I have a 1971 1.7L (with big bore kit) running FI. I'm having some odd behavior between 4,000-4,300 RPM. It runs rough at that RPM regardless of gears/speed.

I've checked timing at 3,500 (fine).
I've swapped spark plugs (bosh) // got rid of some pre-detination ping, but still have the roughness (cutting out)
I've put in 91 octane (best I can get here in CA)

Still happens.

PS - it idles rough as well. When I remove the "retardation" line it idles fine. I've not tried to run it full boar with no retardation though.

Any ideas?

Scott

Distributor. Bad bearings (or weight springs) in it.

Try a rebuilt unit from A1 Cardone to fix your ignition problems.
Once you have done that, what have you done to correct your mix? Are you using 2.0L injectors? An adjusted MPS?

Geoff

Thanks - I'll try a new distributor and come back with my results...

I've not changed any of the FI system, and this one does not seem to have any adjustments in the computer. The crank is the stock one for the 1.7...So it would seem I don't need to change any FI system.

Thanks again and I'll be back in a week or so with the next steps.

s

Can't adjust the computer. You can adjust the fuel pressure and the MPS.
First things first, always look at mechanical parts for the problem. A bad dizzy is the first.
How does it drive at 2500-3000 rpms? Smooth or bucks, mis-fires? How about WOT?

Geoff

It runs fine all the way up to ~4000 rmp, then bucks through to about 4300, then seems to run fine again. No backfires at all, there was some ping, but the new plugs cleared that up (of course they may not be hot enough...Not sure yet).

I ordred the distributor as suggested, so I'll drop that in when it arrives, then see if I need to adust fuel pressure or the MPS. Not sure how to do those, but I suspect I might find suggestions on the Pelican parts site.

Thanks again and I'll be back afther the part arrives.

Cheers,
Scott

The procedure for adjusting the fuel pressure is in the Haynes manual.

The procedure for adjusting the MPS requires specialized equipment; it is NOT intended to be adjusted, and shouldn't be done as a diagnostic.

Ok gents...The rebuilt Dizzy advice was great. Part came very quick, Easily removed and installed the new one. I ended up getting a cap and rotor and cables as well (those were local from Kragen, so wasn't able to get all the good German stuff). The new rotor was no good (couldn't get stable dwell readings) so I used the old rotor and set the dwell to 45 (best I could get to).

I set the timing by the book (27deg at 3500 rpm no retard, or advance air). It runs like its not timed now (alot of work with no HP).

Fuel pressure is at 29.5 (I tried it at 30.5 as well).

The car runs sluggish now (although seems not to sputter much). I'm sure I've misadjusted something (Dwell at 45. timing at 27 (red), fuel pump at 29.5). I must have some other bad component or I'm just daft. I guess I'll sleep on it. Any other ideas?

Cheers,
Scott

Umm... The rotor has nothing to do with the dwell. The point gap controls the dwell.
If changing the rotor affects the dwell, you have other problems going on.

G.

Pertronix. Ditch the points. You can buy them local for 70.00$

Its sounds like your close to solving the problem. Welcome to the BBS.

Too bad you missed our IHOP 914 breakfast in Santa Clara yesterday (Saturday)


B

I know the points set the dwell (I must have messed with that for 2 hours off and on yesterday). bounced between 20 - 60, till I got it at 45. The dwell reading (on the meter was garbage when I installed a new rotor). The rotor looked junky compared to the german one I pulled out. So when I put the old rotor back in, the dwell meter read a constant value. Othewirse It flickered and showed negative numbers etc. Not sure what it was, but when the old rotor went back it, all started to read normal again.

I just installed a rebuilt distributer (with new points). Are you suggesting I dump those points and get some new ones?

I was suggesting an electronic points replacement setup. You dont have to set the dwell with the electronic ignition.

I really wished I had read this thread BEFORE these guy's told you to buy a rebuilt dizzy. I would have led you down another path towards diagnosing the problem.

Points can be finicky in our area during the winter (moisture)... so most of us in NorCal run a replacement setup.


B

Ok - I now understand about the electronic points.

Ok - I've now re-adjusted the Throttle switch (just slightly). I've replaced ALL the vacuum hoses. I've diagnosed the MPS to the quick vacuum test from the renlist. It does leak about 5in in a minute (20-15 in about a minute) so that seems normal.

I replaced the plug wires, new distributor and cap (with copper contacts). The only thing I've not done yet is to check the throttle switch contacts or re-adjusted the valves (although I've been told they seem ok). Re-checked the fuel pressure (just under 30 ~29.6. Rechecked the timing (although I have two red marks on my fan about 1.5 cm apart -- so I split the difference). Dwell was reading between 45 - 50.

Ran it again and its running like crap! Uggh.

So I pulled the new distributor and put in the old one...Ran better (about where I started -- go figure). So I'm concluding that the new Distributor is no good. As that was all that I did.

I couldn't get a good dwell reading on the old distributor...So I guess return the new distributor (as its worse than my old one), try the electronic points and hope that nails it.

Cheers,
s

You really need to adjust the valves. They have a huge impact on how well the car runs. You also need to find the true 27 degree mark and time the car properly. Until these two things are done... I honestly feel your pissing in the wind (which is why I wish I had seen this thread BEFORE you bought the dizzy).


B

OK - I'm going for the valve adjustment next. I also returned and ordered a replacement dizzy. Although, I'll just return it if the valve adjustment does the trick. So, your advice doesn't come too late. I'll just have to call around town to see if I can locate the electronic points (as I'd like them this weekend). Then try to figure out a way to get the exact 27 mark. I think I saw a marking kit somewhere.

I'll be back with an update.

Thanks

HPH stocks the kit. He is in Redwood city. Price it online and take him the price.. he will match it.

650-364-6234 8am-5pm. Dont show up at 5pm.


B

I found this pic, courtesy of Dave D. at the Pelican site. It came in handy last week when I had to time mine. Thanks Dave D. I check it against a 1.7 fan I had too (his pic was of a 2.0). So you can time it relative to the big square rib of the fan

pelican pic


The first thing I would look at is my tach. if it gets jumpy when you have the engine miss then it would indicate troubles in the distributor primary circuit (points/condensor or electronic mechanism). If it's stable, than it's something else.

4000 rpm is above the point where the dizzy should be fully advanced, so it seems unlikely it's the advance mechanism. can you induce the behavior other ways, at different rpm's? is it in all gears ? Does it feel like 1 or 2 cyls dropping out, or a complete failure?

I will say this, I once tried aftermarket points condensor in my teener and they didn't last but 10miles or so. I would only use bosch parts there. But electronic is the way to go.

Thanks Brad and all. I think we've got it. I didn't get the electronic points as there is no one in my area that had them. I'm in Santa Clarita (LA area) as opposed to Santa Clara (Bay Area). I'll order them this week.

Valves needed adusting....I found one valve a .0025 - pretty tight. Many others were between .004 and .008, half were at .006 (as they should be). so tweaking those helped tremendously. (I'm replacing the nuts and screws next time as one is cross threaded, but it was close to .006 already). I have a new new dizzy, but left the old one in, and we are running much much better now. I'll replace the points in them both to see how they run, then I'll add electronic points to one and have a quick switch for racing and normal driving.

The jerking at 4000+ is GONE! I also noticed that the ("temp new bad dizzy") caused the RPM guage to jump all over the place. After reading all your input, I suspect the points were no good on that one, and probably could be replaced on my current dizzy. So when I try again I'll go for the bosch points.

Still idles rough (and stalls), but I'm guessing its due to the big bore kit. loosening the idle screw didn't do too much (Even though I adjusted the switch per rennlist). I guess if I get ambitious I'll see about adjusting the MPS to increase the idle only. Or maybe that was in the FI...I'll have to read that rennlist again.

I wen't with the first notch, then the 2nd notch. I think the second timing notch is the way to go, but I'll test them both again with new points.

Regardless, I think I'm past the dizzy headache. Now I want to tweak the spark plugs. Should I go bosch platinum "4233", or NGK BPR6ES?

Thanks again guys.

s

Stick with the W7CC Bosch Copper core's or the NGK equivelant

Two things:

If the idle screw doesn't do anything, you have a vacuum leak. Fix that 1st.

Timing notch? There is no timing notch. What exactly are you adjusting?


I don't want to sound too much like Brad, but...

There's probably 6 people in North America that can adjust an MPS (properly), and from what I'm seeing, you're not on the list. Do NOT adjust the MPS unless you have the equipment to do so. (Or mayby go ahead; there's lots of people that will sell you another one. Just do the research on the replacement price before you break yours.)

And there is an idle mixture adjustment on the ECU. It's already there, waiting for you to find it.

not if it's a original 71 ...

Andy

W7DC's Bosch plugs. Nothing else.

GaryH is correct. You have a vacuum leak. Find it/fix it.

If its truelly a big bore 1911 then you might find 27deg is too much...and the notches will be worthless to you. I cant run 27 in our 2056 cars without the chance of detonation.

Dump the points...dump the points... stop fooling with them...

Oh.. no more Rennlist references... it makes my stomach turn.


B