hi all. i'm new to your site and hope you can help me out.i got a '89 v8 vogue se 3.5 that runs well except it dies under loadand if you ease off the fuel a bit it picks up ok again.was only doing it cold but strangely after a service its doing it as it likes.it does run a little rich but seems to like it so y mess? its almost like someone is turning the fuel off untill you back off. any help appreciated. speerzie. :wave:
running problem
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Fuel filter is a good thing to check if fuel starvation is the problem. I'm guessing you have a "flat" spot, worn on the TPS (throttle position sensor).
Whe nyou say it "dies", does it completely shut down, or is a loss of power at that position of the accelerator pedal?
The TPS is a (sortof) linear potentiometer, or variable resistor. It's function is to give the ECU an idea of how much throttle opening is being apllied, looks to see if the airflow meter is also metering an appropriate amount of air, and adjusts the firing pulses of the injectors to match.
The slider of the TPS is directly connected to the throttle shaft, and as the gas pedal is pushed down, the slider moves up the winding of the resistor, changing the resistance. It is easily checked. Here is where you want a good old fashioned analog VOM (Volt-Ohm meter) The old fashioned kind with a meter, rather than a digital display. In the 1K range, connect your test leads to the center wire of the TPS (CRS causes me to forget which color, but it doesn't make any difference) and one of the two 'outside' wires. With your hand, gently open the throttle, and watch the meter needle, connected to one of the outside wires the meter needle will rise, proportionally to the amount of throttle applied. Connected to the other outside wire, the needle will go right up, and gradually fall as throttle is applied. What you are looking for is a sudden jump in the meter needle. Contstant driving in one pedal position, as in highway driving, will wear the winding of the TPS to a point where the slider (moving part) looses contact. I'll bet your natural instinct, when it has happened to while driving, is to let off the gas, Right? Well I will bet that if you hold your foot steady at that position, you will discover that the engine is still running, but back at, or near, an idle. The TPS is not really servicable, so if you find it's got a flat spot in it's range, chuck it and buy a new one. People have fooled around with sensors from other cars, but a word of caution here. A TPS with the wrong (lower) total resistance range can burn out one of those little, decision making chips in the ECU. Report back when you can.
Whe nyou say it "dies", does it completely shut down, or is a loss of power at that position of the accelerator pedal?
The TPS is a (sortof) linear potentiometer, or variable resistor. It's function is to give the ECU an idea of how much throttle opening is being apllied, looks to see if the airflow meter is also metering an appropriate amount of air, and adjusts the firing pulses of the injectors to match.
The slider of the TPS is directly connected to the throttle shaft, and as the gas pedal is pushed down, the slider moves up the winding of the resistor, changing the resistance. It is easily checked. Here is where you want a good old fashioned analog VOM (Volt-Ohm meter) The old fashioned kind with a meter, rather than a digital display. In the 1K range, connect your test leads to the center wire of the TPS (CRS causes me to forget which color, but it doesn't make any difference) and one of the two 'outside' wires. With your hand, gently open the throttle, and watch the meter needle, connected to one of the outside wires the meter needle will rise, proportionally to the amount of throttle applied. Connected to the other outside wire, the needle will go right up, and gradually fall as throttle is applied. What you are looking for is a sudden jump in the meter needle. Contstant driving in one pedal position, as in highway driving, will wear the winding of the TPS to a point where the slider (moving part) looses contact. I'll bet your natural instinct, when it has happened to while driving, is to let off the gas, Right? Well I will bet that if you hold your foot steady at that position, you will discover that the engine is still running, but back at, or near, an idle. The TPS is not really servicable, so if you find it's got a flat spot in it's range, chuck it and buy a new one. People have fooled around with sensors from other cars, but a word of caution here. A TPS with the wrong (lower) total resistance range can burn out one of those little, decision making chips in the ECU. Report back when you can.
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127 Posts
Fuel octane...
Hi Speerzie,
Just a long shot, but what type of fuel are you using? I had a friend who was having a similar symptons whilst using "Regular" Octane fuel. He tried switching to the highest Octane fuel he could find & the engine ran a lot better. He then poured some fuel system cleaner additive into his fuel & it ran even better. He has been using 94 Octane fuel ever since (6 months ago) & have never had the "hesitating" whilst accelerating sympton since!
Its a long shot, but worth a try before changing out parts..
good luck,
Andy
Hi Speerzie,
Just a long shot, but what type of fuel are you using? I had a friend who was having a similar symptons whilst using "Regular" Octane fuel. He tried switching to the highest Octane fuel he could find & the engine ran a lot better. He then poured some fuel system cleaner additive into his fuel & it ran even better. He has been using 94 Octane fuel ever since (6 months ago) & have never had the "hesitating" whilst accelerating sympton since!
Its a long shot, but worth a try before changing out parts..
good luck,
Andy
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3,205 Posts
Yes. TPS good thinking there. I forgot about that.
Octane higher = better, but mine runs good on 87 octane.
I also put a couple of bottles of injector cleaner in there right before my oil changes at least every couple of months.
Good luck let us know what you found.
Octane higher = better, but mine runs good on 87 octane.
I also put a couple of bottles of injector cleaner in there right before my oil changes at least every couple of months.
Good luck let us know what you found.
thanks for your replies. it seems to have calmed down for now, however am going to change the fuel filter tomorow anyway. will also put some fuel in as it seemed worse the more fuel i had in. maybe it was coincidence? will find out tomorow. speerzie :beer:
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3,205 Posts
Just a tip here.
Go to the car wash and hose out the area with the filter. On mine it's the right rear wheel inside.
When you get in there with wrenches and screw drivers you will knock a lot of crap down on you each time they strike the sides. If you hose it off an dirt still in there at least it will be mud and not that road dust getting in your eyes.
:bawling:
Go to the car wash and hose out the area with the filter. On mine it's the right rear wheel inside.
When you get in there with wrenches and screw drivers you will knock a lot of crap down on you each time they strike the sides. If you hose it off an dirt still in there at least it will be mud and not that road dust getting in your eyes.
:bawling:
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490 Posts
I would say your problem lies in the fuel pressure regulator. On the 3.9L engine, it is located on the back of the motor, driver's side (US) on the top (inline with the fuel rail) It is a small gray cylindrical device (metal) with a vacuum hose coming off one end and maybe two other lines off this same device. I'd say your car is getting too much gas. I had an '87 Volvo 760 Turbo with this same regulator and it would cause the car to "not go" when you got on the gas; the engine was flooding. This part is the same thing for many european cars; check the above suggestions but I would say this is it.
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2,914 Posts
Dug this thread up, and the same thing happened to me today. It has never done this at all, hesitating, dies off, doesn't shut down all the way, and when I let up, she gets back on track. When I push a little harder when she does hesitate off, she gets back on track.
Weird, now from what I read above (I have the 4.2L) the TPS could have a flat spot? Anyway is there a way to correct this?
Would a fuel filter cause this much hassle if it were that clogged? I mean it starts fine and runs, up until that point where she hesitates, which happens only on acceleration.
Man there are too many problems happening to my truck all at once. :complain:
Weird, now from what I read above (I have the 4.2L) the TPS could have a flat spot? Anyway is there a way to correct this?
Would a fuel filter cause this much hassle if it were that clogged? I mean it starts fine and runs, up until that point where she hesitates, which happens only on acceleration.
Man there are too many problems happening to my truck all at once. :complain:
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3,205 Posts
TPS can have bad spots.
I was guessing fuel filter. When was the last time you changed yours?
In any event it's a cheap part and a good thing to swap out from time to time. And if it fixes your trouble all the better.
If you swap your TPS for a known good one the result should be immediate.
I was guessing fuel filter. When was the last time you changed yours?
In any event it's a cheap part and a good thing to swap out from time to time. And if it fixes your trouble all the better.
If you swap your TPS for a known good one the result should be immediate.
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2,914 Posts
Well she hasen't hesitated anymore since a few days ago, but to answer the question, that fuel filter, I dunno. I haven't touched it at all since I go the truck. The original owners, I dunno if they changed it at all, kinda doubt it, so I will just change it out for the better, shouldn't hurt a thing.
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