MOT Fail - Lambda, but now jerky
 

Hi

I drive an R reg Mazda 626 2.0. I recently had it in for an MOT, which it failed...brake flexi, Track rod end, rear caliper...and the Lambda test with scores of 1.17 & 1.19, Carbon Monoxide and Hydro Carbon tests both passed.

So I got the new brake flexi, TRE and Caliper fitted, and all is good, but in my efforts of problem solving I grabbed a Lambda from an R reg 626 in the local scrap yard, fitted it, which was nice and easy, but when I took it for a spin the car was really choppy and was losing revs to the point it was cutting out.

Did a bit of reading and heard that it could have been a faulty Mass Air Flow Sensor, so I got one (i know from the scrappies again) and refitted my old lambda but now my car keeps its revs but still gets really choppy!!!

When driving casually through the gears through the 20/30 mph streets it is not noticable but when you hit the motorway and try and put the foot down you are almost through the windscreen it kicks that bad...

before I made these changes my car drove like a dream, and could honestly not be faulted...but now it sounds really tinny and doesn't sound the same when you hit the accelerator.

So what I ask is...what was causing my Lam to be high
and 2. what have I done to ruin my car???

for fitting both sensors I unplugged the neg cable to my battery.

Thanks

Hi mate!I've seen your post on here!You said that you've disconnected the negative battery terminal (to reset the ECU I am assuming).The ECU needs some miles to tune the car (learn and adjust),so it can be jerky for the first 80-100 miles.Don't know how many you've done since terminal has been removed.
Regarding both sensors the scrappy is not always a good idea especially for such important parts.They might be faulty.Have you cleaned you MAF sensor yet?Have you run a diagnostic scanner to get some codes?
You can try and clean your MAF sensor first before getting a new one.Clean it with electrical contact cleaner £4ish from Halfords or MAF sensor cleaner from eurocarparts or ebay £8-£10.
What was the colour of your lambda when taken out and did you check the plug and wires going to it?