mfoote

So, I have been doing a lot of searching in the forums to try to find out why my new (to me) 1990 NA 1.6 idles like crap.

It was a known issue when I had purchased the car, and the person selling the car said it "might be a bad temp sensor". The temp sensor seems fine.

Things I have checked/replaced so far include, but are not limited to:
Spark plugs
Wires
Ignition Timing
Prayer
Ignitor
Magic
CAS connector
Vacuum leaks
Compression


What I have learned so far:
Borg Warner spark plug wires are hella-super-_____-bad quality. Every single one I took out and replaced with my original NGK blues would cause my car to idle a little better. Better being a relative term. Idle with the NGK is bad, idle with the BW was terrible.

Advancing my ignition timing A LOT would cause my car to purr like a kitten and be all nice and happy. (Mentions kittens in post: +1)

The ignition timing adjustment range (CAS) is from 10 deg advanced to like 30 degrees advanced. Way off of the timing marks.

The previous owner changed the timing belt in 2004 at 95k miles. I bought the car 2 months ago with 105k miles. He had it sitting for 7 years turning it into a spec Miata racecar before he quit and sold it as parts.

SO-
Timing belt was changed less than 10k miles ago. About the time he stopped driving the car.
Lots of ignition advance (like 25 deg?) makes the car run great.

Hypothesis:
The ignition cam was installed 1 tooth off. So 25 deg advanced really means 13 degrees advanced .


My requests from my peers:
1. Does this seem to make sense?
2. Would there be any harm in setting my static ignition to 20 deg advanced and take it for a spin to see if it pings?
3. Any other ideas for what could be the issue?

If all else fails, I will do the timing belt anyway for good measure, and while I am in there do the HLA cleaning. Bubbles is starting to sound like a Ducati with all the nonsense going on under the hood.


Thanks for the help.
-Mike

P.S. Compression results: 200-200-200-200. My engine is made of pure win!

Udlose

About 2 weeks ago I had a buddy change my water pump at his shop (he owed me a favor). When I went to pick the car up it was idling real low. I figured maybe something was unplugged. I checked and didnt see anything obvious. I then drove the car around the block and had to actually turn the ac off just to get the car to move without slipping the clutch at 3k or higher.

I went back the shop and told them I think they screwed the cam timing up. He tried to tell me he knows for sure its right because he does this all the time and its easy to set.

His was of "fixing" the problem was to advance the ignition timing. I asked him if they touched the ignition timing during the water pump swap to which he said "No". I then asked why would he have to adjust the ignition timing now if the car ran fine when I brought it in. He told me maybe the other person who owned the car had the cam timing wrong. I knew then it was time to cut my losses and get my car the F@$^ out of there.

What I'm getting at is, the intake cam was retarded by 1 tooth. When this is the case (on a 1.6 only), He could only get about 10 degrees advanced ignition timing before the cam sensor hit the adjustment stop.

If you are able to advance the ignition timing to 30 degrees at idle I don't think its the intake cam. Maybe its the exhaust cam or another problem. It is very easy to pop out the #1 plug and remove the valve cover and ignition coil bracket to check the cam timing.

mfoote

Udlose,
Thanks for the info.

The LEAST amount of timing advance I can run is 10 degrees.
As you had put it, the cam sensor is hitting the adjustment stop at 10 degrees.
I could in no way ever adjust my engine, in its current configuration to have 9 degrees of static ignition advance. (With respect to my cam sensor)

It sounds A LOT like your issue, but maybe 1 tooth in the other direction.

Udlose

I would also like the add that your cam timing will not change your ignition timing reading. If it says 10 degrees with the timing light, it is at 10 degrees.
If it says 30 degrees, it is 30. The ignition timing goes by TDC. Installing the intake cam only changes where the timing is initially set, not what reading you are getting after cam sensor adjustment. (hope that made sense)

edit cause I type too slow*

Pull the cover, I think we know what the issue is.

mfoote

Just as a bit of closure, in case anyone ends up on this page from searching in the future, the timing belt WAS off.

When I looked at all of the timing lines on the engine they were all VERY close. But not perfect.

Luckily, I had decided to buy the Flyin Miata Cam Gear Ninja Tool:
Flyin' Miata : Miscellaneous : Tools : Flyin` Miata cam gear ninja tool



This thing saved my life!

I was pretty sure that the previous owner had put the timing belt on correctly by looking at the lines (as I am sure he thought he had also).

But then I tried to slid the Flyin Miata tool in between the two cam gears and there was NO WAY that it was going to slide in.
It seems like it was off just about a half a tooth some how.

So I pulled the belt and tried to get it realigned according to the instructions posted everywhere and I had a hell of a time trying to get it to line up in a position that the cams wanted to be in.

So I removed both camp gears, set the cams to the exact locations they were supposed to be (according to someone elses writeup, bolted down the cam gears, and voila! The ninja tool slipped right in between them.

With the tool in everything else was easy peasy. I would totally recommend this tool.

It really fixed my idle and power and the car feels much better now because of it. The ignition timing lined up correctly, I drove it for a bit at stock ignition timing and I have recently bumped that up to the 14 degrees and the engine feels much better.

I bet that if the previous owner had one of these Cam Gear Ninja Tools, he wouldn't have sold the car soo cheap to me because of the rough running and idle cause from the timing belt job!

-Mike

Braineack

iTrader: (62)

I dont need no stinkin' tool like that. Ask Shuiends.

hustler

iTrader: (6)

Post the MSQ and a log.

wolfram

I know this is an old thread, but figured I'd ask here before i post a new one. Ok, here it goes:

I just put my new build all back together and fired it up for the first time. New block, head, pistons, rings, gaskets, bearings, rods, seals, etc. It starts but idles pretty rough and misfires every few seconds. I have checked fuel and spark to be good. I just took it for an easy drive and it will drive, but you can tell it aint happy. Like its hesitating. The main concern is that it is only at 10"Hg at idle and should be in the 16-18" range. So low vacuum at idle. Pretty sure i have checked all vacuum lines to be solid too. The other strange part is that during engine breaking, it still wont go past 10"Hg. I know it used to go up to about 21-22" during engine breaking.

So, i have double checked the timing belt and cam gears (and even have the Flyin' Miata CAM Ninja Tool) and it all looks right by the marks. My question to y'all is does this sound like an engine timing issue? I really cant find a vacuum leak, and wanted some expert opinions before I rip it down again to triple check the timing marks. To me, thats what it sounds like, but wanted some reassurance.