97 D1 drive ability problem

[boxster]

This D1 has been to shop for diagnostic check for MAF sensor problem! Technician did smoke test for vac leaks none found, fuel pressure 37 psi, still has p1171 code lean condition, I've swapped 3 different MAFS, no change still slow start, poor idle, tech assures me needs new MAF however the OEM $1600. Is there a solution to my problem? Ruled out the fuel pump, replaced FP regulator no change, heard in the Forums that resetting adaptive values could work! However my tech says that his sources say not necessary! Any other ideas are appreciated! Boxster:banghead:

 

[Va_Disco]

did you try cleaning the MAF? Did you check all the sensors with a scan tool to verify they are working proper?

 

[ezzzzzzz]

Check every vacuum hose for cracks, especially the PCV hoses. Don't forget the short hose to the fuel pressure regulator behind and below the throttle body. Is your fuel pressure 37 at ignition on/engine off? What happens to the pressure when you start the engine? Does the pressure vary when throttle is applied? As the above post stated, have you looked at the active data on the scan tool while the engine was running to see if any sensor was not displaying good info?

 

[kk88rrc]

X2 on vacuum leak

check your O2 sensors also.

 

[p m]

It has to be one hell of a vacuum leak to cause lean condition. One profound vacuum leak, like split hose to brake booster.
How are fuel injectors? Have you changed your fuel filter?

 

[boxster]

First thing changed was filter! Fuel injectors are original! Boxster

 

[ERover82]

Try capping off the EVAPS line at the manifold temporarily to see if the EVAPs system is a vac leak source. I'd clean in intake manifold and possibly the IACV passages, but be sure not to push on the plunger and mess up your IACV. Make sure the tube conning the MAF to the intake is sealed well with a good O-ring.

Did you do any work to the truck prior to this issue?

 

[boxster]

No work done on prior to problem!

 

[discostew]

This D1 has been to shop for diagnostic check for MAF sensor problem! Technician did smoke test for vac leaks none found, fuel pressure 37 psi, still has p1171 code lean condition, I've swapped 3 different MAFS, no change still slow start, poor idle, tech assures me needs new MAF however the OEM $1600. Is there a solution to my problem? Ruled out the fuel pump, replaced FP regulator no change, heard in the Forums that resetting adaptive values could work! However my tech says that his sources say not necessary! Any other ideas are appreciated! Boxster:banghead:

Check out the vendor section. I'm sure you can find a used MAF sensor for cheap. They don't usually fail but Its possible. Your mechanic wants to see another one in its place to be sure he's not looking at a bad one.That's reasonable the 1700 isn't. And the fact you have swapped out 3 would tell me one of those had to be good. Sounds to me like he's going about the checking for a vac. leak correctly.
Is this thing running poorly or is it just a check engine light? What is the long and short term fuel trim values? Did you check the fuel? Methenol levels are on the rise and I've seen a few trucks recently that the level was way over the 10% it should have been.

 

[boxster]

STFT 24% LTFT 24% CEL on! Feels like being choked for air, poor throttle response, my fuel pressure check is 37-40 KOER, with KOEO drops off to 0 within a minute or so! At start sequence is high idle up to 1700 revs then drops to 500 revs stumbles dies. Start up again idles seems to lope a bit I hear a lot of air being drawn thru at air box MAF area then some what normal idle no stall out, no cel, good idle at this point. Then when accelerating have to use a lot of pedal to get going, like I'm towing something. Transmission shift correctly, a/c on no overheating no stall out! It was mentioned in forum that possible fuel pump check valve! I have replaced the FP regulator with no change, fuel filter, air filter, Air box to MAF o-ring which was missing still no change. Going to change fuel pump, I have used functional pump maybe it's key to the problem! Boxster

 

[discostew]

it should hold some pressure when the key is off. I would tape a fuel pressure guage to the windshield and watch it when accelorating. I bet it can't keep up with the volumn it needs to drive.

 

[ezzzzzzz]

Is the STFT and LTFT the same for both sides of the engine? Sounds like a very leaky injector to me. I replace mine with late '90's Volvo injectors to get rid of the pintle design LR used.

 

[boxster]

Replaced injectors still have poor acceleration! Changed out plugs and wires and acceleration is better! however upon start up the idle goes up to 2000 revs then stumbles like loping a bit then holds around 600-700 revs! Have been told to reset adapt values by one tech then another says not necessary? Have replaced MAF, fuel pump, fuel pressure regulator, fuel filter, wires and plugs along with new injectors! Still feel there's a another piece of the puzzle missing! Have heard that drive cycles may correct the idle problem! Have spoken to PT and Will about the issue all good advice however no cigar yet! Wondering if IACV is faulty? Starts up ok but now idle is questionable? Any ideas are appreciated! Boxster:banghead:

 

[boxster]

Does IACV need reset when replaced or is it a plug and play? Cleaned IACV BUT WITH NO change IN IDLE! Boxster: :banghead:

 

[96discoI]

I have made the mistake of using a k&n air filter. that has set off an 1171 because the maf doesnt like the oil from the filter. it takes a while for the adaptive values to re-learn after stumbling around with oil on the maf. maybe just disconnect battery for a bit and plug the maf in after that.

 

[XCELLER8]

well here's my 2 cents>>>>have you removed the ecu to check for corrosion at the connections as well as corrosion INSIDE the ecu ??....it happens a lot and can cause a whole lotta crap to happen.
and is this an "advanced Evap" truck....if so roll up the rear carpet and unplug the fuel tank pressure sensor at the pump...mine shorted out (or the wiring to it) and caused all kinds of trouble with the fuel ratio, tps and more....it costs nothing to just unplug it and see if there's any change

 

[MotoBando]

Replaced injectors still have poor acceleration! Changed out plugs and wires and acceleration is better! however upon start up the idle goes up to 2000 revs then stumbles like loping a bit then holds around 600-700 revs! Have been told to reset adapt values by one tech then another says not necessary? Have replaced MAF, fuel pump, fuel pressure regulator, fuel filter, wires and plugs along with new injectors! Still feel there's an another piece of the puzzle missing! Have heard that drive cycles may correct the idle problem! Have spoken to PT and Will about the issue all good advice however no cigar yet! Wondering if IACV is faulty? Starts up ok but now idle is questionable? Any ideas are appreciated! Boxster:banghead:

Did you ever get to the root of the problem on this? I just had this issue same issue with high idle, etc. I had the adaptions reset along with base idle but it now lacks power. My only code is 1171 which is lean condition both banks. Going to get a new MAF and see if that helps per the shop I bring it to on occasion.

 

[kris812]

To note on my D1 with torque pro and an ELM 327 my MAF readings are: 0.1 idle, 0.5 cruise, to 1.2 MAF readings on WOT.

I purchased 2 new Walker MAFs and they both died in less than 5 miles giving bogus readings. I had to unplug them to limp back home. Which leads me to an old school test, you can try unplugging the MAF while it's running; if engine dies the MAF was working, if nothing happens when you unplug the MAF is dead.

Vacuum leaks?? Plug hand over intake trumpet while running to see if dies and sucks intake tube down. If not, you have a Big leak.

I found really bad LTFT fuel trim numbers on my Disco 1 (-24%) no codes though, but I knew something was off. Found my brake booster was bad and causing the massive vacuum leak. Replaced the booster and now LTFT now sits at 0.78%

FYI you can reset the adaptive values at home with RobertF android app called "ECU GEMS for LR"

 

[discostew]

To note on my D1 with torque pro and an ELM 327 my MAF readings are: 0.1 idle, 0.5 cruise, to 1.2 MAF readings on WOT.

I purchased 2 new Walker MAFs and they both died in less than 5 miles giving bogus readings. I had to unplug them to limp back home. Which leads me to an old school test, you can try unplugging the MAF while it's running; if engine dies the MAF was working, if nothing happens when you unplug the MAF is dead.

Vacuum leaks?? Plug hand over intake trumpet while running to see if dies and sucks intake tube down. If not, you have a Big leak.

I found really bad LTFT fuel trim numbers on my Disco 1 (-24%) no codes though, but I knew something was off. Found my brake booster was bad and causing the massive vacuum leak. Replaced the booster and now LTFT now sits at 0.78%

FYI you can reset the adaptive values at home with RobertF android app called "ECU GEMS for LR"

Resetting adaptions is important after you replace a couple components. But normally the fuel trim just goes right back to where it was if you don’t fix a problem.
If your fuel trim was at -25% I would think the light would have been on.
On Disco 2 they run like shit after resetting adaptions if the mass air sensor is bad. It was a quick and easy test.

 

[kris812]

Resetting adaptions is important after you replace a couple components. But normally the fuel trim just goes right back to where it was if you don’t fix a problem.
If your fuel trim was at -25% I would think the light would have been on.
On Disco 2 they run like shit after resetting adaptions if the mass air sensor is bad. It was a quick and easy test.

My engine Light NEVER came on even when the MAFs would die and I would barely limp home. I would say the light is removed as it has NEVER came on even with leaking head gaskets, but it lights up on Key cycles.

But you are right, no matter how many times I reset it, it went right back to -25%. Until I replaced the bad brake servo/booster to fix the vacuum leak, and then I've been 0.78% on LTFT since.