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rough idle and low rpm problems - HELP?!

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Old 04-11-2010, 01:39 PM
Fr0gger Fr0gger is offline
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rough idle and low rpm problems - HELP?!

Hey everyone, was wondering if i could get some help with a rouge idle and low rpm problems.

I have a 302 in a 93 f-150. I rebuilt the motor last year in November. Has been running fine up until 3 or 4 months ago. I started having a loud squeaking problem. After a lot of trouble shooting, it ended up being the bearing in distributor. So, I got a reman distributor and it fixed the problem. Then about a month later i started having starting problems. The coil wire wasn't even firing. Replaced the coil and that didnt fix it. Had the ICM tested (tested it like 15 times in a row, it got smoking hot) and still passed. I got to thinking maybe it was the reman distributor that was causing the problem, so i pulled it off and swapped it out for another one and then problem went away. Haven't had a problem starting since then. probably two months or so.

Now I'm noticing a really rough idle in low rpms of each gear. I mean really rough, and it back fires sometimes too. I notice it most when going to work, speed limit is 25, and when im doing 25mph, it is at low rpm and runs horrible, seem like it is missing. also does it on the highway doing 70mpg in 5th gear. So i think im safe in saying it only does it at low rpm (hoping that helps narrow this down). i got all new spark plugs, didnt fix it. Swapped out my wires with my spare set i keep just incase, and that didnt fix it. did a compression check on every piston and they were good.

My engine codes are 31 and 32 which relate to the EGR valve. something about voltage. I had these codes right after i rebuilt the motor and it has ran fine for a year up until now, so im not sure if those codes pertain to this problem im having.

Could "timing" cause this problem? When rebuiling the motor, we couldnt get the timing light to work right for some reason, so we timed it by ear. we timed it by ear when rebuilding the motor the first time, and it ran perfect for a year, and then when we switched out the reman distrib, we moved it over one tooth to give us more room for fine tuning the timing.

Any help would be much appreciated...I have been trying to figure this out for a couple of months, probably just going to take it into a shop if i cant figure it out this week.

Thanks in advance!
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Old 04-12-2010, 09:19 PM
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Conanski Conanski is offline
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Get yourself a timing light and set it to spec and change the EGR position sensor.. that's what those codes are pointing to.
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Old 04-13-2010, 08:53 AM
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even if my smog pump isnt hooked up and is welded off in the back of the engine, will that sensor still make a difference?
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Old 04-13-2010, 12:55 PM
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Smog pump has nothing to do with the EGR system.
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Old 04-15-2010, 11:11 AM
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OK. do you think that the o2 sensor could be causing this problem? it is the original o2 sensor from what i can tell. so thats 220k miles. I have had it for 100k miles. Im sure that it is time to replace it, but do you think it could be causing the problem? Would i not get error codes related to the o2 sensor if it was?

Thanks again for your help!
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Old 04-20-2010, 09:40 AM
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well, i ended up taking my truck into the shop last week. He has narrowed it down to the number 2 cyclinder that is miss firing, but is still unable to figure out what is causing it. Anyone have any ideas on what it could be? I did a compression check a couple of weeks ago, and all the cylinders checked out fine. Could a miss fire in only one cylinder be something electronic? or is it going to be something mechanical?

Thanks!
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Old 04-20-2010, 04:36 PM
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what plugs are you running?

what is your timing currently set at? when you replaced the dizzy did it have a Steel or bronze cam gear?
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Old 04-20-2010, 11:31 PM
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When setting the timing, you have to unplug the SPOUT sensor, and do it with the engine at a normal working temperature. See and check that your shop do it that way. Most folks around here like having the timing around 12-13 degrees BTDC. If you keep having issues, you could back it up a little (the original timing is 10 degrees BTDC). Btw, did you check the sparkplugs's gap? is should be around .055, you could also reduce this so there is less chance for the spark not to jump. The cables could also be failing...
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Old 04-23-2010, 02:45 PM
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ok, so i just got it back from the shop. it was the distributor again....kinda weird i got to bad ones in a row. the first one caused me starting problems, and the last one is what was causing the miss fire in the number 2 cylinder. I asked the guy at the shop what he timed it to, and he said "10". Its running great now!! now i have to do some stuff to my drive line and get it lined out better. The differential is pointing way up because the back end of my truck was lowered quite a bit before i got it. once i get it aligned better, i will get rid of the vibrations and should be good to go

thanks everyone for your input and help! i really appreciate it!
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Old 04-23-2010, 02:45 PM
 
 
 
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