This is about my 1989 F350 with 7.5L and E4OD. My truck is having problems cruising and idling. At low to mid throttle, it will occasionally stumble, and feel like its losing power. And then it'll just stop and run fine. While cruising, it will lose speed, without dropping RPM much, and then start chugging. It will occasionally start chugging/stumbling and have a pulsing idle while stopped in gear. Putting in neutral stops the chugging, but it vibrates a lot like it's misfiring. And then just stops. 50% - WOT on the throttle and it runs like a raped ape. No issues. While cruising and its stumbling, adding more throttle bogs is down for a quick second, and then it takes off.

Fuel pressure looks good, 31 PSI at idle, vacuum connected, 39 PSI vacuum disconnected. 22-23 IN-hg idle vacuum, and the gauge seems to respond normally. TPS measures 1.06V at idle, and 4.8V at WOT. In the 1 - 2v range, I can count the hundreths of a volt one by one, so I don't believe it has any dead spots. Resistance is 1.1k closed, and 4.6k WOT. I changed the air filter maybe 2 months ago, and haven't driven it much, so that's good. I've also disconnected the vacuum line to the EGR valve. No change. Fuel filter was changed a year and a half ago or so.


When pulling codes, I get a 62 - E4OD excessive converter clutch slippage and a 41 - System was lean for 15 seconds or more (no HO2S switching). The 62 comes and goes, but might just be an old transmission. Fluid looks clean and doesn't smell burnt. The 41 I've had since I got it about 2 years ago. I should probably replace the O2 sensor. I don't think it's relevant as this issue is only a couple months old.

I got to test a little bit this evening. Pulled the distributor cap, the rotor had some black stuff on the end, as well as the contacts on the cap. Cleaned that up with some sandpaper and it didn't change anything. I messed with the MAP a bit. Without a vacuum source, it ran like ****, threw a code and died. Unsurprising. Unplugged it ran the idle up to 1400 or so, and otherwise seemed fine. I'm assuming that's default behavior. I put a vacuum gauge in the line to the MAP, and it's getting a good vacuum signal.

It really only seems to have an issue at less than half throttle. I feel like the issue is a sensor, but I don't know which one, and it won't throw any new codes to narrow it down

So, can someone give me something to test to see if I can figure out what's going on?

 

So many times I've seen these symptoms and it comes down to a vacuum leak. Start there, it's almost free.

 

i have an 89 e350 in a rv doing almost the same did u find the problem