Gen 3 jerking when accelerating?

bees · Post by **bees** » Mon Apr 17, 2017 5:49 pm

I can see plug leads causing a missfire, but its not a missfire.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Mon Apr 17, 2017 8:58 pm

bees wrote:Checked the usual stuff

What have you included in usual stuff?

bees · Post by **bees** » Mon Apr 17, 2017 9:43 pm

Hi, new fuel and air filter. Timed on stobe light new plugs. Throttle body cleaned. Dizzy recently replaced.

Cant figure the damm thing out. Its not coming up with any codes, except where ive been unplugging stuff.

Runs so sweet on the drive, but almost undrivable now.

Thanks for suggestions.

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Apr 18, 2017 1:43 am

I suggest;
Vacuum lines
anything to do with idle/mixture control (can't remember the setup on those, is it iacv and fitv like on 4g's?)
Splits in the inlet plenum (up to the throttle body)
Or possibly inlet manifold gasket leaking?

does the 3g have a knock sensor???

bees · Post by **bees** » Tue Apr 18, 2017 7:13 am

Thanks Iain will try these.

One thing that is confusing me. I cant find the o2 sensor? Theres no sensor in the manifold, or downstream in the exhaust. No cat but pgm-fi... arghhh?? Head scratch??

b20a7

Bees

89 UKDM BA4 4WS (resto job!) · Post by **wurlycorner** » Tue Apr 18, 2017 8:51 am

Have you downloaded the service manual?

Greg · Post by **Greg** » Tue Apr 18, 2017 9:12 am

I used to get this problem on my old grey B20a7. I found it only happened when warming up, not cold or hot but in between I thought it was to do with the automatic choke but I just lived with it being an auto sometimes it wouldn't go at junctions unless you pumped the throttle, once warmed up though it was fine. Also I don't think the B20a7 has an 02 sensor are they not pre programed?

bees · Post by **bees** » Tue Apr 18, 2017 10:04 am

Hi, trawlled through the Service Manual. Its good but not helping. I thought all fuel injection need a o2 sensor to measure mixture and adjust...? Guess im wrong as mine which i believe is a 'KB' suffix is shown in the service manual without. Other b20a7 are shown with them fitted.

Would replace the o2 sensor but guess i dont have one!

Cue, insane laughter!

Greg · Post by **Greg** » Tue Apr 18, 2017 11:20 pm

Don't quote me but I understood the ecu ran a pre-programmed non adaptive map. Pretty sure it only has a crank sensor and temp sensor. If you look on the manifold you will see a flattened circle which is where you find the o2 sensor on American b20a5 and b21a engines.

Post by **NafemanNathan** » Wed Apr 19, 2017 8:21 am

bees wrote:Dizzy recently replaced.

Was this in attempt to solve this issue, or another? Was it a decent brand?