Hope you guys can shed a little light on my issue. The truck starts fine and drives fine. It doesn't even struggle pulling my 24' car trailer. When I first start it, it starts right up. Even has the normal high idle, but it doesn't idle as high as it should and is rough and rich. It has a strong gas odor. Once it comes down it seems to have a pretty steady idle, yet still very rich. Once it gets warmed up the RPM's bounce between 500 and 900. I am averaging 7-8 MPG on the highway and in the city. Now for the things my mechanic and I have done. Between the two of us, we have replaced the fuel filter and checked for proper fuel pressure at the rail. Pressure checked out fine. Cap, rotor and plugs have been changed. New TPS. O2 sensor is functioning as it should. Timing adjusted and EGR position sensor replaced. I also swapped the MAP sensor. However I have not yet cleared the computer since the MAP swamp. Would that make a difference? With all the changes made with the exception of the MAP, the truck ran 10 times better. The engine light was on, but the light has recently quit working. I haven't had the truck very long, so I don't know how long it was on prior to my ownership. My EGR tube is leaking some, and a mechanic informed me that the truck may be running rich because the computer is compensating for a lack of exhaust. Another mechanic seems to think the injectors could be partially plugged. I'm at a whit's end. Any help would be greatly appreciated.
Thanks,
Damo

 

Pull the codes.

The computer (PCM) was and probably still is trying to tell you something is wrong.

 

Welcome to FTE and the Big Bronco Forum. We will do our best to get you the most accurate info we can muster.

WITH THE ENGINE OFF AND COOL pull the vacuum line from the FPR (Fuel Pressure Regulator) on the fuel rail. Vacuum supplied to the FPR pulls the pressure DOWN from the full 45-50 PSI that the pump achieves. If the regulator fails, the ECM cannot draw down the fuel pressure to maintain idle control. If fuel is present on the vacuum side of the diaphragm, the FPR is toast and needs replacement. If not, refer to the steps below.

Clear Codes (disconnect battery for 5-10 minutes) Start and warm to operating temperature. Take it for a 20-30 minute drive (highway and surface streets) so the ECM can relearn the operational parameters with all the new components. Run KOEO test again after the drive. Whatever Codes are present then reflect the source of the problem.

 

Ill give that a try after work and post the results.

 

I am not going to argue with Greystreak92 but I would pull the codes first. That way you know what the starting point is.

 

I am going to get the codes this weekend. My check engine light quit working recently, so I can't do it manually. Unless you guys know of another way besides a reader.

 

Cut from oldfuelinjection.com:

If you are a lost soul that does not have a working engine light, or did not install a light into your dash don't fret. You can still get the codes. You still need that wire to ground out the STI. Now you will need one of the following tools; digital volt meter, analog volt meter, test light, or you can hook up any other 12 volt light that does not draw more than 0.5 watts max.
1. Turn key to OFF.
2. Get a length of wire that can connect the STI to the negative battery terminal or body ground.
3. Ground the Self-Test Input.
4. Attach one side of the test device to the Self-Test Output (STO).
5. Attach the other lead to the positive side of the battery.
a) If you are using a digital voltmeter you'll want to use the continuity setting.
b) If you are using an analog voltmeter you'll be counting the meter make sweeps.
c) If you are using a cheep light you'll count like the rest of us.
6. Get some paper and a pen.
7. Get comfortable in the drivers seat.
8. Try to keep your self from getting distracted from here on.
9. Turn key to RUN.
10. You will hear some relays engage and the fuel pumps prime the system. This is the EEC beginning the test.
11. When the fuel pumps stop be ready to count!


Fuel Injection Technical Library » How To Run a Self-Test

 

Perfect. Thank you so much. I will be doing this as soon as I'm off work.

 

I would typically suggest to pull Codes first. However, given the symptoms described in the initial post, they point towards a fuel-related problem and a dying FPR won't have a specific Code generated when it fails but rather there will be symptomatic Codes as a result of the fuel pressure being higher than it should be.

 

Not much to update. I'm going to be running codes on Monday. I dont feel like working on the truck right now. However I pulled the vacuum line off the FPR and didnt notice any gas. I did a fuel pressure check awhile back, and the gauge read 65 psi at the rail. Does that seem a little high?

 

Ok, ran the KOEO test. I cleared the codes and am going to run another test tomorrow along with the KOER test. The yeast today revealed codes 22- map/bp sensor out of test range, 29- insufficient input from speed sensor, 31- pfe or evp circuit below minimum voltage of .24 volts, code 32, 33- egr valve opening not detected and 41-HEGO sensor circuit indicates system lean on right side.

 

Ran the codes again today to see what came back. 33- egr valve opening not detected and 41- HEGO sensor circuit indicates system lean (right side) Not sure what to make of this.

 

I was having those 2 same codes about 3 weeks ago when I was getting ready for my smog check.

I had vacuum line misconnected and one of the leads to the EVR was not fully inserted - - I had messed that up while doing a head gasket replacement.

If you haven't replaced all that plastic vacuum line in your engine compartment, then I'd recommend you change it all out for vacuum rubber tubing. I did that years ago and it eliminated a multitude of annoying little problems and the vehicle just ran better.

 

I went over the vacuum system with my mechanic. Everything is good.

 

Ok, skip Code 41 for now. The "lean" condition most likely exists because the computer is trying to compensate for Code 33. If Code 33 is received during the KOER the computer could not detect movement of the EGR valve. There are a handful of potential causes for this.

1) Electrical connection to the EVP (EGR Valve Position) sensor is weak or disconnected. The EVP is bolted to the top of the EGR valve. Check the electrical connection.

2) Electrical connection to the EVR (EGR Vacuum Regulator) solenoid is weak or disconnected. The EVR is in the vacuum supply line to the EGR valve on the driver's side of the intake near the ignition coil. If you just checked all your vacuum lines, follow the LT GREEN hard plastic line from the EGR valve back to the EVR. Check the vacuum and electrical connections.

3) The EVR is not opening due to failure and thus not providing the necessary vacuum to the EGR valve for it to open.

4) The EGR valve itself is stuck closed or will not hold vacuum and thus is not opening.

The troubleshooting method for both 3 and 4 is as follows:

A) With the engine off, disconnect the vacuum line from the EGR valve and apply 4-6hg vacuum to the barb on the EGR valve. This should unseat the valve and quickly releasing the applied vacuum will yield a very faint sound when the valve snaps shut.

B) If it is suspected that the valve is not opening, you can carefully lift up on the pintle of the valve THROUGH one of the tiny holes in the lower casting of the valve with a very small screwdriver. Use extreme caution when performing this maneuver as a slip with the screwdriver will punch a hole in the EGR valve diaphragm and render the valve "dead" anyway. If the pintle will not move manually, replace the EGR valve. If the pintle moves manually but not when vacuum is applied, replace the EGR valve.

C) If it is determined that the EGR valve does indeed hold vacuum, reconnect the vacuum line to the EGR and follow it back to the EVR again.

D) Disconnect the vacuum SUPPLY line to the EVR from the intake. (Not between the EVR and EGR).

E) Apply the same vacuum to the line at this point and observe whether or not the EGR valve opens. If it does, the EVR is "dead" and needs replacement. The EVR is a "normally closed" solenoid and if it passes vacuum without the electrical system on, its internal spring has failed and most likely the solenoid coil as well.

F) If you want to double check the coil in the EVR, disconnect it from the main wiring harness at its connector and apply no more than +5VDC to the EVR itself at the connector. It is CRITICAL that the EVR NOT BE CONNECTED to the rest of the electrical system if you perform this test! If, upon applying +5VDC to the EVR, vacuum will pass through it, the EVR is fine. If not... well, you know.

5) Last, but certainly not least, the EVP could be bad. You can perform an electrical resistance test to determine its functionality but given that IF you have gotten to this point and everything else has checked out, this is the only location left for the problem... replace it.

Remember to clear the EEC-IV computer's memory by disconnecting the battery for 5 minutes after you have finished all of these procedures. Reconnect, warm it up, and take it for about a 20-30 minute drive to let the computer re-learn the operational parameters of the engine.