Misfire / Very poor fuel economy - Defender Source
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  #1  
Old February 6th, 2006, 12:16 PM
Jerry
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Jerry Silverman
97 D-90 SW
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Misfire / Very poor fuel economy

Guys…….i’ve been reading through the posts and am still a bit puzzled by what my truck is doing. 97 D90 SW w/115K.



Accelerating from an idle to about 2,500 rpms I have a significant power loss / lag to the point where it almost feels like its gonna stall. If I stay on the gas it resumes normal power after about 2,500 rpms. Twice the check engine light has come on and is displaying the 300 code Misfire on Multiple Cylinders.



So here is the strange part. I only experience this problem when driving on a low tank of gas…… about less than an eight of a tank. On top of this I am getting very, very bad fuel economy. About 180 miles to a tank running 93 octane.



Looking through the service records the plugs have about 15K miles on them, fuel pump was changed at 60K, valve job at 52K, new exhaust and air filter at 105K, and the injectors were cleaned at 105K. Can’t find where the fuel filter was changed.



Any suggestions, insight, help would be greatly appreciated!
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  #2  
Old February 6th, 2006, 02:28 PM
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Stephen Whitaker
1994 D-90
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The symptom of apparently only acting up on a low tank of gas has me stumped, but I have been stumped before - - and often. A clogged fuel filter might starve the engine, but it should manifest itself more often than only when the tank is low. I suppose something might be clogging the fuel line in the tank itself that only affects the flow when the tank is low on fuel (debris in the tank??). As for the rotten gas mileage there are a few suspects in my mind; ie ignition, ignition timing, valve problems. I am sure some others with more experience with a '97 ought to chime in shortly. Start by examining the easy-to-fix things, like ignition parts and timing.
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  #3  
Old February 7th, 2006, 08:07 AM
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George Parthmer
1995/d-90 #2715 yellowST
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i had the same problem. i was driving home from school one night and the 90 jut started to freak out. i parked it, in fear that i would blow an injector or worse. so - i went to my local garage that i have do all of the really tricky rover stuff and they suggested a product to clean the fuel system. it was called SEAFOAM, or something similar to that. i put it in the tank, filled it up and i have had no problem since. it is a great product! i reset the check engine light by disconnecting the battery for a couple of seconds and never thoguht about it again until i read this post. give it a shot - cant hurt, right?
george

i dont think it would matter if the problem is in the fuel system, but i have a 3.9 litre (95) instead of your 4.0 (97)
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  #4  
Old February 7th, 2006, 09:38 AM
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Well, I have a 97SW with 56K miles and have experienced what I consider poor performace since i purchased the truck last June. I've never experience better than 180miles/tank, but on a 3.9 w/ almost 100K miles i consistently got 210-220. This weekend it got worse...This weekend i used a product many people around here rave about called BG44K($25/bottle). After about 30 miles I noticed a little pep so i began to smile. Later however, on the highway, I floored it to see what the reaction would be. First, the engine rev'd to about 5K before the trans would shift which was scary. At a stop light I noticed the idle/timing was real rough; to the point that the truck actually rocks and the check engine light is now on.

This truck has always been maintained by LR, had the 60K service performed at 45K and the 30K service performed at 22K because of the below average miles it was driven.

I suspect i have a clog somewhere, but why is my idle so rough now and the timing shot.
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  #5  
Old February 8th, 2006, 01:03 PM
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Jeff Hoien
1997 NAS D90
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Jerry, if the fuel filter has not been replaced go ahead and do that. As for the missfire code that only happens at 1/8th tank of fuel...the only thing i can think of is fuel pump overheating at low fuel levels. The fuel pump is cooled by fuel in the tank and could be gettin sticky at low fuel levels...of course the only way to verify would be to hook up gauge to rail and drive at speeds and fuel level you indicated...i see the pump was replaced at 60k but after all it is a land rover...one other thing could be vacuum in the tank that the pump cant overcome which would indicate an evap problem but i would think you would see a code for that also..
let us know
jeff
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  #6  
Old February 8th, 2006, 01:18 PM
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210-220 per tank? Boy, I need to take off my roof rack, I get 150 in the winter and maybe 175 in the summer.

-Hans
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  #7  
Old February 8th, 2006, 06:40 PM
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Mike
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Quote:
Originally Posted by Hans
210-220 per tank? Boy, I need to take off my roof rack, I get 150 in the winter and maybe 175 in the summer.

-Hans

Ditto!
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  #8  
Old February 9th, 2006, 09:33 PM
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156 to empty . . .
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  #9  
Old February 13th, 2006, 10:52 AM
Chris V

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In '97 (and with many other Rovers years and models) bad grounding to the main CPU will cause improper fueling.
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  #10  
Old February 13th, 2006, 11:01 AM
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Chris, is it usually a matter of cleaning contacts or a poor design that needs to be reworked?
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Old February 13th, 2006, 11:14 AM
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Jack Walter
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My best so far - 335 miles on a tank of fuel (I'm cheating - Tdi)
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Old February 13th, 2006, 11:15 AM
Chris V

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Thats up for debate, but creating a simple, direct ground to the engine block or the frame (never the body) is a good first step.
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  #13  
Old February 13th, 2006, 01:24 PM
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Sandro
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Just so I understand what kind of economy we're talking about would someone mind converting miles / tank to miles per gallon (US) for me? My tank is of the smaller 'under the passenger seat' style so my frame of reference is a bit off.
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  #14  
Old February 13th, 2006, 04:33 PM
Jerry
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Jerry Silverman
97 D-90 SW
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To answer the question about miles per gallon…….. I’m getting about 8. That’s city driving, not on the highway.

Just an update……. I drove to my local auto store, picked up some Seafoam and a new fuel filter. Fueled up, added the Seafoam and it was running normal so I held off on the fuel filter…….. it was snowing! Next day I had the bright idea to run her through the car wash. Two minutes after heading home the engine begins to stall and while it never died, for about a ¼ of a mile it wouldn’t accelerate past about 15 miles an hour. Then the check engine light comes on flashing its little heart out. I pulled over and killed the engine. After I did a quick check and let her sit for about five minutes it fired right up and off I went with the check engine light on …… but not flashing.

So much for my low fuel problem. Reading about the problem with the ground, could the water from the wash had an effect?

I appreciate the advise but I unfortunately don’t have the time or more importantly the skill to tackle this growing problem. Off to the shop she goes. I’ll report back with the official diagnosis.
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  #15  
Old November 13th, 2017, 10:24 PM
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Luis
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Jerry.

Having same issues with my 97. Did you ever figure out the problem? Please share. Thanks
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