Troubleshooting - is it ignition or carbs - 2.2T/S motor?

[keitho64]

I am trying to troubleshoot the performance of my car below 3,000 rpm. Above 3,000 everything is fine and it will pull strong to 6,800-7,000 without fail. This is a 2.2T case with modified heads and I am assuming S cams but have no idea of the pistons. It is equipped with Weber 40mm carburetors that now have 65 idle jets, 130 mains, 180 air correctors, f1 emulsion tubes and 32mm venturis. The ignition consists of a Marelli distributor with points (.017 gap), Accel coil and a permatune module. The initial timing is set at the Z1 mark at 1,000 rpm but I am not 100% sure of the full advance or when it comes in. The spark plugs are Bosch W5DC gapped at .040. The wires, cap and rotor are all brand new.

The problem is the car will pop out the top of the carbs at steady speed cruising below 3,000 yet if I go above 3,000 it stays smooth. Also, at idle when hot, it seems to pop out the top of the carbs more, yet it is also banging in the exhaust. I just changed the idle jets from 60 to 65 but the problem is still there. It does perform better in the low speed but the popping and banging still exist. Finally, I will add that at very small applications of throttle at the low speed it will pop on acceleration but if you hit the pedal harder it does not seem to pop.

As of this writing the air bleed screws are all out about 1/8 of a turn and the idle mixture screws are all out about 1 turn. I tried taking the air bleeds out 1.5 turns and the car ran very poor.

I have run through the carb adjustments numerous times. The side-to-side balance seems right on and all 6 barrels appear to pull the same amount of air. The float level is correct and the fuel pressure is steady at 4 psi. In some ways it sounds like an issue with the idle circuit but the carbs have been rebuilt and I have tried cleaning the passages multiple times to no avail.

So here are my questions:

Could this still be carb adjustment? (I want to say no because I have been through it so much and the car performs flawlessly above 3,000)

Could this be an ignition problem? (Flaky coil, bouncing points, stick advance weights) A friend is loaning me a Bosch distributor that I plan to try and I am thinking about putting the factory coil back in the car.)

Could I have the wrong plugs? I originally ordered them for a 2.2T when I started this because that is what I thought I had.

Does the timing sound correct? I am used to having marks like BDC 2,4,6 degrees etc. This Z1 stuff is kind of weird and I am not sure how that translates but I am wondering if there is too much advance at the low end.

Sorry for the long-winded post, but this is the only thing keeping me from driving all the time now.

Thanks for the help.

[TimT]

Sounds like its a problem with the idle circuit. If you slowly accelerate and you have popping and spitting, and then if you mash the throttle it doesnt pop, sounds like idle mixture problems.

When you mash the throttle you get a shot of fuel from the accelerator pumps. try and richen up the mixture a bit.

[keitho64]

I was trying to determine if it is still to lean. However, with 65 idle jets the plugs are showing some signs of black and due to the banging in the exhaust (which I attribute to rich) I don't know if I should go to 70 idle jets. That almost seems too rich.

As far as the idle circuit goes, I have sprayed gumout through them and when I rebuilt the carbs I blew the passages out. However, I have never tried spraying out the other passages so I will give that a shot. I tend to agree it seems like an idle circuit issue I just cannot seem to find out how and why it is happening.

Of course, it I never let it drop below 3,000 everything is just fine. Life is to short to let the revs go below 3,000.

[TimT]

Just re-read your original post...the air bleed screws are a set and forget type adjustment.after you have the air bleeds and side to side balance set you should raise the idle to about 1800, and then play with the idle mixture screws... When you have the idle working well at 1800.. reduce the idle back to 900-1000.. and you should be set.....

How are the throttle shafts? If you have air leaking in throught the throttle shafts its impossible to tune the carbs well..

[keitho64]

I will say the throttle shafts seemed fine. I have tried spraying gumout around them and the idle does not change. So using that as the logic, I think they are ok.

I might just try driving it some more and keep 'tweaking' the carbs. As long as everything else is ok I hate to admit it, but it must be the idle circiut in one fashion.

[TimT]

The weber idle circuits basically s*ck, the individual barrels dont produce enough vacuum to finely meter the fuel. You can get a rock steady idle with the webers, it will takes some tweeking though. Id have to tear down my carbs to remember the set up I have, I only get an occasional burp or fart with em though..

[keitho64]

OK, you have confirmed what I was afraid, just when I think I understand the black art of Webers, they burp and fart at me. I will keep playing with adjustments to see what works. Thanks for the advice.

[keitho64]

OK, one more question. What is the best way to test for worn throttle shafts on Webers? I tried spraying Gumout near the shafts but no change in idle was present. I also tries wiggling the shafts and there is no movement nor change in idle.

[jpnovak]

assuming your plugs are not fouled. It sounds to me like your idle circuit is not functioning properly. I would use an air compressor to blow out and clean the entire idle circuit. You can do this through the pickup in the bottom of the float bowl. remove the jets and the needle valves to do this. The lean pop through the top is the reason I think its a partial blockage.

Have you torn them down for a good soak and clean lately? I typically do this once a year as part of general maint.

I don't think you need to go larger on the jets. I have a 2.2T built to E specs with 55 idle jets and it idles smooth once warmed up. I set mine up with 2 turns out on the air screws to start, then balance with flow meter. Idle screws are typically 2 1/8 turns out. Minor tweeking for cold/hot weather.

If the idle circuit is not completely clean they will burb and fart. I run a main filter on the side and individual filters by the inlet banjo fitting. Keep those webers happy and clean.

Jamie

[keitho64]

Jamie

I had cleaned and soaked the carbs late last fall and it has not been driven more than 200 miles. I did install an inline filter before the fuel pump in addition to the ones on the carbs.

All of the comments I am getting about blocked idle circuit make me wonder how bad my fuel tank is. Maybe dirt is getting past the filters and causing this to happen. I should add that prior to me acquiring the car it did sit for a LONG time.

I had tried 55 idle jets and could not get the car to run right, the 60's were a big improvement but still popped/spit out of the tops of the carbs during steady driving and at Idle. The 65 have made an even bigger improvement in performance but it still spits/pops.

I will blow out the passages again tonight. After that I am going to drive the car to work tomorrow, 35 miles on the highway, and then keep playing with the idle adjusts.

Just when I think I understand the Zen of Weber's, Murphy raises his head.

Thanks to everyone for the comments I needed the reassurance that it is still a carb adjustment issue.

[jpnovak]

AHH a clue...

If you have not driven the car much since last fall they could well be clogged. fuel does evaporate and leae quite a mess. I would definately have your tank checked for rust. If its original you may be in for a surprise. A good cleaning and reseal will help your cause with carbs.

Murphy always shows up at the most opportune time...

and yes, driving does help sometimes. Try to spend time around 3k. this will be maximum flow through the idle circuit before the vacuum takes over the main circuit.

Another thought. Sometimes you can hear the fuel flow with a stethascope. This may allow you to ID the bad section.

Jamie

[keitho64]

I attempted to install a Bosch distributor tonight but ran into a problem with no spark. See here if you are interested:

Distributor Questions (Marelli to Bosch) - 2.2 Motor

After I reinstalled the Marelli I set the timing at 5ATDC vs. the Z1 where it was at idle before. From everything I have read Z1 is TDC and the Marelli seems to allow the advance to come in very soon. While I have not driven the car yet, the popping at idle seems to be very minimal. I am wondering if the timing was to early at the lower speed and causing the problem? I will post a follow up after I drive it some more.

[keitho64]

OK another update, I installed the Bosch Dizzy and set the timing at idle to Z1. The poppig is all but gone. From what I can tell there were two problems, first - the timing on the Marelli was set wrong. This was due to a bad timing light and advance weights that would hang up. Hence the second problem was WAY to much advance at the low speed causing the eratic running. Now that I know the ignition is dead on, I am going to rebalance the carbs. I put almost 100 miles on it this weekend with the timing and new distributor and the car is running very good. I still get an occasional pop at idle but never on steady cruising.