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1990 Ford F150 Engine Backfiring
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navicire
New User
Apr 16, 2010, 7:18 AM
Post #1 of 2
(5276 views)
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1990 Ford F150 Engine Backfiring
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1990 Ford F150 XLT Lariat 351 V8 5.8L engine starting/idling rough and backfires when given acceleration. Hesitates and loss of power while driving. Bought truck with 200K miles and now has 210K miles. Have replaced the following in last 6 months: spark plugs, spark plug wires, air filter, breather filter, ECR valve, fuel filter, distributor cap and rotor.
Over last month have now had 4 incidents of this engine problem mainly occuring after the truck was driven and then sat for 8+ hours. Truck now can barely run without much power. Help!
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 16, 2010, 8:36 AM
Post #2 of 2
(5267 views)
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Re: 1990 Ford F150 Engine Backfiring
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I suggest hurry to check this out:
Timing chain - original had a nylon toothed cam gear that is junk by time never mind miles now - almost certainly.
To check if you don't know the history see if you can detect any gasket cement between timing cover and engine block. It's a maybe that it's been done and that would be reason to believe someone was in there. No cement was use originally.
If timing can jump around which would/could cause backfires or an assortment of issues up to no start or run at all!
Try setting pointer of timing mark right on TDC by turning the crank bolt. Clean off marks so you can see them. When put to the mark one way then turn the other way watching the distributor's rotor and how many degrees you turn before rotor turns. More than 5 is trouble - bet you can go 10! That can also be a distributor problem with the gear and a roll pin but not so common. Easy to take distributor out to check.
If chain is known replaced in it's life it's still worth that simple check. I've never seen anyone use the damn nylon (planned obsolescence by many engine makers IMO) one in replacement and all metal lasts well.
Could be all wrong but if this is the issue and can change while operating to good or worse then while worse check compression - all would show low.
If you do determine this to be highly likely see what that gear looks like. Smooth even wear would be nice but you may find chunks missing! Those are in oil pan! Decide if so whether you want to get those out - more work and the chain job isn't so bad but all the bolts and junk getting past water pump can be a PITA,
T
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