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Rough running - B18FT
Posted: Fri Nov 01, 2019 1:36 pm
by djbengan
Hello!
i'm in desperate need of help with my 480 Turbo from 88.
Problem:
Fuel or spark cut when going "positive" on boost gauge, loud pops/bangs from engine bay when trying to push anyway(does not sound like detonation/knock), no power and a strange idle jumping pattern that needs a good rev to snap out of.
Done so far:
New plugs, checked leads, checked and cleaned rotor housing and arm, new coil lead, new fuel filter, sprayed and replaced vacuum hoses, new air intake hoses, new MAF, new intake gasket, cleaned and checked injectors, checked ground points on engine, cleaned battery terminals.
Might be related:
Long time from crank to start, sometimes 1-2 minutes(10+ tries), seems like the fuel system is loosing pressure when not running, bad check valve somewhere?
The symptom is similar or the same that i had when my air intake hose was bust, is there a leak somewhere that i am missing?
Re: Rough running - B18FT
Posted: Fri Nov 01, 2019 6:12 pm
by djbengan
Just for clarification, I've volume tested the fuel pump by measuring. Seemed fine, but not tested the pressure.
Re: Rough running - B18FT
Posted: Fri Nov 01, 2019 8:05 pm
by JP
Check MAF and ECT. Are the plugs getting black? Black smoke when accelerating?. This seems MAF related although it can also be ECU failure ( rare ). You should get 1L/30sec at the return hose.
Check throttle potentiometer also, and knock sensor
Re: Rough running - B18FT
Posted: Sat Nov 02, 2019 2:49 pm
by jifflemon
djbengan wrote: ↑Fri Nov 01, 2019 1:36 pm
Hello!
i'm in desperate need of help with my 480 Turbo from 88.
Problem:
Fuel or spark cut when going "positive" on boost gauge, loud pops/bangs from engine bay when trying to push anyway(does not sound like detonation/knock), no power and a strange idle jumping pattern that needs a good rev to snap out of.
Done so far:
New plugs, checked leads, checked and cleaned rotor housing and arm, new coil lead, new fuel filter, sprayed and replaced vacuum hoses, new air intake hoses, new MAF, new intake gasket, cleaned and checked injectors, checked ground points on engine, cleaned battery terminals.
Might be related:
Long time from crank to start, sometimes 1-2 minutes(10+ tries), seems like the fuel system is loosing pressure when not running, bad check valve somewhere?
The symptom is similar or the same that i had when my air intake hose was bust, is there a leak somewhere that i am missing?
You running standard ECU and boost? Any modifications ?
Re: Rough running - B18FT
Posted: Sat Nov 02, 2019 9:32 pm
by djbengan
jifflemon wrote: ↑Sat Nov 02, 2019 2:49 pm
You running standard ECU and boost? Any modifications ?
I got an robou modded ECU but also the original ecu, same problem with both. The coil is not original, but also nothing special. Otherwise full stock.
Re: Rough running - B18FT
Posted: Sat Nov 02, 2019 9:55 pm
by djbengan
JP wrote: ↑Fri Nov 01, 2019 8:05 pm
Check MAF and ECT. Are the plugs getting black? Black smoke when accelerating?. This seems MAF related although it can also be ECU failure ( rare ). You should get 1L/30sec at the return hose.
Check throttle potentiometer also, and knock sensor
Sorry, but what is the ECT? Plugs ashy, exhaust fine.
Re: Rough running - B18FT
Posted: Sat Nov 02, 2019 10:48 pm
by Robou
All symptoms, except the long time to start, sound like being caused by the MAF. Check first if you replaced it by the correct type, number ending by 007 or 021. Then clean the connector and if no success move the wiring to and fro. You may reconnect a broken wire in doing so.
When idling is normal again you know you found the culprit.
Re: Rough running - B18FT
Posted: Sun Nov 03, 2019 10:57 am
by JohnTurbo
Sounds like an air leak.
Some bolt holes on the inlet manifold go right through. Thats a typical problem spot.
Otherwise seal up the manifold end of the inlet tract, and blow in the air filter end to see if it pressurises.
Or put a tyre valve in a jamjar lid and use a compressor.
Re: Rough running - B18FT
Posted: Tue Nov 05, 2019 9:51 am
by djbengan
Something worked, the cables/connector going to the MAF was not in very good shape when I removed the grommet, but the knock sensor cable was also damaged, so one of them maybe? There is also something wrong with the crankcase ventilation hoses, check valve is not sealing on the oil catcher thing and the check valve seems to be non functional as well.
But all in all the car is drivable again!
Will probably do the air leak test anyway, the robou ECU is not happy with the state of the car.
Thanks alot for the help! Will update when I have a definite answer.
Re: Rough running - B18FT
Posted: Sat Apr 18, 2020 9:15 am
by djbengan
After winter sleep, the car lost it completely. Not sure what is what anymore.
Runs for a few seconds, then vacuum creeps up towards zero and it stalls.
A little throttle added to get enough time for a movie.
https://photos.app.goo.gl/4jTpjGcpuQfbPeS17
Re: Rough running - B18FT
Posted: Sat Apr 18, 2020 10:58 am
by JP
When the engine begins to loose vacuum, is the idle steady or is it loosing rpm?
Re: Rough running - B18FT
Posted: Sat Apr 18, 2020 11:24 am
by djbengan
The rpm drops as the vacuum goes up, pressing the throttle does nothing.