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post #1 of (permalink) Old 02-10-2000, 12:15 AM
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help with a 2.5L

I need some help with my 85 S-15 2.5L engine. It seems to run rich and I can't get the timing right. When I adjust the timing to 8 deg it tries to die out on me. I have to run the timing way high for it to even run good at all. I have checked for vacuum leaks and can't find any. The injector seems to spray too much fuel but I dont know how to correct it. The O2 sensor looks original. Maybe that could be causing the problem? Any advice would be apreciated!

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke
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post #2 of (permalink) Old 02-10-2000, 08:07 AM
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Re: help with a 2.5L

Hey Fredbear, listen this happened to me last month, in mine I changed the map sensor, plugs and wires, oxegen sensor, TB gasket, ERG valve, I was feed up of changing parts and nothing was changing, so I went to a garage to get the computer analized and presto ... all my problem was, was lean fuel pressure so I changed the fuel pump and it runs like a charm. It`s like you said I was running bad, I couldn`t time it it would die out on me on the mark. so check out your fuel pump.

I`d rather push a Chev than drive a Ford
Hachey, 88 Blazer 4x4
post #3 of (permalink) Old 02-10-2000, 10:50 AM
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Re: help with a 2.5L

yea but mine is running rich not lean. I think the O2 sensor may be bad. When the engine is running and I look at the injector it seems to be putting too much fuel to it. If I unplug the vacuum lines at the charcol canistier a little raw fuel runs out. This would indicate too much fuel allso. I think that it may be a bad O2 sensor but I was just wanting some advise. Thanks for your advise but I dont think that that is my particular problem. I have the exact oppisite problem. Too much fuel.

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke
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post #4 of (permalink) Old 02-10-2000, 12:21 PM
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Re: help with a 2.5L

CHECK OUT YOUR VACUME LINES, I DO KNOW THAT WHEN MY VACUME LINE FOR MY MAP SENSOR IS OFF, IT IDLES VERY HIGH AND DRIVES REALLY BAD MAYBE PLAY WITH THAT UNPLUG IT AND SEE IF THERE IS SOMETHING IN THE LINE ITSELF BLOCKING THE VACUME. MY TRUCK IS AN 88 AND I CHANGED A LOT OF MY LINES ALREADY BECAUSE OF VACUME LEAKS

I`d rather push a Chev than drive a Ford
Hachey, 88 Blazer 4x4
post #5 of (permalink) Old 02-10-2000, 05:07 PM
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Re: help with a 2.5L

silly question: when you try to adj the timing are you disconecting the tan wire under
the glove box?

HAWG WILD
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post #6 of (permalink) Old 02-11-2000, 12:12 AM
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Re: help with a 2.5L

no! what tan wire? I know that on older conventional engines you have to disconect the vacuum advance but this engine has no vacuum advance. So do I have to disconect a tan wire under the glove box? Where is it exactly?

92 S-10 Blazer 4x4 Vortec 4.3
85 S-15 Pickup 4x4 2.5 iron duke
post #7 of (permalink) Old 02-11-2000, 12:32 AM
 
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Re: help with a 2.5L

Since you don't know the age of the O2 sensor it's probably good to make the expense and change it out. That silly little frickin' sensor lead is the main cause of a lot of frustration.

Another cause might be faulty injectors. You might want to consider having them cleaned out or rebuilt/replaced. Try the cheaper stuff first and see what you get from there.

Hope that helps.

[img]/wwwthreads_images/icons/shocked.gif[/img]- <font color=purple>J.R.</font color=purple> -[img]/wwwthreads_images/icons/shocked.gif[/img]
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post #8 of (permalink) Old 02-11-2000, 02:29 AM
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Re: help with a 2.5L

Yup, those O2 sensors can be a real pain the the as$. That would be the first thing I would check. I replaced mine after failing emmisions, it ran great...for about 2 weeks. Then, the check engine light became what I called the JFK eternal flame. The brainchild at the autoparts store gave me the wrong one.

post #9 of (permalink) Old 02-11-2000, 05:01 PM
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Re: help with a 2.5L

the reason why there is no vacuum hose is that EST (Electronic Spark Timing)
controls all of the timing ( i.e. no vac adv or centrifugal weights). I was off slightly, later
models have the tan wire, what you need to do is jumper the A/B terminals of the ALDL
connector (screwed to the bottom panel about where your right knee is)the A term is the
one in the upper right corner and the B term is the one to the left.
(THIS IS FOR MOST S/T TRUCKS, LOOK AT IT IT SHOULD BE MARKED)
___________
|F|E|D|C|B|A|
|-----------------|
|G|H|J|K|L|M|
-------------------
Jump the two terminals together with the ignition OFF, this will over ride the EST module
and let you set base timing. by the way if you do this with the ignition on, it should flash
the CHK ENG light 12 times (diagnostic mode) or flash out trouble codes (i.e. O2 sensor)
(get a good service manual for diagnostic codes)
happy wrenching

HAWG WILD
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post #10 of (permalink) Old 02-12-2000, 02:15 PM
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Re: help with a 2.5L

Sounds like you're truck is having the same problems my wife's Nissan Sentra has. For the last year or so, her car has shown horrible accelearation. It hardly accelerates at low rpms and then literally jumps up to speed at a certain rpm (no tachometer so I don't know exactly when). I tried a tune-up and $15 fuel injection cleaner, but neither helped. The vacuum hoses all look fine and are connected, and the motor runs great except for the acceleration problem. Also, the car's oil smells like gas every time I change it. This and some other stuff led me to believe the carb is running too rich.

I was going to change the air/fuel intake ratio, but I came to find out that it is all computerized. Fortunately, a salesperson/ex-mechanic informed me that if the O2 sensor goes out, the computer won't mix enough air because the computer thinks the engine is getting more oxygen than it really is. I called the Nissan service center and they confirmed this. Unfortunately, the sensor costs $70, but if it works, it's more than worth it.

Of course, my wife's Sentra doesn't have the timing problems you mentioned. Also, the lifetime on an O2 sensor is around 100,000 miles, so if your truck has considerably lower miles, I'd look elsewhere first. In any case, I'm ordering the sensor this Sunday. I should have it changed in two weeks or so and I'll post how it went for future reference. If you replace yours in that time, please let me know how it went.


[img]/wwwthreads_images/icons/cool.gif[/img] Steven Fairchild [img]/wwwthreads_images/icons/cool.gif[/img]
[img]/wwwthreads_images/icons/wink.gif[/img] <font color=green> 96' S-10 4x4 </font color=green> [img]/wwwthreads_images/icons/wink.gif[/img]
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