Huge Street Port won't idle right after plug change?
 

Changed my plugs...

It was being a bit stupid before i changed them... and when I pulled out my OLD NGKS I could remove 3 of the 4 with my hand... they were not on there that tight!

Now, I wrenched my new ones down pretty decent... not too tight, but nice and snug... so that they won't be moving anytime soon.

Now, I start her up... and at the typical 900-1000rpm level my boost gauge is reading 10-12inhg and it's bouncing up and down. Now I've experienced this before.. and it was a blown motor. Now my boost doesn't work for crap right now so I doubt it blew...

ANyway, I adjusted my idle screw to keep the idle at 1500rpm... vac sits around 17inhg. When I shift, the vac goes to 20inmg, just like it normally would.

Drives fine... just works like crap at idle.

I have a single turbo setup, but I figured this was geared more toward engine issues as a turbo wouldn't affect the idle.

I want to know why the hell its sitting around at 10-12inmg and bounching at 900-1000rpm idle?

Plugs are standard NGK's... same as my old ones.

THanks
-Darren-

running to fat at idle?

I'm only seeing 12 inches and I've got a eganamousrous port.

Yeah I got a pretty large port myself... it's straight huge...

But idle shouldn't bounce... it straight idles like shiet =P

running lean will cause the idle to surge.....

It's not lean. Guitarjunkie and I used the wideband to check the AFR's. They're good...

I would double check the spark plug wires. If they do not make that "click" sound when going on the plug, they may not be plugged in all the way and may possibly be arcing. Also check the plug for any "arcing-soot" while you're at it.

why not do a compression check while youre at it. . . ive noticed people seem to bounce around this quite a bit. stick a compression checker on there and check for an even pressure on all faces. . .

did you knock off the map sensor?

Map sensor is fine.... I made sure they made that click sound when I put them on =) Spark plug wires are fine too. I am going to take it in for a compression test tomorrow. =/

low vacuum and hunting idle is tell tale of a vacuum leak.

Have you tried slapping the old ones back in? Is it possible to get a dead plug somehow brand new?

Joe

I thought about that also... didn't try it though.

I would do that before I would pay for a compression check.

Eh... $75 for peace of mind if its good.... I'd pay it.

=/

Peace of mind is a great thing and I'm not saying don't do it. By all means have one done. It's just changing the plugs back is free and takes about 20 minutes depending on how you go about it (maybe less). Plus when you're down there again you may notice something you missed. The vacuum leak comment was a good thought also.

I doubt changing the plugs caused low compression.

But for $75 you could buy a piston compression checker and do it yourself. I tend to check my compression every few plug changes just to monitor it.

Good Luck,
Joe

Check it!
One of my brand new NGK's was just dead from the box. Caused idle and power issues.

thats odd, ive never heard of that... can you test it with a multimeter to see if it has any resistance? or is it just a open circuit?

Well the car runs fine aside from my boost problems which have been a problem since I put the new engine in. ANyway... it ran the same as before, just will not hold a low idle. Sounds like it may be pinging, and the engine shakes a lot.

But anything 1100RPM+ it works just fine. Nothing is smoking, and I get the correct vac when I let off the pedal.

=/

thats what i was referring to when i said to get a compression check. . . just use a piston engine checker. . . i TOO doubt spark plugs did this to his engine, but i think he said it was acting up BEFORE the spark plug change too.

I suppose I'll have to use a piston checker. Mazda doesn't have the tool to check the rotary engien anymore... how gay.

Going to do a comp test tomorrow..

Also, I recall when I pulled off my elbow from my TB... the O-ring (on the TB) had split... and i just put the elbow back on without the gasket. I don't know if this is enough to effect the vacuum and idle since it's before the UIM.

Thought I would add that...

If the engine has great compression, you can run it without intercooler and the piping and it would idle fine.

Well, what's the word?

Not sure, but I am leaning to believe the seal is cracked. I haven't had time to work on it lately, but I don't think its even worth doing a comp test... i don't see any reason why it's not blown or has a chipped seal. Bouncing vacuum gauge at idle is usually a good sign.

the o-ring thing. . . it wont do what youre seeing because its BEFORE the MAP sensor. . . though it should still be there. ;)

maybe theres some gasket material left on the flanges in the intake somewhere? youd probably hear that though. . .