Hey, I have an 88 F250 with a 351CU in it. I was having some trouble with my idle surging, so I bought and replaced the IAC unit. I also changed out the fuel filter, as I had no idea when it had been replaced last.

Now I am having an intermittent problem that I think must be something with the fuel delivery. The truck will idle fine (the IAC was bad apparently), but I get into trouble when I start loading the engine. The truck will sputter and buck, like there is no gas going to the engine. The problem is only intermittent as well. It seems to happen more when the truck is cold. It happens in all gears, and I can hear the engine quitting, so it's not a tranny problem.

Someone told me this sounded like it could be either spark plug wires or a fuel pump that is giving out. Either way, I am having either a lack of fuel or a lack of spark.

I can't find anywhere locally that has a code reader that I can use to figure out what is going on. What I was hoping was that someone would be able to tell me what the symptoms sound like to them. Or, vice-versa. That is, would a fuel pump that is going bad act intermittently or would it just quit? Do the connecitons (electrical) to the fuel pump get loose often?

I have dual tanks, but the front tank has a bad fuel pump, so I can't just troubleshoot but switching tanks.

Anyone have any ideas of where to start?

 

You can check you fuel pressure at the fuel injection rail. If you do not have a gauge I believe autozone will loan or rent you one. Also check your timing with the spout connecter disconnected. Check vacuum lines. Another thing to do is to erase the ecu memory by dis-connecting the battery for 10 minutes or so. The ecu will then be at base settings. It recycles a number of times before settling in. All assuming your plug wires are good along with cap and rotor etc. Check around for an OBD I reader. I found one on ebay for 3 bucks

 

The 1st thing I would do is replace the dist. cap/rotor, spark plugs and wires.

 

Happening when the engine is cold smells more like a vacuum line that controls a choke module of some sort. Another idea is when is starts to idle rough under load, can you look at the battery with a meter? I'm thinking possibly an alternator on it's way out could behave that way. You'd see a voltage drop at the same time the engine starts couphing.

 

Ok, i pulled the codes from my computer. that was fun. I just jumpered the self-test and rigged up a light bulb. I got code 33 and code 41 from the memory.

So, 33 is EGR valve not opening and 41 is runing lean. So, it looks like my EGR is crapping out under load.

I checked the EGR connections and the vacuum line isn't connected to anything. So, where do I connect it? My haynes manual doesn't have a vacuum diagram.

I connectecd the line to an empty port on my intake manifold and the truck idles terribly. I couldn't even get it out of the driveway. Is there something else I am supposed to connect this to? Why is it running so badly on idle with the EGR connected?

Let me know.

Thanks,

 

I believe it should be connected to a solenoid. On my 302 the vacuum line from the egr is green. It is bundled with some other lines, is tucked behind the motor and emerges at the solenoid which is to the right of the coil pack. The solenoid is controlled by the ecu. Connecting your egr to a constant vacuum does not allow the ecu to do the switching. I may be mistaken for you application?

 

Ok, now I looked at the EVR solenoid, and there is nothing attached to it. So, I apparently don't have any EGR at all. Whoever had the truck before me disabled it completely.

So, it looks like I run from the EVR to the manifold, and the other EVR port goes to the EGR valve. I am assuming that it matters which one is which? Does anyone know if the inlet for the EVR valve is the upper or lower port?

Thanks.

 

This should be close but if you would post your Calibration Number I can post the sticker for your truck.

 

Is there not a vacuum diagram under the hood of the truck? My truck has a sticker on the bottom-side of the hood that shows where the lines are routed to, what colors they are, etc. That should answer all of your questions if the sticker is still there.

 

This is a picture of what I have on the 302 The green line is the one from the egr it is connect to the far left(forward) solenoid looks like upper port

 

I think the 302 is different, at least a little. This is what my 1990 351W looks like.

Here's the EGR valve with the green vacuum line coming off it:
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Here's the stuff on the driver's side. The vacuum line runs behind the engine to the other side. The green one is real dirty, but it's the top one going to the EVR closest to the camera.
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That should help. At least now you know the egr is connected to a solenoid and not to direct vacuum. From Andys picture it appears that they are similar in that the green is at the top port I cannot tell what color is beneath on Andys but on mine(302) it is red. It appears both are the furthest forward solenoids