Need Help please with miss
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Cross-Country
Joined: May 2013
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Need Help please with miss
I've tried every possible thing.My expy 4.6 171xxx has been missing randomly its never a constant miss its never threw code..I've replaced fuel pump,plugs-n-wires,coils packs,tps and egr along with all rubber hose vacum lines..I've cleaned two different iac with no luck..Seems to miss noticeable at a stop when in gear could take 2 -3 mins before it does a random buck of drop in rpm while sitting waiting to leave light then its very sluggish as i leave the light and passing on freeway ..I checked for spark by pulling the wires off the coils one by one they all had strong constant spark.it seemed to be more of drastic miss when spark was removed from cylinder than the miss I have...Thanks in advance for any help..
Fleet Owner
Joined: Apr 2008
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Based on your description it sounds more like a bad wire connection to me. Find it could prove to be difficult. Have you tried shaking various parts of the wiring harness and connectors to see if the engine is affected?
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Might be crazy idea but for the sake of brainstorming, did you take out the maf and wipe the two little wires to make sure there clean.
My next idea would be pre-detination caused by carbon build-up on the pistons or heads. (i know its not too common on these motors)
I have cleaned the internals by getting the motor hot and then with the motor at idle sucking seafoam (or similar) into the intake manifold I use the brake booster hose.
My next idea would be pre-detination caused by carbon build-up on the pistons or heads. (i know its not too common on these motors)
I have cleaned the internals by getting the motor hot and then with the motor at idle sucking seafoam (or similar) into the intake manifold I use the brake booster hose.
Fleet Owner
Joined: Apr 2008
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From: 0,0,1
FYI, it is not recommended to ever touch the MAF wire because of it being so fragile. The safer way is to spray it with a cleaner and then give it a small shot of compressed air.
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Cross-Country
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I was think a bad wire conection or bad wire could be it too.I havn,t tried shaking the harnnes though try that too..thanks for the re:
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Cross-Country
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Yes, I have cleaned the maf with spray cleaner.Thanks for re:
Logistics Pro
Joined: Jan 2001
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From: Central NYS
How about the infamous PCV elbow?
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Senior User
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Not under minding you because all your posts are pretty insightful but I've . cleaned crud off MAF wires with scribes or needles very genitally wiping them on tons of vehicles with great results.
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Cross-Country
Joined: May 2013
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I did check it.My pcv valve has a hard rubber hose that I couldn't pull off but looks to be crack free.I think the the pcv elbow is on the 5.4..I'm think about replacing the iac next although I dont think its going to fix it at my wits end now..I'm starting to think the worst a slow leaking head gasket letting moisture in a cylinder.
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Cross-Country
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I'll try it I have done this before with the maf cleaner and Q-tip at this point i will try anthing..Just keep hoping for a code mil light...Thanks for re..
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Cross-Country
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Today I tried testing the evr and iac both seem to be working right..Tried the blow threw and grounding out pin 33 to see if it let vacuum to the egr which it did making the engine try to stall..As for the iac test i just unplugged the wire connector and unplugged the intake vac hose connected to the housing both caused a drop in idle I'm just assuming its good based on that..A weird noise has been happening latey too just to add to the headache, only three times in the past week .First time I was siting in the garage car in gear foot on brake then there it went it sounds like a air horn loud bloot..lol..then it stops sat in the car today for 30 mins in gear and it never sounded..Anybody heard of this..Evr maybe
thanks for any re
thanks for any re
Carpenter Local 745
Joined: Apr 2006
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From: on da beach
touch the wires, just spray them.
Also have you actually checked the computer with a scanner?
Please STOP throwing parts at the truck for now.
Look for an air leak after the MAF and before/at the intake.
Inspect connections, hoses and grounds.
Always disconnect the negative battery cable when doing ANY electrical work.
Systematically go back over all the parts you replaced (keeping in mind that new parts can be junk too).
Thread Starter
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Cross-Country
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[/QUOTE]Also have you actually checked the computer with a scanner?[/QUOTE] I just have a obd code reader no codes with that.
[/QUOTE]Please STOP throwing parts at the truck for now.[/QUOTE] Ya im on tight buget right now cant afford it.
[/QUOTE]Look for an air leak after the MAF and before/at the intake.[/QUOTE] I have the k&n cold air intake I did spray carb cleaner all around it with change in idle but will def check again.
[/QUOTE]Inspect connections, hoses and grounds.[/QUOTE]check
Always disconnect the negative battery cable when doing ANY electrical work.
Systematically go back over all the parts you replaced (keeping in mind that new parts can be junk too).[/QUOTE]Will do..new parts fuel pump im kind sketchy on ebay pump fuel pressure test shows (35psi key on engine off) (26 psi at idle fluctuates when reving 26-30 psi) 39 psi reg vac hose off..Thanks for re..
Carpenter Local 745
Joined: Apr 2006
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From: on da beach
Uh, mentioning that this truck has CAI is/was important.
So, you have a K&N reusable oil air filter?
And you noticed idle change while spraying carb cleaner on intake AFTER
The MAF?
Vacuum leaks after the MAF cause "stop light" miss/stumble.
So, you have a K&N reusable oil air filter?
And you noticed idle change while spraying carb cleaner on intake AFTER
The MAF?
Vacuum leaks after the MAF cause "stop light" miss/stumble.
Logistics Pro
Joined: Jan 2001
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From: Central NYS
One fella on this forum changed his IAC and it hasn't happened since.
https://www.ford-trucks.com/forums/1...-fog-horn.html