RB30 Nissan Backfire problem

Submitted: Sunday, May 11, 2008 at 22:18

ThreadID: 57513 Views:3593 Replies:4 FollowUps:7

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Kev C

Hi All

My '93 Patrol was always a good bus, but in the last few months has given me a lot of trouble. It was missing badly & backfiring through the carbi. I have got rid of the miss but it still backfires.

In recent months I have done the following:
Replaced the head
new plugs
new leads
new rotor
new dizzie cap
extractors
tried various timing settings.
run carbi & injector cleaner through fuel
run motor cleaner through oil
removed heater grid from carbi
checked pcv OK
replaced all small vacuum hoses
dimantled & inspected LPG mixer
compression test OK

It backfires through the Carbi at irregular intervals on gas or petrol. It does run better on petrol.

After replacing the head this weekend it ran very well on the test drive, it even idled exceptionally well, which it hasn't done for some time. It used to have a miss at idle. I took it off road to go fishing & found that the backfiring through the carbi is still as bad as ever.

Does anyone have any ideas?

Kev

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Reply By: Member - David P (VIC) - Sunday, May 11, 2008 at 22:23

Sunday, May 11, 2008 at 22:23

I would check the exhaust valve ajustment, not sure , are they shim?.....silverback

AnswerID: 303348

Follow Up By: Member - David P (VIC) - Sunday, May 11, 2008 at 22:27

Sunday, May 11, 2008 at 22:27

and is it more pronounced when hot?....silverback

FollowupID: 569461

Follow Up By: Kev C - Sunday, May 11, 2008 at 22:36

Sunday, May 11, 2008 at 22:36

It has non adjustable lifters. I don't get any tappet noise, so I think they are OK. I have just replaced the head because I thought that the exhaust valves may have been recessed by usuing LPG for 15 years.

The backfire happens hot or cold, no discernable difference.

Kev

FollowupID: 569462

Follow Up By: Member - David P (VIC) - Monday, May 12, 2008 at 19:14

Monday, May 12, 2008 at 19:14

I would check all valve clearances incl inlet....cheers....silverback

FollowupID: 569575

Follow Up By: Kev C - Tuesday, May 13, 2008 at 17:22

Tuesday, May 13, 2008 at 17:22

Hi David

The valve clearances are not adjustable on the RB30. Are you suggesting a worn cam? If so would I have any other indication of a worn cam?

Kev

FollowupID: 569751

Reply By: TD100 - Monday, May 12, 2008 at 20:29

Monday, May 12, 2008 at 20:29

My mates VL did the same thing years ago,we had pulled all our hair out trying to sort this thing out,in the end it was the dizzy worn out.had too much end and side play,rebuilt it and all was good.cheers Paul

AnswerID: 303476

Follow Up By: Kev C - Tuesday, May 13, 2008 at 17:25

Tuesday, May 13, 2008 at 17:25

Hi TD100

I had though about the dizzi as well. I checked it for play whilst it was out. It was as solid as a rock.

Regards

Kev

FollowupID: 569752

Reply By: landed eagle - Monday, May 12, 2008 at 20:53

Monday, May 12, 2008 at 20:53

Had a head replaced on an Econovan years ago and it did the same thing. Checked everything as you have and found that the timing chain was one tooth out after it had been "professionally" done.

AnswerID: 303483

Follow Up By: Kev C - Tuesday, May 13, 2008 at 17:37

Tuesday, May 13, 2008 at 17:37

Hi Eagle

I had a bit of a panic attack when I reassembled the head. When I reattached the cam pully the belt was 2 teeth out from the marks that I had put on it. It took me a while to figure out that it had slipped 2 teeth on the crank & was OK. I can see how easy it could be to remain 1 tooth out.

I did check the timing after the head job & it was OK. The backfiring was happening before I replaced the head. I had hoped that it would have fixed the problem.

regards

Kev

FollowupID: 569754