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Old 03-14-2017, 02:38 AM   #11
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If there was a vacuumm leak it would not idle correctly... A small leak might be enough to cause a issue in drivability. A vacuum leak creates a lean condition and your story mentioned it but it would have to be a good size leak. Swap he ecu and test drive it again see if the code 31 comes up again.
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Old 03-14-2017, 03:13 AM   #12
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With a vacuum line unplugged my rig idled find but just a hair rough. Idled like it had a mild cam. Other than that I couldn't tell. Took me forever to find the issue! My vacuum gauge helped a ton.
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Old 05-06-2017, 02:50 AM   #13
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A leak down test was done and came out fine, but not a compression check.
We put in a new ECM and pretty much did everything that has been recommended on this thread. Vacuum test, fuseable links etc.
It is idling very smooth and quiet. The remaining issue is just no power under acceleration. Pressing on the gas has much less impact than it did before it started with this issue. We are pretty much stumped at this point.
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Old 05-06-2017, 03:19 AM   #14
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Fuel filter or fuel pump OK?
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Old 05-08-2017, 06:36 PM   #15
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Fuel filter and fuel pressure checked out fine at idle and under load
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Old 06-01-2017, 08:54 AM   #16
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It's been suggested that we just covert the TBI to a Weber carb and that should likely solve the problem.
With a 32/36 carb, what kind of drop in fuel economy should we expect?
Because it has a fairly heavy fiberglass rv shell on it, it averaged about 15 mpg when running well. I have read that you can lose 5-6 mpg after the switch. In this case, that would be a 35% reduction in mpg, which is pretty significant.
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Old 06-02-2017, 06:54 AM   #17
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Quote:
Originally Posted by zipzap8 View Post
It's been suggested that we just covert the TBI to a Weber carb and that should likely solve the problem.
With a 32/36 carb, what kind of drop in fuel economy should we expect?
Because it has a fairly heavy fiberglass rv shell on it, it averaged about 15 mpg when running well. I have read that you can lose 5-6 mpg after the switch. In this case, that would be a 35% reduction in mpg, which is pretty significant.
i would love to know who calculated those numbers lol
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Old 06-02-2017, 08:29 AM   #18
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Which numbers? I had read a few threads about going from TBI to carb and several people said they had lost about 5mpg. I was asking if anyone here had any experience with a drop in fuel economy. If this truck was averaging 15mpg, and loses 5-6, that's a 35% drop. Not sure which calculations you are laughing at, so any elaboration would be appreciated. Thanks
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Old 06-10-2017, 06:58 AM   #19
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When you say 'under acceleration,' did you try driving it up a hill? If it gets worse under a heavy load and starts missing, that can point to a spark problem. It idles good, but sounds like something is just shoving way too much fuel into it. Or not enough. Or the timing is wrong. Hopefully you changed the tensioner when you did the belt, otherwise it will jump time very shortly after the repair. Adjusting it from the distributor won't work. And it will KEEP doing it unless you put in a new tensioner. It sounds like the timing is retarded or something. Also, I hope they did a good job lining up the marks on the gears as well.

I have read your posts very carefully. NEVER, under ANY circumstances, change a timing belt without installing a NEW tensioner. I'm beginning to suspect your problem is the truck jumping a tooth on the belt because someone didn't change the tensioner. If it wasn't changed, you have to pull that front cover again and physically look at the timing marks and the belt to make sure both are perfectly aligned. If they aren't, make them right and put in a new tensioner as should have done in the first place. That's my best advice. But you have to eliminate that possibility first. At this point, if you DID install a new tensioner and the timing marks/timing check out, stick your finger and move it around in the exhaust pipe. Black carbon is okay. Wet black and you have to start looking at compression problems, like bad rings. White smoke indicates coolant in the oil and usually means head gasket, although you would probably have figured that out by now. This sounds more like a retarded engine. If it were too advanced it would backfire like crazy. You say you've checked good for vacuum leaks, so you might be able to eliminate intake gasket, which would cause rough idling for sure. Pushing on the gas pedal and no power sounds like it's retarded for one reason or another. It's either that or there is a problem with the gas pedal linkage actually delivering enough fuel to the engine. You could try a test where you take off your air cleaner cover and rev the engine, while someone else sprays more fuel or starting fluid into the throttle body at the same time. If the revs suddenly go up and sound powerful, either the injectors aren't delivering enough fuel, or your gas pedal linkage needs work. Tough problem, I'll admit. I can't wait for the final post where you tell us it finally works, no kidding. I might not be right on all my suggestions, but I hope at least SOME of them help. Good luck and keep us updated.

You have to watch these repair shops sometimes. When they get timing belt jobs, occasionally they will try NOT changing the tensioner just to save a few bucks. ("Oh, it looks okay....") MOST of the time, that engine will be fine for a few thousand miles, but sometimes not if the tensioner was worn worse than they thought. Or they just get greedy. Then the belt will jump time. But if any time passes beyond a few months, they know you can't blame it on THEM. I got screwed once on a Suburu 4WD wagon that way by a shop. That's when I went back to Nissan. I junked the Subie for $250 but before I did I pulled the radiator and the front cover. Sure enough, that tensioner was way worn beyond new, and I knew they had cheated me. I never went back to that shop again. They are no longer in business.
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Old 10-03-2017, 08:52 AM   #20
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Ok. So here is an update. After putting in a 3rd set of injectors, she is running properly at idle and from 0 to 50% pedal depression. Acceleration is responsive as long as you don't press the pedal more than halfway down in any gear. As soon as you press past he 50% point, it will rev up like it wants to push forward, but there is virtually no change in acceleration. (After a few repeated full presses, it will then start to buck and sputter.
Unless anyone has any brilliant ideas from this latest description, I think I might have no other choice than to do a weber carb swap. I was hoping to do the 32/36 for better fuel economy, but weber is suggesting the 38. K644-38. Does anyone know if a special adapter plate needs to be made or found elsewhere? And does anyone know if the 32/36 would work on the vg30i? Thanks again for all of your input. Not giving up yet!!!
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