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2010 RX8 AT - Rough Cold Start, Unstable Idle, Power Loss
Dear Members,
I have 2010 RX8 (AT) with 30K mileage. I need your help with an issue.
I already installed new OEM plugs, coils, cables at 25K miles and regularly change the engine oil at 3K miles (5W30). Everything in the car is stock. Only catalytic converter was removed. The car has been working normally, stable idle and acceleration since I bought it 2 years ago.
But due to a scratch on front bumper, I left my car for a paint job and after a couple of days they turned off the cold engine and flooded..
After removing the cables and cleaning the spark plug holes they eventually managed to turn it on.
But starting from the next day I have been facing following problem:
When I start the car in mornings, the engine starts normally hitting 2500 rpm and gradually decreases. But when it goes below 1500 rpm it starts to cough/choke. It only happens for around 30 seconds after cold starts. After getting warm, especially at “P” (Parking), the idle is not stable (rpm plays between 750-950)
Moreover, when I hit the gas, I can’t get the same power/speed with the same rpm I used to get before (twice weaker).
Following codes appeared at first scan:
- P0301 Cylinder 1 Misfire
- P2096 Post Catalyst Fuel Trim System Too Lean
I cleaned MAF, installed new NGK spark plugs and wires, replaced first rotor coils with the second one’s.
It didn’t solve the issue, the above codes remained.
As a next step, I decarbonized the engine.
The symptoms didn’t go away. After this procedure now I get following codes:
- P0300 Random/Multiple Cylinder Misfire Detected
- P0171 System Too Lean
- P0302 Cylinder 2 Misfire Detected
- P2096 Post Catalyst Fuel Trim System Too Lean
I checked the whole blog, there were similar issues with possible solutions of coils, plugs, wires, MAF, ESS, injectors, vacuum leak, fuel pump, compression loss..
What do you think, what should be my next step?
Thanks in advance,
Ulvi
What else on the engine was touch when they tried unflooding it? The system too lean and misfires point to, among other things, a massive vacuum leak. Since you have a scanne, can you read the LTFT and STFT at warm idle? If they're maxed out at +25, you have a vacuum leak.
The other is have the coils been plugged to the correct spark plugs? It's fairly common to mix that up and the order is obviously important. You can find the correct order on here.
You could perform the 20-time brake press procedure to clear the ESS calibration, but I doubt that's the cause. Easy to eliminate
Dear Loki,
Thanks for your support.
They said, they touched only battery, plugs and wires.
First scan, STFT1: 2.34, LTFT1: 22.65
Second scan (after decarb), STFT1: -0.78, LTFT1: 22.65
I checked coil/plug order for several times.
From left to right,
Coil 1 - Rotor 1 (Front) - Leading Plug
Coil 2 - Rotor 1 (Front) - Trailing Plug
Coil 3 - Rotor 2 (Rear) - Leading Plug
Coil 4 - Rotor 2 (Rear) - Trailing Plug
I also cleared ESS by 20-time brake press.
Today, we also made diagnosis while driving. Foreman said the engine doesn't get stable fuel..
Possible problem could be fuel pump. But I need to be sure before ordering a new fuel pump.
Tomorrow I'll check the fuel pump pressure and share the results as well.
Meanwhile, your other suggestions would be appreciated.
If you put SeaFoam through the intake manifold to "de-carb" the engine, that can foul the spark plugs. It is recommended you replace spark plugs after a de-carb.
Your symptoms point to a sizeable vacuum leak, or possible a messed up MAF sensor or housing. When they took off the bumper there is a good chance they took off the airbox. You can do a quick check that the accordion tube band clamps are tight, the vacuum elbows that plug into the accordion tube are not broken, the MAF is in good condition (clean it with MAF cleaner for good measure) and that the screw holes in the MAF housing are not stripped (it is easy to strip the holes since MAF is held in by self-tapping screws into weak plastic). Also, what is your airflow reading at warm idle?
Sounds like you have a vacuum leak. Potentially introduced whiel the intake was taken apart to install the ignition coils (or some other reason while they were troubleshooting). This is super common lately for some reason. Look for an open hole or loose connector in the intake tract after the MAF.
They can confirm the fuel pump issue easily with a fuel pressure gauge, I wuoldn't go changing things on a guess.
I believe the way to clear the S2 memory is disconnecting the battery and a single brake stomp.
As mentioned, check for a vacuum leak first. You can use carb cleaner and spray around, or use a cloud machine/vape and exhale through the intake directly and see where the cloud leaks out.
Another thing that's common with 8s is that the threads for the screws holding the MAF in place can be easily stripped, so you could have a leak around there. You could make some new threads with JB Weld. Works like a charm for me.
Following your suggestions, I made below procedures:
1. Inspected & cleaned MAF sensor (with Liqui Moli Air Sensor Cleaner). Apart from some dust on front side of the bulb, the sensor was in good & clean condition, screw holes were not stripped. Moreover, if I'm not mistaken, in case of MAF failure, ECU would give its own code (P0100-P0104). MAF airflow rate was 5.42.
2. Visually inspected air box, vacuum elbows, accordion tube, throttle body. Couldn't find any leak. I will make one more thorough inspection for all parts soon.
3. Checked fuel pump. The pump was working normally, pressure was ok. Nevertheless, the filter (sock) inside the pump was extremely dirty. That might be one of the reason behind low mileage. It also hints of dirty fuel injectors..
4. I cleaned the previous codes few days ago and yesterday I made one more diagnostics with OBD2 Bluetooth scanner. ECU gave following codes:
- P2070 Intake Manifold Tuning (IMT) Valve Stuck Open
- P0171 System Too Lean
- P0301 Cylinder 1 Misfire Detected
P0171, P2096, and high LTFT (22.65) hint the main reason behind misfire is inconsistent fuel/air mixture.
My next steps will be:
1. Clean fuel injectors
2. Clean throttle body
3. Balance throttle valve
4. Inspect fuel filter
5. Inspect Secondary Shutter Valve (SSV)
6. Make thorough check for vacuum leak
7. Inspect oxygen sensors
8. Compression check.
Is it possible they plugged the spark plug wires back in the wrong order? I would add that to the list of things to check.
Thr MAF airflow rate is 5.42 what at what rpm?
If it's g/sec at 800rpm warm idle, that's pretty normal and you don't have a vac leak.
How wil you balance the throttle valve? That's not really a thing...
I would put the SSV at the top of the things to clean/replace.
Likewise, oxygen sensors are best examined while on the car by watching their voltage. You can google what you should expect to see. But I doubt that's it.
Focuso on the SSV and spark plug order. Thr SSV is throwing a code and the spark plugs were the last thing touched. Also check that they didn't put trailing plugs in leading positions or something else silly.
Thanks for reply.
After each inspection, I always check the spark plug order:
From left to right,
Coil 1 - Rotor 1 (Front) - Leading (Lower) Plug
Coil 2 - Rotor 1 (Front) - Trailing (Upper) Plug
Coil 3 - Rotor 2 (Rear) - Leading (Lower) Plug
Coil 4 - Rotor 2 (Rear) - Trailing (Upper) Plug
5.42 MAF airflow rate was at 796 rpm warm idle.
During the deflooding procedure the battery completely died, I was informed in that case, the throttle valve should be adjusted by computer.
Regarding to SSV, I don't know why P2070 appeared only after 1 month of misfire..
While cleaning injectors, I will clean SSV as well.
Dannobre also said it might be faulty front oxygen sensor.
The throttle body calibrates itself every time you turn off the car, so don't worry about that. People disconnect their batteries all the time. It could be a bad O2, if you pull the spark plugs you'll see if you're running rich or lean and if they're all installed correctly.
For the O2, watch its signal while you (or better someone else) drives. Stab the throttle and release quickly. The sensor should go rich as you stab the throttle, then lean as you release them stabilize where it was before. If it's slow to react or doesn't react like that, you may have issues. This is a quick diagnosis, a complete one requires a scope and voltage probes.
Good news. The misfire was fixed.
As expected, the fuel injectors were clogged.
SSV was working normally though.
The engine achieved stabilized rpm (810-820).
But after that procedure, following problem arose:
P0411 Secondary Air Injection System Incorrect Flow Detected
Every morning, even after completion of open loop mode the rough sound from air control valve (EGR) doesn't go away.
So in order to remove that sound I have to pull off the tiny tube of air control valve (vacuum hose) and put it back.
I'll inspect it on Saturday and share the results.
Meanwhile, thank you for your support during those challenging times..
Injector clog? That doesn't usually happen, especially since RX-8 officially require premium gas, and those usually have more detergent. Some people can use regular without any issues, but even good regular gas should have enough detergent.
Are you getting gas from Top Tiers? Any fuel additive/particular premix you are using?
Since I bought this car at 20K mileage I used premium unleaded gasoline (91 US AKI / 95 EU RON)
Except pure gasoline, I don't use any additive or premix.
Seems previous owner used leaded gasoline before. Dark fuel pump filter was an indication of it.
Since I bought this car at 20K mileage I used premium unleaded gasoline (91 US AKI / 95 EU RON)
Except pure gasoline, I don't use any additive or premix.
Seems previous owner used leaded gasoline before. Dark fuel pump filter was an indication of it.
Where do they still sell leaded?
If they have used leaded, you should see it on the spark plugs. Yellow spark plugs = leaded gas.
In the country I live (Azerbaijan) 3 types of gasoline are sold:
1. Super Unleaded (94 US AKI / 98 EU RON)
2. Premium Unleaded (91 US AKI / 95 EU RON)
3. Regular Leaded (88.5 US AKI / 92 EU RON)
Because of additives, the regular leaded gasoline is reddish.
I already installed new spark plugs and use only premium unleaded.
I inspected and cleaned air control valve (EGR).
Today I made one more diagnostics.
Following codes appeared:
1. P0411 Secondary Air Injection System Incorrect Flow Detected.
2. P2071 Intake Manifold Tuning (IMT) Valve Stuck Closed
What's interesting, although the vehicle speed was zero, diagnostics showed 1,722 RPM, 12.58 MAF.
Tomorrow I'll inspect SSV & solenoid valves.
Meanwhile, your suggestions would be valuable.
I've had the IMT problem before, mine was gunked up and wouldn't open. Had to get the valve cleaned up, which is a pain in the *** but not too difficult.
I inspected and cleaned air control valve (EGR).
Today I made one more diagnostics.
Following codes appeared:
1. P0411 Secondary Air Injection System Incorrect Flow Detected.
2. P2071 Intake Manifold Tuning (IMT) Valve Stuck Closed
What's interesting, although the vehicle speed was zero, diagnostics showed 1,722 RPM, 12.58 MAF.
Tomorrow I'll inspect SSV & solenoid valves.
Meanwhile, your suggestions would be valuable.
This car has no EGR.
1700rpm and 12.58 g/sec sounds about right for a cold idle (17C coolant temp). What numbers would you expect?
I fixed the air control valve noise.
The valve tube (blue line) was not properly connected to air solenoid valve..
Regarding to the numbers, although I diagnosed it at warm idle (810 rpm, 4.8 g/s, 90 coolant temp), OBD2 scanner showed those old numbers from the cold idle.
Nevertheless, SSV code still remained (now it shows stuck open P2070).
I cleaned SSV before (without removing it). This time I'll remove it completely.
I also suspect from its actuator and solenoid valve.
Just a status update. I checked SSV and solenoid valves.
When you cold start, the engine coughs for around 10 seconds.
Final scan gave following codes:
- P0411 Secondary Air Injection System Incorrect Flow Detected
- P0420 Catalyst System Efficiency Below Threshold
The latter is because of removing the catalytic converter, while P0411 I believe either because of Air Pump or Air Control Valve.
Could it be something else?
01-25-2018, 05:55 AM
