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A. C. Donahue
| | Posted on Tuesday, April 30, 2002 - 10:01 pm: | 
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Here is a weird one. I have a '90 Range Rover classic. While either going up hill or when I stomp on the gas to pass someone, the engine just bottoms out. When I mean 'bottoms out,' I mean the RPMs go to zero. It does not bog down like it's flooded -- you have nothing, zippo, el goose egg. The first time it happened I thought the engine quit completely. If you let off of the gas it will pick back up. You have to accellerate slowly to keep the thing from 'dropping out' on you.
To "fix the problem," a Land Rover dealer mechanic -- who did work on the side and also owned a 90 Rangie -- replaced the fuel pump in the tank and then the in-line fuel filter and then the fuel pressure regulator. None of these worked. We have run gallons of premium fuel in it, added every fuel additive known to man and all with no improvement. He suggests now that it may be the fuel ECU (electronic control -or- computer unit). Now we are talking bigger bucks than the last two unsuccessful repairs.
I would like to quit guessing with money. Any ideas other than firing the mechanic? |
Anonymous
| | Posted on Tuesday, April 30, 2002 - 10:10 pm: |
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Maybe you should read the post a few lines down...
If you plan on getting the ECU check out eBay. There is one for sale for 100 bucks... |
Axel Haakonsen (Axel)
| | Posted on Tuesday, April 30, 2002 - 10:37 pm: |
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Check the fuel pump connector and the wires running into the connector in the rear drivers side wheel well. They are probably corroded. That's pretty common, and can cause the symptoms you describe. |
Randall Smith
| | Posted on Wednesday, May 01, 2002 - 09:57 am: |
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Mr Donahue
Based on the statements in your post, I would say that the "mechanic" is just guessing as you suspected, and that a new ECU probably will not fix it. However you do now have new pump/filter regulator, and that is good. Check the vacuum hose that conects the fuel pressure regulator to the intake plenum.
I would make sure that the entire ignition system is working properly. Examples: The timing advance mechanism and base timing. Plugs, wires, coil, cap and rotor all good??
Examine the electrical connections to all of the major fuel injection components and clean them too: MAF, TPS, ECU, fuel pump.
Replace the TPS. The throttle position sensor tells the ECU when you are accellerating and decellerating, and how quickly. The ECU changes injector pulse times based on inputs from the TPS. The TPS wears out, and should be replaced at 100K. You can replace it yourself in 10 minutes.
Are there any other symptoms at all??
Randall |
Johnny
| | Posted on Wednesday, May 01, 2002 - 11:40 am: |
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I agree with randall. The TPS is basically a Rheostat. There is a tendancy for them to short to ground during the range of motion on all TPS's not just Rovers. You may be testing the proper specs at the begining and end, but incorrect somewhere along the way. Just my .02c |
JB
| | Posted on Wednesday, May 01, 2002 - 12:38 pm: |
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Does anyone think it could be the road speed sensor or somehow related to it ??
Why or why not. Thanks |
Randall Smith
| | Posted on Wednesday, May 01, 2002 - 05:16 pm: |
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JB
On the RR classic the road speed sensor tells the ECU these things:
Is the truck moving or not? If not then the ECU controls the idle speed using the stepper motor and feed back from the coil.
Are you moving to fast? The ECU will cut the fuel supply at 110mph, so don't try to out run the law on the street.
The Road speed sensor is also used for the speedometer input on 90-95 RR classics. And it also provides input/feedback for the cruise control computer.
Randall |
JB
| | Posted on Wednesday, May 01, 2002 - 05:31 pm: |
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Thanks Randall...
JB |
A. C. Donahue
| | Posted on Friday, May 03, 2002 - 08:19 pm: |
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Randall
The plugs, wires, coil, cap and rotor are all good since they were all replaced within the last year. I do, however, seem to remember my mechanic saying something about having to advance the timing way out of spec to get it to run right.
When out rovering one day, we ran through some pretty deep mud holes. A couple of times the mud was over the hood. I later checked the air filter (I don't have a snorkle) and did find some mud in the air filter. The air filter was not soaked with mud, but did have some on one side. My 'mechanic' said that there is a very fine wire that acts like an 'air flow meter' and that the mud may have messed that up if it got past the air filter. Possible reason for all my ills?
I have a few follow-up questions for you:
(1) Where is the TPS?
(2) Is there a way for a 'back-yard mechanic' to test a TPS to see if it needs replacing?
(3) When I order one is "TPS" or "Throttle Position Sensor" what I ask for?
(4) Any idea on the ballpark price for a TPS?
(5) Additionally, what is an MAF?
I look forward to your reply. |
John Henley (Rexydog)
| | Posted on Saturday, May 04, 2002 - 09:52 am: |
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AC,
I will take a stab in Randall's absence. The "MAF" is located right behind the air cleaner housing. It is the large sensor in the intake tract before the manifold. The wire element is very fragile, and the sensor is expensive, so be careful. Inspect the grid for debris and then gently clean.
"I do, however, seem to remember my mechanic saying something about having to advance the timing way out of spec to get it to run right." That sounds like the covering of a problem to me. Running with highly advanced timing is dangerous to valves and other components.
That statement bothers the hell out of me. In my travels, I have seen something as trivial as a bug mess up the resistance of the "hot wire", but what your describing now, sounds like you are getting deeper and deeper.
Do you on a LR shop manual for your vehicle? The Haynes Manual? Throwing parts at a problem is quite the expensive way to go, and electronic parts are generally not returnable. Have you had a "master tech" or "driveability" tech check your EFI? It sounds to me, that given your previous posts, that you may be in a position that you may have to "open your wallet" and give the tech the "complete" story, and let them try and diagnose the problem. If it repeatable, and constant, and doesn't happen just under special conditions, they will find the problem.
You may find that after you spend you time and effort throwing parts at it, then the tech route might have been more productive. |
Randall Smith
| | Posted on Saturday, May 04, 2002 - 12:02 pm: |
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A.C.
The TPS is a black plastic sensor which is screwed onto the intake, right where the throttle plate is. Just disconnect the elec leads, remove the two screws and replace. It will take about 10 minutes of driving for your ECU to learn the new sensor. You can call Rovers North and they will send you the correct part. I would guess that it cost $100. This item does wear out, and it is easier to replace than to test.
I would also verify that the mechanical advance on your dist is working. Unclip the dist cap and you should be able to turn the rotor about 20 degrees, and then it will spring back.
I would also buy a timing light. Use some white paint on the timing marks so they are easy to see. The mark on the far right is 12DBTDC, the far left is 12DATDC, and the one in the middle is TDC. Set it at 6 degrees before top dead center.
You can unclip the air filter canister from the MAF. There is a round wire screen in the opening of the MAF which is used to prevent solid material from entering the intake. If this screen is clean, then you haven't fouled the heated wire in the MAF. On Hitachi MAFs the heated wire is not visable, it's in a tube on the side.
Feel free to post again if you need more info. Or and John posted above "find a master tech".
Randall |
A C Donahue
| | Posted on Saturday, May 04, 2002 - 05:43 pm: |
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Randall S. & John H.:
When I cleaned the air filter, the MAF did have some mud on the screen. I took it apart and made sure it was clean. Like the filter, it wasn't caked with mud, but it did have mud on the screen. Should I disconnect the air breather and shoot some carb cleaner in there?
Here is another thought -- in case it matters -- the cloth flexible hose from the MAF to the plenum is nearly see-through. It probably needs replacing. Even so, would this cause the type of problems I am describing?
Again, the engine just 'drops out'. The RPMs go to zero and it's like someone just turned off the ignition. It ONLY does it (1) going up a hill (where more power is needed to maintain your speed) or (2) when you need to accellerate quickly (like to pass someone). It not a now-and-then issue, but one I can replicate under these two conditions EVERY time.
After the LR mechanic guessed a few times, he finally suggested that we hook it up to the dealer's computer to see what is wrong. Problem - at least for me - that it was a minimum of $200 and $200 for each our after. If one hour could do it, I guess it would still be cheaper than to keep guessing.
As for the manuals, yes I have both the Haynes and both volumes of the Range Rover dealer manuals. If there is something you need to point me to, I have the books.
Unfortunately, I am unable to check out anything right now as it is pouring. I can't wait to get out there with this list of tips and then go through each one of them. I truly appreciate each suggestion. |
JB
| | Posted on Monday, May 06, 2002 - 07:05 pm: |
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You have a readout display under the passenger door seat base remove the cover and it's under there - that gives you the codes to help diagnos and possibly confirm TPS. Post the number it displays here. . But I think its the TPS
You sold me on "1) going up a hill (where more power is needed to maintain your speed)
The TPS is dead easy to unscrew/ unclip and replace. I am cheap and bought a used one from rovercannibal for around $30 (used but tested and guaranteed and looked brand new when I got it). After you put it in the ECU takes a few miles to "learn" the new TPS. I hope you just have to by the TPS (and a Haynes Manual) Look for that readout display and let us know what you find.
JB |
Randall Smith
| | Posted on Tuesday, May 07, 2002 - 09:29 am: |
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Mr Donahue
I would feel safer cleaning the MAF with electrical contact cleaner, but have never done this before. The intake hose really needs to be leak free. If not it would be allowing unmetered air into the engine.
Airflow will always take the path of least resistance. So during normal driving the air may all be moving thru the MAF and air filter. But when you open up the throttle suddenly the pressure differential might be releived with leaking unmetered air thru the hose cracks. This leakage combined with a worn out TPS could result in totally the wrong fuel/air mixture.
Randall |
A. C. Donahue
| | Posted on Tuesday, May 07, 2002 - 10:22 pm: |
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*** UPDATE * UPDATE * UPDATE ****
JB & Randall:
The weather finally broke and I got to do some work on the truck yesterday.
The first thing I tackled was the electrical connector on the fuel tank which can be reached thru the driver's side rear wheel well. As Axel surmised in his post, it was a MESS! The rubber 'shield' had cracked and split open on top and the plugs were corroded and full of mud. I cleaned the male plugs with steel wool and added two new female connectors. Reconnected the rubber 'shield', but did so using silicone sealant which will keep the elements out.
The second thing I did was check out major electrical connections. The wires on the ignition coil looked like they needed brushed up and they got a nice steel wool massage.
Before I read Randall's last post, I disconnected the air breather from the MAF (I guess that is what is the box looking thingy attached to the air breather/filter that says Lucas and has a big plug out the side of it) and took the next step by spraying carberator cleaner into the MAF while the engine was running.
Fourth, I replaced the 'fabric' hose from the MAF to the plenum with a new rubber outfit that now makes the whole thing air tight.
Finally, I disconnected the battery to let the ECU reset itself.
When I hooked it back up I got the O2 code which -- from what I read about fault codes -- is what I should have gotten.
I took the truck out for a spin, and unless it is my imagination it is 'better', but not cured. It is accelerating a lot better than it did. It seems to have more power --- more like it did when I first bought it. BUT it still has the 'engine drop out' issue. I checked the ECU and it now reads 19 - throttle potentiometer. Does this mean it's bad and needs to be replaced? I look forward to your responses. Again, thanks for all of your help and insight. |
Randall Smith
| | Posted on Wednesday, May 08, 2002 - 08:46 am: |
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Proper maintinance can do wonders for a 12 year old vehicle.
The code 17, 18 and 19 ate TPS related. But they could mean faults with the wiring or MAF too. Again...the TPS is very easy to replace and it definatly wears out. I would try it first.
Randall |
A C Donahue
| | Posted on Tuesday, May 14, 2002 - 11:37 pm: |
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*** UPDATE *** UPDATE *** UPDATE ***
I ordered a used TPS from the good folks at Rover Club House (www.roverclubhouse.com). They sale both new and used parts. It should be in Thursday/Friday. We'll install it; disconnect the battery to let the ECU reset and give a whirl. I'll let you all know how it turned out so that we can all learn together.
P.S. - Another source for 'used' Rover parts is www.rovercannibal.com |
Mike
| | Posted on Thursday, May 16, 2002 - 03:41 pm: |
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AC,
I just finished reading this thread and I would agree that the problem you have does sound like the TPS but don't forget about the hose you mentioned between the MAF and the plenium. The air cleaner and the MAF can't do their jobs if you have holes in the hose.
my 2 cents worth...good luck,
Mike |
A C Donahue
| | Posted on Friday, May 17, 2002 - 06:00 pm: |
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************** FINAL UPDATE **************
It's "FINAL" for a reason. Yeah! The problem was the TPS "Throttle Pontentiometer Sensor". I got it in yesterday and installed it. Reset the ECU (Electronic Control Unit) and fired it up. I ran the vehicle a bit before I put it into the two problem areas -- the hill climb and passing situation. Once I did put it under both trouble areas -- IT WORKED JUST FINE. Thank you, thank you, thank you. I'll always come back here. You guys are GREAT! |
Tony
| | Posted on Saturday, May 18, 2002 - 02:37 pm: |
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hey guys,just had a minute to check out your bbs and this post made me think of something just recently in the shop. customer came with a '90 rr with the same probs including the advanced distributer to compensate for his trouble. seems he did a complete tuneup himself and this is where his probs I figure began,seems he already spent about 1200 bucks and 2" other" mechanics and still had the same trouble,although I am a little embarassed because it took me about an hour to find his trouble plus the use of our ROVACOM unit and it all goes back to his mistake on the replaced plug wires,seems he was off by one all the way around the clock.the ROVACOM came up with all kinds of faults and possibilities,good thing their work was obvious, because he "forgot" to tell me about the prior work. we still charged him for 2 hours work,about 130 bucks later and he was good to go, I may have been easier on him if he had told me up front what was done, HAPPY ROVERING from OUT OF ENGLAND ROVERS LTD. in central MASSACHUSETTS!!! |
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