7MGTE running rough after comp. test

[BLACKCAT]

Did a comp. test on a warm engine & now its running rough after start up & lacks power.

The ignition & fuel system was disconnected during the process.

All the cylinders were between 135-140 psi.

No excess coolant pressure.


Put in new spark plugs, re-checked timing (10 degrees BTDC) but still have the same problem.


Is it possible that the cylinder walls may have been damaged during the cranking?

 

[Nick M]

It is possible (very) that a plug gap or three was made smaller upon reinstallation.

 

[BLACKCAT]

Will remove the NGK BKR6E plugs & check the gaps (set at 0.8mm), tightened with torque wrench to 18 lb/ft.

Also noticed that the exhaust note, at idle, is now pulsing a lot more between high & low pressure where before it had a more even note.

 

[suprarx7nut]

Cylinder wall damage? No.

Sounds like maybe a loose or unplugged connection? Have you checked all the connectors and plug wires? With no codes and no other changes it seems likely you've got a misfire because something isn't plugged in (spark plug wire?).

 

[3p141592654]

or perhaps the plug wiring was connected wrong. Easy to do since any wire will plug into any coil.

 

[BLACKCAT]

Checked the spark plugs & they are all at 0.8mm.

All the wiring/leads are fine even tried my spare coil pack but still the same issue.

Did the upside down water bottle trick & sure enough it started blowing small bubbles when really hot.

Took it for a spin around the block & it shuddered & shook, even struggled to get to 60km/h on a flat road.

The ******* 7M is the only engine I know of that can blow a head gasket while you are doing a compression test.

 

[suprarx7nut]

Wait, how do you know it's a BHG? You'd have seen that in the compression test pretty clearly. If it blew somehow during the test it was pretty screwed from the beginning.

What's the bottle trick? Color me confused.

 

[BLACKCAT]

The bottle trick is where you cut off about 3 cm from the bottom of a 1.25l soft drink bottle, put it upside down over the radiator opening, seal it with some tape & run the engine.
As the coolant heats up it expands & the level rises.
If there are any constant bubbles when the engine reaches normal operating temperature than you know there is a leaking gasket or a crack in the head or block.

Trust me I know the signs of a bhg as I have had 3 7M's & have had to replace the gasket on each one.
This one lasted me 5 years of hard driving so I am not surprised.

 

[Nick M]

The ******* 7M is the only engine I know of that can blow a head gasket while you are doing a compression test.

Well, actually it can't.