Timing and idle vaccum issue
 

Hello Miata turbo.net community!

Im having an issue that is giving me headache for couple week or so. I hope anyone here could help me get on the right direction where to search to fix my issue

Im having 1989 JDM miata
-Custom turbo kit with 14b/16g hybrid turbo
-Running 2.5 inch straight pipe exhaust
-Megasquirt Ms2
-Stock coil pack and spark system
-Stock CAS
-Stock fuel pump, stock regulator and 460cc injectors

My Issue is, im having a VERY POOR vaccum on idling, getting a read around 60 on MS and 12inhg on the gauge.

Well first i though i had a vaccum leak , i sprayed carb cleaner all around the intake manifold thinking i would find a leak, no reaction to that..
Then i checked all my vaccum line, even replaced them in case there would be a little hole somewhere, then no improvement
Then i double checked my timing belt in case i skiped tooth or whatever, i get it check by a friend too (2 pairs of eyes are better than one!) and we confirmed timing is perfectly where it should be.
Then i checked spark plug wires and spark plug, replaced spark plug in case i had a bad fire or whatever. Still so far nothing helped

Then i decided to check timing because when i put megasquirt i needed to be REALLY OFF timing to only keep the car idle or it died. Im running a idle timing of around 25degree or the car is dying.. that is my point we tryed to set timing with a timing light but as soon as we are dropping the timing the engine have NO POWER even just to idle , If i am for exemple at 15 degree of timing and i floor it, i roughly can idle the engine and it wont increase in rpm, will stay a 1200 rpm and wont go higher ( i can hear by the noise that the engine is making no power at all)

SO, i cant set my base timing at +10, I get a idle around -12inhg and the car doesnt have much power like it should have..

PS: yes i know in MS how to set timing at +10 degree fixed

so if anybody here could help i would really appreciate, I know i write a lot but i wanted to explain more possible in details

does it sound like it's running on 2 cylinders?
Try disconnecting some plug wires and see if it runs same or not.

Are you absolutely positive that putting cylinder #1 at top dead center puts your timing marks on the pulley in line with the +10 degree indicator marks? Check it again.

While you have it that far apart take the timing belt pulley, boss, etc off and verify your crank keyway and woodruff key are intact.

yea sorry i may havent mention it, but when i checked the timing belt i also though about the keyway but it is intact! im kinda lost...

I also removed wires today to see if it runs on 4 and yes confirm runs on all 4 cylinder... I did a leak test didnt found any leak , didnt had much time to work in mimi today! will have to try out tomorrow if i have a chance to!

i really need to do a compression test.. ill try to hook a gauge to someone..

I even had the idea to plug in the STOCK injectors , STOCK maf and STOCK ecu to see if the car would run a better vaccum on idle. could be a good idea to try after compression test

Sounds like a B6 to me.

It was a shitty design 24 years ago, and it hasn't improved with age.

Mine (1990) runs about the same. Part of me is embarrassed by it, part of me doesn't care.

More timing.

And them more again.

Eventually, you'll crack a piston- that's how you know that you have too much timing. After the rebuild, dial it back a few degrees.

Or just trash the engine and install something that wasn't in production when Ronald Reagan was president of the US.

try to check fuel pressure since u have almost double size injector with stock regulator n pump .... should be around 60psi

According to what?

Factory spec is 38-46 PSI with key on, engine off, FP jumpered to GND at diagnostic box. (Nominal is 300 kPa / 43.5 PSI above MAP)

And that's not his problem.


And don't use the letter "u" as a substitute for the word "you."

Seriously, your time is not so valuable that typing the extra two characters is a major hardship. Same goes for "n" as a substitute for "and." That's fine if you happen to be a popular SoCal hamburger chain; not so much otherwise.

omg, the more i read about that short nose crank issue the more i find people with similar symptoms that i actually live with for a while..

OMG tomorrow sounds like im gonna remove everything and then check to build a custom keyway... :(

i'm sorry i was thinking about my 99 ... from what i get on ALLDATA fuel pump max 64 - 85psi, FPR put out 31 - 38psi. from what i'm thinking that he is running speed density, if he has a vacuum leak the idle will go up. and he has to advance timing to keep the car running , a little lag of fuel maybe? too lean maybe? on a normal car timing belt jumped 1 or 2 teeth will lower vacuum, no power but it still idle roughly with normal timing.

Use the dipstick method to confirm top dead center and then make a new mark on the crank pulley to set your 10 degree timing. Be aware that the worn out balancer will continue to move and possibly fail completely at some point, but hopefully it will still allow you to set your base timing initially.

If your engine is worn you will get less vacuum.

Use the dipstick method to confirm top dead center and then make a new mark on the crank pulley to set your 10 degree timing. Be aware that the worn out balancer will continue to move and possibly fail completely at some point, but hopefully it will still allow you to set your base timing initially.

If your engine is worn you will get less vacuum.