Tune-up time, stumbling, breaking up under acceleration

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Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Tue 25.10.2016, 02:53

Background under this thread:
viewtopic.php?f=31&t=25680
MOVING THE ABOVE ISSUE FROM "TURBO" CATEGORY TO THIS "IGNITION" CATEGORY, since we've narrowed down the problem to the ignition system.

SUMMARY:
51K miles, no modifications except Everest chip, running rough, bucking, stumbling on acceleration.

To continue...
I just this past week flushed the coolant system and while doing so, back flushed and water poured out from the expansion tank rad cap all over and onto whatever was below it.....namely the coil packs!!!
So it's probable now that somethings amiss there. "hind-sight is always 20/20" !

I pulled the plugs and noted they were the brownish tan color which is a good thing, but the electrode and gap were wide on #1 & #4 plug (noticeably wider than #2 & #3 which were only slightly wider than spec). I re-gaped the plugs and re-installed (temporarily until i get new replacements). I took it for a test drive and although a "bit" better, there was still a "breakdown", missing and stumbling noted.

Today, I pulled the coil packs to see if anything obvious was noted. All connections, wires, terminals, etc., appeared normal. I measured the ohm resistance across the two HT leads and they read 5.5 ohms. This appears consistent and normal with what i've read elsewhere on this forum.

What i did notice was the ignition control module has a stainless steel or aluminum plate under the coil packs and i was concerned the coloring was tarnished brownish gray as opposed to pictures i've seen of them with shiny bright silver metal color. Does this color change indicate "burning" or excessive "heat transfer"?? or is that normal with age and corrosion?

I know a moderator or member of this forum has sold both items and made them available here, however i did a little internet homework and my own research and readily found equivalents on Ebay at very cheap prices. The ignition coils are GM with part# DR39 and were $10 each w/ free shipping. The ignition control module are also GM with part# D1927A, but this one is actually a Delphi unit # GN10092 and cost only $24 with free shipping. Now i'm also searching for exact replacement spark plug wires and get everything done and replaced at the same time.

Can anyone confirm I'm doing the right thing and buying the right parts???
TED
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby Simon_P » Tue 25.10.2016, 09:10

Yes coils DR39.

The module is less likely to fail but
If you have a correct x-ref for $24 buy it as they are usually expensive.
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby Fredjohn » Tue 25.10.2016, 09:29

Ted

Try Kingsborne leads: we had a mini group buy in the UK for some: fitted and cured my slight high-rev under load misfire :D

US sourced: Kingsborne website here
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby theelanman » Tue 25.10.2016, 10:09

:agree:

as it happened mine turned out to be the coil packs giving up........
however I changed the leads first as they were the cheaper option....
then the coil packs....... :-D
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Tue 25.10.2016, 20:12

Thanks FredJohn, i just ordered the 8MM set from them. They are located in California, USA so it should arrive in 3 days. Although reasonably priced at $21.99, the upgrade from 7MM to 8MM and a color choice cost $5.00 more dollars (total $26.99) but unfortunately i got screwed on shipping charge of $15.37 as their cheapest shipping cost option. But even so, $42 bucks for custom made wires for the Elan with upgraded thickness and color is still a good deal.

I did find 8MM wires on Ebay for only $32 bucks (tax included) with free shipping, but the picture on Ebay showed only two wires (as samples) and one was totally wrong (probably a distributor to coil wire for another type vehicle), so not having the right picture shown scared me away.

Once all these new parts come in this week, i'll report back on the success or continued failure. Plugs, wires, coil packs, ignition module, that's really all there is to the electrical spark aspect of the engine function, correct? should not be anything else, i'm hoping.
TED
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby HJ2 » Tue 25.10.2016, 20:20

did you check the CAS for broken shaft or other irregularities?
When you set the base timing, was the 16 deg pos. stable?
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Tue 25.10.2016, 22:10

I do not have any check engine lights or code 41 issues, so do i still need to check CAS? I've never touched it.
TED
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby CalElan » Wed 26.10.2016, 19:16

If your timing is consistent at 16° your CAS is probably fine.
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby Simon_P » Thu 27.10.2016, 00:13

tedtaylor wrote:I do not have any check engine lights or code 41 issues, so do i still need to check CAS? I've never touched it.


Both fuel and ignition are downstream of the ECU, so if fuel or ignition don't happen the ECU doesn't know about it. so No CEL.
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Sat 29.10.2016, 15:51

UPDATE,
OK, well now i'm really miffed!!!
I just replaced the ignition module and both coil packs and went for the test drive.
well partial success, the stumbling and bucking/missing is gone. Hurray...
HOWEVER i now have minimal boost.
Before (w/ everest chip), my boost would range from .75 to 1 depending upon driving demands, but i had plenty of boost power.
Now the boost only registers less than .25 and no more "kick in the pants".
WHAT HAPPENED???
does the ignition module have any control on boost? did i buy one with the wrong application?
Please experts, chime in....
the absolute only change i made was the ignition module and coil packs, NOTHING else was touched.... and i had plenty of boost before this.
TED
"Driving a Lotus is a triumph of bravery over intelligence." Stirling Moss

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Re: Tune-up time, stumbling, breaking up under acceleration

Postby Brit-Car-Nut » Sat 29.10.2016, 19:26

tedtaylor wrote:UPDATE,
I just replaced the ignition module and both coil packs and went for the test drive.
HOWEVER i now have minimal boost.
Before (w/ everest chip), my boost would range from .75 to 1 depending upon driving demands, but i had plenty of boost power.
Now the boost only registers less than .25 and no more "kick in the pants".
WHAT HAPPENED???
does the ignition module have any control on boost? did i buy one with the wrong application?

What coils and ICM did you use? Are you sure you didn't disturb any vacuum lines?
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Sat 29.10.2016, 20:42

The coil packs are the generic DR39 found here: http://www.ebay.com/itm/152176046750?_t ... EBIDX%3AIT

the ignition module is the generic GN10092 (D1927A) found here: http://www.ebay.com/itm/171286932779?_t ... EBIDX%3AIT

these are the GM (General Motors) parts used for many late '80's early '90's GM vehicles.
question remains, is the "Lotus specific" ignition module different than the GM shelf units??

no, I really didn't mess with anything else, just coil packs and ignition module. What's interesting is that the stuttering, stumbling is cured, but now this lack of boost issue pops up!!!
TED
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Sat 29.10.2016, 23:14

DISREGARD EVERYONE
when i took my test drive, i only fitted the intake plenum hose without securing the hose clamps!!!! Dummy me, I thought just making the connection would suffice and didn't realize how much positive pressure is actually in that tube. I found the top connection actually pushed off.
Well after securing tightly with hose clamps top and bottom, i am happy to report coming back from a blistering test drive, with all the boost as before.

So in the end, my "stumbling, stuttering, break up under acceleration" was either the coil packs or the ignition control module. I didn't go about test one or the other in varying combinations, mainly since the parts were SO DOG GONE CHEAP via Ebay. So for under $50 bucks, i have new coil packs and ignition module in place and my problem is solved!

Now i'm still going to install new spark plug wires and new plugs while i'm doing this.

Thanks everyone for your help and input. I'm a happy camper once again!!!
:D :D :D
TED
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby steve matthews » Sun 30.10.2016, 00:10

:clap: :clap: :clap: :clap: :clap: :clap:
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Re: Tune-up time, stumbling, breaking up under acceleration

Postby tedtaylor » Fri 04.11.2016, 18:35

Just as followup...
I installed the new "8mm" spark plug wires in RED (as original?) from the link FredJohn gave me above (US entity) and installed new NGK spark plugs.
Went for a more thorough drive today, through the complete range of driving speeds/acceleration, etc., and happy to report it is running very nicely.
It did initially stumble once, maybe twice at the onset and I don't know why, other than maybe everything is settling in, all the new parts "communicating" with each other, sounds silly, but that's all i can think of to explain it, but for 99.9999 % of the drive, it ran perfectly.

One note, on my last empty gas tank fill up, i used Techron fuel system cleaner for my injectors, so it may be possible that it is doing its job and cleaning out the injectors, thus a hiccup or two as experienced above.?

Next project = brake pad replacement, brake fluid flush and bleed. :roll:
TED
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