When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 90 302 efi that is acting similar. it idles fine when its in gear it shakes,, enough to take notice and wonder what the heck is wrong now ,, but under full acceleration no miss. it shimmies at when i'm not hard on the gas. I'm guessing new wires roter and cap and quite possible a new coil. seems like it gets enough spark when the rpms are higher. I did put new plugs in it . 1500 miles ago
I have the EXACT same problem......hmmmm...hopefully we can figure it out!
well i put a new cap and rotor in and it didn't help. I heard the synthetic combined with the risoline might have really loosened things up as far as rings . i'm going to go with a little heavier oil , clean the plugs and see what that does i'll keep you posted .
ok here is an update. new wires installed drained and changed the oil. still doing the same thing. I pulled the plugs and looked at them and they are lighter colored than new but not all oily and nasty looking. This thing still runs like crap unless its wide open. only thing not new electrical is the coil. but would that be the problem. I have done minor changes with little money involved. Would a fuel filter cause this or maybe a fuel regulator? I just don't know. is it possible I lost compression with the synthetic and risoline and need a rebuild. It did burn 3 qt.s of oil in 3 weeks. I will try to check codes but i have been working weird hrs and I don't have a garage to check them in.
Use separators on your plug wires - it's not likely since they're new, but you could have a crossfire. Also, the plug wires that go to the cylinders on the passenger side run very close to the tube that takes exhaust gas to the EGR valve. That tube should be insulated, but if it's not and you have a plug wire too close to it the insulation on that wire could be burned enough to make it arc...
I just had the same exact problem on my truck. It turned out to be the oxygen sensor.
That was my next step after spark plugs. But, spark plugs did it so I can hold off on the O2 sensor.....for now. I am just happy that my girl is running again (properly!). It feels so nice to be driving and not shaking around from the misfire!
I had a problem that would come and go on my 89 Ford 302. Misses at low end, it turned out to be a leak in the fuel regulator. Gas was being pulled directly into the manifold thru the vaccume line . This progressively became worst with time. When I pulled the vaccume line gas blew out of the line.
well I have spoke with my garage guy and he thinks the oil i lost is in my cat. he says what i'm telling him sounds like it could be clogged. I'm in the process of pulling off the exhast to see if that helps it . Them manifold bolts are a bugger and I havn't had a lot of time to do it . "driveway mechanic" I go on vacation soon so I'm working ot to get ready. I got one nut off tonight i'll have to wait till tommorow night if it doesn't rain on me. an o2 sensor makes sence since I did loose 3 qts of oil in 3 weeks .
Finally found my problem. It was the hose leading to the PCV valve. It was a loose fit on the barb of the valve causing it to leak air making No. 8 cylinder missfire at low rpm and slight acceleration.
Lots of posts about the PCV routing. Some reroute the PCV line to the vacuum tree at the top of the upper intake to distribute the flow more evenly and stop dumping everything into #8. That cylinder has more than it's share of problems because of that. I hear that the later model Ford production setup is also revised accordingly.