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Discussion Starter · #1 · (Edited)
I was curious how far I could go on a tank (city driving). Filled it up ($42.00) and ran it until the fuel light +15 miles. I got 162 miles on the odometer. That's about 8 mpg. Slightly better than a Semi. That's pathetic

2001 SE Crew Cab 2WD Auto (non turbo)
 

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Yep, sounds like your 16 or 17 year old engine may have some issues or you have a fuel leak.
 
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Discussion Starter · #3 ·
I know it's not a fuel leak. My guess is it's a combination of my aggressive driving and shitty 16 year old auto transmission technology. Every time I need to accelerate quickly from a light to get ahead of everyone the truck redlines until I let off the gas, then it shifts into the next gear and just sort of slow crawls until the RPMs get up into the powerband. It's almost as though it needs another gear in between.

I'm a manual transmission guy, so I'm not sure if this is normal or not for older vehicles. I've read that modern autos are comparable to manual due to more gearing, but back in the day (early 2000s) the auto trans were horrible on gas and acceleration. Can anyone confirm this? Should I be driving it like an old lady?
 

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My guess is it's a combination of my aggressive driving and shitty 16 year old auto transmission technology. Every time I need to accelerate quickly from a light to get ahead of everyone the truck redlines until I let off the gas, then it shifts into the next gear and just sort of slow crawls until the RPMs get up into the powerband. It's almost as though it needs another gear in between.

Should I be driving it like an old lady?
This ^^
 

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The VG33 is reliable as hell but has little power. It makes up for this with lousy gas mileage :)

Really, do a good tuneup and if driven normally should be fairly good on gas. i average about 19 combined hwy/city. On the highway, use cruise it helps a lot.
 

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Discussion Starter · #6 · (Edited)
Well I know for sure there's no fuel leaks. I did all the basic tuneup stuff... Plugs, wires, injectors, Air filter, fuel filter, seafoam, converters, MAF, etc. but I imagine there's still work to be done. My dryrotted intake hoses for one. I know the main hose into the manifold has a few large cuts in it. And the entire EGR system has been blocked off. Plus the truck idles around 2k on startup and stays until put in gear and driven for a couple minutes. I guess I'll start there next.
 

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Well I know for sure there's no fuel leaks. I did all the basic tuneup stuff... Plugs, wires, injectors, Air filter, fuel filter, seafoam, converters, MAF, etc. but I imagine there's still work to be done. My dryrotted intake hoses for one. I know the main hose into the manifold has a few large cuts in it. And the entire EGR system has been blocked off. Plus the truck idles around 2k on startup and stays until put in gear and driven for a couple minutes. I guess I'll start there next.
If both your pipes pre and post the MAF have leaks in it, tHat is unmetered and added air. That will wreck havoc on your air/fuel mix and thus your MPG. If nothing else duct tape those hoses/pipes.
 

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Discussion Starter · #8 · (Edited)
... If nothing else duct tape those hoses/pipes.
I agree with you on the air/fuel mixture being thrown out of whack. I'm also wondering now if it's only idling high on initial start up due to the air temperature. I'm sure I read somewhere that there's a sensor that monitors air temp and factors that in. The smaller hoses are wrapped in electrical tape at the clamp points due to rot and tearing. The main hose is so tightly compressed between the manifold and airbox that I can't hear any air being sucked in through the cracks. Obviously this isn't an ignorant attempt at ruling them out of the equation. Just me fooling myself into believing it's not an emediate priority (been restoring this truck for a while). They're definitely high on the list for this month. And while I'm not overly clueless on the intake system in general I am very much a noob when it comes to the ECU, so all of this is good info. I appreciate it.

I'll contact a few dealerships today for the factory hoses and update on any status changes.
 

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You can get a generic replacement main intake hose off eBay for 15-20 dollars. Courtesy Parts has it for around 50. Mine needs replaced as well. I currently have it wrapped with electrical tape, but I haven't ever had idle problems.
 

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I agree with you on the air/fuel mixture being thrown out of whack. I'm also wondering now if it's only idling high on initial start up due to the air temperature. I'm sure I read somewhere that there's a sensor that monitors air temp and factors that in. The smaller hoses are wrapped in electrical tape at the clamp points due to rot and tearing. The main hose is so tightly compressed between the manifold and airbox that I can't hear any air being sucked in through the cracks. Obviously this isn't an ignorant attempt at ruling them out of the equation. Just me fooling myself into believing it's not an emediate priority (been restoring this truck for a while). They're definitely high on the list for this month. And while I'm not overly clueless on the intake system in general I am very much a noob when it comes to the ECU, so all of this is good info. I appreciate it.

I'll contact a few dealerships today for the factory hoses and update on any status changes.
I believe that the mass air flow sensor on these trucks are of the heated wire variety. Thus colder denser air is compensated for. Your truck should go into "cold start enrichment" right when you start it with the higher RPM as a result. This is based on a coolant temp sensor. When the coolant temp is warm your car should idle back to normal. In some cases this temp sensor is faulty and the car stays in cold start mode. This will defiantly eat your MPGs, cause low power and pollute like a MFer. You might be able to test this if you get the resistance (ohm) spec for specific temps. However testing at the sensor might not give the reading which the ECU reads. The connection might have corrosion (green death) and will increase the resistance. Reading at the ECU pins is the best place. Or just remove the sensor and clean the tip as well as the connector.
 

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Discussion Starter · #11 ·
... In some cases this temp sensor is faulty and the car stays in cold start mode.
You may have touched on a game changer there. I thought that the two-wire connector and temp sensor was purely for the temp gauge. My connector broke, so I ghetto-rigged the wires in there to get the gauge working. It's possible the connection isn't good. Though I doubt the temp gauge would work if both wires weren't snug on the leads, but worth a shot to double check when I get home later (drove the 95 Pathy in today... because I like it better lol).
 

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Don't know how my Frontier does it as it is new enough I hardly work on it (as far as engine stuff). But on my 300zx there are 2 temp sensors. The 2 wire unit is for the ECU. There is another single wire unit that is for the gauge. If this convention holds true for newer nissans, the 2 wire temp sensor you have is for the ECU. Just check the parts. It is still like this. 2 temp sensors, one for the ecu the other for the gauge.


 

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Discussion Starter · #14 · (Edited)
You can get a generic replacement main intake hose off eBay for 15-20 dollars. Courtesy Parts has it for around 50. Mine needs replaced as well. I currently have it wrapped with electrical tape, but I haven't ever had idle problems.
Yeah, definitely need to go aftermarket on these. Dealership wants nearly $300 for everything I need. And I still haven't found the two molded intake hoses that come off the main. Be nice if they just had a ''hoses" section


Oh, and tried manually attaching the temp sensor wires to the leads. No change to the high idle. Also tried jiggling intake hoses looking for idle fluxuation. No changes. Held steady at 2100 RPMs. Thus far putting it in gear is the only thing that drops the RPMs to normal. Still... I'll swap everything out with new parts and repair the wiring before closing the book on them as suspects. Needs to be done anyway, so nothing lost from the cost.
 

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Discussion Starter · #16 ·
Solved half the problem. Removed the TPS a while back without understanding what it is or what it does. I made sure it engaged the throttle body when I put it back on, but didn't adjust it. The connectors were facing downward as far as it would go.

I simply adjusted it up some until the RPMs were normal, then tightened it back down.
 

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TPS adjustment is critical on these engines and you don't just turn it and lock it down. The adjustment needs to be set using an ohmmeter and a set of feeler gauges. The closed throttle position switch is "learned" on these engines, so that has to be relearned after the adjustment. I'm attaching a TSB that describes the procedure, however, use the measurements for the R50 Pathfinder for the VG33E motor as the D22 Frontier specs are for the KA24DE (the only available engine for the D22 Frontier at the time of the TSB's release).
 

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Discussion Starter · #18 ·
TPS adjustment is critical on these engines and you don't just turn it and lock it down. ...
Sorry, I didn't mean to give the impression that I was going to leave it as is. I went to a pick n pull this afternoon and scored new-ish hoses. After replacing them I noticed no change in the 2000 rpm idle. I also cut some connectors from a decent harness to replace my aged temp sensor connectors. Still no change. I then remembered watching a video on TPS adjustment for the Frontier, in which the guy had his TPS screwed just about dead center. After remembering this I thought 'what the hell' and checked mine. It was way off center, so I turned it to center, the RPMs dropped, and the rest is history.


I intended on following that same video to adjust my TPS tomorrow.

 

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Well, it is your truck and if you want to adjust your TPS as done in the vid, that's fine. However, that is NOT the correct way to adjust the TPS and he also never relearned the closed throttle position switch. If you want to do correctly, then follow the procedure for the R50 listed in the TSB I provided, which is the same as instructed in the updated FSM for your Frontier. Good luck!
 
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