Rhythmic Surge

[SouthwestSpider]

With these cars you need to maintain a parts warehouse with an inventory of spares for everything.

[bradartigue]

With these cars you need to maintain a parts warehouse with an inventory of spares for everything.

No you don't. If people would replace parts with good quality parts and do so in a manner that isn't contradictory to the cars design they would last longer. A 20-30 year old electronic part should have failed by now. You shouldn't repair it, you should replace it with a new Bosch part. Same with suspension components and lots of engine parts. Per another thread on this forum, the guy who lets Meineke work on his car is going to have a crappy exhaust system. The guy who does the work himself or lets a competent mechanic who knows sports cars do it will have a system that will last and last.

How often does something you fix on these cars fail again and again?

Sadly most of the parts you can buy today aren't OEM, aren't very good quality, and don't last. And people buy this crap in DROVES instead of seeking out better quality and paying more for it. So people stop making good parts. Yes folks, it costs MONEY to own old car - and if you are doing one of these on the cheap then it will fail again and again and again.

[SouthwestSpider]

I like your passion Brad.
My comment was brought on by frustration. This car wants to run, I've always liked that. But in reality when you are working with a 30+ year old car, parts begin to fail. Rubber, metal and plastic fatigues; paint, leather and cloth wears. So to ensure it keeps running - it's necessary to have a lot of those little parts. If anything - I would love to have a nice inventory of all the little goodies on hand to immediately replace the worn and tired pieces instead of relying on Fedex, UPS and the USPS to bring my replacements. With an auto that has as much open road personality as the Fiat Spider, it's just not right to see it parked in the garage while waiting for another gasket, seal, mount or part. Since I began on the project of replacing the head gasket, I've come to realize that this machine has continued to run under circumstances that would have junked most vehicles. You should have seen the erosion in the water jackets on the head.
Speaking of such - should I re-torque the head bolts now that she's been running for a while? Even though it hasn't been out of the garage much farther that 50 miles accumulated - it has been in 100F+ heat.

[SouthwestSpider]

Finally - found the cause of the surge. I went back to square one - Brad's step by step which starts with the Brake Booster.
Booster was fine.

I shut off the engine:
Then I loosened the throttle stop screw until it wasn't touching the throttle plate, slackened the two retaining nuts for the cable until there was slack in the cable.
A) I noted the orientation of the Throttle Positioning Switch (TPS) on the intake.
B) I loosened the two screws that hold the TPS on the intake. I used a meter (pins 2 and 18) to reset the TPS according to the ohm reading. When this was finished I noticed that the TPS was in a completely new orientation.
C) The idle screw was snugged down.
D) The distributor retaining nut was loosened to allow adjustment of the timing.
I started the car.
Very slow idle (close to stall) this was part of the goal. No surge - also part of the goal.

SO - the problem was the TPS. I had not loosened the throttle stop screw enough before I set the TPS in the first evolution - so when I set the TPS, it wasn't set correctly at the base (or slowest) throttle setting - even though the ohm reading was right.
Reset idle once the vehicle had run through two fan cycles, used the idle screw to set the idle and all was good. Not perfect yet, but real close.

Didn't have a chance to run it in the really hot afternoon, (100F+) but it ran well in the garage after two fan cycles and that was when it would begin the surging before.

I would still like to know if it's okay to reseat the cylinder head bolts? AND - out of curiosity - if one of those bolts was overtightened, would I have to redo the entire head gasket or simply replace the bolt?

[azruss]

If you recently replaced the head gasket, then it has had time to moosh without going thru any heat cycles. sure wouldnt hurt to retorque. I wouldnt worry about the overtorqued bolt unless it was overtorqued a ton.

[courtenay]

"Has no one commented on much they enjoy the rhythmic surge?"

Ok, I'll bite... while I have no comment on the rhythmic surge, my wife certainly enjoys it...

[SouthwestSpider]

So many of my ex-Forces trade retired to Courtenay and Comox area - you have the same sense of humour that I remember. Which is a good thing.
I hope that my discovery of the cause of this issue helps anyone else who notes a similar sign and symptom.

Very important to loosen the throttle stop screw fully (not touching the throttle plate) - BEFORE adjusting the TPS.
OR
RTFI (Read the friggin' instructions). Thoroughly...

[bradartigue]

wow, works then? super.

retorque - i'v only ever retorqued if there was a problem, as in tiny seepage. but it doesn't hurt to do it. I'd also say that on a cold motor it probably wouldn't hurt if you had to replace a single bolt. But I would have another head gasket on hand...and bolt.

[SouthwestSpider]

Thanks Brad.
There will be a tweak needed I'm certain because just recently after a good long 40 mile run through the mountains when I returned to the garage I noticed that there is a falter. The engine runs wonderfully smooth, then falters for a beat and then smooth again and then falters. This occurs at idle, not while under load.

Whatcha think?

[bradartigue]

Thanks Brad.
There will be a tweak needed I'm certain because just recently after a good long 40 mile run through the mountains when I returned to the garage I noticed that there is a falter. The engine runs wonderfully smooth, then falters for a beat and then smooth again and then falters. This occurs at idle, not while under load.

Whatcha think?

I would adjust the timing slightly a degree or so (in one direction or the other, whichever works), it should get rid of the popping.

[narfire]

Glad your car is getting real close as I had a bit of a setback.

I think I do have a pooched or tempermental brake booster. Car still idles with a bit of a lump and noticed a couple of times stopping at a traffic light, the pedal was hard. Lots of pedal pressure to stop, while cruising(3000rpm+) and having to touch the brakes, no issues.
Going to have to check again I guess.
Chris

[SouthwestSpider]

Thanks Brad - I'll give that a try.

My brakes have worked very well fortunately once I replaced my center flex hose. When I replaced the hoses under the hood, I replaced the brake hoses also, I got the OEM hose (or what passes for that these days) and I used a better hose clamp on them to ensure they clamped a full 360 degrees at the fittings.