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Old 12-28-2007, 06:09 PM   #1
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Default Still Can't Find MISFIRE!!!

Hey guys,

I am at my wits end here. I have an '87 F150 302 Auto 2 wheel drive - 190,000 miles. I have been having misfire problems with the truck since I bought it 8 months ago.

Previous owner replaced both fuel pumps and filters. I replaced:

-all new fuel injectors
-new plugs and wires (correctly gapped)
-flushed and replaced coolant, changed T stat
-new distributor and module (plus rotor and cap)
-new coil
-new alternator w/belt
-Also, passed California smog back in May

All of this was done in the past 1,000 miles. Yesterday I went and bought new plug wires again thinking that one of them might be bad. I also read that there is a TSB on the correct wire routing, so I did that (since I didn't do that before) hoping that it would solve my problem. Started my truck and it runs ok at idle NOT under load. As soon as I shift into Drive or Reverse it chuggs badly - even worse when I give it gas.

So, changing my plug wires and routing them correctly according to the TSB diagram made it WORSE!

It is timed correcly, but it is definitely an ignition problem. Under a timing light, when you give it gas, it first retards then advances...that doesn't seem right to me....

I was thinking about taking these plug wires back to Napa and getting yet again another set to see if the $25 set from Napa is junk or not.

Anybody have any clue what is going on here?!?!

Paul
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Old 12-28-2007, 06:18 PM   #2
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put a can of sea foam in it. Run it directly into your injectors. Costs 9.00 at autozone then change your fuel filter, costs probably 20.00.
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Old 12-28-2007, 06:30 PM   #3
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Originally Posted by levi127 View Post
put a can of sea foam in it. Run it directly into your injectors. Costs 9.00 at autozone then change your fuel filter, costs probably 20.00.
I forgot to say... i've done that about 2 months (500 miles) ago
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Old 12-28-2007, 07:30 PM   #4
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Plug wires could be a possibility. About pulled my hair out before finding that the new set of cheapie wires were the problem. Invested in a good set (about $60), and the world was right again.

May try taking resistance measurements first to see if that turns anything up. Should be less than 5,000 ohms per foot, IIRC.

Also, perhaps a bit of a WAG, but inspect the MAP sensor for any pinholes or cracks in its sensor line.

Did the new distributor include the pickup sensor inside?

Does the 'check engine' lamp work, and does it come on at all when running?

What quality / brand of parts did you use? I've had issues with the chain-store low-end stuff.

How much slack is in the timing chain with 190K miles? Your actual timing could be retarded (late in firing) by several degrees, even though it's set to spec.
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Old 12-28-2007, 07:48 PM   #5
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Plug wires could be a possibility. About pulled my hair out before finding that the new set of cheapie wires were the problem. Invested in a good set (about $60), and the world was right again.

May try taking resistance measurements first to see if that turns anything up. Should be less than 5,000 ohms per foot, IIRC.

Also, perhaps a bit of a WAG, but inspect the MAP sensor for any pinholes or cracks in its sensor line.

Did the new distributor include the pickup sensor inside?

Does the 'check engine' lamp work, and does it come on at all when running?

What quality / brand of parts did you use? I've had issues with the chain-store low-end stuff.

How much slack is in the timing chain with 190K miles? Your actual timing could be retarded (late in firing) by several degrees, even though it's set to spec.

The plug wires are from Napa (Mileage Plus $25). I will take them back and get a better set.

Slack in timing chain - I imagine that I need get another soon, but I have not done the timing chain slack test as of yet (you just turn the crank and see how many degrees it will go until the rotor moves? Right?)

Also, MAP sensor... where is that? I know it doesn't have a MAF, but where's the MAP? I have 2 big air hoses from the air box straight to the butterfly valves. Wouldn't the MAP be in line with the hoses?

New distributor - I would guess it has the pickup sensor inside.... I'll have to check, but the truck acted the same when I had the old distributor on it as well.

Like I said, its weird that I changed the plug wires out and routed them correctly and the problem got worse. (just a side note, I changed the drivers side valve cover gasket last night and had to disconnect a few connections (the plug to the coil and one other one=I made sure these were plugged back in correctly, even cleaned off the points of contact).


Paul
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Old 12-28-2007, 08:44 PM   #6
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Ok first make sure to get the blue wires from Napa, best anyone can get.. Then do a compression test and see what comes up...I know my cam sensor went out and it did the same thing,but I can't remember if yours works the same way as mine...
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Old 12-28-2007, 09:54 PM   #7
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Slack in timing chain - you've got the right idea - rotate the crank with a wrench in one direction until the rotor moves. Note the position, perhaps with a chalk mark or the like on the crank pulley. Then rotate the crank in the opposite direction until the rotor moves - and note the position. This distance observed on the crank pulley is approximately how much the timing should be advanced from spec. If there's a big distance, perhaps it's time to consider changing the chain as there's no way to adjust the relative camshaft timing. But for a stop-gap measure, this adjustment may get things back in the ballpark as far as ignition timing.

Not sure about your model year - my MAP sensor is bolted on the firewall just under the hood seal, slightly to the passenger side above the intake manifold. There should be a sensing line from the intake plenum up to the sensor - this is the line of concern.

The pickup sensor is inside the distributor - if you replaced distributors and the truck even started, then it had a new sensor.

At this point, with the info given, I would highly suspect the wires as a leading cause, since when you altered their positions, the problem changed. Suggest to resolve this first before going after other potential causes.
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Old 12-30-2007, 10:03 PM   #8
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could be a burnt valve or a stuck valve to i would do a compression check on all 8 cyl.. also could be a bad distributor check
let me know how ya make out man
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Old 01-06-2011, 11:19 PM   #9
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I just joined and saw your post. you sound like i do now . what did you find out .
i have allot of arcing at each wire/plug boot . new motorcraft wires /plugs . replaced fuel filter twice . cap /rotor fairly new .
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Old 01-07-2011, 10:50 AM   #10
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Originally Posted by gassign94 View Post
I just joined and saw your post. you sound like i do now . what did you find out .
i have allot of arcing at each wire/plug boot . new motorcraft wires /plugs . replaced fuel filter twice . cap /rotor fairly new .
Hi - yes, I did figure it out... multiple issues, but first, make sure you have new plug wires and they are routed and separated CORRECTLY - if not you will have some issues. Find the correct routing diagram for your truck and do that. I might have that somewhere...let me know if you need it and I can try to find it and scan it for you.

I ended up getting a new long block since I had two cylinders with low compression and oil pressure issues. But, that wasn't what fixed the main issues. 2 things.
1) Being in California, we have to have our emissions system working well. Even with the new motor, new EGR valve, EGR Position Sensor and EGR Vacuum actuator, my EGR valve doesn't open and close properly (it opens and closes intermittently). I still haven't figured out why is the issue, but once the vacuum line to the EGR valve is disconnected, the problems go away. When I have to smog the truck, I just plug the vacuum line in again (yes, some of the issues come back, but I have to to pass smog).
2) My computer. I had hard cold starting issues and drivibility issues (hicupping and lack of power). I went to the junkyard and picked up the same computer (must match engine size, transmission, and California emissions requirement - only for Californians). ALSO, the computer must be for the earlier F150's in the same generation - I think you can get one from 87-91. The reason is, that, after those years they changed the wiring for the fuel injectors - bank injectors vs. individual injectors. Mine had bank injectors (meaning the computer only has to send 2 signals to activate all the injectors instead of 8 compared to the newer models). Plugged it in and presto - worked wonderfully. The motor works great now with those 2 changes. I put the old computer back in the see the difference and sure enough the programs came back.

Hope that helps.

Paul
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Old 01-07-2011, 10:50 AM
 
 
 
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