need help badly
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New User
Joined: May 2010
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need help badly
i have a 89 f 150 witha 302 got good spark but yet i have a misfire on #3 cylinder check compression all cylinder are between 125 -140 psi all plugs and wires are good and getting spark if anyone has any ideas please let me know thanks
Logistics Pro
Joined: Mar 2005
Posts: 4,698
Likes: 47
From: Mexico, Missouri
When did this problem occur?
Since there isn't a cylinder balance test for this vehicle, other than shorting the injectors out, what leads you to #3 cylinder not firing correctly?
If you are completely sure that #3 isn't firing correctly, I would check the plug itself. I have heard of the porcelain having a stress crack from overtightening, just from age itself, or if it were hot and water hit that plug, causing a miss. You need to disconnect the plug wire from the plug and check for spark to that cylinder.
Let us know what you find.
Also check that the plug wire itself is GOOD! I have heard on here that plug wires, though new, have been bad out of the box. Check for resistance with no more than 5K. Wiggle the wire to ensure it isn't shorting out.
Since there isn't a cylinder balance test for this vehicle, other than shorting the injectors out, what leads you to #3 cylinder not firing correctly?
If you are completely sure that #3 isn't firing correctly, I would check the plug itself. I have heard of the porcelain having a stress crack from overtightening, just from age itself, or if it were hot and water hit that plug, causing a miss. You need to disconnect the plug wire from the plug and check for spark to that cylinder.
Let us know what you find.
Also check that the plug wire itself is GOOD! I have heard on here that plug wires, though new, have been bad out of the box. Check for resistance with no more than 5K. Wiggle the wire to ensure it isn't shorting out.
Postmaster
Joined: Mar 2008
Posts: 2,703
Likes: 7
From: Des Moines, Iowa
don't forget the obvious... check your cap and rotor. I would swap around a plug and wire to see if you still get spark. Is your plug wet with gas? does it smell rich? if so you are getting fuel but it still might not be enough. I'd swap a couple injectors and see if the miss moves cylinders.
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New User
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i removed the # 3 plug wire from the cap while it was running and the engine stayed idling the same way verses the the other cylinders made the engine run rougher. i also ohm check the wire and it checks out good
Postmaster
Joined: Mar 2008
Posts: 2,703
Likes: 7
From: Des Moines, Iowa
I would think it's an injector... Like I suggested before. Swap your #3 and #5 injector and see if the miss moves to #5 with the injector. If it does I suggest getting a set of refurbed and flow matched 19# injectors... You can also go to RJM and get a refurb kit yourself and then do a self clean with a injector wire from the JY. If you want to know how to do the home clean on the injectors let me know...
1992 F150 Fuel Injectors 5.0 302 5.0L 4x4 Rebuilt Set 8 on eBay!
1992 F150 Fuel Injectors 5.0 302 5.0L 4x4 Rebuilt Set 8 on eBay!
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Joined: Jul 2020
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From: Near Salt Lake City
Get a few injectors at the junkyard and replace the one in cylinder 3
You can buy new o rings for the fuel rail separately
Take the rail too so you can test a few of yours using injector cleaner
I put a pressure gauge on the car and monitor the pressure while I manually fire the injector
If your injector is no good the fuel pressure will not drop like the good ones do
Have fun
You can buy new o rings for the fuel rail separately
Take the rail too so you can test a few of yours using injector cleaner
I put a pressure gauge on the car and monitor the pressure while I manually fire the injector
If your injector is no good the fuel pressure will not drop like the good ones do
Have fun
Logistics Pro
Joined: Aug 2010
Posts: 3,717
Likes: 585
From: Chillicothe
Get a few injectors at the junkyard and replace the one in cylinder 3
You can buy new o rings for the fuel rail separately
Take the rail too so you can test a few of yours using injector cleaner
I put a pressure gauge on the car and monitor the pressure while I manually fire the injector
If your injector is no good the fuel pressure will not drop like the good ones do
Have fun
You can buy new o rings for the fuel rail separately
Take the rail too so you can test a few of yours using injector cleaner
I put a pressure gauge on the car and monitor the pressure while I manually fire the injector
If your injector is no good the fuel pressure will not drop like the good ones do
Have fun