Transmission problem or engine problem?

R

RayDunn

Well-known member
Jul 21, 2004
83
0
42
Nashville, TN
OK, The following things lead me to believe that my truck is broken or in the process of breaking. Any help would be greatly appreciated as no land rover also means no mountain biking.

When I start my truck and it sits idling in park it will idle fine. When I put it in reverse or drive, but not moving it starts idling rough (RPM surges up and down from about 500 to 1000). When I drive it and this is going on it continues to surge, but I also feel a thumping type of sound from underneath. It can still be driven, but I can't go over about30 mph when this is happening. This has happened every once in a while for about the past 2 years (at first once every three months or so and then gradually increasing in frequency), but recently it happens everytime I start the truck; it seems to go away after the truck has been driven for a while and it has been restarted.

Stats on the truck:
1995 Discovery
Automatic Trans
136k
No suspension lift of aftermarket components
Fluid levels are correct
No offroading in a while

I have a mechanic that I trust here in Nashville to do the work if it's something that I can't do, but as with most shops they don't have a lot of experience with LR's so diagnosing problems can be tricky. If anyone knows what this could be or has any advice I would appreciate it. Thanks for the help.
 
ptschram

ptschram

Well-known member
Sep 27, 2004
21,955
50
In the shop doing the Lord's work one broken Rover
www.ptschram.com
It's almost certainly not the VSS as there is no output from it until the vehicle begins moving.

Without an opportunity to look at the sensor outputs in realtime, I'm not much help on this one except to say it doesn't like the load of the torque converter.

I'd start with brute-force troubleshooting things. Develop a baseline by replacing the plugs.wires, cap and rotor. Replace your emissions hoses, clean the flame trap, change the oil. If it doesn't fix it, it won't hurt anything either.

PT
 
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barefoot

Guest
any codes on the ole dash?

has it been raining there a lot? sounds exactly how mine ran (before water proofing) when the engine got a good soaking. or like an o2 sensor is fucked. however, to do it sometimes and sometimes not alone rules out a lot of normal crap.

the sputtering/thumping sound/feel from underneath is most likely the cats sputtering...it can feel like someones kicking the underside of the truck at times.

i will go ahead and say-not transmission....

like pt said...the simple shit

new champion plugs
check the wires with a mister for arching
make sure none of the plug wires are crossing any metal parts like the oil dipper stick
clean the iac/tps
see what `kind of fuel pressure u get while this is happening
make sure no rats nests anywhere
seafoam the piss out of it
check the t-piece
any sweet smelling/colored exhaust
you running shitty gas?
fuel filter replaced recently?
air filter recently?

just start ruling stuff out...the more info you get about it...the more we can narrow down! i am guessing the truck has not been maintained to par and you have multiple issues contributing to the end result....based on the 2 yr statement with no list of replaced/checked parts to follow. good news is, your at the right place for info! use the search thinggy a lot and tell us what you find out!
 
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barefoot

Guest
uuum...95...yeah, i knew that!

we cant all be detail oriented and observant....

so, any spiffy little red lights flashing?
 
R

RayDunn

Well-known member
Jul 21, 2004
83
0
42
Nashville, TN
No dash lights are on and it's kept in the garage, so it's not a water issue. Someone mentioned the torque converter and that was my initial thought. The engine runs very smooth when in park and neutral, but runs like crap when in a drivable gear. Fluid levels are good and just had an oil change. Thanks for the help, it's always tough to diagnose w/o seeing the vehicle.
 
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barefoot

Guest
the ce light on a 95 is either under the pass seat or footwell (ive never owned one so im not sure)
 
lgoldd1

lgoldd1

Well-known member
Feb 24, 2005
368
0
Granbury, Texas
Untighten the IAC Valve/Stepper Motor and clean with carb/choke cleaner spray and put it back in and test. If problem persist, replace with new unit. If it has 136k on the IACV it is probably toast. You may also want to test fuel pressure at the rail when engine is at idle and in drive. See if the pressure drops when you shift into drive. Might have a fuel pump going out. Hell, it could be both with 136k miles on her.

p.s. Your engine uses fuel/spark/air to run. Just like all other types of gas combustion engines. If a mechanic can't figure it out, find another mechanic. Nothing special about your engine. It's a Buick for god's sake! Good luck.
 
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