|Originally posted by mike-ohio:|
Why did the first engine fail?
My jeep engine went out, swapped in a new engine and the new engine would backfire under load. Clogged cat took out the first engine and would have taken out the second one if I didn't find it.
Make sure the cat isn't clogged.
Check the fuel pressure.
Make sure EGR is not stuck open.
Well the first engine had a knock, and was drivin with the knock for a year, the engine just wouldn't die, it never did die, just stopped driving it. (Got another Fiero at the time)
The 87 engine in it, came out when I did my quad 4 swap.
This did not happen from the swap etc, I swaped in the engine and sold it to a girl she has been driving this 84 for almost a year.
BTW I forgot to say I allready checked for a clogged cat, I did alot yesterday.
First thing, I start the car, runs fine, stab the gas, no pop, nothing.
So I take it for a drive, lug it no backfire, no pop, good. drive about 4 blocks around and decide to try it again, lug it pop, pop, pop, it's back.
so something got hot and failed, I check everything with a laser temp gun, things are only about 97 deg F, so not really hoy at all.
Now having borrowed a st-125 spark tester, and one with even a bigger gap. I try the 125 on one, then decide may as well try the bigger gap, more load.
I get spark jump on all 4 cyl. and this is jumping like a half inch gap, huge load.
Then to check fuel pressure, I hooked up the adapter after the filter. I get about 10 1/2 solid. With the gauge hooked up, stab the gas, pop, no change in fuel pressure.
So good pump and non cloged filter.
Now I have ohm'd the wires before, so I check them again they range from 380-500 ohms, great.
But since I haven't swaped wires to test, I swap wires, I make sure it is still popping to be sure, check again for the pop, and its still there.
Put on different wires, not even new, stab the gas, no pop.
So I take it for a drive, put it in 5th gear at like 5mph to lug the hell out of it, no pop, no backfire. GREAT
Here is what happened, closer look at the wires I pulled off, they don't have the straight boots, they have a 90deg on them, I used them as after doing 2 V6 cars with V8 wiresets I had a set of 4 wires, not a perfect fit with the 90 but ran fine for years. After time the boots stretched out from being crammed on, well when they got hot, just a little bit, they would deform more just enough to leak spark under load.
Thanks all for trying to help, I wanted to finsh up this thread with the results.
[This message has been edited by sardonyx247 (edited 02-17-2015).]