[TryHard]

Hey guys been having some problems with my suzuki sierra
It has missfire underload about 40 kph then stalls iv change the head recently from a 16 valve set up to 8 also I had this problem with old head and Carby so I changed whole top end I'm starting to think its Bad fuel

Things i have changed
Leads
Plugs
Dizzy
Cleaned cap have not changed yet
Also changed fuel filters and went from electic
Pump to mechanical
It also has weber Carby
Igntion timing set at 10 * before tdc
At 800rpm

The motor does not have best compression 90-100
And only had extractors so does not have back presure
Ideas guys
Cheers

[TryHard]

Might try reseal intake manifold and another coil although its fairly new

[SuziBlu]

Try starting it on a pitch black night n look under the bonnet, see if you have any lightning round the dizzy, could be a cracked cap.

[TryHard]

Yep cheers il try that tonight

[Gwagensteve]

The ignition system doesn't know how fast you are going. What revs and load is the engine at when it fails? Does it break down at full or light throttle?

Did you rejet the carb? You have massively reduced airflow through the head if you've swapped from a 16v head to an 8v. Maybe it's just running rich and stumbling.

Steve.

[SuziBlu]

It does know what revs and load it has, and at the speed OP taking, i would have thought heavy take off load.

[Gwagensteve]

I think you've misunderstood. The engine doesn't know how fast the car is moving. That's not relevant. Engine revs and load (throttle position) are relevant.

Steve.

[SuziBlu]

Thats what I was meaning Steve, 40k and he is possibly in third or forth, hard throttle, speed means bugger all.

Most people try n keep up with "normal" cars in their lil suzis, so I suspect close to WOT.

Lot of pressure electronically at that gearing and throttle pozzy.

[dtchch]

I've got a similar problem, only does it once hot misfires up to about 3000rpm then stops. Done all the ignition apart from the coil - starting to suspect fuel.

I'm going to get a fuel pressure/vacuum tester and check that - worth you doing the same. Dodgey fuel pressure due to pump or regulator can cause similiar issues

[TryHard]

Hey guys thanks for the replys to clear it up iv
Had same problem with old head the Carby is a different one
Since inlet manifold was different ATM I has weber
It happens about 3 k rpm under load 3 gear
The Carby float level had been adjusted but i do not think its Carby issue because
As i have said before it done this before head change

That's why I'm thinking doggy fuel or igntion
Might run tonight for stay sprak