Home Project 1MZ-FE VVTi Conversion

[rainen]

Take the point of being worse still learning. All looks normal in the engine bay and the intake is all present including the air filter. Did the compression test this morning with these results:
Cylinder 2 - 195
Cylinder 4 - 190
Cylinder 6 - 195

Are these ok? Rather not take stuff off to get at the other bank at this stage as the fault condition is affecting both banks the same.

I'm going to have to order a new MAF just to rule that out.

[Paul Woods]

The compressions are great, I would not bother with the rear bank at this point.

On your scanner, what reading is the MAF giving out at idle?

Also when you hold the revs at 3500-4000rpm for an extended period, note what the fuel trims do, I would expect them to get "better".

You can also rule out a leaking injector, because it would have to be two leaking injectors (on each bank) and both leaking by the same amount.

It does point towards MAF or fuel pressure too high, but I've never seen that happen before.

[rainen]

At idle the MAF is reading 4.95 g/s and IAT 24. Holding at 3,500 both trims (short and long) on both banks are working around 0 and only drop out to around -2, the MAF reading at that engine speed is 18.5 g/s.

[Paul Woods]

Ok, I think the MAF value is too high at idle, from memory more like 2.5g/s is what it should be.

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[D2W]

I know this is really geeking and my wife is rolling her eyes to heaven, but I find this a very very interesting conversation. Looking forward to reading the final outcome.


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[rainen]

Ok Paul thanks, I've got a new MAF coming tomorrow so hopefully it will sort it out. Quick install so will report results when I've tested it out.

[rainen]

Well time to feel good as the engine is now running perfectly . It was a faulty MAF that was causing the trouble. When the engine got to temperature I noted the following:

STB1 -3.1
LTB1 -5.5
STB2 -2.3
LTB2 0
MAF 3.42 g/s (now the faulty one was reporting 4.95 at idle - more air than it was actually getting)
RPM 700

The AFR on bank one seems to take longer to start to work than bank 2 so I might replace that one. Engine responds instantly to throttle now.

So I now have a benchmark running engine so hopefully during the conversion I will not be introducing any new faults.

Thanks Paul for your valuable input so far in the early stages of the project. Back on track now so time to start the removal process.

[Paul Woods]

Good stuff, I really should consider doing this for a living.

[Paul Woods]

Oh and worth pointing out I replace the O2/AFR sensors for brand new ones on every customer conversion, it's quite normal for an RX300 to have faulty or slow responding AFR sensors, I would advise replacing both of them and keep your current ones as spares.

[rainen]

Makes sense Paul as I've already got one slow one. Will add that to my list of things to buy!