1989 7.3 IDI has me stumped

[7.3coutryboy]

Hi guys I am hew to the site, I hope you all ca help me with issue I am having. My 7.3 started cutting out at low rpms it seems to do it between 30-35 and 40-45 mph. Its not cutting out all the way but just enough to drasticly drop my rpms, but when I bare down on the throttle it picks right up and goes on without any issues. Look at the video and notice the tach going up and down.



http://youtu.be/53I124pRBqM

 

[icanfixall]

Welcome to the forum and thanks for the viedo. Its difficult to determine whats going on. It almost looks like the tach sender is failing by the way it jumping up and down but can't say from here. Are you feeling the engine cutting out. If so what level as the fuel tanks. If they are down to 1/4 they are probably sucking air. The suction heads breaks off in the tanks and then we can't use the last 1/4 tank of fuel so we effectively run out with a 1/4.. Easy fix if you want to or just don't get down that low again. Engine sounds ok but more infor is required to really tell you whats going on. How many miles are on the injecters and injection pump. normal life is 125,000 miles. Some more ans some less.

 

[warhog]

i'm guessing it's just the tach too. Going around that corner the tach was reading zero....the engine was definitely spinning.

 

[redneckaggie]

turn the radio off, roll the windows down, and listen to the engine. You might still be losing power if it is just the tach because of the automatic tranny. what you need to determine is the engine really stumbling or trying to die or is the tach just telling you that.

 

[laserjock]

If you listen close you can hear the engine cut out. Radio aside. I have no idea unless it's running out of fuel. Seems like the most likely scenario. It's not like a gasser where it could be spark or fuel. Could be at any point in the system from the tank to IP. I suppose it could be an intermitent electrical problem. Might check the line to the FSS on the IP. That would certainly cause it to cut out completely. If it were me, I'd check the easy stuff first then work my way through the fuel system front to back.

 

[Can30Diesel]

Take another video without the stereo on so we can hear the engine better. It sounds like its cutting out then catching itself. It could also be the transmission bouncing from one gear to another.

 

[icanfixall]

Try the wires on top of the injection pump. The large spade connection is the power to run the engine. Its called the fuel shutoff solenoid or FSS switch. If that's tight try running a jumper wire from any hot on the battery. But know this. When you have the hot to that plug with the wire removed that's normally on there you can shut down the engine with the ignition switch. You have to remove the jumper wire. Not a big deal. Just kind of scares some once in a while. Several members run like this now for various reasons.

 

[7.3coutryboy]

Thanks for the replies guys, it still does it even with a full tank, I also tried the jumper wire and it still continues to do it. I apoligize for the radio in the video but every time I tried to make a video it seemed not to do it so I had to catch it when I could. I have also replaced the TPS sensor and the fuel filter also so I am stummped. It only does this at low throttle for example while you are in a curve. The truck runs great otherwise. The truck is a 1989 model but only has 142,000 original miles on it.

 

[Agnem]

Any possibility this is a key-on power issue? Your whole instrument panel could be loosing power, but the tach is the only thing that is going to show such a brief interruption. Connect an alligator clip lead from the positive battery post to the injection pump FSV solenoid and go for a drive. If it stops doing it, that's what it is. Note that if the power cuts out too long, the little lead you connected won't have enough amp carrying capacity, and may well get hot or burn up. Especially if it's not a break in the harness, but a short. :O

 

[riotwarrior]

weak lift pump?

 

[bennersaw]

mine did some thing like this and it was the tach sensor. my transmission is an e4od and it needs the tach sensor to shift right.

 

[Moosebob]

I vote tach sensor also, that needle moves to fast for it to be an accurate reading. My tach won't register anything below 1500rpm but jumps right up there when you step on it. Can you see bare wires at the sensor? Mine are exposed more than half an inch (sounds so dirty!) but I haven't felt like coughing up the cash for a new sensor yet.

 

[icanfixall]

Tach sensors are a required part that must be in working order for an E4OD auto trans to function properly. Not so on a standard trans. The E4OD has several important electrical pickups that must function properly for it to shift correctly. Tach, Speedometer feed sender at the cable on the rear of the trans and the tps on the injection pump. I suppose you can throw in the mlps on the shift lever at the side of the trans. On the 92 and up years the speedo is electronic so there is no cable input but there is an input from the rear differential