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Discussion Starter #1
First off thanks for all the info already folks. I just registered but I end up on this site all the time for various things, so thanks.

So here's the problem. I just put headers on my 90 5.0 connected to sidepipes (yeah it looks awesome) but now sometimes it runs terrible, at an idle it will pulse up to about 2k rpm and completely bottom out, usually it eventually dies. When driving the engine will complete cut out for a split second and then go again, kind of feels like water in the gas, doubt that's the problem. But for about an equal amount of time during this mess it runs perfectly, it will idle great at about 700 rpm and show no evidence of issue. Very random.

My first thought was ignition module. I just put a new one on a month or so ago but it was a $10 one off ebay, just assumed it was garbage like the idle air valve I got at the same time that didn't work and the module I got for my ranger at the same time that also didn't work. So anyway I dropped the $50 on a real brand and also went ahead and put a new pick up in it at the same time.

Some of the other new parts I've put on it include:
O2, MAP, both coolant temp, coil, cap, rotor, wires, plugs, fuel pump, pressure regulator, filter, intake gasket, timing chain, tps, I dunno pretty much everything else... tires.

Any thoughts would be great. I'm leaning towards egr issues or possibly something to do with the air system. I really don't know squat about either of those systems. I pulled the codes and got 22 and 23, map and tps but I don't trust it, for one thing the engine was off so I'm not sure how the map vacuum could be off and also both of those sensors are new, though to be fair seems like half the parts I get anymore are bad out of the box.

Alright, thanks a lot for any help.
 

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Discussion Starter #3
Well I figured it out and it's pretty irritating. It seems I can't buy good parts at all. I was heading home for lunch today and it was running worse than ever. I opted to work on it some more then. So I started swapping new components for old. Went through several parts and got to the MAP sensor. As soon as I plugged in the old one it fired up and ran perfectly. This seems to be a nonstop problem. I'm probably getting functional parts around 40% of the time. Solenoids that stick, an alternator that rattles constantly, 2 bad ignition modules, and now a faulty map sensor, probably more I can't remember. Just FYI most of these parts have come from Advance Auto Parts. A few of them way too cheap parts off ebay. I guess I'd recommend only replacing one piece at a time and expecting the new parts to be faulty. That's the way I'll be doing it from now on. Although the map didn't fail for about a month. Dunno what to do I guess.

Just to be sure how would I reset the computer exactly? What I've been doing is removing the power from the battery for a while in hopes that would reset it. Is there a better way?

Anyway it's running fantastic now, better than ever. I accidentally broke the tires loose earlier and I haven't changed the gears yet to accommodate the 36 inch tires, not bad.
 

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Premium Member
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5,774 Posts
So your old MAP sensor was good. Are you just randomly replacing working factory parts with aftermarket junk?
You really should test before you replace, and when you do find a defective part use Motorcraft.
 

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21 Posts
My daily driver '88 was iding rough and likely missing ans the tacometer would spike about 200 rpm... I though water in the fuel 'cause a buddy has an F350 with the BB fueled there too and was kinda suddenly doing that too. But, after a full tune up. I took the Flame Thrower ignition module off (that I've run for at least 2 yrs) and put the orig. MotorCraft back on and it ran perfect...
 

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Eric
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2,625 Posts
I just took off a brand new IAB valve from O'Reilly that tested fine, but, caused a fluctuating idle. Put on a Motorcraft IAB and solved the issue. Smooth as glass now. Parts store stuff just seems to keep getting worse and worse.

Eric
 

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Discussion Starter #7
No the old sensor was bad as well just worked better than the new one. I got a new motorcraft one the other day and the problem is solved. Motorcraft has an issue too though, I had to save up my money to get that piece of plastic.
 
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