| Author |
Message |
    
Larry Grubbs (Larryg)
| | Posted on Saturday, June 01, 2002 - 12:08 am: | 
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I originally thought this might be the fuel pump. But am now thinking differently. The truck hesitates it seems between around 1800 RPM and up to 3500. It is definitely worse when it is warm outside. It doesn't matter if I am accelerating or maintaining a constant speed. It still persist when the temperature is lower, just doesn't seem as bad. It doesn't seem like a miss, more like when a truck/car runs out of gas and starts to hesitate. Not that I have ever done this. wink wink!!
In case you missed it this is a 1990 Range Rover Classic with a 3.9L.
Things I know are OK:
Plugs, wires, cap and rotor. Replaced them all about 3 months ago with genuine cap and rotor and the usual plugs (Bosch Platinum, I think) and Magnecore wires.
Fuel filter is 2 years old. I originally replaced it.
I'll go to the dealer if I have to, but would rather not. They aren't so good at diagnosing problems that don't kick out codes.
Larry |
Larry Grubbs (Larryg)
| | Posted on Saturday, June 01, 2002 - 12:34 pm: |
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Anyone! |
A. Ali
| | Posted on Sunday, June 02, 2002 - 03:49 am: |
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Larry,
Check the stepper motor to see if it has a smooth sweep using an analog ohm meter. Sometimes they can develop a dead spot from many years of service.
Next, check out the fuel press regulator to see if it's working ok with engine vacuum. Sometimes I have engine stumbling while heavily loaded (uphills, etc). To be honest, I don't really know how to diagnose a fuel press regulator unless you have a press gauge remotely mounted and you're keeping an eye on it while driving. Try not to kill anyone while doing this test! |
Larry Grubbs (Larryg)
| | Posted on Sunday, June 02, 2002 - 03:13 pm: |
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I will look at this stuff. However I feel it might be something else. The problems don't even persist until well after the engine has warmed up. It's like about 10 minutes into driving, and the engine temperature guage is at operating temperature in just a few minutes. It almost seems like something around the engine is heating up and not working properly.
Also, there is no particular range that this happens. It is all over the board and it doesn't seem to matter whether I am accelerating or just maintaining a constant speed.
Someone had mentioned the possibility of a vapor lock problem. My only experience with these is when a car just won't start at all. I have never experienced this while driving. I think the thought was that maybe a fuel line was heating up over the 10 minute period and then once it got hot it started to vapor lock.
Larry |
KevinD
| | Posted on Monday, June 03, 2002 - 11:22 am: |
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Larry, after the engine warms up is the hesitation constant or intermittent (cycles on and off periodically)?
You noticed that it is worse when it is warm outside -- does it make any difference if you are using the air conditioning or not?
Check the alternator. Compare the hesitation when you have light electrical/engine loads versus heavy electrical/engine loads (high beams on, aux lights on, a/c on, windshield defrost on, seat heaters on, cocktail blender on, etc). See if this makes any difference over the 1800-3500 RPM range.
Kevin |
John C.
| | Posted on Monday, June 03, 2002 - 11:45 am: |
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Hey Larry, I also replaced the dist cap, rotor, coil, plugs, etc etc a few months ago with original parts and my problem was the rotor. It had a hairline crack in it and the hesitation problem would get worst when hot. Just double check the rotor....might sound stupid but it might save you time and money. |
Randall Smith
| | Posted on Monday, June 03, 2002 - 06:26 pm: |
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Larry...here are some ideas
The purge valve on the charcoal cannister can get stuck in the fully open position. This will cause a problem such as you discribe beginning at 2000rpms(it's programed to open for a moment at 1900rpms). Try unplugging the electrical connection to the purge valve and/or plugging the hose to the plenum.
Also the O2 sensors don't begin to influence the fuel/air ratio until after they have heated up. If for some reason they are faulty in some way, you wouldn't know it until they have reached their operating temp. What's your mileage and O2 history?
Another thing to try for cheap is the ECU's coolant sensor. It looks just like the temp sensor in the fuel rail and is easy to replace.
The fuel injection system is very sensitive to voltage problems, so alternator problems are possible.
Randall |
Paul Schuetz (Schuetz)
| | Posted on Thursday, June 06, 2002 - 04:45 pm: |
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Mine had the same problem and it turned out to be a bad alternator. It would run fine above 3000rpm, had to limp home from a trip in 3rd. Try this, while driving in the daytime turn on all the elctrical items in the car you can, lights, stereo ect. If the problem gets worse all of the sudden then it is probably the alternator.
Good Luck, Paul |
JB
| | Posted on Thursday, June 06, 2002 - 05:55 pm: |
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The module on the side of the distributor gets hot and can cause this but only when it's nice and toasty. There is a LR tech Srvce bulletin about it on this board somewhere. You can relocate the module or maybe replace it if this is the issue. I'll look for the article. |
A. Ali
| | Posted on Sunday, June 09, 2002 - 09:54 am: |
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Larry,
I second the "check alternator" route. Since you installed a 5.0 alternator, it maybe pissing off your ECU by producing "not so clean" power. One possibility is your diode switching freq interfering with the electronics. I had this issue with an older Delco SI alternator but only came alive after the engine was warmed up. A newer CS130 solved it.
Simple test: drive with the alternator disconnected and see if the problem goes away. |
Larry Grubbs (Larryg)
| | Posted on Sunday, June 16, 2002 - 07:14 pm: |
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Since my fuel pump was kind of old I have now changed it along with the fuel filter. I also made an access hatch to ease the pain and suffering in the future. I also changed my coil out with my spare, checked caps, rotors, plugs etc.
Problem still persist. Once engine gets warmed up it hedsitates or misses. I did disconnect the alternator and the problem seemed to go away. I then reconnected it and since the battery was low on charge it really ran badly. Alternator voltage is about 14.0 when charging and just a little above that when battery is fully charged.
So, it does look like the alternator. And as Ali A. pointed out I have converted to a '95 Mustang GT alternator which puts out 130 Amps. I did this a little over two year ago and no problems.
OK. since all signs point to alternator, how do I return an alternator that puts out 14 volts under load? I bought it from Pep Boys and it has a lifetime warranty. Any suggestions?
Thanks,
Larry |
Larry Grubbs (Larryg)
| | Posted on Sunday, June 16, 2002 - 07:16 pm: |
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BTW, it does run a lot better prior to the hesitation. Probably due to replacing worn out fuel pump. But of course, problem still persist as noted in above post.
Larry |
Rob Davison (Pokerob)
| | Posted on Sunday, June 16, 2002 - 09:32 pm: |
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lie to them... hopefully you can bullshit your way thru.
also look for a girl at the desk.. maybe consider dating her, then try to return it 
rd |
A. Ali
| | Posted on Monday, June 17, 2002 - 10:49 pm: |
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Larry,
Your alternator diode pack is the problem so either replace it or make it so that it needs to be replaced :-) They're getting too hot and causing havoc, sorry dude! |
Larry Grubbs (Larryg)
| | Posted on Tuesday, June 18, 2002 - 03:13 am: |
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Well all, I was wrong. I removed the alternator belt today and problem still persist. I apparently didn't drive it enough earlier to see the problem. I have since checked for cracks in cap and rotor, codes from computer and air leaks to intake manifold. I am at a loss. I am not sure what the symptoms of a failed ignition (amplifier) module are? I haven't checked this one yet. I now think the problem is related to ignition somehow.
Any ideas?
Larry |
John C.
| | Posted on Tuesday, June 18, 2002 - 08:24 am: |
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Larry, I can send you a used amplifier for you to test with. It still works but it has a crack on one side (plastic). I installed the relocation kit last month. The only problem is installing it; you have to remove the dizzy. Now that I mention dist, did you check the base plate and the gap in the dist? When I removed mine I noticed some broken pieces inside, obviously I replaced the base plate. The advance timing mechanism needed to be fixed also.
Just my 2 cents.
Good luck,
John C. |
Ali
| | Posted on Wednesday, June 19, 2002 - 09:54 am: |
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Hmm, a failed ICM should make you stall or prevent startup, I thought. At least that's what happened to mine. I know you relocated your unit so it should be fine now. |
Larry Grubbs (Larryg)
| | Posted on Thursday, June 20, 2002 - 09:53 pm: |
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Well, problem solved. Turns out it was the Ignition Amplifier after all. All the local guys told me it either works or it doesn't. Well they were wrong. On the way over to a buddy house to fix the problem the truck finally stalled. As I called my buddy from the side of the road he told me to get some water and spray it onto the Ignition Amplifier and then try and start the truck. Sprayed water on the amplifier to cool it off and the truck started right up.. Made it to my destination and replaced part with new one.
Voila! no more hesitation problems. Hopefully this thread can help someone else soon.
Thanks all!
Larry |
A. Ali
| | Posted on Thursday, June 20, 2002 - 11:27 pm: |
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Larry,
Congrats on your final discovery! Why do you think the ICM failed even after you relocated it? Was it the original unit or a new one? |
John C.
| | Posted on Friday, June 21, 2002 - 08:16 am: |
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Ali, I don't remember Larry mentioning that he installed the relocation kit. Maybe I missed something. Right Larry? |
Larry Grubbs (Larryg)
| | Posted on Friday, June 21, 2002 - 11:06 am: |
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John,
You are correct. It was never relocated. It is still not relocated. The belief is that the new electronics are more reliable than the stuff of 12 years ago. That's right I replaced the original Amplifier Module. I might relocate it myself as a project this winter. All you need is those Bosch connectors and some wire. Easy job. Besides every relocation kit I have seen cost $100 more than the standard kit. What a ripoff!
Larry |
John C.
| | Posted on Friday, June 21, 2002 - 11:54 am: |
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Larry, you need a dummy amplifier or something to cover up the hole on the side of the dizzy. I have some pics, not too clear but it will give you and idea of what the kit consists of.
John |
Ali
| | Posted on Wednesday, June 26, 2002 - 09:19 am: |
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I kept my old ICM to use in my relocation kit. Although, I need to know where to get the Bosche connector. John, can you send me some pics as well?
Thanks |
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