Missing/Idle Problems

[CajunKenny]

Friday at lunch, my car was idling really bad. I can hear a vibration/rattle type noise coming from the CPS area. I thought I had it pinned to the CPS; but, I switched it out with my spare and the noise is still there along with the miss.

I had some trouble getting it timed. I can't get it to 10*BTC with the jumper from E1 to TE1. The best I can get it to is ~13. Jumper out, ~16.

There was a code 25.

After getting it all buttoned back up and drove it around a bit, there is a noticible lack in power and idle vac is 15psi instead of the normal 17psi. Boost is pretty close to the same however.

I came back home and pulled the EFI fuse to clear the code. After that, it wouldn't idle on it's own. I had to help it. After ~4 minutes of helping it, it idles on it's own. There are no codes; but, it still misses.

Plugs: ~4k miles.
Wires: ~7k miles.

I'm sure a compression/leak down test is in order; but, aside from that has any else experienced these symptoms?

Sorry for the long post. Any ideas would be great!

Thanks everyone!

 

[grimreaper]

vac readings a bit low, any leaks? my stock bottom end with near 100,000 miles pulls a nice 20-22 inhg of vac.

 

[CajunKenny]

Hmm...trying to covert that and if I was at 15psi of vac that puts me at 30.54 inhg. Right?

Well, I took it out for a drive earlier and it was idling better; but, not near what it used to. This stupid Evo ended up messing with me. I did run him; but, it was from a dig. After we launched and he took his 1.5 cars, he didn't get anything more. We met up and he dyno'd at 320. Not too shabby...

I'll probably post my loss in the race section. He he...

 

[jdub]

Kenny - You might have jumped a tooth on your timing belt. Suggest you check valve timing is set up correctly.

Check for boost leaks too.

 

[CajunKenny]

You know what!? When I was changing the CPS I noticed a hole in my upper timing cover. It's just to the left of the left cam gear. It was NOT there before.

When I was trying to time it, I verified TDC by noting that the intake cam nose was pointing up so I wonder if it's the exhaust side...?

If it skipped a tooth, would that indicate a faulty/failing timing belt or tensioner?

 

[jdub]

The CPS does work off the exhaust cam.
Could be either...or, the rubber inside your crank damper decided to twist itself up.

 

[CajunKenny]

The CPS does work off the exhaust cam.
Could be either...or, the rubber inside your crank damper decided to twist itself up.

Right. Which could be why the sound sounds like it's coming from the CPS.

Could there have actually been enough slack in the timing belt to smack the timing cover and break it!?

Does that mean the crank dampener needs to be replaced or is this just something that happens from time to time with hard runs?

 

[jdub]

It would all be speculation Kenny - There wouldn't be enough slack to smack the cover, but enough to jump a tooth.

Do this (pull the EFI fuse while you do it):
- Put the damper index at zero
- Confirm BOTH cam gear index are pointing at the rear cover mark
- Remove the #1 spark plug and insert a 12" small dia wooden dowel (or chop stick) in the hole
- Rotate the crank damper a few inches either side of the zero and confirm the height of the dowel max's out at zero

If the dowel max's out at any other place than zero on the damper, your damper is FUBAR. It will have to be replaced. Might as well get an ATI damper...cheaper than a new one from the dealer and a better made part.

If it does max out at zero, the belt jumped a tooth if the cam gears are not pointing at the marks. You will have to inspect/re-set it...I'd replace the tensioner spring. Make sure it's at the proper torque...do NOT over torque.

 

[CajunKenny]

That covers it. Thanks Jdub!

 

[jdub]

There is one other possibility...the damper key way. If the damper bolt is loose, you need to pull it and inspect. I really, really hope this is not the case...it's bad

 

[CajunKenny]

Yeah. That would be bad!

Ok. Thanks... (big sigh....and will probably have nightmares now...)

EDIT: It wasn't loose at all when I was turning the crank to set TDC! So, maybe I dodged that bullet!

 

[grimreaper]

Your boost gauge reads in psi of vac?

 

[CajunKenny]

Ha ha... Nope it reads in inhg. My mistake. I actually just looked at it about 20 minutes ago and realized that. I was getting on here to let you know that.

So, yeah. Ever since I've had the car it has read ~17 inhg of vac at idle. That's on a 6k rebuild.

I haven't had a chance check the things suggested by jdub; but, I have new information on this.

I took a 12v tester and attempted to short each cylinder out to see which one was not firing correctly. As soon as I got the tester close to some of the plug wires, it arced to the tester. Not all of them did this though.

I proceeded to short each one out and found that 6 and 4 were not firing.

The plug wires have ~6k on them and they are the expensive ones from SupraSport.com. Can't believe they would be bad already...

I'll pick up a set tomorrow just to rule that out.

 

[92TealSupra]

There is one other possibility...the damper key way. If the damper bolt is loose, you need to pull it and inspect. I really, really hope this is not the case...it's bad

Had this issue with my '91, they estimated cost at $300.00 to weld new material in, and regrind it off for a new wood druff key.

 

[CajunKenny]

Ouch!

 

[jdub]

Arcing plug wires will definitely cause a miss Kenny...I was assuming they were good.

What kind of plugs are you using and what is the gap?

I would still check what I suggested previously...you should be able to time at 10 deg BTDC. What was your idle speed when you checked it?

 

[CajunKenny]

Arcing plug wires will definitely cause a miss Kenny...I was assuming they were good.

What kind of plugs are you using and what is the gap?

I would still check what I suggested previously...you should be able to time at 10 deg BTDC. What was your idle speed when you checked it?

Yeah, my bad. I assumed they were also. I'll get some cheap Autozone ones tomorrow for testing purposes and will eventually end up in the trunk for 'road-side' spares.

NGK BCPR6ES/2330 gapped to .030. These are new. I just put them in 2500 miles ago.

Yes, I will still check out the other things. I am too much of a cautionary type to leave related things unchecked once a problem surfaces.

 

[jdub]

That gap should be ok for the boost you're running...if you get a high RPM miss, drop it down to .027".

 

[CajunKenny]

Will do. I'll post my findings tomorrow after I get the new wires installed and all timing marks verified.

 

[grimreaper]

tick tock kenny, whats the hold up?

i run the NGK's but i run the 7's or a step colder then what stock calls for at .028" for an added margin of error. Cheap and never had a missfire or ignition break up issue from 14-18psi.