emission test failure, 400 pre-serpetine, cat-model

[LLantrisant]

pre-mot visit in my garage for testing emissions turned out the following:

engine warm:
2,8% CO, ~800 HC at idle-speed, fast idle (3000rpm) similar values

car is running fine, starts well, pulls well.

for a short test we unplugged the ECU.

after re-connecting, we started engine and Co/HC readings where suddenly quite low @idle...until throttle was opened the 1st time....than readings went up again and stayed high.

car is a 400, pre-serpentine, cat-model, pre-cats removed, ignition-leads and coil are new.

any ideas where to check first?

Edited by LLantrisant on Thursday 15th November 13:13

[LLantrisant]

i thought it might be more the coolant temp sensor giving too low readings, hence the ECU thinks that engine is on cold-start?

anyway....i found inside the documentation-folder of the car a rovergauge cd-rom and and USb cable....is this diagnostics tool suitable for testing all sensors`?

the problem is, the car has no registration at the moment, so i cannot drive in a garage to check with a emission tester....now it was just an exemption, as a freind of mine picked-up the car with dealer-plates for driving to the mot-station and pre-mot check in usually "emission" friendly garage


high CO & HC is usually indicating: to much unburnt fuel or too rich.--correct?
feedback for ECU is done by the oxygen sensors --> correct?

Edited by LLantrisant on Thursday 15th November 19:42

[LLantrisant]

just to clarify: the car is not road legal....so i cannot do ANY test drives nore any "burn the cat-out of dirt" drives.

now back to rover gauge:

went to my car today, searched for the ECU and? it was underneath the dash!!! must have been altered from the former owner i guess

ok....nevermind i thought, but where the heck is this ECU-diagonostic plug no.2?



i can just find the black conector no.6

my car is a very early 1993 chimeara.......than i searched again the footwhell....and i was lucky to find the plug

Edited by LLantrisant on Saturday 17th November 12:25

[LLantrisant]

managed to connect rovergauge.....but there isnt any fault code shown.

but i guess this is due to the fact that i have disconnected the battery b4? isnt it?
if its like that....how long does the engine need to run ntil a fault code may appear.

please keep in mind, i can only run the engine in my home-garage as the car is not road-legal.

Edited by LLantrisant on Saturday 17th November 21:23

[LLantrisant]

ok...here we go.

cold start in garage (winter arrives):
ignition ON, engine NOT running:



engine is warming up (idle):



engine becomming warmer (idle):



engine becoimming warmer (throttle a bit open)



engine now warm (idle):



engine warm but off, ignition ON:




Fault-Codes: None
but se thing seems not ok with1 of the oxygen sensors?

Edited by LLantrisant on Sunday 18th November 13:21

[LLantrisant]

at the moment its quite cold here...so takes ages until the fan´s kick-in....and my neighbours are not so amused when i´m reving the car for so long time.

what i can see, with engine at 2000rpm that 1 oxygene sensor is at 6% , the other at 100%.
and the CO & HC readings are extreme high...means the oxygen sensor says "lean", the ECU is giving more fuel...and CO& HC is going up.

in theory this should mean the oxygene sensor is giving wrong info...or am i wrong?

[LLantrisant]

yes...i have the plug- extenders, new lucas leads (no fancy silicon, hocuspocus-internet-aftermarket-raceleads) and new ngk plugs, but.....the car was only started in my garage, multiple times in the past months, but never driven...only just recently pre-mot it was driven n trade-plates for 30km to a local-garage for emiision test and the other day back.

as said, car is NOT road-legal.....all tests/investigations can only be done in my home-garage

[LLantrisant]

car has been taken off the road, exported, now in process of re-registrting in his new location.

technically the car passed local MOT, but new reg-documents cannot be issued as long as i do not bring a valid emisson-test certificate, hence car is not road legal and cannot be driven , even 1m, on a public road.... i have now 3.5 weeks left to bring the certificate, otherwise the MOT test will expire and i have to do all again.

back to the car:
i´m still waiting on mr. dpd-man bringing me a pracel with the special socket for removing the oxgygene sensors....and mr. dhl-man a parcel with 2 new oxygene sensors.

temperature sender was changed 1 year ago (invoice found in folder), MAV 2 years ago, but the rotor and cap is also a good advice, as those are the only parts in the ignition system which i havent changed.

Edited by LLantrisant on Tuesday 20th November 10:59

[LLantrisant]

great advise.....but the socket is already in order....and 25,-€ do not hurt....;)

[LLantrisant]

finally my lambda-probe socket arrived today....changed sensors within 5min...connected rover-gauge and here we go:

when engine is warmed-up and lamda-probes start to regulate, they are "dancing around" zero on both banks...depending on throttle position. long-term trim shows zero.

looks like we have a result? (provided the CO-& HC readings would have improved too, but i can already "smell" a difference on the exhaust)...what do you think?

by the way i checked also dizzy-cap and rotor: they are new (i had them replaced , but didnt remember)


short term




long term:

[LLantrisant]

borrowed an old emmission tester from a mate:

2500rpm: 0,1% CO

when going down to idle-speed CO readings went up to 0,4 for a few seconds b4 going down again to 0,1-0,2%

[LLantrisant]

today it was the time for the "offical" emission-test: car passed!!!!

what i want to mention is:

i have thrown-out the TVR-recommended spark-plugs (the ones with recessed electrode) even they had been only fitted since a few weeks & had around 50miles on the clock and I fitted "standard" plugs:
better start
smoother idle
smoother acceleration
in general a more stable engine run