Analyze my Datalog. . .tell me what's causing this

[Italian LX]

Can anyone tell me what could cause what's happening at ET=122.767? :shrug:


In addition to the obvious Spark loss and ECT drop, the ECU also goes into OL for
about 45 seconds after the occurance (similar to a start-up condition) which you
can tell by the commanded fuel enrichment at that point.

:hmm:



http://www.deepstageperformance.com/pics/pwt-01.jpg

[86GT]

Are you sure it is not the tweecer just dropping data? If the car is acting funny as you stated, then maybe the TFI module is on its way out.

[Italian LX]

Are you sure it is not the tweecer just dropping data?
I'm positive. The car totally loses ignition usually for about 1 or 2 seconds. I've been chasing this damn issue for about 6 months now. :fuss:

If the car is acting funny as you stated, then maybe the TFI module is on its way out.
I replaced it shortly after this started happening. Since then, I have tried going back to the stock one, and putting a whole different distributor/TFI module on the car.

I'll try to make a list of what I have already tried while chasing this problem and post it here.

[86GT]

How about the coil itself. Maybe it can no loger handle the short dwell time.

[Italian LX]

How about the coil itself. Maybe it can no loger handle the short dwell time.
I switch to a brand new MSD Blaster coil after the problem showed up last Fall. I also recently borrowed QWKSNKE's Screamin' Demon coil a few weeks ago and the issue still exists. :(

[86GT]

cap rotor?

I guess Ill wait to see the list of things you tried.

[Italian LX]

For those of you that may not be familiar with my car, here is a run down of the vehicle specs and current engine mods:

1988 Mustang LX (previous 4-cyl automatic car)
5-speed
Stock 302 short block from ’91 GT (approx 278,000 miles)
EEC A9P
TwEECer R/T
TFS TW heads w/ Stage II porting*
E303 cam
TFS Track Heat Intake
1.6 RR*
24# Injectors*
70mm TB
76mm C&L MAF (with 24# sample tube)**
MSD Blaster Coil
Autolite 3924 Spark Plugs***
MAC LT / off-road H-pipe / MAC cat back
255lph
AFPR = 41psi*

* These mods have been added since I first noticed the problem. Previously, I had GT-40 iron heads, 1.7 RR, and 19# injectors, I had the AFPR, but I was running 39psi at the time.

** I had the same C&L MAF when I first noticed the problem but had the 19# tube in it. I will also point out that I ran a stock 70mm MAF out of a ’93 Cobra for about 4 months since the problem started.

*** I was running Autolite 104 spark plugs with the GT-40 heads per my machine shop’s recommendation; now use Autolite 3924 per Trickflow recommendation.

A complete list of all mods currently on the car can be found at this link:
'88 Mustang LX coupe (http://www.deepstageperformance.com/88lx-mods.html)


________________________________________________



This is an intermittent problem that I have been having since sometime around late last summer. It seems to be a total loss of ignition that typically only last about a second, but has often lasted for 2 to 3 seconds. It has also been worse; twice I actually was forced to pull over, cut the car off, and crank it back up. On both occations, I would crank the car back up and drive off with no hint of a problem.

I usually experience it while steady cruising on the interstate (anywhere from 60 – 80mph). I do notice that a lot of times it happens right when I hit a bump on the highway (there’s a lot of construction going on), although it has happened during smooth cruising just as many times.

I’m pretty sure it’s not fuel related. I have a mechanical, cowl-mounted gauge so I know my pressure is staying normal during the events. There is also a strong smell of unburned gas just after the car regains power, which must be the fuel that was dumped in the cylinders while the sparks weren’t igniting.

Although the problem does mostly happen on the interstate, that is not the only time it occurs. I will point out that I drive 50 miles (one way) to work Monday through Friday with 40 miles of that being the I-20 interstate. Therefore, at least 70% of my driving is interstate. I have had the issue happen many times while driving around town. A few times it happened under WOT acceleration and almost put my head to the steering wheel when the ignition dropped out.


________________________________________________



I have already replaced many of the components that would most likely cause this problem and none of them have fixed the issue. Here is a list of parts that have been swapped already – the problem was present during the use of all of them:

Fuel Injectors-
Fall 2004 -- replaced stock 19# injectors with another set of used 19# injectors.
Jan 2005 -- replaced with a set of 24# injectors out of Lee’s ’93 Cobra (they were new replacements with less than 50,000 miles)

Ignition Coil-
Fall 2004 -- replaced brand new MSD Blaster.
Mar 2005 -- tried Lee’s Screamin’ Demon coil off of his Cobra
Mar 2005 –- went back to MSD Blaster

Plug Wires-
Feb 2004 –- installed new Autolite wires
Fall 2004 –- replaced with Ford Motorsport wires
Apr 2005 –- tried a Taylor coil wire from a known running vehicle

TFI Module-
Fall 2004 -- replaced the TFI module with one from a local parts store.
Feb 2005 --tried it with stock module back in.

Distributor-
Mar 2005 –- replaced with stock distributor (with TFI module)

Spark Plugs-
Fall 2004 –- replaced Autolite 104 spark plugs with the same
Mar 2005 –- installed new Autolite 3924 spark plugs when doing head swap

Mass-Air Meter-
Fall 2004 –- changed from 76mm C&L to a stock 70mm Cobra MAF
Mar 2005 –- went back to 76mm C&L; changed sample tube from 19# to 24#

EEC-
March 2005 -- Swapped in an A3M computer from a working vehicle.

TwEECer R/T-
April 2005 -- Swap to a brand new unit; including all new wiring and selector switch.

[Italian LX]

I have always suspected a loose or exposed wire that is either shorting out or causing an open circuit, but have yet to find anything. I have (on many occations) left the car running while probing around the different harnesses under the hood and dash and tugging on wires but only found one thing that may have caused the issue -- I fixed that and the problem still came back. :(

[86GT]

Have you changed the EEC out? What a bout a loose connection on the TFI to EEC. Look at pin 16, 36, 56. Make sure there is no corision and so forth. I would slao check the shield wire. It is supposed to be grounded.

[QWKSNKE]

yes he also tried the EEC out of my 88 GT

[Italian LX]

Have you changed the EEC out?
Yeah, I guess I forgot to add that in there... I'll edit my post and add it in. :nice:

[86GT]

humm, let me think about it a while......

[Italian LX]

What a bout a loose connection on the TFI to EEC. Look at pin 16, 36, 56. Make sure there is no corision and so forth. I would slao check the shield wire. It is supposed to be grounded.
I concentrated a lot of my "loose wire testing" around the distributor/TFI module with no luck. I've tugged and tapped on the TFI itself with no luck in reproducing the problem. I have also inpected the EEC connection when I swapped computers, but didn't notice anything unusual.

What really throws me off is why the ECT drops down and slowly climbs back up. :think:

I thought it could be the ECT sensor dropping out and some how causing the EEC to do weird stuff with the timing. I tried pulling the connector while the motor was running, but the datalog just shows the ECT staying at the same position it was in. I bought a new sensor to try, but I haven't put it on yet.

[Italian LX]

humm, let me think about it a while......
Take your time. . . I've been thinking about it for half a year now and still haven't come up with anything. :D

[86GT]

I just replaced my ECT too. Do not buy the cheap plastic one. They tend to go bad after a year. I have gone through two of them already. I now have the original Borg Warner version.

Another food for thought, If the EEC power relay was on the fritz then it could cause what you are seeing. Since you are monitoring the EEC while this is happening, the EEC loses power, but the Tweecer plugged into the laptop is supplying the minimum voltage. The PC will not be able to supply the full current and things begin to drop off.

[Italian LX]

I just replaced my ECT too. Do not buy the cheap plastic one. They tend to go bad after a year. I have gone through two of them already. I now have the original Borg Warner version.
The one I bought cost $20 at AAP. Thanks for the tip; I'll check and see what brand it is.

Another food for thought. . .
Hey, I'm grasping straws, so I appreciate any direction that you can point me in.... no matter how far fetched it may seem. :yup:

. . . If the EEC power relay was on the fritz then it could cause what you are seeing. Since you are monitoring the EEC while this is happening, the EEC loses power, but the Tweecer plugged into the laptop is supplying the minimum voltage. The PC will not be able to supply the full current and things begin to drop off.
This has also happened without the laptop hooked up. It's also weird that the ACT stays normal while the ECT fluctuates. :hmm:

I've got a DataQ that I can tap into the EEC power circuits. I can use it to datalog in the WinDaq software -- that way, I can see if the power relay maybe causing an issue.

[86GT]

Another thing to check would be the MAP sensor. There is a spark multiplier associated with it. If the BP is real low it applies a multiplier of 0. Anything multiplied by 0 is 0.

Maybe, Maybe

[Italian LX]

Another thing to check would be the MAP sensor. There is a spark multiplier associated with it. If the BP is real low it applies a multiplier of 0. Anything multiplied by 0 is 0.

Maybe, Maybe
Definitely worth a try. I'll just add Barometric pressure to my datalogging and see what it does next time it cuts out. :nice:

[Wicked]

I don't remember, does the ECT and distributor harness run through the same leg of the engine harness. Maybe there is a loose wire as you said.

Also, kinda off the wall, but my Cobra would do the same thing when I first put my switchable chip in. The switch was not fully secure and would bounce around and the ignition would cut out for a split second over bumps. Only occured 2 or 3 times but it was an easy catch. I know you don't have a chip, but maybe your Tweecer wiring or connection.

[Italian LX]

I don't remember, does the ECT and distributor harness run through the same leg of the engine harness. Maybe there is a loose wire as you said.
Nope, the ECT, ACT, TPS, Injectors, etc. are on the injector wiring harness. The TFI, SPOUT, etc. go back to the CPU wiring harness.

Also, kinda off the wall, but my Cobra would do the same thing when I first put my switchable chip in. The switch was not fully secure and would bounce around and the ignition would cut out for a split second over bumps. Only occured 2 or 3 times but it was an easy catch. I know you don't have a chip, but maybe your Tweecer wiring or connection.
Well, the TwEECer basically ressembles a chip on the J3 port and it does have an RJ11 connector on both it and the selector switch. However, as mentioned in one of my pervious posts, I have replaced all that with new and the problem still exists.

[86GT]

The chips that plug on the J3 connector have one pin that is dedicated to disabling the internal ROM. If this is nice and secure and has no connection issues and any one of the data bus pins are not making a good connection, then all kinds of weird things could happen.

He has tried two different EEC's which would lead me away from this theory, but what if the Tweecer has a bad solder joint internally. It was used on both EEC's correct? I might have missed it, but did you try a different Tweecer?

[Italian LX]

I might have missed it, but did you try a different Tweecer?
Yeah, it's not hard to miss something in this thread....


. . . but yes, we had another brand new TwEECer in stock and I swapped everything including the USB cable, RJ11 cable, and selector switch -- the problem still exists. :(

[93Cobra#2771]

How about the 10pin connectors on the back of the intake? Have you dissasembled them and checked for good contact? A lot of people take a pick and tighten up the female side of the connectors so they get better connection with the male side...

[Italian LX]

How about the 10pin connectors on the back of the intake? Have you dissasembled them and checked for good contact? A lot of people take a pick and tighten up the female side of the connectors so they get better connection with the male side...
I had the SPS apart when I did the head swap, but I didn't look at the contacts. I'll check them when I get a chance.

[jwillburn119]

hey, i would also think about any moving parts... mechanically... like in the suspension... maybe check any wiring that gets near the suspension/ STEERING systems... ans they might have rubbed a wire... and its grounding out... or maybe im stupid... :drool: