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post #1 of (permalink) Old 11-13-2001, 05:25 PM
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fuel economy/stalling

Hmm, another mind boggler from my truck

after installing my new motor, i have been having trouble with her stalling every time i stop at a light. if she doesnt stall, it almost stalls, surges, and rarly idles smooth. this is the same manifold computer and injection as the old motor, and it idles smoother then anythign i owned before. at first, i presumed new motor break in, a little dirty, etc, but if anything, it has gotten worse. sounds like a vacum leak possibly to me. then, i noticed poor fuel economy, which i expected it to be lower then before, as i have the np235 with no overdrive now, as opposed to the overdrive rail transmission, but i finally checked it, and got 9.2 MPG!? i was getting about 15 or 16 before. my brother gets 8 or 9 with a 78 bronco with a 400, why doi have this little motor, with fuel injection, for the same economy. now with my experiance, a vacuum leak could also cause this, but i am more familiar with carburators. i know steve should be able to help me as usual, someone sure can i hope!!? i cant afford to drive her like this anymore, or worse, the guy that might buy it wont want a truck that barely idles. HELP!!!

Dominic

"MUD BUCKET" 1984 bronco, 88 302, 32x11.5 , I am at screen name iskybantilus on instant messenger.
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post #2 of (permalink) Old 11-13-2001, 06:36 PM
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Re: fuel economy/stalling

its your oxygen sensor

89 Bronco XLT, V8 302, superwinch hubs, 31x10.50 trailhandlers
post #3 of (permalink) Old 11-14-2001, 10:46 AM
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Re: fuel economy/stalling

hmm, thats a very good idea, cant believe i didnt think of it. do you think its bad for the o2 senser, when, after firing the new engine, it was blowing mud and water out of the tailpipe, as it has been sucked through the old engine before it died? i cant imagine a hot o2 sensor tip could like that.

Dominic

"MUD BUCKET" 1984 bronco, 88 302, 32x11.5 , I am at screen name iskybantilus on instant messenger.
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post #4 of (permalink) Old 11-14-2001, 06:11 PM
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Re: fuel economy/stalling

yeah the mud would do it. mine was surging and shat like you say yours does and i put it on the computer and the oxygen sensor code came up. i replaced the sensor and pulled the battery cables for like 2 minutes and all is good now. good luck

89 Bronco XLT, V8 302, superwinch hubs, 31x10.50 trailhandlers
post #5 of (permalink) Old 11-15-2001, 09:44 AM
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Re: fuel economy/stalling

If the sensor change doesn't work, you might want to start searching for some packed up mud in the exhaust system. I would start with the muffler, then work my way up to the convertor. Excessive backpressure gets you the same type of symptoms. I would think the HEGO sensor is trashed as well.

post #6 of (permalink) Old 11-15-2001, 09:50 AM
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Re: fuel economy/stalling

hmm, i would agree with the backed up exhuast, except that at higher rpm, it runs pretty good, and i would think a clog would get worse with rpm. HEGO sensor? heated exhuast gas oxygen sensor?

Dominic

"MUD BUCKET" 1984 bronco, 88 302, 32x11.5 , I am at screen name iskybantilus on instant messenger.
post #7 of (permalink) Old 11-15-2001, 03:46 PM
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post #8 of (permalink) Old 11-15-2001, 03:47 PM
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post #9 of (permalink) Old 11-15-2001, 03:48 PM
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Re: fuel economy/stalling

Did you check to see what kind of vacuum its pulling?

sorry about all these posts, this damn forum keeps freezing up on me.[img]/wwwthreads_images/icons/crazy.gif[/img]

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post #10 of (permalink) Old 11-15-2001, 10:53 PM
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Re: fuel economy/stalling

gonna check the vacum tommorrow, prolly put a new o2 in regardless, it has over 130,000 miles on it, and then let my brother take it to work and put it on the scanner. i have never pulled codes since i installed the setup in my 84, i imagine it has to be pissed about something.

Dominic

"MUD BUCKET" 1984 bronco, 88 302, 32x11.5 , I am at screen name iskybantilus on instant messenger.
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