beenlookin

Fellow SC'ers,

I've been posting on someone elses topic now in reference to this. Completed a head gasket replacement. After complete, the car has a steady misfire when stopped in Drive and at a constant speed on the highway (regardless of RPM). It sounds like it's the same cylinder each time it stumbles.

For reference, plugs, wires, cap and rotor have been replaced. During the head gasket replacement the following items were replaced as well:

-Fuel pump
-Serpentine belt
-Timing Belt
-thermostat
-coolant hoses upper/lower
-valve cover gaskets

The timing has been checked and is spot on. ignition components mentioned above are new. Snap On Modis diagnostic used, not throwing any codes - no check engine light. The issue was non existent before the head gasket replacement.

Any help is greatly appreciated for myself and the others on the board that hare having similar issues.

THANK YOU ALL in advance - if you need more info lmk!

2jznosht

any codes? How did you initially hurt the motor?

beenlookin

Not a single code.

CAUSE: The car was leaking coolant (i wasn't aware of) and overheated. I filled the coolant and as it progressed noticed i saw no leaks and came the conclusion that the head gasket (HG) went bad.
When open, it was noticeable that the area in which the HG was leaking was into the rear cylinder. The valves were discolored and the plug fouled.
My mechanic (good friend) and I spent 2 weeks repairing it precisely to the OEM specs.

The issue was non existent before the repair. I can best describe it as a misfire and hesitation or stumble. At steady speeds and at idle, the misfire is strong and loud enough to be heard and felt while in the cabin - seems like clockwork, the same cylinder.

Definitely sounds ignition related but everything is new. I did however see some corrosion on the cap and rotor (maybe from sitting out for so long), so i did RE purchase those items and am waiting for them to come in. If that doesnt work, i just hate to keep guessing or tear it open again for nothing.

Any help is greatly greatly appreciated.



FYI the car is a 92 bought from the original owner with just under 90k miles. It was mint up until this happened

beenlookin

Anyone!?!

If it helps at all, the hesitation is non existent while the motor is cool (at least I do not feel it). It only happens after it is at full operating temperature and close to it.

2jznosht

valve lash, spark arcing, vacuum leak...did you get the head machined prior to putting it back on?

beenlookin

Head is straight, all vacuum lines are in (no problem with a rough or high idle), and just replaced the spark plugs (again) with Iridium Denso's... NOTHING.

I cannot figure this out. The valves are definitely okay. I was reading about the potential of a TPS problem but I'm unsure about it.

Anyone know what the accurate reading is for the TPS at idle? I want to hook it up and take a look.

spitfire7

My car does the same thing. All of a sudden it cut off and didnt start again. After it cooled off it started rite up. I wonder if it is a sensor.

beenlookin

Yeah man, i'm gettin real tired of dumping money and time into this thing. I thought it may be the coolant temp sensor but my friend tells me that it would be the opposite.

What you may want to look into if you're having problems at cold temps is the MAF and ecu. The car runs off its memory when cold. Once warmed up, it runs off the MAF and the comp uses the readings from the 02 sensors to make adjustments.

These could be the issues for you and SupraDrmr.... i'll link him to this, hope it helps you guys.