OK, where to start....a bit of history first me thinks....
Sept 17th - was driving over to Sheffield on the '61 when I heard a horrendous clunking noise. I pulled over immediately as I was fortnuately passing a turn off. Basically engine had run dry of oil, yet no warning light!! I don't want to spend too long on this (v.painful topic!) but the repairs were as follows:
Re-ground crankshaft with oversized bearings
New piston rings
New connecting rod
Set of sparks
Engine re-built basically. As part of the work I had my man remove the pre-cat as per well documented article.
Took receipt of the car on the 16th Oct. Having done approx 15 miles Engine Warning Light came on. Had mechanic re-check all his good work (not Mr T I might add) and he could not find a problem. Had a diagnostic check - it was throwing code P0171, P0174 - basically car is complaining of lean fuel trim i.e. too little fuel in banks one and two (cyclinders 1 & 4 and 2 & 3 respectively). Anyway, last week I had it back at the diagnostics centre - they could only advise replacing the MAF. I don't believe this to be the problem however, as prior to the above work it had never caused me a problem. Have tried the MAF clean and reset as per one of the other posts, but this did not resolve. I'm starting to believe it's the absence of the pre-cat that is causing the error. Has anybody who has removed their pre-cat found this to be the case? Any ideas as to a fix (other than getting a new pre-cat!?)
Cheers,
Bidz
Sorry - haven't left car spec:
W Reg, 2000
No Mods
1zz (repaired)
35K miles
Driving Style: Too spirited!! s:cry: :cry: s:cry:
Its not the precats. The lean/rich measurement is carried out in teh manifold before the gasses reach the precats. I would go with you mechanic on this one, definitley sounds like a MAF sensor problem.
I have a fellow enthusiast who has an '03 Roadster so was considering borrowing his MAF for a week if he would let me s:) :) s:) However, I thought that the 02 sensor after the main cat, compared its readings with that of the first two - that's why I thought it may have been the pre-cat removal.
Also, the ECU has been reset since the rebuild - do you think it may be 'learning' again? As far as I can tell (and my friend, and the mechanic) it is driving v.well with no notable drops in the performance - I'm confused!
Just checking the workshop manuals for this.
The possible causes, in order of liklihood are:
1/ Induction system. (check for leaks after the MAF)
2/ Injector blockage
3/ MAF
4/ Water Temp sensor
5/ Fuel pressure
6/ Gas leakage on exhaust (would have to be at cylider head to manifold joint)
7/ O2 sensors
8/ ECU
The performance (or not) of the pre-cats is not listed as an aread to check, or a possible cause.
Hmmm......good stuff. Thanks for that. I'll try the MAF swap for starters - if that doesn't resolve, I'll get the mechanic to double-double check the things you've listed. I'll update the post as and when I get to a resolution.
Cheers, matey. Bidz.
Quote from: "GSB"7/ O2 sensors
You got there before me s;) ;) s;) But I was just wondering - if the car spat all it's oil out through the exhaust (well, cylinders first) say, it could feasibly have killed the O2 sensors.. (Though sadly I can't remember if it'd end up reading rich or lean, so it might not be that)
was it the pre-cats that caused the engine to lose all its oil in the first place?
Checked the pre-cat once the engine etc. had been dismantled - visually it looked fine. No degradation or damage.
To be honest the root cause of the problem has never been completely identified...although I have a few theories....there is an article on spyderchat about the 1zz piston rings having the material upgraded on the 2zz, so it could have been a weakness there that has caused excessive oil burn and subsequent damage.
Spoke to my friend this morning, he has agreed to 'lend' me his MAF for a few days at the cost of some cans of wife-beater - bargain!
I'll keep you posted...
So - swapped the MAF over and reset the ECU no probs. Light did not return.....until tonight!! Quite confused...have clocked 150 miles since reset and was actually starting to believe my car had mysteriously fixed itself (performance seems ok too - after previous reset the light returned after only 70 miles). My friend has had no problems running with my MAF so I think that rules that out as the cause.
Wasn't doing anything extraordinary when the light came on - no excessive revving or harsh acceleration. I think it must be (as suggested) a slightly suspect O2 sensor that might be having good days and bad days s:? :? s:? Anyway - enough is enough.....I'm throwing in the towel and will be booking it in for an appointment with Mr.T - I'm hoping they have suitable equipment to pinpoint the exact cause of the problem.
I'll let you know how it turns out...
The car is fixed! Took the car to Mr.T who checked the VVT for starters - no probs there....they then suggested putting some injector cleaner through the sytem to see if that would improve the situation - the car is running v.well now. No EWL for over 600 miles...hate to tempt fate, but it seems the nightmare has finally ended (until the credit card bill turns up).
Bidz