Rough running - B18FT

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djbengan
480 Newbie
Posts: 11
Joined: Mon Apr 15, 2019 10:55 am

Rough running - B18FT

Post by djbengan » 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?
480 Turbo 1988
Southeast Sweden

djbengan
480 Newbie
Posts: 11
Joined: Mon Apr 15, 2019 10:55 am

Re: Rough running - B18FT

Post by djbengan » Fri Nov 01, 2019 6:12 pm

Just for clarification, I've volume tested the fuel pump by measuring. Seemed fine, but not tested the pressure.
480 Turbo 1988
Southeast Sweden

JP
Started learning about 480
Posts: 55
Joined: Wed Sep 20, 2006 9:42 am

Re: Rough running - B18FT

Post by JP » 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

jifflemon
480 Is my middle name
Posts: 1025
Joined: Sat Dec 17, 2016 11:03 am

Re: Rough running - B18FT

Post by jifflemon » Sat Nov 02, 2019 2:49 pm

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 ?

djbengan
480 Newbie
Posts: 11
Joined: Mon Apr 15, 2019 10:55 am

Re: Rough running - B18FT

Post by djbengan » Sat Nov 02, 2019 9:32 pm

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.
480 Turbo 1988
Southeast Sweden

djbengan
480 Newbie
Posts: 11
Joined: Mon Apr 15, 2019 10:55 am

Re: Rough running - B18FT

Post by djbengan » Sat Nov 02, 2019 9:55 pm

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.
480 Turbo 1988
Southeast Sweden

Robou
Knows an Aerodeck isn't a 480
Posts: 257
Joined: Sun Jul 08, 2007 11:34 pm

Re: Rough running - B18FT

Post by Robou » Sat Nov 02, 2019 10:48 pm

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.
Too old to bother
480 Turbo midst '91

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JohnTurbo
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Re: Rough running - B18FT

Post by JohnTurbo » Sun Nov 03, 2019 10:57 am

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.
Past:
94 Turbo - Red
94 Turbo - Black (Converted from NA 2.0)
92 Turbo - Red
90 Turbo - Silver
Now:
00 Exige
15 GKD Legend
16 Skoda Superb

djbengan
480 Newbie
Posts: 11
Joined: Mon Apr 15, 2019 10:55 am

Re: Rough running - B18FT

Post by djbengan » Tue Nov 05, 2019 9:51 am

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.
480 Turbo 1988
Southeast Sweden

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