I just finished replacing a 351W on my 1988 F250. My hat is off to all of you who have done this job.

The truck runs phenominally well with more power and smoothness than I can ever remember in all of its previous 186,000 miles.

Electrically I replaced the wires, cap and rotor as well as the distributor in the rebuild. I had the injectors cleaned and pattern tested to within 2% of each other.

From a fuel standpoint the tank is new as are both pumps and filter. I also put in a new clutch assembly and steering gearbox. What a different feeling!

This issue is at idle. With the spout off the timing is dead steady and smooth at 10 BTDC. As soon as the spout is reconnected the idle becomes rough and the timing mark is all over the place.

My code readings shows an EGR below low limit so I'm going to put in another EGR sensor tomorrow. I also recently replace the TPS and ECS sensors .

It seems obvious to me that with the EFI sensors sending info to the PCM (with the spout connected) the rough idle has got to do with one of those components.

Any input on what I might try would be appriciated. My code testing is limited to an ohm meter. I don't have a breakout box.

 

I could imagine a stuck/sticking or non op egr could do that. It would be trying to regulate off of false input.

 

i just had close to the same problem.... Pull egr vacuem hose and plug it. Idle will smooth out if thats the issue

 

I have no vacuum at idle on the green EGR hose from the EGR solenoid to the EGR sensor.

Is there suppose to be vacuum on that hose at idle?

How does the EGR solenoid work? The solenoid on my vehical sits on a bracket next to two vacuum switches to the right of the coil. It has a white cap and two vacuum hose outlets with a two-stage electrical connector. Inside one of those stages is a small in-line resistor.

How does this thing work and is there a test for this?

 

How about the IAC? I believe there is a check for it in the haynes manuals.

 

IAC might be a possibility. I change out the EGR sensor and fixed the code problems. I now get 11 - system pass. However the rough idle continues. I don't have a Haynes manual - I have Chilton. I tested the IAC sensor as per the Chiltons a while back. Seemed OK. I'll take another look.

What does Haynes say to do?

 

Have you changed plugs on it lately? How about wires? Might start with a good set of plugs, and ensure the wires are routed correctly. If that doesnt fix it might put a set of wires and cap and rotor. Just a thought........

 

Electrical except for coil is all new including distributor. Fuel delivery is virtually new or reconditioned as well. In my mind everything is eliminated except the EFI components. The truck runs smooth at idle with the spout remove and like crap when it's reattached!

 

how about distributer module.... I thnk autozone can test those.... Have you checked fuel pressure yet

 

THe ignition module came new with the distributor and the fuel pressure regulator was also replaced.