3.8 running rough. Timing issues or something else?

Topic: 3.8 running rough. Timing issues or something else? (Read 2086 times) previous topic - next topic

3.8 running rough. Timing issues or something else?

January 29, 2016, 08:01:56 PM

Hello all,
I'm having some rough running issues with my 1985 3.8L. Since I replaced the head gaskets, the engine constantly cuts out when cruising at 35-45 MPH. I'm also having problems with it stumbling/coughing when putting it in gear when cold.
I tried to put the distributor back in the same place it was when I took it out. But since then I've had to retard the timing a couple times. It seems to be a little better each time, but the distributor seems like it's retarded farther than I remembered.
I am running it without the smog pump, just in case that might have something to do with this, even though I'm not sure why it would.

Thanks in advance.

3.8 running rough. Timing issues or something else?

Reply #1 – February 04, 2016, 07:07:44 PM

it wouldn't be too hard to drop the dizzy in a tooth off with a lot of slack in the timing chain.

rotate crank the direction it spins when running
-continue around until you can land your timing pointer directly to the 0 on the harmonic balancer
-take off or peek under the dizzy cap

*knowing the dizzy spins the opposite direction as your crank with respect to clockwise and counter clockwise, ...
does your rotor button seem to be ahead of or before the #1 spark plug terminal?

to check for slack,
repeat process above and dial up to zero.
now going the opposite directly **VERY GENTLY** and using feel.. stop when you feel the crank seems a tad harder to turn.
now document on your harmonic how many degrees that is,,,

in my diy link below there are better steps to start from scratch ,, since your CFI, taking off the valve cover is easy so you can use that, the crank, the empty #1 spark plug hole and the dizzy to take er' from the top and redrop it.

the reason I say to check the slack is so that when you redrop it in, you can mentally and mechanically compensate for that when getting the right dizzy tooth to cam orientation correct. feel free to call if you need verbal talking through it,, 304 772 3411

3.8 running rough. Timing issues or something else?

Reply #2 – February 09, 2016, 05:29:51 PM

Hey guys,
I made sure it was timed correctly, I decided to hook the smog pump back up, and I checked all the vacuum lines. It runs 95% the way it did before the head gasket blew. I took it out for a long drive on Sunday and it performed great! I drove it again today and when I left the parking lot it coughed and sputtered for a little bit. After I got out on the road a little bit then it ran great again. I'm just discouraged because it's still acting up a little bit. I can't think of anything else that could be causing it. Any ideas?

3.8 running rough. Timing issues or something else?

Reply #3 – February 09, 2016, 07:51:48 PM

get your compression numbers posted up

3.8 running rough. Timing issues or something else?

Reply #4 – February 09, 2016, 09:39:27 PM

Any KOEO or KOER codes?

3.8 running rough. Timing issues or something else?

Reply #5 – February 10, 2016, 10:16:57 PM

Thanks for all the good suggestions guys. It's been a huge help. I think I've finally gotten the engine side of my problems taken care of.

3.8 running rough. Timing issues or something else?

Reply #6 – March 01, 2016, 01:08:08 AM

Hey guys, it looks like I haven't gotten all the problems fixed after all. I bought a code reader and it gave the codes for the O2 sensors not having a strong signal/running too lean. Since I didn't think to replace the O2 sensors when I had the heads off (blown head gasket), i figured the sensors were probably plugged with old burnt coolant. I replaced the sensors and ran it again. No codes came up this time, however I am still getting a rough idle when the engine is cold. It almost seems like it's misfiring every so often. When the engine warms up it runs great. I'm at a loss since it's not throwing any new codes. I've checked every vacuum line, every electrical connector, and made sure it was timed correctly. Any ideas?

Thanks again guys.