Rhythmic Surge

[narfire]

Sorry to hi-jack again but I'm thinking I might have a bum booster.I Set idle, then set tps idle was all over between 850 and 1300 rpm as car ran for about 5 minutes,(it was warm/hot to start with). I'll get some plastic and cap the booster line at the intake and see if that smooths things out. Plugs are good.
Those top two booster nuts are a pita.

[SouthwestSpider]

I have no problem with this interaction Narfire - I'm learning a lot in the process.

The way I interpret all of this is - when the FI is commanded (by the ECU) to draw air - it pulls the air through one source but that source (the intake hose) has two inputs. One from the AAR and the other from the AFM - correct?
So any other air sources can cause the FI to choke out (for lack of a better description) because the AFM and AAR regulate or measure the air flow because they are also controlled by the ECU. To confirm this I loosened the intake hose connector at the AFM and when I pushed the intake hose slightly off of the AFM the engine would shudder and stall, but when I restored the intake hose on the AFM - the engine would restore itself to a smoother idle.

I followed Brad's directions which include the brake booster (Thanks Brad) and the only thing I can find that causes this surge and/or the engine dying when fully warmed is an air leak.
I can only conclude that the reason the engine develops the surge at fully warmed idle or when I'm driving it - is because whereever the leak is - it is affected by the heat of the motor (We have 100F daytime temps here and that's when I was testing the car). I will replace the vacuum hoses at the AAR (less than a foot of hose) and see what happens.

[SouthwestSpider]

The other part of what I'm learning from Brad and Mark is that as I advance or retard the timing I can influence the idle speed. Based on that - if I adjust my timing to a point where I get both the 10 BTDC and the correct idle speed - then I can use the Idle Screw to adjust my idle.
Is that about right?

[narfire]

Did the brake booster check with a leak down tester and after putting one bar on the booster, it did not move after 10 minutes.
Used some meps gas to check for leaks, nothing found but did not check one place..... the shaft on the butterfly on the intake plenum. Have some starting fluid now.
Changing out the plugs as well.
I'm sure I have an air leak somewheres, check the bolts on the top/bottom of the plenum as well. have to be carefull as they strip easily.
What a great way to spend a holiday Monday

[narfire]

Update again.. Changed out the plugs.. binned the Bosch platinums and installed the NGK BPR6Egp's , gapped to 28 thou.. Car smoothed out, at least the idle stayed steady. Checked air leaks agian with starting fluid. Sprayed a small shot at the air cleaner for a base-line, then the shafts and other air / hose conections. Got a slight surge at the afm/plastic hose. Re-aligned the hose and clamp and tightened. sprayed and .....nothing
Now to re-check the tps when the engine cools a bit.

[SouthwestSpider]

Did the engine smooth out after changing the plugs and tightening the plenum?

[narfire]

Yeup, way smoother than what I had before.The tach on the timing light stayed steady, or more so than before. My neighbor came over to see what I was doing. He is/was an fiat mechanic Loooong time ago when he was in So-cal (double bump era). he said the Bosch plugs gave him grief and he now uses NGK's in everything.
I'm going to check the clearances eventually as well. Still has a lump in it.
With the idle now set, I could set the tps properly as well.
Chris

[SouthwestSpider]

Lucky you - a Fiat Mechanic next door!
My tps set up without a problem - if you continue to have problems try another meter.
I think I might have a leak around my AAR. I'll check that tonight after work. I was told by a mechanic once that certain makes work best with certain spark plugs. He advised that it wasn't always what we would perceive as "top of the line" that really made an engine run the best. His simple recommendation was that I should purchase the basic plug for that specific engine (whatever was recommended by the manufacturer) and see how it ran. Thus far - he hasn't been wrong. I used the NGK on the Spider and so far (touch wood) it's been fine. It's an air leak issue I believe - it gets so much air when it demands it that it chokes out.
The nice part is that with experience like Mark's and Brad's manual and guides, as well as confirmation by others who are dealing with these things, when I get stuck - I just go back to square one and start again.

BTW - I used to live in Sidney BC.

[bradartigue]

Verify his advice, most FIAT dealer mechanics were ill-trained at best. Did as much to ruin the brand as FIAT the company did.

However, he is right about Bosch plugs, especially platinum plugs. They did all kinds of wacky things in the TC head. No idea why, but if you wanted to foul out a few plugs in quick order you'd buy Bosch. Marellis would never foul out, or NGKs. Golden Lodge also worked great but you can't buy them any longer (well, for $16 each you can). Funny thing is I wouldn't run any of my cars on anything but Bosch parts EXCEPT for those plugs on FIAT motors.

Glad to see it is working out.

[narfire]

BTW - I used to live in Sidney BC.

Another jewel on the island.. If we were not in Naramata, we'd be on southern Vancouver Island somewheres.

I found the starting fluid really helped, just a micro shot made the engine speed up enough to notice any air leak/suction issues.
The fiat guy next door is a guru with the old carbs found on the english cars. These FI spiders are a bit new for him, he was the old 500-600 and Lancia's. However he has set up the IDF's in the past and evidently has a few parts for the things.
Chris

[SouthwestSpider]

Brad, the only thing I haven't been able to do is the o ring on the idle screw. But I've sealed all the other air sources used propane and had no indication of a leak. The engine will run almost idling upward, then it will drop down in a falter, then start back up again, then drop - it does this consistently when its hot. My temperature gauge is way over 190 - maybe 210 and if I sit at idle for a while it rolls up to 230 (these are guesses since the gauge isn't marked clearly). The surge goes away when I'm under load, unless I let off on the gas and then it falters. As long as I have the engine under load it is fine. I still don't get the idle down much below 1000.
I've also noticed that my fuel consumption is outrageous. I've not driven it more than 50 miles, it's been idling for the most part - yet it has gone through about a half tank of gas.

[narfire]

A far fetched guess...how old is the fuel filter? pressure regulator? can you put a fuel pressure gauge on the cold start line and see what or if the pressure is bouncing around. Perhaps check the pressure before swapping stuff out though.

Previous posts I thought I had a bum booster. before mucking about for two hours, checked and it was fine.

[SouthwestSpider]

Good question Chris. The fuel filter and fuel pump are new. I don't know about the regulator.

[So Cal Mark]

have you checked the resistance of the temp sender at various temps? Also, connect a voltmeter to the O2 sensor connection and see what the voltage is, that will tell you if you're rich,lean or inbetween

[bradartigue]

Brad, the only thing I haven't been able to do is the o ring on the idle screw. But I've sealed all the other air sources used propane and had no indication of a leak. The engine will run almost idling upward, then it will drop down in a falter, then start back up again, then drop - it does this consistently when its hot. My temperature gauge is way over 190 - maybe 210 and if I sit at idle for a while it rolls up to 230 (these are guesses since the gauge isn't marked clearly). The surge goes away when I'm under load, unless I let off on the gas and then it falters. As long as I have the engine under load it is fine. I still don't get the idle down much below 1000.
I've also noticed that my fuel consumption is outrageous. I've not driven it more than 50 miles, it's been idling for the most part - yet it has gone through about a half tank of gas.

One thing at a time, change out the o-ring. A $0.50 solution. In the case of my 82, which did the exact thing you are describing, this fixed it all. No kidding. That o-ring is probably hard as a rock if it is even there.

Then start fooling with other things. If it isn't the o-ring then at least you have a new one. Move along to testing every single fuel injection component, electrical and otherwise. It isn't hard to do and you may find more problems than you know with old sensors or seals.

If you are idling at 1000 then you are burning a lot of fuel. Idle is not an efficient mode of operation.