V8 4,0 Motronic misfiring

[tychoS]

DII 2002 V8 4,0 Motronic

When pushing the engine to perform, it misfires badly.

Eg. when trying to accelerate briskly from 100 to 130 km/h, the engine will most often misfire, loose its will to accelerate, and only reach say 115 km/h. When cruising at 110 km/h it will sometimes start to misfire and the speed drops down to 100 or 95 km/h. At other times it will happily drive at 110 or 130 km/h for quite a while without misfiring.

Replaced during 2020 by myself: camshaft(LR), hydraulic lifters(LR), timing chain(LR) + sprockets, injectors (Bosch), sparkplugs(NGK)

The camshaft was well past its prime, as were the other parts. Replacing all these parts took the engine from undriveable to working ok, unless I push it above say 75% or so. I did the replacements in increments, and each increment made the engine perform significantly better/less badly.

So whats likely to be the next step? I could keep on replacing parts, the next step would be either the ignition coils+leads or the lambda+maf sensors.

But I am wondering if the problem could be elsewhere, eg. either the ECU itself or the wiring harness for it.

How to best diagnose?

Nanocom has this sorry story to tell:

P0134 = LAMBDA SENSOR UPSTREAM
CATALYST BANK 1 DRIVE CYCLE C
OCCURED 21 TIMES
SIGNAL INVALID

P0172 = MIXTURE ADAPTION FACTOR FRA
BANK 1 DRIVE CYCLE C
OCCURED 1 TIMES
SIGNAL TOO HIGH

P0175 = MIXTURE ADAPTION FACTOR
FRA BANK 2 DRIVE CYCLE C
OCCURED 1 TIMES
SIGNAL TOO HIGH

P0300 = EMISSION RELEVANT MISFIRE
MULTIPLE CYLINDERS DRIVE CYCLE C
OCCURED 2 TIMES
SIGNAL TOO HIGH

P0303 = CATALYST DAMAGING MISFIRE
CYL 3 DRIVE CYCLE C
OCCURED 64 TIMES
SIGNAL TOO HIGH

P0305 = CATALYST DAMAGING MISFIRE
CYL 5 DRIVE CYCLE C
OCCURED 64 TIMES
SIGNAL TOO HIGH

P1000 = EMISSION RELEVANT MISFIRE
CYLINDER 2 DRIVE CYCLE C
OCCURED 2 TIMES
SIGNAL TOO HIGH

P1000 = LAMBDA SENSOR UPSTREAM
CATALYST BANK 2 DRIVE CYCLE C
OCCURED 7 TIMES
SIGNAL INVALID

P1300 = CATALYST DAMAGING MISFIRE
MULTIPLE CYLINDERS DRIVE CYCLE C
OCCURED 66 TIMES
SIGNAL TOO HIGH

P1668 = ANTI-THEFT ALARM SERIAL
LINK FAULT DRIVE CYCLE A
OCCURED 1 TIMES
SIGNAL TOO HIGH

NA
OCCURED 65 TIMES
SIGNAL TOO LOW
FAULT IS CURRENTLY PRESENT

NA
OCCURED 193 TIMES
SIGNAL TOO LOW
FAULT IS CURRENTLY PRESENT

NA
OCCURED 0 TIMES
SIGNAL TOO LOW
FAULT IS CURRENTLY PRESENT

 

 

 

 

 

 

 

 

Edited January 27, 2021 by tychoS

[elbekko]

I'd clear the faults, reset the adaptive values, and drive around while keeping an eye on the lambda values. If a lambda isn't switching, it can really screw with the tune (been there, done that).