Running VERY Rough After Head Gasket Job

[vcp]

Thanks guys. Adjusted the dis, although it didn't seem to respond much even when I moved it all the way to the other side. (Didn't leave it there. Moved it maybe 1/4 inch from where it was before.) Suspect it might be a little fast now, but here's what it sounds like: http://youtu.be/vY_OB20nP5A

Heading down the highway in an hour so wish me luck! (Taking the 12mm with me )

[larry mcgrath]

vcp you need to look fsm and go through the prosedure to adjust the valves. these are adjusted way too loose they need to be set properly, while the engine is at operating temp. this contition will cause a decrease in power . Larry I sholud have asked first is this your car in the viedo ,this car needs the valves set.

[dlb]

no, you do not need a kit to work on the dizzy. IIRC, all you need is a phillips screw driver. if you're able to drive the car here, i could also show you how to set the timing but that's a pretty big drive for a car that's bucking and acting up.

[vcp]

Made the drive safely!

Running rougher since I manually changed the timing (before leaving) but no big 'pops'.

A new friend though - an intermittent squeal reminiscent of a water pump problem decades ago with another car. Grabbed a new water pump online in case. (I read your posts about them Petros.) Hoping I'm getting closer to the end of this particular adventure rather than just opening up new problems. Didn't intend to start a complete rebuild

[vcp]

Larry - forgot to mention - my mechanic went back in and adjusted all the valves as the 2nd part of the job, so they should be ok.

[vcp]

Well, after almost a month of searching, replacing parts, and gracious help from so many (Thanks!!), the problem has been solved.

But to make it interesting, I'm gonna run a bit of a contest on what the problem turned out to be

I've placed ten possible causes of the problem below, with one of them being the correct answer (in this case). Which one do you think it was?

Place your bets and in one week I'll post the correct answer. (Members posting the correct answer will win a No-Expense Paid One-Day Luxury Vacation to your Basement, Man Cave, or Garage. Your choice.)

1. distributor indexed wrong on cam

2. choke not working properly

3. timing belt on wrong

4. faulty spark plug

5. faulty mechanical advance on the distributor

6. bad timing

7. vacuum hose leak

8. fuel filter clogged

9. leaky fuel line

10. valves needed adjusting

[irowiki]

Well, my first guess would actually be a plugged fuel filter, because after reading the thread again... that is kinda what my 87 did.

After that, bad timing, which is the same thing as the timing belt being wrong or the distributor being indexed wrong on the cam and related to a faulty mechanical advance.

Faulty plugs or wires would be my last guess.

[dlb]

i have the unfair advantage of having seen the car but i'm going to get in on this anyway and go with either #9 - leaky fuel line or #2 - choke not working properly, due to the gas smell i noticed.

however, the mechanical advance on the dizzy is definitely jammed so even though the car may be running better now i would still suggest replacing it. you'll likely notice a big difference in both fuel economy and performance.

1 week! i can't stand the wait.

[Petros]

I would guess #1 and #5, it would be easy to get the index wrong if the mech advance was stuck in one position. It would also account for why the timing mark was so far off.

[xirdneh]

i'll go with #4

[vcp]

OK, time to post the result.

But first I gotta say I was very fortunate to hook up with dbl during this adventure and he said something that really rang true.

Said he loves owning these old Tercels and helping folks out with them because of the people he meets. They just seem to be different from most mainstream folks. Helpful, friendlier. More down to earth. Not so concerned about owning the latest-greatest gadget, more tuned into long-term quality, more respectful of the environment.

Thought about it and realized that was my experience, too.

So hats off to y'all! You made this adventure a fun one. I learned a lot and met some great folks. Including 'B', the retired mechanic/farmer in the Comox Valley on Vancouver Island who sussed out the problem.

Fuel filter? Nope. Replaced it, no difference.

Distributor? Nope. Mechanical advance and vacuum advance were both faulty so replaced the dissy, but problem remained.

Timing belt was on correctly.

Valves were fine.

No major vacuum leaks found. (Replaced a couple aging hoses but no difference.)

No fuel line leak.

Choke working fine.

All the spark plug wires firing perfectly ...

But when we kept pulling the individual plug wires while it was idling, we noticed something subtle but different about cylinder 4.

So we pulled the plug. And there was absolutely no gap. At some point during head gasket job the head must have been rested on that plug even for an instant and it closed the gap.

So xirdneh, you nailed it! Enjoy your luxury vacation on me. (Check is in the mail )

And Petros, you were right - slappin' our heads over something so simple we missed.

Dbl - you were incredible. Invited me to your house and tried rebuilding the dissy. And we'd never even met before.

And to everyone else who joined in on this mystery - thanks!

And a special thanks to 'B' who methodically and painstakingly went through every possible scenario until he solved the mystery, even though all he had intended to do was sell me used distributor.

Great car. Great folks.

[Petros]

The "power drop test" is a good and simple one: pull each plug wire in turn while it is idling and see how much the speed drops off. Each should drop off the same amount of course, if no change, or little change, the trouble is with that cylinder. A quick and easy test that should have been done early on to help isloate a misfire. BTW, you usually can tell if one cylinder is not running by the way it runs, you never gave symptoms of running on 3 cylinders, only it was running "rough", not really the same thing. So you gave us a bum steer.

I have an interesting story about this test, that serves as a cautionary tale: I bought one Tercel4wd sight unseen for only $180, the guy even had it delivered to my house. He said it ran rough and needed a carb rebuild, along with a few other items to be fixed (including a trashed rear diff, but that is another story). Needless to say it was in far worse shape than he said it was (perhaps he did not know all of it), and it was issues you can not tell from pictures (at least the body was decent).

It ran like crap and I found misreported vac lines all over, some just hanging, some lines damaged. all in all I found 9 vacuum leaks, but it was still running weak and acting like it was not running on all cylinders. I did the power drop test and found the rear two cylinders were not producing any power at all, no speed change when I pull either #3 or 4 spark plug wires. my first thought was the head gasket was blown between the #3 and 4 cylinders (though that is very rare, it usually blows between #1 and 2 where is is much hotter). It had a newer radiator which usually is a sign that it was overheated, so I figured the gasket was likely toast anyway. I started to prepare to remove the head, but than thought I should double check the head gasket with a compression test. I did not want to take the time since it was very likely the head gasket, but figured it was good to always verify my diagnoses if possible, particularly for such a big job as replacing the head gasket.

So I did both a dry and "wet" (with oil) compression test. All the compression was almost identical and good, on all cylinders (WTF????). Than I was completely stumped. I could not think of a thing that would make it run on only the front two cylinders. I even verified the spark and the spark plugs, swapped wires and plugs around, no change. I scratch my head for a while, it was like the intake manifold was blocked off. than I noticed the brake power booster vac line was on that half of the manifold. Perhaps the booster was shot, I followed the hose and found it was completely unplugged from the booster, hanging over the nipple in such a way it was not noticeable that it was unplugged. I plugged it in and BEHOLD, power restored! Ran great, the easiest head gasket I ever did! the booster line allowed so much air into that side of the intake manifold it leaned the fuel/air mixture so much it acted like it was generated no power at all. Glad I double checked it. I never did rebuild the carb, just sprayed it with carb cleaner while it was installed. Never needed a rebuilt carb at all, it was just poorly maintained.

It just goes to show that you should ALWAYS DIAGNOSE THE PROBLEM BEFORE YOU TRY AND FIX IT!!!!

[dlb]

wow, crazy. good on you for figuring it out! how's the car running now, all well and back to normal?

and you're very welcome, vcp. it was a pleasure!

[vcp]

Running great, dbl! Smooth as silk. Thanks.

re "you gave us a bum steer"
Jeez, sorry you feel that way Petros. I certainly shared every single thing I could think of with my very limited experience. Even posted video as well as a recording of the car idling. And in my defence, 4 qualified mechanics had the car in their hands and only the last one was able to identify that spark plug as the core problem, and that was only after having enough time to methodically eliminate a bunch of other possible causes. The timing problem at idle and lower speeds was very subtle. (I don't understand why - the spark plug gap looked completely closed.) Only at higher speeds did it become pronounced. And it was intermittent - not continual. So we did our best. Thanks for your help.

[Petros]

perhaps it was still sparking in the reduced gap enough to ignite the fuel irregularly. I suppose that would be understandable, if was running on three cylinders it should be obvious to any mechanic, and most non-mechanics as well. but if it was igniting the fuel mixture some of the time somehow, than I would understand how it would be hard to find. Intermittent problems are the worst to isolate, and the bane of all repair shops. I guess you were lucky to find it with a power drop test than too.