5.4 2v with lightning conv. running 12psi, stock lightning intake, and custom exsaust with high flow cats, shoty headers. I have about 12,000 mi on this (mostly towing) with no problems. was comming home from trip up north (live in michigan). Crusing 55-60 mph towing my 16' trailer like always. Then bam engine started running like when a cop pukes (Im sure any 5.4 2v owners know where im comming from)but this time no check engine light. Long story short limped home and still no check engine light. pulled code for iat high. Pulled iat sensor it was melted
did compression check and found no compression on 2,6,4,8. motor is now tor down and by the way those pluges were melted in those cylinders.
I want feed back on my rebuilt
1: what went wrong
2: Do I stay stock heads or ported (Remember this is towing rig)
3: Do I need intercooler upgrades.
Here is a theory that I have about your issue. Well first thing, you mentioned that the IAT was melted. This to me would suggest that you were running extremely high Intake air temps which could lead to an extremely lean fuel mixture burning some valves. You said you have the engine torn down? How do the pistons, rings look? do you have a wide band oxygen sensor to monitor air fuel ratio? If so, what are normal values? My boosted 4.9L runs some high intake temps, probably in the 170ish temps and I have never melted an IAT
Engine tuner guy says that I had some kind of intercooler failer. I the trailer that I normaly tow is almost 2 times as big (with no issues). He also busted my balls because he told me to get gages and I may or may not have seen this comming before I had engine damage. Speaking of engine damage, the pistons and cylinders look like they have 100mi on them (lucky me).
He's right about the gauges. A gauge to monitor A/F ratio, plus a IAT or EGT gauge could have prevented this. What kind of tune were you running? Was it custom tuned on a dyno? How did he determine intercooler failure?
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Did you hear any pinging? Based on what you've said, I'm guessing lean mixture causing the valves to burn (done this myself), but I just can't figure how the IAT melted (I just can't see the intake charge temperature being high enough at 12 psi to do that).
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Do it right, do it once (perhaps twice if you try to run more than 14psi on stock rods, or if you don't read the instructions properly).
I'm not sure how one could diagnose an intercooler failure as the reason for burnt valves and melted sensors - for intercoolers can only fail one of two ways - something large gets sucked in and plugs it up, in which case your engine would receive no or extremely limited airflow and that you'd notice long before the valves burned up. The other way is they leak - usually by splitting like a banana - and that you'd notice also as it would make an incredibly loud howling sound that loosely follows engine RPM (but closely follows boost level of course).
An intercooler is nothing more than fancy radiator that cools the intake air rather than engine coolant.
What probably happened is you briefly lost your fuel pressure.... and went ridiculously lean very quickly... and the fact that you limped home tells me whatever stopped working, is working again - I would check out the electrical to the fuel pump to make sure this can't happen again.
When I disassembeled the motor I found nothing abnormal (except cracked valve seats on 6,4). The sparkplugs were black, and 4 were melted (2,6,4,8). All fluid levels were normal.
Would the fuel pump throw a code?
Have new heads just waiting for gasket and bolt kit.
Should I go colder than stock on the thermostat?
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Burnt valves and melted iat
and I may or may not have seen this comming before I had engine damage. Speaking of engine damage, the pistons and cylinders look like they have 100mi on them
(lucky me).
