Engine shakes after replacing head gasket but no consistent codes

Hi All,

Replaced a head gasket on a gen 3 with 240k miles on it. Before reassembly I checked the head and block per the Toyota manual and they've better than required tolerance. Completely cleaned out the EGR system and intake with a combination of purple power and a 0 degree pressure washer. I did release the timing chain tensioner and visually verified that the hook was released and the tensioner arm was engaged.

Engine shakes on start up but at higher RPM (not driving it, just pressing the gas) shake goes away at about 1500 RPM and above. Shake does not go away if left running at lower RPM.

Code reader initially reported a misfire on cylinder 1, started testing that by swapping plugs/coils/injectors, code went away but the shake didn't. I think the initial misfire on cylinder 1 was related to the initial start with a drained fuel system, but am not sure. It's hard to troubleshoot without codes.

I need a sanity check please.
If the timing was off, there should be misfire codes or at least some code being thrown. Is that correct?
If it were you, what would your next step be? I was thinking of getting techstream operational and trying to pull codes with that rather than my little handheld reader. Is that a reasonable thing to do or is there something else I should try first?

Thanks

 

Thank you for the reply.

Sorry, I left out some information. This engine was running fine prior to being reassembled. Very slight shudder on start up that went away in a few seconds, classic early head gasket failure symptoms. No coolant in oil that I could identify. Unless the piston got bent during the reassembly process, which I don't think it did, I don't think it's a piston or I would think it would have been running poorly before the head job as well. That's what's so puzzling about this to me. I took an engine that was running well, replaced the head gasket, and now it's running horribly. I clearly did something wrong, but without codes it's hard to tell what. I find it especially puzzling that it runs fine at higher rpms but shudders violently at lower rpms.

 

Thank you for the reply.

I did find physical signs on the old head gasket. Small penetration point. Haven't been on here long enough to post links so can't show the photos.

Will check the EGR and the fuel pressure. Thanks. It occurred to me that the EGR cooler was completely clogged. Compressed air wouldn't go through it. Neither would water, oven cleaner or anything else, left it soaking for days and nothing passed through. Pressure washed it out and then it took about a minute before any water got through. If nothing could get through the EGR cooler that means this vehicle was running with a blanked off EGR for an unknown amount of time. Since the test to see if the EGR is causing a problem is to blank off the EGR, I have absolutely no idea if the EGR valve is working or even worked when I drove the car home.

Bit long but here's everything I know: I purchased this car used from a nice fellow who had it as his daily driver for a weekly 300 mile commute. He told me that he changed the coils and plugs and then stopped troubleshooting. He parked the vehicle and purchased another Prius about a week after noticing the problem and being unable to correct it with new coils and plugs. He concluded (correctly based on what I found) that it was the head gasket and didn't feel he had the time to take on that job. Car would shudder intermittently for a few seconds on start and then run normally. He pulled codes and found a misfire on cylinder 2. That was the only symptom. I started the vehicle and drove it a few miles to get it home. My observations matched his report: the car shuddered very slightly on start up and then ran smooth. A code was thrown for a misfire on cylinder 2. On getting home I turned the vehicle off and checked the oil again to see if there was any coolant present in the oil. There was not. I then started the tear down. That was about 2 weeks ago. Other required tools and parts finally arrived and I've been working on it as time allows since. Vehicle has 240k miles on it. Previous owner has records of regular oil changes and other maintenance going back about 7 years, car appears to have been well maintained. He was the second owner.

I replaced the head gasket with a new felpro one that a lot of folks seem to use (the blue one.) Followed the Toyota service manual for torque specs and head/block tolerances. Also cleaned the EGR system, replaced the PCV valve, replaced various other gaskets that were exposed, triple checked timing and that tensioner was released, and then finished reassembly. Added oil and coolant, let the car sit overnight and checked under it for any leaks. No leaks and everything seemed sealed up well so I started it. It shuddered. Got a cylinder 1 misfire code. Tried to troubleshoot but that code didn't persist past the first start/shut down cycle so I think it was related to the fuel system being partially drained. No other codes are being thrown, but shaking persists.