View Full Version : 5sfe backfires? At 3800-4200 rpms

92 celica
11-11-2012, 11:41 PM
I have a 5sfe with 220k miles on it and not to long ago my passenger side mount bolts came lose and dropped my motor and my cam gear dug in to my motor mount eating the metal of the mount

At first it was okay then a few days went by and then my car started to shutter really badly under a load and was missing a lot so I did a tune up and that didn't help one bit so I changed my fuel filter and that didn't help so I changed my dizzy that kinda helped so I changed my injectors and that helped a bit

I later found an injector wire grounding out and since then I've had this really annoying shutter/backfire thing at 3800-4200 rpms

Is it possible that I bent my cam gear? Or ruined an injector by shorting it

My compression is 180 185 180 185

11-12-2012, 12:58 AM
You have a picture of the damage? That's a long way for the motor to drop if the cam gears are hitting the motor mount. The other 3 mounts should of held the motor up if the one mount came off. I would first check the other 3 mounts and the north/south crossmember connections to the chassis. That's a LONG way for the motor to drop if all the mounts are connected and in good shape.

If it was an injector having problems it would display symptoms throughout the full RPM range and not just at a certain range. The came gear could of been damaged from the hit depending on how long it was doing that. Chances are that your timing is knocked seriously off between the falling motor and the distributor work you did.

92 celica
11-12-2012, 03:56 AM
My timing is spot on and my other mounts are fine but it really isn't that big of a fall and it was a slow fall and the engine seems fine for the most part other then this annoying rpm thing

Ill take a picture tomorrow

And how would I be able to tell if I bent a cam

11-12-2012, 02:36 PM
I would have thought mechanical timing being off could/would account for backfiring and rough engine running at the higher RPM's too. When your camshaft belt sprocket hit the motor mount, that would have put a lot of resistance on the belt, so I could easily see how it could have jumped a tooth or 2. How do you know your timing is good? Did you check your timing before you changed your distributor? When you changed your distributor, I'm sure you adjusted it to get your ignition timing OK, but what we are talking about is your mechanical timing. Your ignition timing would have been off if your mechanical timing was, but if you removed your old distributor before checking your ignition timing, you wouldn't have known it. 5S-FE engines are not easy to get the mechanical timing right, if you do the mechanical timing with the engine in the car - the position of the camshaft timing pulley makes it extremely difficult to see the timing marks when setting up mechanical timing.

92 celica
11-12-2012, 03:37 PM
Yes I checked my timing right after I lifted the motor back in place at work with in 10 mins of the motor falling and with the cam gear timing mark I used a dental mirror to check it

Anyways here's a picture of the mount http://img.tapatalk.com/d/12/11/12/ejy8atab.jpg

I know I have a really dirty engine bay I had a bad power steering leak and valve cover leak for a while last year

11-12-2012, 07:35 PM
After your motor mount bolts came out followed by you putting the bolts back in, you had no problems at all with engine immediately following, right? Ran great, no misfires, no shuttering, no backfires, right?

Then, a few days go by, and you start gettibng shuttering and misfires.

So you did a tuneup (with no improvement).

Then you did a fuel filter (with no improvement).

Then you replaced your distributor (and in what way did this change cause a symptom change)?

Then you replaced your injectors (and in what way did this change cause a symptom change)?

Then you fixed an injector wire that was grounding (and in what way did this change cause a symptom change)?

No you don't have a misfire, but you have shuttering and backfiring happening only at engine speeds from 3,800-4,200 RPM. Do you have no symptoms at engine speeds below 3,800 RPM? No difference if engine is under acceleration, steady load, or coasting at speeds under 3,800 RPM? But do you have shuttering & backfire issues between 3,800-4,200 RPM irregardless if you are coasting at that engine speed, under a steady load, or accelerating while within this engine speed)?

I don't believe a bent camshaft timing sprocket will cause any of your stated symptoms. Your camshaft likely is not bent (they tend to crack/snap apart before they bend). Depending upon how you answer these questions would depend upon some other things that could cause your current symptoms, but I don't know enough yet to offer any ideas up.

92 celica
11-12-2012, 09:54 PM
It only happens at a steady rpm hold it won't happen while alceration it won't happen if I let off the gas but only if I hold it there like while being on the highway 75-85 mph in fifth gear

92 celica
11-12-2012, 09:55 PM
When I replaced my injector it stopped missing and sounded right other then when I hit a bump in the road and caused the wire to short when I repaired that it just left me with this annoying problem