Misfire underload and misfire when cold toyota 3y

Hey guys,

just recently bought a hiace. When cold it has a misfire in cylinder 2 at idle, it also has a slight misfire or hesitation when under load and is worse when it colds and slightly noticeable when it's warm. It has spark, fuel, no vacuum leaks and good compression. It doesn't have oil in the coolant or vice versa. I took it for a drive up the range and could only make it up half way as it started to buck pretty badly when under extreme load. Luckily for me I drove back down the mountain and drove home.

I have replaced the leads, dissy cap, rotor button, fuel filter, air filter, checked plugs(which are fine).

Is this fuel injected or carbureted?

Carby

How do you know it's #2?

When the engine is cold you can remove the lead from the spark plug and it doesn't change the way it runs. When the engine is warm it doesn't miss at idle. I changed the plugs around and leads and have isolated the cold misfire to cylinder 2

Well, that rules out plugs. Did it do this before changing the cap and wires?

Yeah I went for that drive before I replaced those said parts. I found one of the leads had high resistance, fuel filter still had Japanese writing all over it and was semi blocked, air filter was pure black, dissy cap and rotor button were quite suspect.

To Be honest I have been a bit offish to take it for the same drive due to it being 2hours away and it was more then frustrating the first time.

When you pull the wire on #2 did you verify spark on this lead during the misfire? If there's spark there, then I'd probably check the float bowl on the carb. Make sure the float level is adjusted correctly and verify the bowl is clear of water and/or debris.

Yeah there is definitely spark there. I'm a bit of a newbie when it comes to carbs. If it were the carb though shouldn't effect all cylinders?

Yes, but it's the under load part that points to possible float issues or contamination in the float bowl. It might be a 2 part problem.

Yeah I have thought from the state of the fuel filter that the carb would be the same. It's strange that when the engine is cold I can remove the lead on that cylinder and it stays the same(misfires) but when I do it when it's warm it changes.

The misfire under load is frequent but not rhythmic(is intermittent).

Yes, if it's a fuel issue, with a carb they should all be the same, but if it's a marginally lean issue, depending on manifold runners, atomization, etc, one cylinder may be affected slightly more than the others. Hard to say really, just grasping at straws. Do the plugs look white or tanish around the electrode area? Does #2 look any different (color wise) than the rest? Tim

All look the same, did notice when I was doing checks that the number two plug was wet.

FYI, We don't have carbed vans in the US. Everything here is fuel injected. I have however had some experience with other carbed vehicles. Had a similar problem on an old Corolla years ago. Turned out to be a bunch of junk in the carb. Yours is a little different though. This one ran good at idle (hot & cold). Tim

Assuming that's been run for over 100 miles, that looks good. Shouldn't be wet though. That indicates a possible spark issue. If you have an inductive timing light, put it on that wire while it's missing to verify a consistent spark. Tim

Lucky you guys. Well I'm going to do a leak down test asap just so I can rule out the valve train/head. Thanks for your advice, I'll give the carby a good clean the following weekend when I get some time off.

Cheers Matt

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Originally Posted by timsrv

Assuming that's been run for over 100 miles, that looks good. Shouldn't be wet though. That indicates a possible spark issue. If you have an inductive timing light, put it on that wire while it's missing to verify a consistent spark. Tim

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I put one of those spark testers inline when I was testing them. It looked like it had a consistent spark.

Good luck. Let us know what you find out. Tim

I was thinking that the coil could be the culprits but then again it should effect all cylinders

Yeah, I considered that briefly but discounted it. You never know though. Sometimes weak ignition parts can have more effect on some cylinders. Coils are cheap here (not sure about over there). Sometimes I'll just swap stuff to rule it out. Does your van have ignition points or does it have an igniter?