rich

 

Yes it seemed rich because of the unburned fuel in the dead cylinder. It was a steady miss below 1000 rpm's just like a plug wire was off, so thats where i started I tried everything before doing the compression test. Wished i would have started there first.

just my 2 cents

 

thanks, i brought it to a shop monday. He still hasn't figured out what's wrong with it, other than one coil pack is bad, and it appears to be out of time, he said it looks like someone installed the timing belt improperly.

 

Well, I broke down and brought it to the mechanic. He told me he did everything he could think of, tested every sensor, tested fuel pressure, checked the timing, etc. etc. and he was just about ready to give it back to me and say sorry he couldn't get it. But because this guy is awesome he remembered that there are two heads that could fit this truck and he said it looked as though there was some recent head work done to it, so he pulled the timing cover off again and moved the notch forward and now it runs fine. He thinks they either used the wrong head or the wrong cam and it was causing the timing to be off although the marks lined up.

 

Does this sound correct to anyone?