Stock 6.9 IDI acceleration.

[thx997303]

I was looking at an 85' F250 with a 6.9 IDI earlier today, and test drove it.

This was the first time I remember driving one of these, and it seemed like the thing would only barely accelerate after you mashed the gas pedal. Keep in mind I'm used to stock Honda 4 cylinders as I own three (though one is a motorcycle and fast) and they don't really move quickly.

It almost seemed like the engine wasn't doing any accelerating, though the truck did move. If I got over 60% throttle or more, you could actually eventually hear the engine and then it would accelerate.

Is this normal for the NA 6.9 and 7.3 IDIs? Or is it possible that truck needed some tuning?

Trying to decide whether I want to buy one or not.

Edit: Might also mention it has a C6 transmission.

 

[fordf350man]

i have a c6 with a 7.3 idi n/a and its the same way, when i mash it will kick at first then it just drags, i think it mainly because of the c6, there are members on here that say there n/a idi trucks are pretty fast but i am pretty sure they all had 5 speeds in them, i will say that after changing my fuel filter the truck did accelreate better

 

[icanfixall]

Usually poor acelleration is due to timing. These engines are very timing sensative. A 2 degree change means a lot more than it does in a gasser engine. Age and miles on the injecters and injection pump have a lot to do with a good running engine too. Finally the rear end gears are very important no matter what trans you have.

 

[franklin2]

I was looking at an 85' F250 with a 6.9 IDI earlier today, and test drove it.

This was the first time I remember driving one of these, and it seemed like the thing would only barely accelerate after you mashed the gas pedal. Keep in mind I'm used to stock Honda 4 cylinders as I own three (though one is a motorcycle and fast) and they don't really move quickly.

It almost seemed like the engine wasn't doing any accelerating, though the truck did move. If I got over 60% throttle or more, you could actually eventually hear the engine and then it would accelerate.

Is this normal for the NA 6.9 and 7.3 IDIs? Or is it possible that truck needed some tuning?

Trying to decide whether I want to buy one or not.

Edit: Might also mention it has a C6 transmission.

Yes, they are slow. These are old school diesels with no turbo. They are built heavy, and you can hold the pedal to the floor with a load behind it and it will putter happily all day long. That's just the way they were built. Empty mine accelerates about the same as my smogged up 351w with a 2bbl in my old f150. Where they shine is when you are hauling something. With the 351w it was noticeably slower with any kind of load in the bed or on a trailer. The diesel slows noticeably less with a load behind it.

 

[NO_SPRK]

i feel 85% of power loss in these engines is just old pumps and bad injectors.. also timing.

ive learned that some engines run fast and some run slow.. right now my crew cab has a NA 92 engine painted cat yellow and only jebus knows how many miles are on it.

it starts right up and runs great. pushes a 4wd cclb with 33s faster then my single cab.. with the same trans combo.. the IP and injectors are brand new on the crew cab. my single cab has a freebie unknown pump from towcat on it with new injectors. both 4.10 trucks.

a 6.9L with a C6 and 3.55 could feel like a dog. my 4.10 e40d puts down the torque and this is without a lockup converter (still tracing wiring)

 

[argve]

First off let me welcome you to the site. You have found hands down the best site on the internet for information concerning the InDirect Injected Diesel engines Ford used from 83-94.

Now as for your accel question. Yes they are slow and a lot of that comes from the automatic transmission that was used behind the 6.9's the C6 is pretty much a work horse but she's not gonna win any races. The fact that it doesn't have a 4th gear (overdrive) and is also lacking a lock up torque converter causes the engine to spin up more and less power to get transferred to the drive wheels. Now that being said it's not a bad combo because it will run for something short of forever just won't win any races along the way. So it sounds like the one you looked at is just like the ones I have driven and owned. Now as Gary mentioned if you do pick up the truck you might have the timing checked as it might be out. I know mine makes a lot of noise but she's not really moving a lot but I can feel the torque in my lower back as she takes off as she is moving a lot of weight - these trucks aren't light by any measure.

 

[thx997303]

I won't be buying that specific truck. There were many things that suggest poor maintenance. The seats didn't fold as they should, the ignition was bypassed, the headlight knob was missing, the paint was rattle canned, and it wasn't 4x4.

Thanks for the welcome. I'll keep looking, but I will be looking for either overdriven autos in later trucks, or 5 speed manuals.

 

[icanfixall]

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The overdrive auto trans called the E4OD was first offered in our rigs in 1989. I got one of those trucks in the single rear whel crewcabs. It has 3.555 gears and I'm finally changing them for 4.10 gears. The truck weighs 6200 lbs mt but moves out well enough. With the overdrive trans and the gear vendors aux overdrive trans behind it I can cruise at 85 mph in double overdrive turning 1850 rpm. My starts from a dead start are slow and thats the only reason I want to change the gears.

 

[thx997303]

Any known issues with the 5 speed that came in these? And when did they first install those? Same year as the E40d or later?

 

[icanfixall]

The only issue I read about the zf 5 speed trans is the gear rollover noise when you replace the dual mass clutch flywheel setups. The single mass whell and clutch does not dampen the gear noise. Some hate the sound and others have no issues with it. Heavier oils wil not fit that without causing other issues like cnycros wearing out quicker. Others with more 5 speed experiance will chime in.

 

[thx997303]

Well, I looked at a 92' four door today. E40d trans, and NA 7.3

This one was nowhere near as slow as the other one. It smoked pretty well the whole time. Started ok. Its 2wd though. The oil was Los, so I would assume that the coolant wasn't maintained right. Still looking I guess.

 

[chris142]

Mines acceptable. I bought the tool and timed it and that made a huge difference. Stock I could merge on the fwy about 35 mph. After timing I can merge at 50-55.

 

[franklin2]

You will find transmission problems with most of these trucks you are looking at. If they are the early pre-95 trucks, those E4OD trannies had a lot of problems, and most are rebuilt by now, or are sitting in the weeds somewhere or have been swapped out. The rebuilt e4OD's usually do well from what I am told, and are usually upgraded when they are rebuilt.

The zf's are a good tranny, but most will want to pop out of reverse. It's a little quirk they seem to develop that can be fixed by tearing it down, or you can just carefully hold pressure on the stick while you let out on the clutch, and it will work ok unless it's really bad.

The biggest problem with the 5 speeds was already mentioned, the flywheel. I don't know if you are familiar with dual mass flywheels, but it's really two flywheels in one, with springs connecting the two. The diesel really hits hard when it fires, and this hard hit is transmitted through the driveline to the tranny, and it makes the tranny sound like it's falling apart. The two piece flywheel dampens this noise, but just like the clutch, it wears out. When the clutch is replaced, the flywheel should be replaced also, but it's expensive. So many people convert to a solid conventional flywheel, but of course you get the noise from the tranny.

 

[79jasper]

I think it was 87 that the zf-5 started. Maybe 88. I know my 88 had one.

I haven't heard of this reverse popping out issue.

 

[IDIBRONCO]

I've seen 2 5 speeds in '87. Mostly they were in '88 and up. I like my two. I think they feel better than the 4 speeds when shifting. They were prone to synchronizer troubles when not shifted right. If you have one apart, replace them. If you shift them like a truck and not a race car, you'll have few problems with a zf5. Also don't start out in 2nd gear, 1st is there for a reason. I uised to work for a guy who had a 1995 ccdw, psd, and a zf5 (same basic transmission). He used it to pull around his front end loader and always had it loaded down with stuff for his scrap iron business. At about 206,000 miles, I had to pull the transmission because the dual mass flywheel came apart. I put a new clutch in it just because, but the old friction disc still had half the lining left on it and could have been reused. He drove the truck for several years until he upgraded to a 1999. His 1995 then became a dedicated car hauler pulling around his three car hauler for his car auction. No one ever had any transmission troubles that I heard of.