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PMRacing
PMRacing GRM+ Memberand SuperDork
7/5/19 7:34 a.m.

After the last track day, my lifters were done. They were clacking like crazy. I have already cleaned them out once and been running STP oil additive (recommended by a SpecMiata shop near me). I was offered a set of lifters out of a blowed up SM engine that were known to be good (engine dropped a valve). So I disassembled the top end of the engine, being careful of keeping the cam bearing caps in the right order, cams in the right spot, etc. While I was in there, I noticed one of the coil packs was missing a screw so I took those off as well. I replaced the CAS o-ring, cam seals, and new spark plugs, too.  Everything goes back together without an issue (except a couple of tries to get the timing belt teeth correct). 

Anyway, when it comes time to start the engine, it sounds like it struggles, then is only running at what sounds like a few RPM and I could smell the fuel. 

Long story short, I redid the timing belt twice, replaced it once (just in case it stretched), triple checked plug wires (4-1-2-3 on the coil packs), checked spark (purple sparks on all 4 plugs), switched the harness wires to the coils (engine wouldn't turn over more than a couple times before it sounded like it would get stuck), checked all harness connections. 

I am stumped. I have done Miata timing belts before.  I know this must be something simple/stoopid that I am missing. The CAS seems to fit in only one way so I don't think it is 180* off. The E and I are lined up on the timing cover, 19 teeth between tick marks on the cam pulleys, cylinder #1 cam lobes pointed out, crank pulley notch lined up, etc.

Thanks in advance for any advice! 

NickD
NickD PowerDork
7/5/19 8:37 a.m.

It cranks hard, sounds like the engine is fighting the starter? Too much base ignition timing. The Cam Angle Sensor only goes in one way, but it is slotted and adjustable to set your base timing. You need to set the timing.

PMRacing
PMRacing GRM+ Memberand SuperDork
7/5/19 8:55 a.m.

In reply to NickD :

I marked the timing before removing the CAS. It is still lined up.  

Vigo
Vigo MegaDork
7/5/19 10:19 a.m.

Shot in the dark here but if you replaced cam seals you had the sprockets off so is it possible you switched cam sprockets between the cams and now they're each using the wrong timing mark? I don't remember if early miatas had cam gears with marks for both I and E on them in which case this wouldn't matter. 

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/5/19 10:44 a.m.

They did, but if the cam lobes are pointing out at TDC then it's probably okay.

So it fires and runs, but badly?

Did you happen to disconnect the fuel lines? It's a popular thing to reinstall them the wrong way around, which means no fuel pressure at the rail.

dean1484
dean1484 GRM+ Memberand MegaDork
7/5/19 11:17 a.m.

Will it crank freely with the plugs out?

Compression test? (And I mean do one now not one from befor you did the work)

Verify TDC on #1? (plugs out use a dowel or something to get #1 at TDC)  Then see where the cam is and the marks for all the timing stuff

Get back to us on all this and we can go from there.

dean1484
dean1484 GRM+ Memberand MegaDork
7/5/19 11:18 a.m.

I suspect timing is the issue but I dont know if it is cam or the ignition.  Or both.  

NickD
NickD PowerDork
7/5/19 11:20 a.m.

I know you said that you marked the CAS, but I would still throw a timing light on it and double-check that it has 10 degrees base timing. It's pretty quick and easy

PMRacing
PMRacing GRM+ Memberand SuperDork
7/5/19 4:13 p.m.

1. Did not disconnect fuel lines.

2. Cranks freely with plugs out. 

3.  Crank position mark is at TDC and timing mark on pulley lines up with 0deg on front cover.

4. Car won't run well enough to set timing. 

I did hose down the front of the engine with brake kleen including the crank position sensor which was covered in oil. I'm wondering if that is causing issues.

I also pulled codes and the only ones were for EGR and cat efficiency.  

I am looking how to test the crank sensor now. Any other suggestions?

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/5/19 4:28 p.m.

That crank sensor is primarly to detect misfires, I don't think it will cause running problems. 

Any chance of a massive intake air leak in the pre-TB plumbing? Like, forgot to hook up the IAC hose or something?

PMRacing
PMRacing GRM+ Memberand SuperDork
7/5/19 4:38 p.m.

All hoses hooked up. I only took the intake crossover tube off and the one hose under it. I'll double check to make sure nothing else came off.

chief8one
chief8one Reader
7/5/19 7:14 p.m.

When I rebuilt my 1.8l 12 years ago.. I swear I had the same issure and it was because i install the CAS wrong.  But others say it only goes in one way... so I dunno.  I would look there first from my experience.

PMRacing
PMRacing GRM+ Memberand SuperDork
7/6/19 6:32 p.m.

No hoses ornwires disconnected or in the wrong spot that I can see. All vacuum hoses are connected.  

I will check the CAS again but it feels like I will be forcing it if I turn it 180*. Right now it slips right in.

Is there a procedure for checking CAS function?  I will probably dig in again tomorrow but with the belt seemingly correctly timed I'm blanking

Thanks for all the feedback! Once this is figured out hopefully it can help someone else, too.

PMRacing
PMRacing GRM+ Memberand SuperDork
7/7/19 4:06 p.m.

Ok. Redid the timing belt one more time. It has to be right at this point (pic below). CAS can only go on one way (see pic). Car cranks very hard and seems like it wants to catch than struggles again and stops. Maybe the battery is low even though it is newer and been on a charger.  12.37V at the terminals.  Found an almost broken wire in the temp sensor and fully broke it unplugging it (see pic). So now I have to fix that and I don't have the right connectors. I have tomorrow off and a track day Tuesday. I don't think I'm getting it done due to other commitments. I have no idea what to check next. 

Any more suggestions?  Thanks!

Knurled.
Knurled. MegaDork
7/7/19 4:53 p.m.

What is the battery voltage when cranking?  Ideally you would measure this at the starter terminal and starter ground, but this is not a terribly accessible location on a Miata, so the battery will have to do.

 

If there is only one of you, this is where a voltmeter with a min/max function is nice to have.  Set to min/max, walk around to crank the engine, complete the lap around the car and verify that the battery voltage minimum is higher than 10v or so.

 

You mention that you marked the CAS - you marked it relative to where the old timing belt was, right?  That may be wrong if it had been messed with at some point.  If the cam was retarded before, and the CAS adjusted to compensate, it would be over-advanced.  Now, I don't see the timing belt stretching enough to cause this kind of starting symptom, but if the old cam was a tooth off then it could.  Twiddling the CAS around one way and the other as a diagnostic wouldn't be a bad idea.

 

 

After checking the battery voltage when cranking.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/7/19 8:29 p.m.

Interesting idea that the previous belt was misinstalled. It’s a source of much paranoia in the Miata community, but really when it’s off it’s really obvious by looking at the marks. It’s never off by less than a full tooth and that’s impossible to miss. 

Knurled.
Knurled. MegaDork
7/7/19 9:01 p.m.

In reply to Keith Tanner :

You know more about the EFI system than I do... does the airflow meter have any authority when cranking or at idle?

 

As far as cam timing goes... as we liked to say where I used to work, it's thin, but we check all of the obvious, likely things already.

Vigo
Vigo MegaDork
7/7/19 11:10 p.m.

Your cam timing looks correct both by the pulleys and the position of those #4 cam lobes so on the right dowels etc.  It sounds like your timing is '180 out'. That suggests your CAS is installed wrong. 

PMRacing
PMRacing GRM+ Memberand SuperDork
7/8/19 4:35 a.m.

In reply to Vigo :

It can't be installed wrong. The teeth on the CAS are offset and it can only go on one way.  

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/8/19 6:21 a.m.
Knurled. said:

In reply to Keith Tanner :

You know more about the EFI system than I do... does the airflow meter have any authority when cranking or at idle?

 

As far as cam timing goes... as we liked to say where I used to work, it's thin, but we check all of the obvious, likely things already.

Cranking, no. Idle, it’s got just enough authority to shut off the fuel pump if the engine isn’t running. Mixture at idle has to be really, really wrong to cause a problem. 

It’s not really possible to  put the CAS in 180* off, by design. 

Knurled.
Knurled. MegaDork
7/8/19 8:40 a.m.

In reply to Keith Tanner :

Got it.  Was thinking something weird like something getting into the AFM and wedging it open.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/8/19 8:44 a.m.

It's worth checking. I don't know what would happen if it was indicating maximum airflow.

I'm going to bounce this one off the boss. He's the Miata Whisperer and excellent at the weird ones.

Keith Tanner
Keith Tanner GRM+ Memberand MegaDork
7/8/19 10:17 a.m.

Bill's thoughts:

- is it possible the oil pump bypass is stuck and giving extreme oil pressure so the lifters are being held open? ( KT - actually, you did change the lifters, any chance some are stuck open?) Maybe do a compression test.

- how long has the car been apart - stale gas and plugged injectors?

 

PMRacing
PMRacing GRM+ Memberand SuperDork
7/8/19 11:28 a.m.

I fixed the water temp sensor wiring and charged the battery overnight and it now runs and stays running but the CAS has to be maxed out CCW (looking from front) and it sounds like it is not running on all cylinders. I can also smell fuel in the exhaust.  Here's a video. This is the best it has run. 

97 Miata running rough

It sounds like it is either not firing on all cylinders or the timing belt is still somehow off. The pulleys are on correctly. I verified by pulling them off and looking for the witness mark of the pin in the cam. 

To add insult to injury, there is now a small electrical butt connector in the oil pan. When rewiring the water temp sensor, it fell into an oil passage in the head.  I tried to grab it but it fell down. I ran a piece of safety wire down the passage and had no resistance and could hear it hit the crank scraper. I may just end up pulling this engine yet (it needs resealing anyway)....

PMRacing
PMRacing GRM+ Memberand SuperDork
7/8/19 3:59 p.m.

In reply to Keith Tanner :

I'll try a comp test soon. The car has only been down for 2.5 weeks. Left the track with noisy lifters and by the time I got home 2.5 hrs later they were quiet again. Now I'm wishing I had just left them alone.  

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