Engine Hunting/Surging/Lagging/Power Loss etc

January 6, 2018

Hi there guys,

I made a post about 3 weeks ago asking for an opinion on whether or not to buy the car in question. I decided to go for it, and it's turned to be okay. It's been mostly trouble free except for one fairly severe issue.

I never really noticed it until a day or two after I drove it home. That would be because the car was new to me so I drove it very hesitantly preventing the issue from becoming apparent. Now I'm more comfortable in the car it's very apparent.

The issue is as follows - When I go to move off the engine decides otherwise. When I press the gas, the RPMs drop and the car rumbles pretty hard, and then it can take a good 2-5 seconds for the engine to start revving up. The further down, and the quicker I press the gas, the worse the issue is, sometimes it can be as bad as to stall if I max the gas quickly. I have noticed that if I shift back to neutral and then back into first it seems to get the enging revving as expected. Finally, I must add I checked the diagnostics, and it returned 2P0172 - System Too Rich (Bank 1)".

Things I've tried to remedy the issue:

Cleaning the Mass Air Flow sensor.
Checking and cleaning the spark plugs (which are in good condition).
Checking the air filter, which according to the service history was replaced recently, and upon looking that seems very much true.
Running fuel system cleaner through the car (Yes I know people have mixed opinions on it, but I thought for £3 I might as well give it a go).
Disconnecting each spark plug to see if one was misfiring.
Getting a relative to press and release the accelerator while I was under the hood to see if the throttle butterfly was catching.
Increasing the idle speed from around 550 to about 800 (I'm aware of the consequences but it's the only thing that's made any improvement).

Any ideas anyone? I'm lost, I don't want to start replacing things without a decent hope that it will work. If you want/need more info, just ask and I will be happy to provide it.

Many thanks, Michael.

January 6, 2018

Hi
I guess you have a code reader, that just shows fault codes.
Ideally you could do with a smart phone or laptop and using a cable or wireless obd2 device. This will be able to show sensors and hopefully a better idea of the problem. Usually you can record the obd data while you take the car for a drive, the recorded data should shed some light on what kind of problem you have.

Judging by the fault code, it doesn’t sound like an o2 sensor.
You could have a faulty air flow sensor that is fooling the engine management into thinking it’s getting much more air than it really is. So the fuel added is increased and the o2 sensors are detecting the mixture is too rich.
This is just a guess, but using the obd data should be able to highlight what is actually happening.

Sent from my iPad using Tapatalk

January 6, 2018

Hi Anthony,

Thanks for the input. I have a wireless OBD2 scanner. Do you have any experience with the android OBD2 app named "Torque"? I am unsure how I would go about recording sensor data using that app. FYI, it's the only app that seems to work with my scanner.

Regarding the MAF, I believe that is a definite possibility, as when I cleaned it, there was a huge buildup of gunk on it, a layer easily 0.5mm thick. I cleaned it and there was a minute difference, however it may be minute because the MAF could be totally shot.

Many thanks

January 6, 2018

Torque logs certain OBDII items by default (unless you specifically turn this off) but you can change what it logs within its settings. When you say "OBD2 scanner" you mean an OBD2 dongle that plugs on to the car's port right? Which dongle (ELM327 or compatible?) and which smartphone are you using? Using WiFi or bluetooth (better)? From your description of the symptoms, I would be inclined to check out the CCV (Closed Crankcase Ventilation) system and all its associated vacuum lines/valves for perishing and/or splitting causing air leakage...

January 6, 2018

7 minutes ago, CPN said:

Torque logs certain OBDII items by default (unless you specifically turn this off) but you can change what it logs within its settings. When you say "OBD2 scanner" you mean an OBD2 dongle that plugs on to the car's port right? Which dongle (ELM327 or compatible?) and which smartphone are you using? Using WiFi or Bluetooth (better)? From your description of the symptoms, I would be inclined to check out the CCV (Closed Crankcase Ventilation) system and all its associated vacuum lines/valves for perishing and/or splitting causing air leakage...

Hi Colin,

Yes, it's an ELM327 dongle, connected by bluetooth. My phone is a cheapo Chinese android. As for checking the CCV, I will try that on the weekend, I'm not too experienced with motors yet, and am learning as I go, so I haven't looked at that yet (or even known of it's existence in all fairness) so thank you for the advice.

I'll add that to the list of "to dos" and get back to you with the results.

Thank you :)

January 6, 2018

No problem. It's just one of many possibilities that would be worth checking... Certainly in a car that old anyway...

January 6, 2018

You should clean the intake and throttle body.

January 6, 2018

Check the PCV valve is not jammed ..top of cam cover on left as you look from the front. at rear.

My money on a duff MAF.

January 11, 2018

So I got some screenshots of the data on the OBD2 scan app. These are taken with the following conditions:

Warm engine, after 2 mile drive
A/C off
Idling + Stationary for a couple minutes
No accessories/ancillaries in use (except the radio)

I have read somewhere online that at idle the MAF should report (in Grams / Second) roughly the same as the engine displacement (in Litres). The MAF is reporting exactly double the engine displacement at idle (MAF reading = 2g/s, engine = 1L). So if the issue is rich mixture, this seems like a very likely culprit. Based on these readings, do you agree?

NOTE: Ignore any Trip related readings, as I haven't set it up properly yet, so they're just plain wrong ¯\_(ツ)_/¯