surging 4zc1

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davixmuch
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surging 4zc1

Post by davixmuch » Mon Oct 05, 2015 12:05 pm

I recently bought a 1988 impulse turbo as my youngest sons
first car.
I'm a pretty car savvy guy but turbos are a thing I really haven't had much
experience with with
anyway
after replacing many many vacuum lines
cleaning out the fuel tank and a fouled plug
it runs great idles great just no power
after 2000 rpms and it starts to surge
any suggestions or help will be greatly appreciated

IZU069
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Location: Melbourne (Orstralia)

Post by IZU069 » Wed Oct 07, 2015 8:42 am

Checked some of the web pages... like plugging in OBD etc diag tools, or checking for slip in the axles...???
LOL - I'm having a dig at some of the crap else irrelevant info out there.

Have you checked the engine compression? (And hence splug (spark plug) health?)

Also check battery connections - ESPECIALLY the flinks (fuselinks). I suggest disconnect & reconnect and in bad cases - or for bolted connections - a clean as well.
FYI - IMO disconnecting and reconnecting fixes 95% of electrical faults. Sometimes that includes ROTATING fuses - ie swap fuses of same size & rating to transfer intermittent fuses to other circuits as well as the usual break & remake contact cleaning.

Not that I recall exactly what the Piazza has but things that come to my mind are EGR etc valves and especially the brake booster - ie a holed/split diaphragm. The latter is easy to check - just disconnect the brake booster's vac hose & block its manifold intake - but be careful, extra bake pedal pressure is then required!!
And is there is a MAP or similar sensor...? (A faulty oxygen sensor should merely result in rich running, not surging.)

Then the usual stuff like fuel & air filters, and fuel pumps.


Also intake gasket leaks. I used to test by squirting with oil but that's a bit messy - and may be dangerous - and may miss underside leaks.
Maybe spraying with soapy water (as done to find engine & tyre leaks) will work instead. The same can be done for leaks in general.


You said 1988 and Impulse so I assume it's an I-TEC EMS? That should have a locked optical distributor which tends to be go or no-go or the occasional miss unlike our GMH-Isuzu Piazza's with their recalcitrant mechanical dizzies where the usual vac-advance (diaphragm) and RPM advance (broken springs) problems can occur though usually not surging (they are more erratic). The dizzy's vac advance diaphragm could act like split brake booster diaphragm but its hose is usually too small to have much effect on air intake.


Alas there is something bugging me about 4ZC1-t surges (4ZC1-t being your Piazza's engine)... it may come to me later. (Apols but I'm out of practice; out of memory, and likely soon to be out of here (IsuPiazza).) I suspect however it may be the flink connection checks... A mate experienced erratic engine behaviour upon rain, then a few vehicleless weeks whilst his moron mechanic blew up his ECU and replaced working fuel pumps etc. The problem proved to be the flink connections at the +ve battery terminal - something I had warned him about several months earlier.


Like all fault finding you should be able to track or isolate the fault. Sure, you can randomly replace stuff - and I am VERY grateful to those that use that technique before scrapping their vehicle so that people like me can get new sparts at ludicrous prices - but many problems are isolatable. IE - disconnect or bypass things to obtain stable running noting that performance may be reduced or that continued operation may be damaging.
IZU069 - ISUZU means a lot to me.

davixmuch
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Joined: Mon Oct 05, 2015 11:55 am

Thank you

Post by davixmuch » Wed Oct 07, 2015 9:11 am

Thanks for the response
It is much appreciated

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