Hi Guys

Ever since my '94 940s headgasket replacement, I get what seems like a miss fire at start.

It will miss for 5 to 30 seconds then run and idle great. Revving the engine seems to clear it out. I looked at the properly gapped plugs and they seemed OK. (But that was after a longer run...next step is to check them right after it misses.)

BTW I replaced the plugs (platinum), dizzy cap & rotor when I did the headgasket. Wires look good (Volvo-brand).


EDIT: This is a '90 engine with the distributor on the left-front of the engine, running Rex-Regina engine managment.

 

Did it overheat very bad before you blew the gasket?

If so could also be a possibility that the coolant temp sensor is off/bad.

 

Thanks Tech,

No, the engine didn't overheat at all. The HG was seeping coolant between cylinders 1 & 2.

But, I changed both the head sensors (ECU temp & gauge temp) while I had it out.

I'm thinking now that perhaps I messed up an injector cleaning out the intake manifold while the head was off.

 

Hey Carbuff, I have just a little seepage between cyl 3 and 4. Just a few drops when I park it. My first question is, Is a head gasket job hard on the 940 and also with such a little bit of seepage, I was thinking about some kind of stop leak till it gets worse. The car runs so good otherwise I'm afraid I will wind up with a problem simular to yours. Whatta ya think?

 

Best thing to do is replace the headgasket ASAP. That is to be safe.

Is it Turbo or Non-turbo?



Carbuff are you sure you have no vaccum leaks?
Maybe the idle motor is slacking.
Maybe an injector is a little clogged.

 

The headgasket was not that difficult, just time-consuming (when you are working 12 hour days). I just loosened the intake and exhaust manifolds and bungeed them to the sides.

Since having the start/miss problem I have cleaned the throttle body and IAC, checked plugs (they are new platinums) and replaced the distributor cap & rotor. There is no fuel smell at the Fuel Pressure Regulator and vacuum lines are tight. Sprayed the intake with cleaner looking for vacuum leaks. All had no effect (well, the plugs smoothed it out a bit but the miss was still there).


++++++++

If the engine is turned off then back on immediately there is no miss. If the engine is off for say an hour (temp gauge 1/4 way up on the scale) or overnight, the miss is there. That's why I'm thinking injectors now. (Dirt causing poor spray pattern or flooding in one cylinder.)

More to come.

 

Also try to monitor fuel pressure and make sure it isn't bleeding back overnight.