engine popping under load

[danzick]

So my 88 gl 1.8 spfi is popping and backfiring really bad under a load. It runs fine if you can maintain under 1/4 throttle but as soon as you get in a load situation it just backfires and has hardly any power new maf sensor new o2 sensor pretty new engine coolant temp. Tried swapping distributors and didn't help. Any thoughts?

[MilesFox]

have the timing belts been done? how long has it bee doing this. sounds timing related. nmay be the timing belt is a tooth off.

[danzick]

Well when its on the interstate it will run ok but just kinda miss every once in awhile. That's kinda why I didn't think it was timing.

[danzick]

Well I drove it home tonight (commute 60 miles a day) and on the way home it was running soo bad. Zero part throttle. It would sorta run at wot and I limped it home that way never letting off the throttle. Did a compression check and all cylinders are 150 and one is at 130. All the plugs were a good brown accept one and it was pretty black? Took all the spark plugs off while it was running and found that its firing on all cylinders. Timing belts? I wouldn't think it would run at all if they failed? Car used to run just fine when I got it.

 

And might I add that's it tearing out the center of the air filters? Did it to my original and I figured it was a fluke and just old and I put a brand new one in and it was tore out aswell? Im guessing it has something to do with the fierce back fires?

Edited April 25, 2012 by danzick

[skingry]

I'd check the wires with a meter, just because you are seeing spark when the plug is out of the head doesn't mean it's giving spark when the piston is up and compression is barreling down on the plug (it's a whole different world under compression).

 

I pulled these values from the "How to Keep Your Subaru Alive" book that tboned linked me to:

 

OHC models: The resistance for the coil and spark plug wires should be within the following values:

 

SPFI

Coil Wire - 2.43k-5.67k

Wire #1 - 8.38k-19.56k

Wire #2 - 2.99k-6.97k

Wire #3 -7.90k-18.44k

Wire #4 - 2.41k-5.62k

[czny]

Sounds like you've got a cracked distributor cap & it's cross-firing some cylinders. Check the inside of the cap & rotor for tracks.

[danzick]

Brand new cap and rotor too. Forgot to add that to the list.

[TomRhere]

Just a thought here,

 

A worn cam lobe, or worn cam follower for an exhaust valve can cause an above idle backfire thru the intake.

 

Burnt gases can't escape the cylinder if the exhaust valve isn't opening properly. Higher engine RPM's will leave those gases in the cylinder when the intake valve opens, causing a backfire.

 

Have repaired a few OHC engines with that problem. Haven't done a Subaru yet, but it is possible on these engines also.

 

Like I said, just a thought...

[LPGsuperchargedBrumby]

i had my carby'd EJ22 do a similar thing to me a couple of years ago....turned out it was the plug leads breaking down under load...it would run fine until i got to around 10" manifold vac... any lower than that sounded like a battle was happening up front.

 

it drove me nuts trying to find what was wrong as the cap rotor coil leads and plugs where all only about 3 months old at the time....'newish' bum leads aren't the kind of thing i had struck before

[ivans imports]

lean misfire lean misfire check feul preshure and volume bad pump or slight intake leak or hydrolic lifter seat has creeped up and not alowing lifter to work properly do's it pop out the exhaust or just intake ?