beasterling said:
In reply to AWSX1686 :
Howdy, I've been through almost the exact situation you're in now. With my na6, I replaced all the normal wear items and confirmed timing, but couldn't get rid if the low rpm stumble/ miss. As a last shot kind of thing I ohm tested injectors and had one read slight high on the resistance. This led me to pull all the injectors and attempt to redneck clean them with the spray through method. Turns out another injector would only open intermittently and was my main source of trouble.
Thing was, when running, I would pull the harness wire from the injector and the engine would stumble worse, leading me to believe live it was a good injector. Good luck on your troubleshooting!
I'll add injectors to the list of things to check! I was thinking about a fuel additive to try and clean them, but I do have an ultrasonic cleaner too. That is a good troubleshooting technique, we'll see if it works for me. It seems like my issue is more under load, but the idle is a bit rough too.
So I've been busy working on the drift e28 and haven't had time to mess with this much. That said, I am supposed to mess with it a bit tonight. I was contemplating what could cause this issue on it while I was driving home last night, and had a thought. Then I googled it, and I think the odds are pretty good that this is it. It's a simple thing. It's a stupid thing. But, to be fair, it is something I haven't heard much about on miatas, much less done it myself.
I'm guessing it's the CAS needing to set the timing correctly.
When I put it in, I did think to myself, "Hmm, this has built in adjustment, I wonder if it needs adjusted." but I must have brushed it off. I think I was looking at the head installation procedure in the shop manual, and it mentioned installing the CAS, but didn't mention adjusting it. At least, not in that section. I'm going to kick myself if that's the issue. Then I'll PTL because it could be much worse. Here's hoping.
I am almost willing to bet a CAS adjustment will do the trick.
In reply to Professor_Brap :
I have a good feeling it will. Only a few hours till I can test it out!
In reply to AWSX1686 :
The last NA I bought ran like poop, it had zero timing in it.
So the timing was at about 4* BTDC, I have it set to ~10-11* BTDC now.
Unfortunately the issue persists.
Under 4k RPMs, it is blah, even with the pedal on the floor, then once it hits 4200 RPMs or so, it kicks in and runs like it should. It also blasts out quite the cloud of white smoke.
So I finally did a compression test. I was hopeful, because all the cylinders where right about the same pressure... Then I looked up what the pressure should be. Apparently normal pressure is ~180psi, and the manual states a minimum of 128psi.
All my cylinders had ~120psi.
Now I'm guessing something is bad in the bottom end.
My little BIL is going to bring some fogging oil over tonight, and a second compression tester, just to verify, but I don't have high hopes.
Most likely this Friday night we'll toss in my spare 1.8l engine and hope for the best. He wants to take it to Autocross at Carlisle on the 17th & 18th.
You can spray some WD-40 in the cylinder right before compression testing. If that makes a significant difference your rings are probably toast.
Cam timing will also change compression test results.
Crackers said:
You can spray some WD-40 in the cylinder right before compression testing. If that makes a significant difference your rings are probably toast.
Cam timing will also change compression test results.
That's what the fogging oil is for too. We'll see tonight hopefully.
Compression test was after I got the timing set. :(
I really don't think 120psi versus 128psi would make a big difference in power output. Certainly not the amount you're describing. Heck that's probably within the tolerance of the gauge.
dculberson said:
I really don't think 120psi versus 128psi would make a big difference in power output. Certainly not the amount you're describing. Heck that's probably within the tolerance of the gauge.
True, but I can't imagine that an engine running at minumum compression is going to run very well. Plus there's that fact that it's buring quite the cloud of oil. Something is wrong.
Stupid question... But are all the plugs new?
A bad plug (or two) can cause all of those symptoms. Granted, smoking would also mean marginal oil control rings etc.
In reply to Crackers :
Plugs were NIB that came with the car. Installed them along with the head.
So my brother in law brought his compression tester and got 150-160 PSI across all the cylinders, put in some fogging oil and had a pretty consistent 160 PSI across all the cylinders. Still smokes a lot till it's good and hot. Still seems to run better once it's been driven a bit.
As far as the smoking. I don't notice it at idle, or just revving the engine parked a bit. It only seems to be when it's under load. Does that help anything?
Going to test fuel pressure tonight.
So here's a seemingly random question, how has your brake fluid level been with all of the testing and running you've been doing?
One of the issues I had but didn't solve with my last miata was brake fluid disappearing, and while I have no concrete evidence to support this hypothesis, my best guess was motor vacuum pulling fluid out and running it through.
Stumbled/not happy until warmed up, blue smoke that turned white after a little running before disappearing all together, even without ever leaving the driveway the brake fluid level would go down without leaving puddles or sprays anywhere.
It's probably not your issue, or at least not your main issue, but checking or marking the MC might not be a bad idea, and would only take a few seconds and a sharpie.
In reply to RevRico :
Huh! Now that's a weird issue! I'll have to check the brake fluid. I know it should have a good level because I just did brakes, including new rubber lines and a fluid flush.
Cars that suck off their brake fluid do make white smoke. I have seen the failure frequently on non Mazda vehicles, so why not on a Mazda.
I wouldn't be surprised if some good hard running makes all the difference in the world. Miata like to stick oil control rings for some reason. My old NA would tell my I needed to abuse her some because it would start to use some oil. Run it really hard and it'd go away.
Tried a different MAF, verified fuel pressure best we could, and used some electronics cleaner on the ECU connectors last night. Still nothing.
It's definitely burning oil, not brake fluid. Brake fluid is still full. Oil was a bit low.
BIL wants to buy it, so he has something to run autocross at Carlisle. We were talking about swapping to my spare engine Friday night, but I think we might keep it like it is and run the crap out of it for a while. Autocross is mostly in the upper RPMs anyway right? Just keep the oil topped off. Then maybe in a couple weeks we can swap the engine if needed.
Hows the PCV valve, when I blew up my motor I bought a "used motor that smoked" and it had a clogged PCV valve. New one installed and ran like a champ.
Professor_Brap said:
Hows the PCV valve, when I blew up my motor I bought a "used motor that smoked" and it had a clogged PCV valve. New one installed and ran like a champ.
Haven't looked at that! Will definitely check it out.
AWSX1686 said:
Professor_Brap said:
Hows the PCV valve, when I blew up my motor I bought a "used motor that smoked" and it had a clogged PCV valve. New one installed and ran like a champ.
Haven't looked at that! Will definitely check it out.
PCV Valve didn't help. :/
So if any of you have seen my drift e28 build, the running joke is: "Oil Leak? Better swap the engine!"
You probably see where this is going...
It is obvious that the oil burning issue is something to do with the engine. The running issue may or may not be related to the oil burning issue.
So, long story short, I swapped in my spare miata engine on Saturday night. Had it running (very briefly) that night. Water pump was leaking, so Sunday afternoon I took the brand new water pump, timing belt, and pulleys off the engine that was in the car and put it on this one. Haven't gotten to start it up again yet as I ran out of time yesterday, but today I should be able to put the cat and air box back on, and it should run. Need to put the front bumper on as well, and some cleanup and then we'll see what a test drive shows. Fingers crossed it's all good, if so I think my BIL wants to do the title ASAP so he can drive it for Carlisle this weekend.
Got it pretty much buttoned up last night and took it for a drive. It's got the power it should and seems to be running well. Couple things to do before Carlisle:
-Replace Heater Core hose. (Have one already, current one is leaking.)
-Verify Timing. (Via CAS adjustment. For the life of me I could not see the mark on the pulley last night.)
-Test/Replace CAS? When I had the jumper in to set the timing, apparently that also triggers the Check Engine light to flash any codes. (Learn something new everyday!) It was flashing 4 flashes, which seems to be a CAS code. The CAS in the car now is the same one that was on the old engine. I swapped it to the spare because the plug on the spare was broken/bent. Might have to give the other one a shot anyway. Moving the CAS to adjust timing definitely makes a difference though, so I'm not sure what it's having an issue with.
-Fix fuel smell leak. Looks like the guy snapped 2 of the Phillips screws that hold the fuel pump onto the tank. I think if I pull the pump, I can probably get vice grips on them from the underside to remove the stuck part, then find some other screws.
All in all, not too bad of a list.
Jacob took it up to the Import show at Carlisle this weekend and probably got ~12-15 autocross runs in between Friday and Saturday. The car seems to be running well! No major issues to speak of. He seems to be happy with his purchase, and since it's close to home, I'll probably keep some updates coming on here.
He is obviously new to the car, but didn't do too badly on autocross. The car also only has some not sticky 185 tires on it right now, so there was not a lot of grip to be had. 15" wheels and 205 tires are probably his first move. I'll be making some door card for him too I think.
