99 & up 7.3L Power Stroke Engine and DrivetrainDiscussion of the 99 & up 7.3L Power Stroke diesel engine and drivetrain in the 1999-Up Super Duty trucks and Excursions. No gas engine discussion allowed except on transmissions and drivetrain that pertain to all models. Please confine discussion of topics in this forum to those items that are specific to the 7.3L Power Stroke engine.
Hello, we have an early '99 7.3L truck with 133,000 miles that has an intermittent miss (edit- now consistently). No engine light and no codes (using a simple code reader tool). One day last winter it ran poorly and some frozen water was found in the bottom of the fuel bowl. That was cleaned out and a new filter put in. It ran fine up until a couple of months ago and then started to miss with loss of power of course. Some days it will run fine, other days it's just slight, and still others are very bad. The fuel tank has been dropped out and is very clean inside. The fuel pump has been replaced.
Sometimes a cold start will be fine and other times it misses and starts a little hard. When it misses it will smoke a little, but clears up quickly and runs with just a very slight miss. Usually it will clear up nicely in just a couple minutes and drive fine. As it warms up though it will start to miss and loose power- don't notice any smoke though other than at start up.
About a month ago I used an infrared thermometer on the exhaust and found the manifold was cooler on #1 and 3 exhaust ports. I also checked connections on the injector wiring at that time and installed clips on the under valve cover harness. That seemed to take care of it. It ran great up until about a week ago and then started up again. It hasn't been a consistent thing, although it seems like it is now because it's been acting up every time recently.
Yesterday I fired it up to check it out. It started hard and ran bad (dying once). I let it warm up for about 10 minutes and then took it down the road. It had a single miss, but quickly started dropping more. Within 1/2 mile it was so bad it would only pull the truck at about 10 MPH and shortly after it died. It's like I was turning injectors off 1 by 1 with some fading back in once or twice (kind of like a cough/ chug if you were to run a truck out of gas). Trying to restart would get some fire, but not enough to run. We pulled it back to the shop where it fired up again (about 10 minutes after dying) and ran with a miss. (I'd say probably 2 cylinders down).
Today I pulled the valve covers and fired it up. It had a definite miss at cold start but better than yesterday. While running I unplugged injectors and both 1 and 3 didn't make a change. The others you could tell would drop off when unplugged. After a few minutes it was running with just a slight miss. #3 would drop off when unplugged and #1 would act like it was about 1/2. You could tell a slight change, but not as much as unplugging another injector. I've checked continuity on the under cover harness and the gasket and all seems fine.
I'd suspect maybe a couple of injectors, but what has me puzzled is how it will drop off more than just 2. The oil has been changed and was just done so recently. Would anyone have a suggestion or thought? I don't have a tool to buzz or check contribution, but have been considering getting the Auto Enginuity one. Any suggestions without that right now?
hello,
I have a very similar problem with the same truck/year. however, mine is even more annoying in that it goes away totally and comes back. If I shut the truck down and restart, sometimes the miss goes away. I have not done anything as far as trouble shooting. what is the deal the with injector clips? (I saw that on another post too). I am thinking electrical??? let me know how you make out I, I might try the same things
Same problem with my 96 250 7.3. I'm taking mine to the dealer Monday for a recall issue, I'll post what I find out. Back in 2002 I had similar problem on a larger scale (almost constant) and the problem was a crankcase ventilation sensor?
hello,
I have a very similar problem with the same truck/year. however, mine is even more annoying in that it goes away totally and comes back. If I shut the truck down and restart, sometimes the miss goes away. I have not done anything as far as trouble shooting. what is the deal the with injector clips? (I saw that on another post too). I am thinking electrical??? let me know how you make out I, I might try the same things
This one won't restart fine if it's missing. It doesn't come and go that bad. The clips are for the under valve cover wire harness. Where the harness plugs into the valve cover gasket, the catch to lock the connector in place can weaken and come loose. When this does it will break circuit to the injector(s). There are clips to install in order to keep the connections locked in place.
I'm going to work on the truck more this week to try to figure it out. Any suggestions are still welcome though.
This one won't restart fine if it's missing. It doesn't come and go that bad. The clips are for the under valve cover wire harness. Where the harness plugs into the valve cover gasket, the catch to lock the connector in place can weaken and come loose. When this does it will break circuit to the injector(s). There are clips to install in order to keep the connections locked in place.
I'm going to work on the truck more this week to try to figure it out. Any suggestions are still welcome though.
I have the exact same problem. I have a 99 F350 dually 7.3 4x4 with 80,000 miles. I have installed the clips.......no change. I would love to know what you find out. I own a 96 F350 7.3 2wd with 150,000 and the difference is night and day. You would never know they are the same motors.
Hello, we have an early '99 7.3L truck with 133,000 miles that has an intermittent miss. No engine light and no codes (using a simple code reader tool). One day last winter it ran poorly and some frozen water was found in the bottom of the fuel bowl. That was cleaned out and a new filter put in. It ran fine up until a couple of months ago and then started to miss with loss of power of course. Some days it will run fine, other days it's just slight, and still others are very bad. The fuel tank has been dropped out and is very clean inside. The fuel pump has been replaced.
Sometimes a cold start will be fine and other times it misses and starts a little hard. When it misses it will smoke a little, but clears up quickly and runs with just a very slight miss. Usually it will clear up nicely in just a couple minutes and drive fine. As it warms up though it will start to miss and loose power- don't notice any smoke though other than at start up.
About a month ago I used an infrared thermometer on the exhaust and found the manifold was cooler on #1 and 3 exhaust ports. I also checked connections on the injector wiring at that time and installed clips on the under valve cover harness. That seemed to take care of it. It ran great up until about a week ago and then started up again. It hasn't been a consistent thing, although it seems like it is now because it's been acting up every time recently.
Yesterday I fired it up to check it out. It started hard and ran bad (dying once). I let it warm up for about 10 minutes and then took it down the road. It had a single miss, but quickly started dropping more. Within 1/2 mile it was so bad it would only pull the truck at about 10 MPH and shortly after it died. It's like I was turning injectors off 1 by 1 with some fading back in once or twice (kind of like a cough/ chug if you were to run a truck out of gas). Trying to restart would get some fire, but not enough to run. We pulled it back to the shop where it fired up again (about 10 minutes after dying) and ran with a miss. (I'd say probably 2 cylinders down).
Today I pulled the valve covers and fired it up. It had a definite miss at cold start but better than yesterday. While running I unplugged injectors and both 1 and 3 didn't make a change. The others you could tell would drop off when unplugged. After a few minutes it was running with just a slight miss. #3 would drop off when unplugged and #1 would act like it was about 1/2. You could tell a slight change, but not as much as unplugging another injector. I've checked continuity on the under cover harness and the gasket and all seems fine.
I'd suspect maybe a couple of injectors, but what has me puzzled is how it will drop off more than just 2. The oil has been changed and was just done so recently. Would anyone have a suggestion or thought? I don't have a tool to buzz or check contribution, but have been considering getting the Auto Enginuity one. Any suggestions without that right now?
Thanks guys.
I have had a stalling problem with my 2000 f350 since I bought it 3 years ago. I've also had cold start problems, replaced glow plugs, cover gaskets, a few months ago. It did'nt help much, but I did notice 2 of the existing glow plug connectors were loss. Anyway, yesterday I decided to finish the job an install the supplied wire harness ends for the cover gaskets. I put things back together but could'nt get start up. So I went hunting for what I missed or inadvertantly disconnected. Here's what I found. While moving the wire harness, the solenoid on the IPR moved slightly toward the rear of the engine causing a no start. The nut that hold the solenoid in place was missing allowing it to move slightly back yet held in position enough by the wiring harness to cause an intermittent problem. Anyway after removing some packrat nest that I had noticed in the engine V since I got the truck, there underneath was the missing nut. So I suspect the previous owner was likely having the same problem. Put the nut back in place and started right up. Still having rough idle when cold kind of like is missing because it shakes.
Yeah, the IPR nut could cause problems for you. I've pulled this one out and the seals are in good condition and everything is in place.
I ran a Buzz and CC test. The Buzz tested fine. CC showed #8 which is not where I've been having the problems. I've got problems with a miss on 1 & 3 when I unplug injectors. Couldn't find anything else. I'm going to install new valve cover gaskets and under cover harnesses and see what happens.
I installed the valve cover gaskets and under cover harnesses and have the same problem yet so that didn't fix anything. I plugged in the scanner again for some live data. The exhaust back pressure sensor showed 52 PSI constantly and the MAP reading didn't change. The tube for the sensor wasn't very good and also plugged so I replaced that- no change. Then I took the sensor and MAP sensor from a good running truck to see what would happen and still no change. Runs terrible yet.
It is consistently running bad now. The miss doesn't go away- the amount of it just varies. I can start it up (although not easily) and drive it. It definitely has a miss, but within a few minutes or less it just drops off bad. The harder I push it, the worse it runs. If I floor it and keep it hammered it will soon run bad enough to die and not restart until it's sat for a few minutes. If I baby the throttle it won't clear up, but at least it stays running. Neither way with enough power to reach 60 MPH.
I'm beginning to wonder if it may be related to the high pressure oil pump. The scanner didn't show any problems there though so I'm still puzzled.
I checked the fuel bowl heater and in the process removed and checked the plastic check valve inside the bowl. Did not notice any problems, yet after reassembly the electric fuel pump buzz sounded different. truck started properly for two days, then the no start returned. fuel pump? Truck go to ford today, see what they can find.
Here's what ford said. Scan showed nothing wrong, glow plugs ok, IDT contribution cylinder test #5,#2, #7, cold. Pressure test at filter 60 psi running under load, 30 to 60 psi spec key on engine off fuel pressure test 45psi, crank case pressure test 0psi, monitor ICP cranking ok. Truck did start cold at -2 c the morning of tests, although it ran rough compared to the two mornings following the fel bowl incident.
In short ford wanted to change some injectors and do a compession test, although they were unable to contribute this to the irratic cold start issue.
Well we finally found the problem. I had tried swapping IDM, MAP, Exhaust Backpressure Sensor, and a few other things without any changes. It ended up being some junk had gotten into the mixing valve in the tank and plugged it up. When the fuel level got low enough it was mixing air into the fuel suction. It still maintained fuel pressure, but with air in the fuel. That was cleaned up and it's work great now.
Well we finally found the problem. I had tried swapping IDM, MAP, Exhaust Backpressure Sensor, and a few other things without any changes. It ended up being some junk had gotten into the mixing valve in the tank and plugged it up. When the fuel level got low enough it was mixing air into the fuel suction. It still maintained fuel pressure, but with air in the fuel. That was cleaned up and it's work great now.
That's good info to know. Usually air in the fuel causes the problem to erratic and seem to move around. As I read through the post I was leaning toward and electrical problem as it seems you were from the repairs you were trying.
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