I'm going try and keep this short but I want to make sure that I provide all of the details. I live in N. MN and I don't really have anyone who is very familiar with the Dmax. If someone would be willing to help me w/ my truck, I am willing to travel to your location. I would like to find someone in MN or WI, but I would be willing to travel within reason.

So here is what is going on..
My truck starts fine and does not run rough. No smoke. I am having a lack of power and poor throttle response. I drives like a dog.

Things that I've had done
Check air filter
Clean map sensor
Multiple fuel filters tried
New coolant temp sensor

I had it scanned and the cp3 checked out
There were two codes. Onefor headbolt heater and one for tranny, I had put it into limp mode once.

I had been smoking white/gray at idle and take off. My #1 and 7 injectors were out of tolerance. I changed all four passenger side injectors two days ago. The smoking is gone but I still do not have power and throttle response. I was hopful that by changing them it would have helped w/ better throttle response.

About two weeks ago, I had done the injection cleaning with the cleaner from dealer. I mixed 13 oz of cleaner w/ 1/2 gal of fuel. Truck idled for about 1:45. Immediately after the cleaning the truck ran AWESOME!! Very good power and throttle response. That only lasted that day. The next time that I drove the truck, it was back to running like a dog. I changed fuel filter and it did not make a difference. That's when I decided to replace injectors.

PLEASE someone help me figure this out!!!
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2003 LT crew cab EFI w/dsp5 Banks 4" exhaust. Autometer gauges.

 

do you have a way to see the desired rail pressure vs the commanded rail pressure?

 

did you actually replace them or just decided to? if you already did then i would think that the CP3 is the next one in line to get replaced

if you have a way of monitoring your desired fuel pressure vs actual fuel pressure & balance rates, this would tell us a lot.

if your shop has a tech2 (or know someone with EFI Live) they should be able to command max fuel pressure while idling. if the injectors are returning too much fuel that will drain your fuel rail and make it hard to build pressure. a weak CP3 will also do this

Jason

 

Yes, I replaced the passenger side injectors. The balance rated were ok on the other side. No, I don't have access to a scan tool. Last time I brought it to dealership the charged me $92.00 to tell me nothing was wrong even though I was smoking at idle and my #1 inj was at a -4.5 in park. The guy told me their tolerance was +/- 6.

Anyways, I had brought it to another place and we checked the desired vs actual on the cp3.
It was calling 23,000 and it was putting out 23,000 at wot.

I'm wondering if my problem might be with a contaminated tank. Several months ago I got a bad batch of fuel and my truck was chugging a little. I ran tank down and replaced fuel filter. It ran a little better but still not great. I would do the chugging thing again. Not bad but enough for me to notice and not all of the time. I changed filter again. This time no chugging but still no power/ throttle response.

This is when I did the inj. Cleaning. Right after cleaning I checked rates and my #1 went from a -4.5 to a -2.5. I drove it right away and it ran great but that only lasted for that afternoon. The next time I ran it, back to running like a dog.

I changed fuel filters again and still not any better. This is when I decided to replace the injectors with hopes of getting better. The truck isn't smoking anymore but it didn't make any power gains.

Is it possible that my tank has crud in it and it keeps clogging my filter or that it's clogged somewhere else? I've been running lots of additives and that isn't helping either.

It's like I have a dead throttle. I have to put the peddle down to where I start to feel resistance to go like 60 mph.

 

wow, that's a lot of filters.

right now it would be hard to say with out monitoring the desired vs actual fuel pressure. there are several reasons one can have low fuel pressure. restrictions like you mentioned, collapsed fuel lines - the rubber lines in the engine bay around the filter and CP3 pump, excessive returns from the CP3 or one or more of the injectors.

in my opinion one should not solely relay on balance rates to determine which injectors to replace. excessive return from the injectors can play havoc on the trucks performance and you wont see this in the balance rates.

you could check the return on each bank and compare the two. the side that you replaced can be used as a reference.

there is also a return line coming out of the CP3 that could be checked for excessive return.

these will all cost money unless you could do this yourself, there are several good write ups on these and other forums.

when you command 23K PSI this should be done at idle to see if it can obtained. the CP3 is driven off of the engine so when you are at WOT/3200 RPM the CP3 can supply more fuel then when at idle.

others might be able to chime in on this and provide more information.

Jason

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reading over your post again, was thinking.

if you where able to maintain 23K PSI at WOT i don't think it would be a restriction in the fuel lines. otherwise the PSI would drop. Flow = PSI, PSI does not = Flow. if you cant maintain the flow then you cant build the PSI. you need more flow then what is being used otherwise you cant build pressure.

seems that we may be dealing with another problem.

Jason

 

I don't know if this will be helpful to know but it seems like it defuels for a split second before it shifts.

I am going to get it scanned. Other than cp3 desired and actual, what else is important to check? With the possibility of it being a line problem, how would I check for leaks etc...

Thanks

 

these trucks are supposed to defuel during shifts, its not supposed to be harsh and make you spill your coffee in the morning if that's what you mean.

if the leak is on the high pressure side you should see it. if it is on the supply line to the CP3 then pressuring the fuel tank may help. most people use a rag and air hose stuffed in to the filler hose. 5 to 10 PSI should do it, no more then 10 PSI so you don't damage the fuel tank.

if a leak was on the supply side and large enough to cause problems it would likely to cause it to have excessive cranking before starting or needing to prime it to get it to start, it it was a large leak and you did manage to get it to start then it would probably stutter while idling.

Jason