What do you think is happenning...

[SunlitComet]

You start your vehicle and go driving when under almost full throttle the engine start to ping under load and misfires on two cylinders. Now it is continuously misfiring on two cylinders and will ping when you raise the rpm.

You pull the plugs and find nothing unusual on them. You stick a boroscope down a cylinder and can clearly see the cross hatching on the cylinder wall a piston that looks a little dirty but no build up same with the exhuast valve.

You just installed A CAI unit 20 miles ago and were out putting it through it paces.

 

[19Yukon97]

mine pings when i get on it... but its just watery gas...

 

[99Yuk]

Bent valves?

 

[raptorforme93]

What is cross hatching? The ping isnt back firing is it? Our old inboard boat with a 350used to back fire when the dizzy was messed up and it was a loud pinging sound

 

[SunlitComet]

no backfiring at all the cam retard was withing specs on all the data dumps from -0.3 to +.9

A 7 minute drive showed 1801 misfires on cylinder #4 and 3966 on cylinder #6.

Injecter bank 1 average was 388.7ms, bank 2 was 3.5ms

At one point the knock retard was over 7 degrees and the puter backed off the advance as expected.

It sure chugs real hard when in gear so it does not seem like I lost compression suddenly. I still need to get my hands on a good compression gauge to verify each cylinder.

It seems like two adjacent injectors suddenly starts jamming. and suddenly run very lean with total misfires at idle and lean on load causing the pinging.

I will eventually boroscope all the cylinders as well.



Raptor,

When a cylinder is overhauled or repaired the surface of it's walls are honed with abrasive stones to produce a rough surface that will help wear the piston rings in. This roughing up of the surface is known as "cross-hatching". A cylinder wall that has been properly "cross hatched" has a series of minute peaks and valleys cut into its surface. The face or portion of the piston ring that interfaces with the cross hatched cylinder wall is tapered to allow only a small portion of the ring to contact the honed cylinder wall. When the engine is operated, the tapered portion of the face of the piston ring rubs against the coarse surface of the cylinder wall causing wear on both objects. At the point where the top of the peaks produced by the honing operation become smooth and the tapered portion of the piston ring wears flat break in has occurred.

---------- Post added at 08:29 PM ---------- Previous post was at 08:23 PM ----------

Something else to add I had a timing light on both cylinders monitoring the firing of the two plug and while doing so they seemed to firing evenly but occasionally started to have a rapid multiple fire effect. I have not looked at the others the same way yet. Have not been able to review the tech data on puter ignition control yet. So i am not sure if the puter is working over time to fire them.

 

[sumo]

Are they coils? Can you swap them around? Id also swap spark plugs see if they follow to what ever they were swapped. If nothing changes your probably looking at bent valves

 

[SunlitComet]

I use scan xl Pro for my vehicle data if someone else here uses it and wants to seem my log files I will post them. Trial version will play them back as well.

 

[h0tr0d]

I'm not an expert, but that sounds an awful lot like some clogged injectors.

 

[SunlitComet]

I am so hoping that's what it is although I would not have suspected the the new spider would have failed in a few hundred miles especially two injectors at the exact same time. Unfortunately I don't have all the diagnostic tools I need to a function test of injectors. So testing may have to wait till next month when I can get them or let a shop do it which gives me the chills. The injection break-out box is only $100 but the injector firing initiator is $250. The Midas shop I had diagnose it last time charged $134 and suggested I spend $500 to replace two different injectors with the original type and claimed something wrong with my MAF which went away after the injection assembly was replaced. And the overfilled my oil during a change. And pull the cylinder head as well.

I was supposed to have just some steering alignment issue left over to deal with and I would be back on the road for work again after two years with no personal vehicle. I was kind of hoping to start a new exhaust system next month from headers to tail and work on a BBtune too. Stalled yet again.

At any rate the improvement I had with the new intake however brief has me wanting more.

 

[SunlitComet]

Swapped a few plugs to no avail. Still can not get my hands on a compression or fuel pressure gauge. Maybe in a few weeks. However there are a few things to add. No signsof cross fluid contamination yet, no bubbles in the cooling system tanks. the engine won't even get as hot as it use to, and an infrared gun reading shows that 4 and 6 exhaust manifolds ports are significantly colder then 2 or 8. The heat that is registering is probably from #2 passing by it. The maf reading indicates that it is flowing air for normal idle and it still bogs down ******* the two cylinders when under load so it would seem to be that the valves and maybe piston rings are intact. Still knocks under load but misses those two cylinders all the time can't get a smell of fuel residue on any plug so I can't do a comparison that way. Spark was verified.
Anything I have missed? It really sucks not having the money to get some more diagnosis tools. The only thing I had left to fix before this was a steering problem. Then borrow my travel money and get back to work. Now I may not even see that money for a while for other reasons.

---------- Post added at 02:11 AM ---------- Previous post was at 02:09 AM ----------

Also tried adding two more gallons of gas to the tank thinking I may have had some freak octane problem. 20 minutes of circulating new fuel did nothing.