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  #1  
Old September 20th, 2012, 05:26 PM
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Andrew Dance
1994 D-90 ST
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Won't accelerate

I know this could be one of a million different things, but I'll throw it out there in case someone has any ideas.

Recent rebuild, '94 D-90 3.9 V8 NAS.

Tachometer stopped working and it won't accelerate past 2-3k revs (guessing because tach is not working). Doesn't matter if I accelerate gently or WOT. Sputters so bad it won't pull through the rev range. Pulled a couple of plugs on both banks and really, really black and sooty. Obviously getting way too much fuel.

Has new distributor, coil, plugs, wires, alternator, ignition module, condenser.

I don't think it's the TPS because it doesn't matter what position the throttle is in.

The O2 sensors read 6.9 ohms between red and white wires which I think is normal.

I have continuity between the alternator and the tachometer but I'm not sure what kind of signal I should be looking for? Is it a pulse, or a linear voltage?

Haven't checked the MAF because I don't know what to look for as far as voltages, etc.

I don't think its the injectors, unless every single one of them when bad at the same time.

The ECU is not throwing any codes either.

Maybe fuel pressure regulator?

I'd like to eliminate the MAF, anyone know how to test it?

Thanks
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  #2  
Old September 20th, 2012, 07:51 PM
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Jay Geaney
1994 D-90 ST #282
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Sorry if this is too basic, but my '94 did the same thing and strangely enough the hose between the MAF and the plenum had separated (slipped off) at the plenum. Reconnected and tightened the clamps and I was golden.

Good luck
Jay
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  #3  
Old September 20th, 2012, 08:11 PM
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chris
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from what your describing no power around 2k-3k is indicating a faulty alternator internally erratic signal will cause the injection pulse to be out of time or non at all but start with the basics check alt output and load test ... defiantly check fuel pressure most sputtering situations are caused by a weak pump...all Grounds ... yes I've seen ecu crap the bed with no codes ... just my .02
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  #4  
Old September 20th, 2012, 08:54 PM
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Jason England
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Quote:
Originally Posted by genie90
Sorry if this is too basic, but my '94 did the same thing and strangely enough the hose between the MAF and the plenum had separated (slipped off) at the plenum. Reconnected and tightened the clamps and I was golden.

Good luck
Jay
Yep ... This is most likely ....
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  #5  
Old September 21st, 2012, 09:49 AM
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Andrew Dance
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The hose between the MAF and the intake is good. If it was leaking I would assume that would create a lean condition because the MAF would be reading less airflow?


Alternator is new, fuel pump is new. Again, if it was the fuel pump, I would expect a fuel starvation problem, not excess fuel.
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  #6  
Old September 21st, 2012, 09:57 AM
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chris
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is the alternator a rebuilt unit from box store ? checked for chaffed engine harness for injectors , the theory behind the lack of fuel is one the ecm sees lean condition it opens the injectors longer to compensate, you would actually get a rich condition .. like i said just start with the basics check fuel pressure first eliminate that and then move on .. faulty maf would also do that , check the resistor in the maf harness going to the coil should be 7 ohms
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  #7  
Old September 21st, 2012, 10:01 AM
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Is there water in the computer?

Mine did this when the computer got wet. Being that the tach is out, I would suspect the alternator is bad and may have or is playing havoc with your ignition system.
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  #8  
Old September 21st, 2012, 10:27 AM
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Andrew Dance
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Alternator is brand new, not reconditioned. The "chicklet" is good, 6.8k ohms. The computer is bone dry. No chaffed harness, I checked it carefully during the rebuild.

I don't have anything to test the fuel pressure, but I do have a new fuel pressure regulator so I'll put that on and see what happens.

Thanks for the ideas.
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  #9  
Old September 21st, 2012, 05:19 PM
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Andrew Dance
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So I took the alternator to the auto parts store. They tested it and said it's bad. Must have lasted all of 10 minutes.

Hopefully a new one will fix the issues. It's strange that the battery warning light wasn't coming on?
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  #10  
Old September 25th, 2012, 08:48 AM
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Andrew Dance
1994 D-90 ST
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Just a quick update. The alternator was bad, even though it was brand new, I guess it happens.

I have to say thanks to Rovers North. They paid for the repair at a local rebuilder even though the alternator was way over its 12 month warranty.

Thanks to everyone for the help.
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  #11  
Old September 25th, 2012, 10:12 AM
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Good deal!!!
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  #12  
Old September 25th, 2012, 11:31 AM
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IMPORTANT LESSON:

All new after market alternators are CRAP. So many of them are broken out of the box or shortly thereafter it is insane.

New Magnito Merelli [sic] is the way to go. Yes, you pay [much] more, but it is worth it.
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  #13  
Old September 25th, 2012, 12:02 PM
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Joshua
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Magneti Marelli is the name - . There are a bunch of us who are also running alternators from Action Alternators with good results. Ron I thought you were a Mean Green man?

James Pierce on the board here is also a good source for the 120 Amp Magneti Marelli alt.

http://www.eurorestorations.com/Euro...r_Upgrade.html
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  #14  
Old September 25th, 2012, 12:03 PM
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I have a new in box mean green and had one on a prior truck. After having a bosch shit the bed in 20k I am now firmly in the MM camp and have fitted a new one to my LWB and run one on my D90.
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