I've got this problem with my daily that's getting worse.. It's an O/T vehicle but I think the symptoms and problem is probably something universal. So it started with a periodic lack of power coupled with some pinging under load. Not a lot just a bit. I thought it was bad gas so I bought an additive which seemed to help. There has also been a scary 'lurch' from time to time under heavy load and at high RPM. Almost like a rev-limiter kicking in but just one lurch and it's only at about 4k. That only happened in a blue moon though and seems to have gone away... As time goes on I've noticed it start to shimmy under accelleration and under load. Just a bit at first going up slight hills. Now much more pronounced and more often. It's pretty much all the time now except for long flat or downhill areas of the freeway or under hard accel at high rpm, in 3rd gear. Other things I've checked other than the additive: Cap and rotor, plugs, wires, air cleaner... There was a dryer sheet on the cleaner which I removed with out much effect. Everything else looked good. The plugs and wires have some time on them but the rotor, cap, and coil are fairly new and look it too. I've recently replaced the clutch and throw-out bearing, and rebuilt the rear including the posi. At first I thought maybe the injectors needed cleaning but I noticed the shimmy is just as bad when downshifting. Now I'm wondering about the clutch? Any ideas.
A little more info like what it is might help,but have you looked into the timing chain/belt? A leaking intake gasket can also cause some of this. And the shimmy? possibly an engine miss?
It's an injected 351W backed by a 5spd... It has 150k on it but it's been running strong and has been well maintained. I hear you on the intake manifold gasket and timing chain... I'll squirt some carb cleaner around the intake... I don't know about the timing chain though... I guess if all else fails. The last thing I did was pull the trans and change the rear main and clutch. It also has a new fuel filter...
Had a similar issue with a different O/T car....BUT exhibited wickedly similar symptoms...I had two plug wires that looked good from the outside but were dead, as well as a cracked distributor cap that you could only see from the inside....check your spark on each individual cyl....
There is a good chance with that many miles that the timing chain has a lot of slop in it... This is a weakness of the SBF... I had a 302 and a 351W both with strange drive ability problems and both were due to timing chains... Have you tried moving the dist a bit just to see what happens?
check your cateletic(sp) converters. Ive had 3 sets of them replaced, (some) of what you are describing was also going on with my truck when my Cats went bad. the media on the inside collapsed and plugged up the exhaust enough to cause some real erratic engine functions. Just a thought.
Pull the dist cap off. Mark the balancer where it sits now with the timing tab. Rotate the engine slowly by hand until the rotor just starts to move. Mark the balancer there. Rotate back until rotor starts to move again, should be at first mark. This measures timing chain slop.You'll always have some, but not excessive.
Thanks guys... I've never touched the dizzy on this motor beyond the cap and rotor. I'll check the spark at each cyl... Good idea. Should have done that already anyway. Interesting idea about the cat... The exhaust has sorta sounded different and smelled different for a while now. Good thing is, where I live I don't have to smog my cars to maybe I'll just byp*** it for now and see if it helps. I'll check the slop in the chain in the way stated above this weekend. That's an easy enough procedure for a simple elimination... Thanks. I'll see what I come up with and post the results.
I tried some of the suggestions... No slop in the timing chain... Noticed some currosion on the coil terminal so I cleaned the terminal and replaced the coil wire. This helped but the bucking is still there when I get up to about 40mph. The right bank of this thing is a PIA to get to so if I have to check the wires and plugs, I might as well just replace them. I might do that next. It might be time for duals on the exhaust end as well but that might have to happen a little later. Thanks for the suggestions guys, it's good to be able to eliminate the timing chain...
Not sure if this will help or not,, but my Mom-n-Law had a tbird had the same symptoms and they chased it for over 400 bucks in sensors,, turned out to be EGR position sensor, worth a shot, this wont show up on a code scanner either.
egr should trip a light on a ford 351w, plus moving the distrib on a F/I ford does nothing without byp***ing the comp cause the computer will keep moving the advance to reset itsilf you have to unplug the 2 wire plug to set base timing. my thoughts cats shove a pipe through the as long as they dont sniff ya they will never know by lookin.
I had a problem like that when I was twelve...you say the coil is fairly new? I did a tune up on my dads van when I was twelve and pluged the coil in backwards. I ran fine for about 1500 miles and then it acted similar to what you describe. It may not be, however it does sound electrical.
you are more tan welcome to come to my shop in brooklyn il, and play with the mustang formerly a 5.0 car with a 351w out of a 94 ford lightning and pul wires or change it out with the junk one i have here in my trash can and see for your self just changed it last week.
sorry tin ill admit i was wrong should have paid more attention to detail, thank you for the lookback. i appologize
also sounds like the symptoms of the ignition module going out. i don't have any test specs on it but you shouldn't have too much trouble finding them. watch out if you do have to replace that though, the pug is what denotes which one you need and it's relatice to the clock positions of the alignment ribs on there. there's only 4 different ones that ford used on that engine
If you when you changed your dist.cap ,you have ign. wires touching each other on any adjacent firing cyls. ,it can cause your discribed symtoms. In other words ign wires next to each other on the dist cap that go to 2 adjacent cyls. on one cyl. bank ,and these ign. wires are touching each other or are layed on top of each other,induction will fire both at the same time. Be sure these adjacent fire wires are separated from each other at the dist. cap all the way to the spark plug. Ever wonder why the factory never ran all ign wires neatly to each cyl. bank?
Thanks for all the input guys... Is there anyway to just byp*** the EGR system to eliminate it as the problem, or will it **** with the computer system?
it'll **** with the computer system...plus it'll make it run worse. the whole purpose of the EGR system is to lower the ***bustion chamber temp at certain times like heavy acceleration, high load etc. this helps the engine to be able to run lower octane on higher compression with more timing to work more efficiently so that is has less emissions. all the while making my life hell when one of the systems goes bad and it's in my shop
Maybe the throttle position sensor is bad since it's bucking at the same speed all the time. The rheostat in there will get wear spots where the thing is driven at steady speeds; 35, 55, 65... About every EFI Ford I've owned has done that!
Well maybe it was none of those things... I blew part of the 6mo/old FMS 4.10 ring-gear halfway outa the pumkin this morning... Was running pretty good too. I was just leaving a stop light nice and easy too...
Dang.. were the gears binding? Or maybe a carrier/pinion bearing issue? For what it's worth, I was going to suggest a fuel filter, they will cause a buck. After that, a TPS, and finally a new set of plugs/wires/cap/rotor (which you've already halfway done). Sorry about your axle man...
I think it was a pinion issue... It made a helluva noise when it went though... And left a big stinky synthetic mess that the AFD had to come clean up... Not to mention the traffic jam. Sometimes you just have to laugh...
check fuel filter& pump mine just did that and it was a fuel filter with 172000 miles.. looked like mud coming out and pump was whinning cause the restriction..
Well I finally had the heart to pull the cover off the rear and check the damage... It wasn't the R&P... The carrier grenaded... I've never had a rear fail in anything my family has ever owned... But I expected it to fail at the ring or pinion... Never would have thought it would be the carrier... Guess I gotta find a Trac-lock for an 8.8 now...
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