Running rough, need help.

[MrFML]

I have a 95 xe with 176k , under normal driving it acts like it's running out of gas. For example, while driving down a road and you start an incline on a hill and the transmission kicks down, it just bogs. I basically have to put my foot in it to get the engine to pull.

 

I have replaced the fuel pump and filter and ignition coil. Also did my best to find a vacuum leak but couldn't find anything.

 

I am at a standstill. I have considered that maybe it's the transmission but I'm really not sure at this point.

[Cuong Nguyen]

how's the air filter?

rubber intake hose isn't cracked?

none of your vacuum hoses are cracked?

There's a whole bunch right around the throttle body area and driver side engine/exhaust area

and then you have the fuel pressure regulator in the back of the engine near the firewall.

 

[silverton]

my thoughts are air filter, O2 sensor, and distributor optics

 

air filter is easy.

 

O2 sensor can be bad enough to make the truck run like @!*%, but not bad enough to trigger a CEL. Also, relatively easy. Mode 4 or 5 is the test for the O2 sensor, but I've had one test just barely in their "good" range, replaced it anyway and it made the lights blink like they were on uppers instead of the downers from the old one. Made the truck run better too.

 

distributor optics are annoying. the best way is to swap a known good distributor in the truck but you have to take note of where it's pointing else you risk throwing the timing out and then it just wont run at all. If you replace it with the distributor in place just be careful not to bend the plate with all the notiches in it. 360 little ones and 6 big ones, be careful with this piece! the optics (like a cd rom laser) are right underneath it. It's essentially the cam position sensor.

Edited March 26, 2016 by silverton

[MrFML]

honestly sone of the vacuum lines are hard as a rock. mainly on the bigger onesthat run under the intake on the drives side.

 

what about the air regulator? I hear ithe could cause issues.

[MrFML]

oh and I drove it earlier. after it warms up I can hear a slight miss in the exhaust note. it's pretty smooth when it's cold.

 

imagine if you were driving along and lost 75hp. that's how it feels.

[JackStraw1]

Might want to clean MAF sensor if that hasn't been done. Also, fuel injectors will sometimes fail intermittently when engine hot but run perfectly fine when cold.

Edited March 27, 2016 by JackStraw1

[adamzan]

If it is good while cold but bad when it warms up, it is definitely sensor related. Check the o2. The easy test is to unplug it then drive the truck to see if it runs better.

[silverton]

Now that you mention that, I'm certain it's the O2 sensor. It doesn't really start doing its thing until the truck is warmed up, and that explains why when you go full throttle you get more power because then the ECU defaults to a "throw all the fuel at it" map.

[MrFML]

I will definitely check the O2. What about codes? I don't know much of anything about OBD1. I hear there is a way to check for a code? Even if there is no CEL?

[silverton]

You can check codes by turning the dial on the ECU all the way clockwise until you see the lights blink three times, then turn it back to where it was. codes will start blinking shortly after, red light for the first digit, green light for the second digit. 55 is all clear! If you go from mode 3 to mode 4 the codes will clear if there are any. Turn the knob clockwise again, wait for the lights to blink 4 times and turn it back. You have entered mode 4 which is where the O2 diagnostics begin. Mode 4 makes sure it works and has output for both open and closed loop functionality. Entering Mode 5 checks that it's reading the mixture properly. Here it can tell you if it's more than 5% out of spec. But what you want is for both the red and green lights to blink in unison rapidly.

 

Reference pages 36 and 37 in the EC section of the FSM for more information. Page 37 contains the decoder for the CEL blinky lights.

[MrFML]

I changed the O2 sensor. it runs like a top.

 

 

Thanks!