All cylinders misfiring after head gasket replacement

Help me solve the mystery. High mileage 255k ran literally perfectly but very slight head gasket leak causing coolant system to pressurize and burp coolant into overflow reservoir so I replaced the head gasket. Never overheated or even run hot. No oil in coolant and no coolant in oil, put it back together and it started right up but won't idle below 1200 RPM. It just dies if you take your foot off throttle. If you press lightly it will run fairly smooth above 1500 rpm, no codes even show but if you nurse it, keeping it running 600-1200rpm it will throw all cylinder misfiring P0300,1,2,3,4 plus P0171 too lean. Replaced coils, injectors but not plugs yet. Any ideas?

 

Did you verify the exhaust cams are timed correctly?

 

Vacuum leak will cause aĺ of the above

 

OPs profile says 2.7, so likely wrong screenshot

OP, confirm engine details please

 

Check the 90* vacuum hose on the back driver side of the intake manifold. I have missed this one when putting mine back together in the past and it definitely caused some issues

 

Oops I missed that, good catch.

 

Wow-you guys are awesome. 2.7 2TR-FE engine. At work right now but will check vac lines tonight. I was super paranoid about the cam timing but will pull the cover and check that if the vac line is correct. Fingers crossed that I made a rookie mistake as there is a lot to reconnect and reassemble... Will update tonight. Thank you all!

 

Verify that TDC on #1 piston is TDC on the harmonic balancer, they are known to slip.

 

to Glamisman: I would need to remove the entire timing chain cover to check that, correct? I believe I can verify the timing chains by going to TDC and verifying both camshaft marks? When reassemblying, I was very careful to align the crankshaft and camshaft marks to the yellow and orange marks on the chain. The other chains were not touched. Would the engine run just fine above 1200 rpm if the timing was off?

 

As to your description on checking for TDC yes. Take the plugs out so that it turns over by hand easier. Turn the motor over slowly with a long wooden dowel or screwdriver in the sparkplug hole and look at the timing mark on the harmonic balancer. Lets hope that it is this simple. As to the running well above 1200 rpm, the answer is yes, this is what variable valve timing is all about, advancing or retarding the cam at certain rpms for greater power and a cleaner burn.

 

Thank you all. The problem turned out to be the vacuum line against the firewall on the intake manifold. It had come off during the install and it is fairly difficult to verify whether or not it is on. First we verified that hte timing was spot on then took the manifold off, put the vac line on, reassembled and all problems went away. Except that it has a somewhat difficult warm start. Cold it fires immediately but you have to crank it about 3 times before it will fire when warm. I'm going through the forums today to see it I can find somebody that has had the problem. Seems like it might have something to do with not enough fuel pressure? Anyway, thank you all, I really appreciate it!