Weird engine behavior while driving

Give input on tuning as well as any tips and tricks you may have. Also feel free to share base mapping files for various engine types.
matthud322
Posts: 14
Joined: Wed Aug 03, 2011 1:38 pm
ECU Model: S60 Pro
Firmware Version: 56
Location: New York, USA

Weird engine behavior while driving

Post by matthud322 »

I've got my base map very close by tuning on the road. I know that its not optimal, but the car runs well. There is one spot that I am having trouble with. At low engine speeds, 1500-2000 rpms, varying loads, even though I have a lambda of 0.88, I get this weird behavior. I will be running along steady state, and I will get this sound and feeling of fuel loading up then popping. Wideband O2 shows steady state lambda while this is happening.. As soon as the engine speed gets back up, everything smooths out.
What could be causing this? Is it the slow air velocity? Does this sound like a spark advance issue? Too rich at these low speeds?
stevieturbo
Posts: 3577
Joined: Tue Aug 02, 2011 12:08 pm
ECU Model: No ECU
Location: Norn Iron

Re: Weird engine behavior while driving

Post by stevieturbo »

too rich can cause issue as can too lean. And too much timing at low loads can also cause weird behaviour.
VR6Turbo
Posts: 329
Joined: Wed Mar 17, 2010 9:24 am
ECU Model: S80 Pro
Firmware Version: 62

Re: Weird engine behavior while driving

Post by VR6Turbo »

0.88 is a bit rich for that rpm and load surely?

What engine is it? Does it have air speed problems at low rpm? I know my old engine did and I got the popping etc as well.

Are you TPS or Map as load? TPS is OK but by and large but it can be a pain at low rpms and loads. Sometimes a small butterfly movement won't register a change on the DTA but does change the airflow.

I suspect you may not shift these low rpm anomolies until you get it on the dyno and experiment a bit.
matthud322
Posts: 14
Joined: Wed Aug 03, 2011 1:38 pm
ECU Model: S60 Pro
Firmware Version: 56
Location: New York, USA

Re: Weird engine behavior while driving

Post by matthud322 »

Well it seems to happen across the load range at low rpm.

Its a 2.2L GM Ecotec. I don't know if it has air speed issues at low rpm.

I am using MAP as load
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Weird engine behavior while driving

Post by x30xe »

Can you describe more what happens. Is engine misfiring ? You name "popping", do you mean that intake is "popping" due too lean mixture ?

Better log everything you can and check if there is any signs of problems.

Is it N/A / Turbo / throttlebodies... or whatever is the configuration ?
matthud322
Posts: 14
Joined: Wed Aug 03, 2011 1:38 pm
ECU Model: S60 Pro
Firmware Version: 56
Location: New York, USA

Re: Weird engine behavior while driving

Post by matthud322 »

Its not popping in the intake. I will be cruising along, with a smooth exhaust tone, then it will hesitate for a brief moment, and the exhaust will have like a subtle pop to it. Not a backfire. Almost as if there was extra fuel being burned off.

What would cause a misfire at low RPMs with load, that I would not see anywhere else in the fuel table?

Its a N/A setup with the stock throttle body. Running Coil on plug and full sequential. My crank and cam signals are good with no errors.

I have a log from when it happened. In the attached log, in excel format, from time 5:06 I upshifted, engine revs dropped below 2000 rpms, and it started happening, so I downshifted around 5:22 to get the revs back up, and then it stopped.
I also included the raw .dat file.
Attachments
9-18.Dat
(1.12 MiB) Downloaded 247 times
9-18.xls
(543 KiB) Downloaded 377 times
User avatar
ignitionautosport
Posts: 577
Joined: Wed Jul 27, 2011 5:30 am
ECU Model: S80 Pro
Location: New Zealand
Contact:

Re: Weird engine behavior while driving

Post by ignitionautosport »

I have had a car with a worn TPS that floated around causing the throttle pumps to become active and add fuel randomly. The owner didnt want to spend any money so I increased the dead-band. Was on a different brand ECU, but did a similar thing.
| '94 GSR Lancer | '96 Toyota Carib 20V | '83 Toyota Starlet | www.ignitionautosport.co.nz |
matthud322
Posts: 14
Joined: Wed Aug 03, 2011 1:38 pm
ECU Model: S60 Pro
Firmware Version: 56
Location: New York, USA

Re: Weird engine behavior while driving

Post by matthud322 »

The TPS is dead steady while this was happening, it only changed when I tried to increase the throttle to get out of this area of the map.
VR6Turbo
Posts: 329
Joined: Wed Mar 17, 2010 9:24 am
ECU Model: S80 Pro
Firmware Version: 62

Re: Weird engine behavior while driving

Post by VR6Turbo »

It could be that your injection angle needs tuning for that rpm range. Does the popping happen in batched injection mode?
x30xe
Posts: 64
Joined: Tue Jul 26, 2011 2:56 am
ECU Model: S60 Pro

Re: Weird engine behavior while driving

Post by x30xe »

I recommend calibrating water and air temp sensor tables before mapping engine.

But it's not related to this problem.
Post Reply