97 2.7 4cyl mystery single cyl misfire

I’m stumped. 2nd cylinder misfire. Good spark at coils and plugs, replaced plugs with ngk, replaced with good injector and took a stethoscope and can hear it clicking, swapped plug wires and injector wires and the misfire did not follow, removed fuel rail and no blockage there, checked compression and was good on all 4 cylinders. Where should I go next? I think my next step may be intake manifold gaskets.

 

How are the valves for cyl2?

compression test and holding?

 

I didn’t hold compression for long but it held while I was testing, I haven’t had the head off to check valves, or did you just mean valve lash?

 

If I remember correctly, this model has a distributor cap and rotor ignition... if so I would look closley at the cap especially at the #2 terminal. It doesnt take much for the spark to find a differernt path to ground.

 

1/2 of 97 had distributor cap and the other 1/2 had coil packs, mine has 2 coil packs each running two cylinders

 

P0302 was code?

 

manifold/plenum gaskets could be checked with chlorinated brake cleaner while engine running
(surge up or down with idle would show u leak)

Old Silver told me about another member struggling with V leak for weeks....turned out to be a cracked injector cup
(that was enough for me to RR all my injector cups.....when i was in there)

 

I did an injector cup job a couple years ago cause they were all warped and cracked, I’m waiting on intake gaskets to get here so I can replace those. My worst fear currently is needing a valve job

 

You can try doing a RUNNING compression test, comparing #1 & #2, you wont hurt anything by doing so...
Might give you an indicator if valves are leaking...
Leakdown test is correct way, harbor freight has a cheap leak down tester but you need a compressor...
I hate leak down tests as a engine tech for 32 years....

compare numbers as the Running compression rises, may be an indicator if you have a leaking valve.

 

Hmmmm

read original post 3 times…..didn’t see if you swapped coil packs and misfire stayed on #2

 

It did stay, I swapped coil packs, coil wires and injector wires, it’s a constant misfire from cold startup to running warm, did compression test (moved from cylinder to cylinder without testing long) but all cylinders were consistent around 150 psi

 

What would I look for while doing this? Would the needle bounce as the compression strokes?

 

im sure theres YouTube videos, or maybe not, never checked.
basically you will watch it climb....
think if I remember correctly the highest it will go is about 1/2 of a normal compression reading.
ground the plug wire so it doesnt spark, or get it out of the way so it does hit anything..
put the gauge on & start it, watch the gauge climb & try to pay attention to the increments...
Run it
20 30 50 60 80....
end of the day compare the end # to a good hole & the questionable hole.
But the climbing #s could also be an indicator if you have a "lazy" insufficiently working cylinder due to compression loss one way or another.
during the running comp test, you can reset the shader valve & restart the climbing process over & over till you get a feel of what's going on...
if one cylinder is reading max of 40 while the other is at 65, you know you have an internal issue of some sort...

The most important # is the end #, it wont just keep climbing the longer you run it, it will max out & stop climbing. Look at that #, compare...

It will make more sense once you do it....

 

Thanks, that was well explained! Currently I’ve got it torn down with the intake manifold off waiting on a gasket, so once I button it up and if it’s not fixed I’ll try that next to get a better feel for what’s going on.

 

just another sometimes useful tool when us pros think its possibly an internal issue that doesnt present itself when performing a manual compression test & we think / suspect its a compression issue while running...
or atleast rule it out...