1jz boost problem

[Ribfeast]

Did you check under the actual boots on the coilpacks for cracks? And even see if there is any burn marks on the boots from where the spark has been arcing to the head and causing the misfire.
Adjusting the TPS is a tricky job, even when I was using the Throttle% readout on the SAFC it took some VERY fine adjustment to get right. Don't play with it unless you are definitely sure it is at fault. Can't even imagine how much of a bastard it would be to do without the SAFC fitted.

[JP]

the TPS is pretty easy to set following the procedure in the JZA70 service manual. Only takes a few minutes.

I used some terminals out of an old loom to make connecting the multimeter to the TPS easier, as the trickiest part is holding the multimeter probes on the TPS pins while you're adjusting it.

[RollaBabe]

Need some help guys diagnosing a problem with my 1jz cressy. Just got the conversion finished and decided to take it for a test drive. All was good until it started to come on boost, the motor will not rev past 3.5-4k rpm and just backfires/hesitates. Things that i'v changed and checked so far:

Coils
Ignitor
ECU
Map sencer
Spark plugs (2 different types)
Fuel filter
Walbro fuel pump
Checked all ic pipes for leaks

This did nothing to help it. What do ya think i should try next. It's a jzx90 motor aswell.

This sounds Identical to the problem that I'm having. And it's driving me crazy. I have done the liquid tape and heatshrink coils trick. New plugs BKR6E's end even made sure gaps were spot on .8mm. The only other thing i can think of is tps so i'm tryin that next.

[SL666]

This is going to sound stupid, but is the map sensor on the right port of the manifold? - seeing boost as well as vac?

[RollaBabe]

Map sensor is connected to the same point it was from factory.I thought this was boost related but after another drive this morning it seems more than feasable that it could be related to TPS. I thought as it was builkding boost it was breaking down but the problem seems to get worse related to throttle position. I can bring it on boost with very gentle throttle and it goes ok but the harder the pedal is pressed the more hesistant it becomes and pressing it all the way to WOT just causes backfires.

Now just to find out why? :S

[SL666]

Might be worth checking the CAS position, could be timing related..

is it throwing any codes?

[Dieseltrain]

Cam Angle Sensors can also be a bastard and cause missfires on 1jz's. If your cam covers are leaking back there, they can play up.

[RollaBabe]

TPS seems ok.
Brown wire Earth.
Pink 15mV closed then alternator voltage when opened slightly
Wh/Rd 0.6V closed increasing to 3.76 as throttle is opened
Blk/Yw constant 5V
I cant pull fault codes coz the e1 wire from the ecu isnt connected and no info to tell me where it goes.
I'm at the stage where I'm just gunna hand it to someone me thinks.

[131OWN]

I would try another ECU, when the CAPS go bad they won't rev.

[SL666]

I'm at the stage where I'm just gunna hand it to someone me thinks.

That could be an exceedingly expensive solution.

[RollaBabe]

I have a few freinds with workshops that owe me a favour or 2.

[PeteH]

Map sensor is connected to the same point it was from factory.I thought this was boost related but after another drive this morning it seems more than feasable that it could be related to TPS. I thought as it was builkding boost it was breaking down but the problem seems to get worse related to throttle position. I can bring it on boost with very gentle throttle and it goes ok but the harder the pedal is pressed the more hesistant it becomes and pressing it all the way to WOT just causes backfires.

Now just to find out why? :S

Could be related to the BOV. Are you still using the standard unit?

When you mash the throttle and hold it down does the engine continue to cough and buck when it backfires? Or does the engine backfire once followed by a sudden drop in revs and when you release the pedal from the floor do the revs start to build again?

Just another thing to consider.

[triptek]

Just an update on what was the problem with my car. The NSW was wired incorrectly and was putting the ecu into limp mode.

[SL666]

Nsw?

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[triptek]

Neutral start switch