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Discussion Starter #1
When I got home from a drive the other day I noticed that my engine was idling a little low. Today I started it up and it idled extremely low, almost stalling, and backfired through the carb. Any idea what could cause this kind of problem just by going for a drive and then letting it sit? Thanks.
 

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Need more info. This is on your 67 standard 289? Its stock? Idles slow and smooth or rough? Popping when you try to rev it up? Single pop or multiple pops with a rhythm to it? Rhythem increases with rpm? Is there any engine noise, ticking? Three things can cause popping through the carb. Ignition, Lean A/F ratio and valve train problems. Ignition, wet or carbon tracked cap, open plug wire or crossfire between two plug wires etc. In stock form Fords rarely lean pop so I doubt it. Valve train, anything that causes an exhaust valve to not open fully will cause a rhythmic popping when you rev it up. Flat cam lobe, bent push rod or rocker arm problem. A burnt intake valve will cause rhythmic popping all the time. As JeffJ said its possible the timing chain jumped.

Bill
 

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You didn't change plugs or wires recently and cross one did you....
 

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Discussion Starter #5
Thanks all. The engine is a stock 289 with about 112,000 miles on it. At idle (just above dead) there is no backfiring, but when I rev it it backfires. I only saw it once, but I'll have to go play with it and see if it's rhythmic or not. I don't think the timing chain has ever been changed, though, so I should probably check that out.
 

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Thanks all. The engine is a stock 289 with about 112,000 miles on it. At idle (just above dead) there is no backfiring, but when I rev it it backfires. I only saw it once, but I'll have to go play with it and see if it's rhythmic or not. I don't think the timing chain has ever been changed, though, so I should probably check that out.
It definitely sounds like the teeth on your aluminum cam gear have worn down and the timing chain jumped a tooth or two.
 

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do you have a timing light? Check the timing first because it's a pain to change it and you want to be sure. PLugs could be crossed, or distributor needs a little adjusting twist. sometimes that distributor retainer screw gets loose.
 

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If you haven't done any other work recently, I would also say the timing gear is slipping, or did slip. I would highly recommend planning an afternoon to change it out. The downside to not fixing this, is valves smacking pistons, so the heads get to come off, and a valve job can get done, while the heads are off...
 

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I didn't want to be alarmist when I read this post, but the first thing I think of when this symptom is a wiped intake lobe. Here's hoping that is not the issue!
 

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I didn't want to be alarmist when I read this post, but the first thing I think of when this symptom is a wiped intake lobe. Here's hoping that is not the issue!
Please explain how a wiped intake cam lobe would cause popping through the intake? Exhaust lobe yes, intake I can't see it. It would just be a dead hole.

Bill
 

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Bill,

When an intake (or exhaust for that matter) lobe wears off, what happens is the lifter pumps up as far as it can. The result is a lobe which has extremely long duration and not much lift. The result is a valve that is open when the spark occurs, thus backfire.

Bob
 

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Discussion Starter #12
I hope that's not the case too. It seems to me like a worn cam lobe would cause an uneven idle as well, though, which I don't have. I'm still kind of a newbie as far as engine work goes, though, so I guess I'll watch the valves while it's running to make sure I don't fix the timing chain and put the engine back together only to take everything apart again.
 

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Bill,

When an intake (or exhaust for that matter) lobe wears off, what happens is the lifter pumps up as far as it can. The result is a lobe which has extremely long duration and not much lift. The result is a valve that is open when the spark occurs, thus backfire.

Bob
OK now I can see how its possible for a wiped intake lobe to cause popping though I would think the popping would be all the time or much less related to throttle angle. The cams I replaced back in the day were mostly SBC's. Customer complaint of low power and popping on acceleration. It must have been a fluke but all had wiped exhaust lobes. I also had several Pontiac and Olds motors come in with the same complaint though the cause was exhaust rocker arm related. I'd sure like to see some pictures of Ford cams found with wiped lobes to get a better idea of what is happening. Several members have posted with symptoms matching flat cams but I have never seen the out comes posted.

Other thoughts: Cams go flat either because of lack of lubrication or cheap materials. ZDDP only works when the engine and oil temp are over 160F. So what protects the cam and lifters during warmup? Well quality cam and lifters. I would guess most of the cams available today are Chinese crap.

Bill
 

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IDK - about the temps being as critical as the particultes being there - the zinc is supposed to act like graphite as I understand it - it creates a "cushion-film" between the lobe and the lifter, which the modern oils have no need for anymore since engine designs have altered and the engine requirements are pretty different now. Hopefully aggie has been using additives (or the PO) because it doesn't take long to wipe one - people get sucked in by synthetic is better - yada, yada....but, in our case, it's actually even worse!! IF it comes down to needing a new cam, I'd definitley go with a name brand like Crane, Lunati, Motosport, etc. and then of course, stick to the oils and additives to keep it purring.
 

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Discussion Starter #15
Hey all, just an update. I've been busy with school and things, but I finally got down to the timing chain, and it has major play. I can't say for sure that the chain was causing the problem, as I may have damaged it with a crowbar trying to pry off the timing cover which had corroded itself to a bolt, but I think that was the problem. Thanks again for the help, and I'll post back when I finish up for anyone having the same problems.
 

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Yeah the aluminum and steel bolts don't get along and corrode each other over time - Use some no-ox or anti-sieze when you re-assemble on the bolts. If the chain has never been replaced the nylon teeth have fallen into the oil pan many moons ago....it was supposed to make it run quiet....not one of thier better ideas! Now might be the time to just swap out the cam anyway - your into it 80% there. I hate to see you have to go back again if the chain doesn't do it - but I guess it's not that much trouble now that you have freshened up the bolts and made it easier! ;>) If your feeling lucky throw a new timing set on there and see what happens.


Just make sure to follow the book and line up the sprockets correctly......
 

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Discussion Starter #17
Whoop! Finals are over and I finally got a chance to put her back together. For anyone interested it was just the timing set, it'd slipped a tooth, even with its metal gears. With a little work (and prayer, as this was my first semi complicated project without my dad and I was terrified I'd ruin it), she's running beautifully! Now all I have to do is get the PS and hood latch back on, then I can finally get back behind the wheel!
 

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So, you did replace the failed timing gears? Please say yes..
 

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Thought the same thing....lining it back up is temporary at best - need to go new - especially if you went to all that trouble!
 
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