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To Much Fuel Presure To Eng


SaDow's Avatar
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07-30-02, 03:50 PM   #1  
SaDow
To Much Fuel Presure To Eng

I have a I-Roc (89) with a tpi 350 port injec eng . I have been doing alot of work to it lately . I am getting to much fuel (45psi in stead of 40psi ) . at first I was told my mass air sys was bad because when you unplug it the car should shut down , mine just ran like crap when you did. I was also told that it might be my cadilatic converter which was completly wasted , but the problem still is happening after I replaced it. and the top it off when I unplug the mass air it runs the same as it did with the old one . I would think that if you unplug the mass air it not longer part of the sys , what ever tells the car that it is unpluged and that it should not work is what is really broken . know they tell me that it's the fuel regulator ( which you know is no fun to get to on this eng- about $200 worth of labor ). I also hear that it might be some kind of feul control chip which runs the about the same as the regulator in price (but I would assume less in labor). I have a brand new fuel pump, and the catalatic converter i needed to replace anyway , but the mass air was $447 for just the part (labor was $35) . I don't want to replace the regulator then find out it's some chip (what's it called any way , and how hard is it to replace?) What is the more likely of the two that is bad, or is there another possiblity that could be the problem ? And if it was you what would you do ? I could use the addvise , my car is in great shape so getting ride of it not a choice. thank you for your time .

 
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07-30-02, 05:11 PM   #2  
sounds like you have had several problems with this car in the past if you really want to stick with it then i would suggest you take it to a different shop and have it diagnossed, 447 dollars for a maf sensor is ridiculous, not to mention it sounds as if they are guessing and dont really know what the problem is i dont know the exact fuel pressure specs for your car but i know anywhere in the 40-50 range with the key on engine off is close enough and doesnt require a fuel pressure regulator replacement.
know getting back to the problem is it still losing power on hills or exactly what problem are you having with it currently, really the best advice is to find another shop and have them test drive the vehicle and diagnoss it.

 
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07-31-02, 08:31 AM   #3  
SaDow
hill power

Yes I still have power loss when I go up hills , as a matter of fact if I push it to hard to fast the car will bog down big time . I was talking to my room mate yesterday and he told me he could get me a high performance chip for about $150, I wanted one any way but I was thinking that if the chip was a after market on my car now and was going bad, changing it might fix the problem( they could not scope my car so they think I might have a after market chip). any way the new chip should change the fuel mix . I can smell the un burned gas , and when they checked the car they said I had spark , so I don't have a dead cycl. any idea's

 
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07-31-02, 01:35 PM   #4  
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Most aftermarket chips are poor quality and change the fuel mapping. The best chips are what the old General put in there from the factory. It gives the best performance and economy.

But, you must verify your fuel pressure and soundness of the rest of the systems first before condemning any parts.

 
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07-31-02, 02:51 PM   #5  
SaDow
fuel sys has been checked or replaced

my mack told me that my pressure is to high 45psi not 40psi. I have a new fuel pump, fuel filter . the injectors don't control presure in the line what's left ? the only things left are the fuel reg, and the chip. what I have to know is wheather the chip is the problem , and since I know the rest of the sys is working what a the sign that I may have a failing chip?

 
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07-31-02, 04:50 PM   #6  
Joe_F
Check your fuel pressure with a regulated, calibrated gauge. Autozone can rent you one for free. Tell us what you find. Must do this before you go any further.

 
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07-31-02, 05:06 PM   #7  
the computer chip has nothing to do with fuel pressure and most likely you could replace both the regulator and the chip and still have the same problem with a power loss on hills, computer chips rarely fail it is more common for the ecm to fail than the computer chip, [you say they couldnt scope your car and they think you may have an aftermarket chip,]most shops have what is called a scanner they use to check the computer system out on a vehicle and if the computer will not communicate with the scanner often it is due to a blown fuse or burnt out ses light but can be a bad ecm or prom they do make test procedures to figure out why so i would suggest you take it to a shop that is willing to take the time to do the test to find out why, cause without being able to scan your computer they have no idea if all the sensors is reading correctly.
a scope is generally used to test secondary ignition system and individual sensor readings if they couldnt scope your car there scope must be broken.
just because your fuel pump has been replaced does not mean that it isn't bad there is alot of aftermarket pumps that are junk right out of the box.

 
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08-01-02, 02:39 PM   #8  
SaDow
stumble home mode

I just read in article in third gen .com that if you chip goes south your car goes into a stumble home mode . the car runs very rich . what would the simptioms of a car in stuble home mode be, ps . the line pressure is 45psi .

 
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08-01-02, 05:40 PM   #9  
most cars computers when they see something wrong or way out of specification will turn on the check engine light and can go into limp in mode depending on what the fault is and when in limp in mode the vehicle will run on specifications built into it, in the early 80's gm carburated car was in limp in mode it would run extremely rich, however a fuel injected vehicle in limp in mode will not run as rich and wont really be as noticable other than a chack engine light.
a vehicle running excessivly rich will be blowing black smoke out the exhaust pipe and will idle rough possibly even die when idling will miss due to fouling of the spark plugs but will usually run alot better at higher rpm than at lower rpm.
does your check engine light ever come on while driving ?
does your check engine light come on with the key on engine off while performing a bulb check it should.
usually you will have to test fuel pressure under a load or while driving the vehicle, most of the time a pump will show good pressure just idling in a shop bay but you go drive the vehicle and when it bogs down see if pressure has fallen off.
oh and by the way according to chilton web site the key on engine off fuel pressure should be between 40- 47 psi for your car.


Last edited by bejay; 08-01-02 at 06:05 PM.
 
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