Cylinder #1 Misfire -- can't figure this out

[SamirDarji]

I searched endlessly for some other threads on this, but didn't come up with anything really good.

Well, I was just driving down the road coming back from a VW club meeting the other night and I felt a wobbling on my left front while taking an exit ramp. I thought it might have been a tire, so I slowed down and stopped on a road I know really well.

Found the engine shaking pretty bad and the idle really wierd. Checked the exhaust and found the engine putting in bursts like it was no longer doing multi-port injection and was on some sort of limp home mode program.

Pulled the spark plugs the next day and found #1 to be fouled out. All others good. Swapped #1 and #3 plugs to see if I could recover #1's plug and see if #1 will fire with a good plug. Still nothing. Checked for spark on #1's wire and it was good. Got a brand new plug for #1 and put #3's back where it was. Still nothing.

Last night, my buddy who is the lead Porsche tech here in town (and also Ferrari, Aston Martin, Maserati, GM, and Toyota certified and a ASE Master Tech) brought a obd2 scanner and his tools. The OBD indicated 3 codes--IAC, a rear o2 and cyl #1 misfire.

We changed all the spark plug hole gaskets and changed the plug wires to Magnacor. Still nothing. We're getting spark from the wire and fuel so it's puzzling. He's not run across something like this before. I'm going to head over to his work during lunch and he's going to do a quick compression test and see what we can come up with.

So what do you think? Compression? Distributor? O2 sensor? I know the distributor is the stock one on the car since I bought it with 92k (has 156k now). There is oil leaking into it from the o-ring seal (which I have, but haven't replaced yet). So this could be it, but then why would we be getting spark?

According to the FSM, the following items are suspect:[LIST]ignition coil[*]Ignition power transistor[*]Spark Plug[*]Ignition circuit[*]Injector[*]O2 sensor[*]Compression pressure[*]Timing belt[*]Crankshaft position sensor[*]Air intake[*]Fuel pressure[*]Crankshaft position sensor circuit and connector[LIST]I think we've eliminated the Spark plug, wires, injector, timing belt (since nothing else is off), crankshaft position sensor (no code), air intake, fuel pressure, and crankshaft position sensor circuit. That leaves compression, ignition stuff and o2 sensor.

So what do you think? Especially if you've had any personal experiences with this. Any assistance appreciated.

[n3oAcid24]

i4 or v6?

[SamirDarji]

i4, 4g64 sohc

[SuperGALANT]

<div class='quotetop'>QUOTE(n3oAcid24)</div><div class='quotemain'>i4 or v6?</div>

hes in the 7g section.. lol


well you said you have good spark so that takes out half of your list of possibilities..

it could be a leaky injector.. you said #1 was fauled out im assuming w/ gas not oil.. or white w/ cooked antifreeze

it could be low compression i.e blown head gasket, how does your antifreeze look? clean, full?

or it could be low compression from a bernt valve..


just a couple of thoughts

-Jason

[SamirDarji]

Thank you for the replies. Here's the result of a compression test:
4 - 180
3 - 185
2 - 185
1 - <25

Adding oil only increased it by about 10, so looks like a head gasket. I was smelling some coolant in the ac for the last few weeks upon startup, so maybe I had some indication. Now what really scares me is that my Corvette also has the same smell upon startup. :?

So now what? Is this the end of my G? Probably not. I'm going to pull my Accord out of storage and see if my buddy at the Porsche dealer can get it back up to snuff. The Accord will serve as the daily driver, and the G will then be a backup car until I have enough funds for the Ulimate 7th G project.

[RedGalant2k1]

When you said the #1 plug was fouled..how exactly? Oil? Fuel? Burnt?

[seth98esT]

To ME it sounds like it possbily could be a balance shaft belt or a timing belt jump. But having good compression in all but once cylinder would lean more towards a head gasket. Drail the oil and see if theres coolant mixed with it. Usually(but not always) a popped headgasket will puff white smoke out of the ehxaust, just depends on where it failed at I guess. Anyway, pull the timing cover, see whats going on with the belts. Drain the oil, check for coolant, ect.

[manybrews]

probably a burnt or bent valve in that cylinder.
a leakdown test would tell you for sure.
incidently, i havent had to replace a head gasket on a mitsu in over 10 years (not including severly overheated cars, which usually have damaged cylinder heads).

[djmtz263306]

if have white smoke coming out the tail pipe at all engine temp. than you have a blown head gasket if no smoke check your valves and i'd have all the other things taken care of also just to see if the bad IAC is contributing to the problem

[SamirDarji]

<div class='quotetop'>QUOTE(RedGalant2k1)</div><div class='quotemain'>When you said the #1 plug was fouled..how exactly? Â*Oil? Fuel? Burnt?</div>I believe it was fuel and oil (leak from valve seals in all cylinders). Mainly fuel.

[SamirDarji]

<div class='quotetop'>QUOTE(seth98esT)</div><div class='quotemain'>To ME it sounds like it possbily could be a balance shaft belt or a timing belt jump. Â*But having good compression in all but once cylinder would lean more towards a head gasket. Â*Drail the oil and see if theres coolant mixed with it. Â*Usually(but not always) a popped headgasket will puff white smoke out of the ehxaust, just depends on where it failed at I guess. Â*Anyway, pull the timing cover, see whats going on with the belts. Â*Drain the oil, check for coolant, ect.</div>The coolant actually looks good and doesn't have any of the normal indicating smells, accorrding to my mechanic friend. He was hearing a slight hissing that led him to believe it's actually an exhaust valve, but didn't say so because of how upset I already was. :? We are now leaning towards that.

[SamirDarji]

<div class='quotetop'>QUOTE(manybrews)</div><div class='quotemain'>probably a burnt or bent valve in that cylinder.
a leakdown test would tell you for sure.
incidently, i havent had to replace a head gasket on a mitsu in over 10 years (not including severly overheated cars, which usually have damaged cylinder heads).</div>That's what two people have told me--one of them being a respected Mitsu tuner in the area that owns the only street legal EVO7 in the states.

[SamirDarji]

<div class='quotetop'>QUOTE(djmtz263306)</div><div class='quotemain'>if have white smoke coming out the tail pipe at all engine temp. than you have a blown head gasket if no smoke check your valves and i'd have all the other things taken care of also just to see if the bad IAC is contributing to the problem</div>No white smoke, so I'm leaning towards the valve.

[SamirDarji]

Thank you all for the replies. Keep them coming if there's anything at all that I may be missing.

[manybrews]

it's a valve.. you could do a leakdown test and know within 5 minutes.

[SamirDarji]

<div class='quotetop'>QUOTE(manybrews)</div><div class='quotemain'>it's a valve.. Â* Â*you could do a leakdown test and know within 5 minutes.</div>We'll probably do that this week and confirm it so we know what parts to order.