What other reasons for running rich?
 

After:

1. Replacing engine
2. New coils/plugs/wires
3. New front O2 sensor
4. Cleaning MAF
5. Cat diagnosed as "efficient"

I'm told my '04 (still in the shop) is "running rich," and they don't know why. Any ideas that I can suggest for him to check if all of those things are OK? I can't think of anything else to try. He suggested fuel injector cleaner, but I can't imagine what that would do for running rich?

What shop is this? Does this shop know rotaries? Because I know our cars run rich while warming up and (someone correct me if I'm wrong) I'm pretty sure they run (more rich? richer? I don't know which term is correct) but anyways they run more rich than piston engines.

It's a dealer. I don't know. I'll ask tomorrow ;)

But there can't really BE anything left, can there? I think they said it was running rich when they got it, but... all that stuff was replaced since then, so what else could it be?

It would almost make more sense, as I guess you're all implying, that the testing itself is wrong.

But thing is, I'm at 79,000 miles. I'm afraid I'll bring it home, and the richness will fail my cat in a thousand miles, and... yay.. need a cat out of warranty now :(

Charles you are more knowledgeable about this than me so I'm going to direct this question to you. Is it possible that something like the ssv is stuck open causing more fuel to be mixed with air at lower rpms?

I wish I could personally say how well it runs lol, but I haven't seen my car for over two weeks now (still in shop).

I'm told that the new engine is running OK, just that it's "running rich" without knowing why. But the engine has only been in for a day, so maybe they'll think of something after another day to ponder it.

I had the usual issues with it not starting easily when the engine was hot (fine when cold), and not always accelerating well above 4,000 rpm or so when the engine was hot (again, usually fine when cold). Nothing terrible yet, it DID always start, and DID accelerate... just not like it used to.

So I took it in for a compression check and it failed, so... "new" engine was put in, along with plugs/coils/wires, front O2 sensor, battery, clutch... and probably having to now do the SSV and clutch master cylinder too. Ouch.

LOL, hmmmm, sorry I posted my prior post before reading this. I'm told the SSV is "frozen" now and needs replacing, but not sure if open or closed. It had "moved freely" when first tested days ago, but I assume the silly thing can be kinda sporadic. I always figured it caused my acceleration problems, which were sporadic. So maybe that IS it?

But I guess if we don't know what, when or how they're testing the richness, we probably can't say... ?

I just now realized you had a new engine. The remans are just the core though right? If I was a Mazda tech working on your car I would have at least checked the ssv. All it would have been was just a pull out and spray carb cleaner. Couldn't have been that much work. But it more than likely is not that. I'm just more curious so I'm asking charles. I don't know enough yet to actually be of any help lol. If it is the ssv though there is a good diy. I learned a lot about my car doing that. Also I believe I threw a lot too in small fits of rage. Good memories

The ssv will be really expensive at the dealer unless they cover it. And more than likely they won't do a very good job either. More than likely they will take the uim off and just spray carb cleaner in it instead of taking it out and cleaning it well

Well, they said they'll replace it without a labor fee. Naturally more than DIY, but I'm just a normal consumer, not a techie like you kids :)

Without a labor free is great. That $1200 price i was quoted caused me to do it myself lol. The job is all labor unless they swicth to the upgraded ssv

Is it possible the "new" engine could be flawed somehow, causing it to run rich? Such as... if it came shipped with a compression problem from the start, might fuel leak past the seals causing a "running rich" condition? Should I insist on a compression test of the "new" engine perhaps?

I'm guessing that wires/plugs/coils and front O2 sensor pretty much covers all the usual, possible "bolt on" causes?

Can it have anything to do with dirty fuel injectors?

People have had problems with low-quality remanufactured engines from Mazda.

If the front O2 sensor is working properly, the engine computer will try to adjust the fueling towards an even mixture. If a failure prevents this somehow, you should see more problems with stumbling, hesitation, etc.

So, I think it will be hard for us to diagnose the problem remotely when the dealer mechanic either doesn't understand or is not willing to explain to you what is actually happening with the car.

I buried the lead: running rich is, by itself, not a problem for a rotary. The Renesis loves to run rich.

Erratic fueling and ignition mean the gas isn't being burned at all. Those are problems. It may smell the same as running rich, but it isn't quite the same.

Well I went and talked to the mechanic in person. Nice man, knows his rotaries ;) It may be nothing, here's what happened...

New engine went in (and new wires, plugs, coils, front O2 sensor). No actual compression test was done on it, but it did pass a "vaccuum" test, which I believe is similar?

Shortly after it's first start, it threw a CEL saying it was running rich. He measured it somehow (sorry, don't know how, but actually did measure it somewhere) and it was indeed rich. Not OMG! rich, but enough to cause a CEL.

At some later point, he cleared the CEL and took it for a test drive (10+ miles), and the CEL didn't return. He measured it again after the run, and it was still rich, only not nearly as bad, and not enough to throw a CEL anymore.

Working theory that it's is/was a leaking fuel injector, caused by some debris becoming dislodged during the engine replacement and the parts being disconnected/reconnected. He assures me it's nowhere near bad enough right now to damage the cat.

The SSV is bad (sticks when hot), although I don't know if that's related at all. Being replaced today.

So I'm just going to bring her home, maybe run some fuel/injector cleaner through it, and hope it fixes itself and I never see a CEL again ;)

Excellent, thank you Charles! Great reassurance to hear :) The SSV is being replaced today.

Now the question is... after two weeks of not having an 8, and a year+ of it not running/accelerating quite right... how do I possibly resist "exploring" the new engine's abilities during the break-in period? ;)

Kidding, kidding, it's going to drive me crazy resisting, but I intend to "do everything right" as much as possible with my second chance ;)

Thanks again to all of you for the reassurance and advice.

Well I guess that's a whole other debate here, isn't it? Whether to baby a new engine, or push it a bit?

I'm guessing the smartest compromise is to drive normally, vary rpm's and load a lot, maybe occasionally let the revs climb a bit, but don't drive it for an hour while beeping every shift, lol. Then an oil change around 500 miles and enjoy normally from there? ;)

Hey, is there any easy way for me to tell (once I get the car back) if the engine was truly new, or a remanufactured one? Maybe the paperwork? Or a stamped ID somewhere?

It's more than likely a reman. Very few get new engines.

Well, still no car. Went to dealer to pick it up:

Started it... idle shoots to 3,000 rpm, then sounds like the fuel is cut for an instant, drops to 1,000 rpm... shoots to 3,000, cut, catches at 750.... shoots to 3,000, cut... stalls.

Repeat for a number of tries.

Showed it to a tech. He tried. Same result. But they can't look at it until tomorrow.

I know none of you can diagnose the problem. I'm just venting.

Well it wasn't "rough" if you know what I mean. Smooth idle, but it hunted up and down until it fell too slow and stalled. My friend actually yelled at me to stop giving it gas lol, as it sounded like I was blipping the gas pedal.

They tell me they ran fuel injector cleaner through it (they recommended that before to fix the "rich" condition, suggesting debris was causing an injector to leak) and say it's running beautifully... but are now going to let it sit for a few hours to cool off and try again to be sure.

I'm not a big believer in chemical fixes, but hey... if it's working, I won't argue.

I'm just not sure how a leaky/clogged injector could cause idle hunt issues?

Just to close this issue too, the tech not only cleaned the injectors, but also the throttle body, air intake system and intake valves. It's apparently a Mazda "service" they can do. A new SSV was installed too.

And while I haven't literally measured anything, there's been no CEL since, so I'm assuming the "running rich" issue was fixed by this cleaning service (or the new SSV), as well as a cold idle hunting issue it had too.