Pinto Misfire & temperatures

[davidimurray]

Pinto Misfire & temperatures

I've got my Pinto running now. It's an 1800 fitted with ZX6R carbs - jets are standard, needles are 1 below middle groove and idle screws are 3 turns out. This is all running with a Megajolt - timing has been set and checked and the map I have is one of the 'standard' base maps doing the rounds.

When the car is sat idling (it currently idles at about 1050 RPM) every 10/20 seconds I get a pop from the exhaust. You can hear it on this video here at 15 and 35 seconds - http://www.youtube.com/watch?v=6JVmMO2R4WY

If you watch the video further, when I raise the revs at about 40s second up until 48 seconds you can hear quite a few pops but they don't seem consistent. In the rest of the video I raise the revs further and the pops seems to decrease but there are lots coming off the throttle.

Has anyone got any suggestions on what could be causing this? An initial though I had could be air leaks into the exhaust?

Second question is about temperatures. Let the car get up to full temp. I've got a digidash and that shows that the engine fan comes on at about 105C and turns off at 98C. The fan switch is rated at about 75C so I am guessing this is just a function of the position of the fan switch against the temp sensor in the head. Does this seem like a normal sort of operating temp for a Pinto? If I hold the engine at 3500rpm for a few minutes, with the fan on the temperature sits happily at 101C so it would seem that the cooling system works.

Thanks in advance for your help.

Cheers

Dave

[twinturbo]

Did you have it running on the Pierburg Beforhand?

Do you still have the Pierburg to test with against the Jolt?

Has the Cam Timing been checked?

Cheers

TT

[deezee]

Sadly there is seemingly no solid settings for carbs to get the engine to run perfectly. From experience your going to need to check for air leaks (A common causes of exhaust popping), balance the carbs, do a compression test and fit a wideband lambda to the exhaust. Unless you can see what's going on in the engine, your going to struggle to tune the car. Popping can be caused by lean conditions in your engine. Which you have no way of knowing without a wideband.

[baz-r]

you might still be able to get a colourtune that may help see whats going on with the mixture

[mark]

Air leaks are quite common when people are doing the bike carb thing and the syptoms are exactly as you describe

My old cvh install did a similar thing until i got the manifold skimmed

Try using a blow lamp unlit on full, aim the gas around all the flanges and joints at idle and see if the engine picks up

If it does then its an easy fix, if not could be carb settings

[baz-r]

Originally Posted by mark

Air leaks are quite common when people are doing the bike carb thing and the syptoms are exactly as you describe

My cvh install did a similar thing until i got the manifold skimmed

Try using a blow lamp unlit on full, aim the gas around all the flanges and joints at idle and see if the engine picks up

If it does then its an easy fix, if not could be carb settings

or use wd40 to get in the gaps

[davidimurray]

Hello everyone

Had another play yesterday and made a discovery - I am an idiot

It seems while playing with the idle screws I had been turning them the wrong way and leaning out the mix rather than richening it up

Reset the carbs yesterday and it now runs a lot lot better although it still has the odd pop and bang on the overrun but that is probably an air leak. A wideband lambda is on the shopping list for tuning. I popped a CO meter up the can and at idle I was getting 1.5% CO.

For purely educational purposes I checked my shift lights were working as well - http://www.youtube.com/watch?v=SBZ497TwyII

On the temperature front I've been through the cooling system again and rebled it all and the engine now sits happily at 89C with the fan cutting in and out so it looks like I must have had an air lock somewhere.

Thanks for all the advice guys. I've whipped the exhaust off at the moment topolish it and wrap the headers in the engine bay so when I get it back on I will report how things are going.

Cheers

Dave

[baz-r]

Originally Posted by davidimurray

I popped a CO meter up the can and at idle I was getting 1.5% CO.

ok but that is going to be avrage co % and a wide band could be a pricey option
that will not give you what each cyl is doing you could still have too rich and one real lean

two options would be use a colour tune to set each cyl mix and carb ballancer to check you have equal vac at all cyl (how i would set up old multi su's)
or check exaust port temp with a ir gun and total co and keep carb ballance in sync (how people do inj bodies)

[robo]

Baz is right but there is a third option.Do the best you can, shake the car down and book some rolling road time with someone thats got the kit to re jet and time your set up. I have been down this road with mapable ecu`s and itb`s on v8`s, thought after playing about for weeks that we had got it near enough. Wrong !!! we had the map rich in some places lean in others and basically i had wasted my time . A rolling road is money you wont regret spending. Also with fuel prices the way they are it would almost certainly pay for itself by running the engine efficiently.

Just my 2pc

Bob