3.8TransAM

I hate doing this, im usually the one helping everyone else grrrrrrrrrrrrrrr but even i have my limits so here goes..

My 91 Formula, heavily modified and tuned(prom) by me, is breaking up past 3.6-4k range. It is a new problem, occured gradually(within week or two) and the car used to fly. Im to the point that I've eliminated the majority of the problem, but its still there and it doesnt rev lke it used to...

This happened gradually and I noticed it but got very bad over a 2 day period.

Fuel pressure has been verified(fuel filter replaced as well) and is holding steady at WOT

Swapped cap/rotor, wires, ign module, and coil . I do have an MSD6a and yes I've tried it both ways, with and without it hooked up it is the same.

Checked related coil and ign module wiring and no open/shorts or low voltage situations present

Pickup coil has been replaced within the last yr

Diacom reading from logged full throttle runs show no problems and no codes are being stored.

TPS, ECT, MAT are all normal and no dropping off of any readings exist when u review the log, but u can literally see the drop in rpm or the fact that its holding (like hitting a rev limiter) at a given rpm when it happens....

Considered possible valve float as well(dont think its an issue), but chip limits fueling to 5700-5800 and its not a consistent issue, it occurs most of the time but sometimes will pull thru relaitvely well and the next time break up at 4.5k then break up at 4k the next etc......

Distributor possibly worn out and causing spark scatter or?????
Im just getting frustrated and trying to be methodical(have 2 91 and extra stuff lying around so i could eliminate the basics).
Later and thanks
Jeremy

PS Vader for the love of *** gimme some input :-P lol

Z_Ghost

Have you check to see that the ground strap is still hooked up and in good shape?
What about the other ground wires on the back of the driver side head?
Is there anything in the air tube going to the TB that could be causing a restriction?
Do you have a cat on the car and is it still good?
I know you pulled the dist and changed the pickup coil, how did the gear look on the dist?


Hope you find the problem.

3.8TransAM

ttt

3.8TransAM

Ohmed the pickup coil today, full hot after coming from work and its a 960ohm so it should be ok.......its generating AC voltage when cranking. Its not shorted to grd either....

Going out when car cools to double clean and diaelectric grease the pass head grd straps(actually came loose and off 2 weeks ago), i cleaned and reassembled at the time and noone are broke reverified today (it hurts working on a tpi when hot)

LAter
Jeremy

3.8TransAM

STUPID STUPID STUPID STUPID STUPID AM I
lol
..........well i officially got my @#$#@ kicked by a neg battery terminal :-( Im not proud of it lol

i checked it the other day and diaelctric greased it like i do almost everything i tend to take apart thats electrical and i tightened it up and went about my business....

Today after i did the other stuff i leaned on it and it took a inch spin and i was like what the $@%#$^ . got to poking around and the cable stud was junk i didnt pay any attention before and just greased a retightened lol

Si i made a homemade cable stud from some washers and a header bolt for testing and guess what happened? No more stuttering/holding rpm and my hot start issues went away to(solenoid clicking) lol....

I cant believe all that lol even the idle is much more stable since its not glitchiing out the ecm every other millisecond..........

just goes to show, im the one who plans and assists almost are whole group on eng,wiring, prom , etc...

We even get kicked square in the nuts too every now and then to keep us real :-)

Thanks for your help guys it was much appreciated
LAter
JEremy
PS Am i supposed to feel embarassed now lol

3.8TransAM

grrrrrrrrrrrrrrrrr
it aint over :-(

she competely 100% cut out on me on rt 41 thank *** i had a opening to blow a redlite and cruise in under momentum :-(

cutting out made me lose to a lightening too and i had him till it went chug chug chug :-(

but brite news if thats possible it cut out completely....would not crank or anything, but everything inside the car worked let it sit and i could hear the solenoid engage now. But just click clikc click, got out and played with the pos. cable towards the starter(fun with headers let me tell u) and i got it to crank. Some more playing and praying and a lil more cool down time and she cranked and fired and i headed for home asap(keep my never needed a tow truck yet status intact).

So if i cant get a pos cable on it easily(mine is original so i might as well replace it) its getting a mini starter at the same time to eliminate any heatsoaking. Im hoping the termianl is loose so i can get by for a week or 2. Got too many projects and im killing myself tween working all day (jaguars) and then coming home driving myself nuts on my own cars... I like to plan things out not get beat into the grd .
LAter
JEremy
PS why do i keep going? :-( uggghh

3.8TransAM

TTT

I've basically eliminated everythign from under the hood as being a culprit :-( what couldnt be checked 100% has been swapped from my known good car...

Heading inside and starting at the fuse block, but the Ign switch first, brainfart today made me realize when i put the ehaders in i had to shove the column over and it screwed up my highbeams wondering if the ign switch was affected too or it just may posssibly be giving up the ghost..........

will report back t'row findings and hopefully(pray for me) a fix

LAter
Jeremy

3.8TransAM

*smashing head into brick wall*

Well went ahead and replaced my ign switch. U could say it let the smoke out plus a little.(now the question is why did the smoke come out?) Got it in and pout it back together and started car. WOW! was i impressed everything was better, started great, came down and idled great.........

walked away and came back, cars idle started going up and down and then it stalled and now is a crank, but no start condition. :-(

going to go thru the ecm and ign related power and grd sources inside the car and see what i find... when it stalls the cut is instant and complete and usually will start after 15-20 minutes of sitting with the hood up... got late and skeeters were out in force hunting so i retired for the nite

just frustrating
Later
Jeremy

Z_Ghost

You got one evil electrical gremlin living in your car.

3.8TransAM

ttt

Vader

3.8,

Wow. You've got a good one. I've been in the Northwoods for about a week, so I missed most of it. Mosquitoes? You ain't got no stinkin' mosquitoes. The smallest ones at the lakes are running at least one Pratt & Whitney radial, drop tanks, and a 20mm cannon. The more mature ones would make deHavilland blush. About three of them tried to carry one of the kids away for a later snack. I must've donated at least a pint or so in a few days. And that doesn't even consider the deer flies. But that's O.K. Watching the eagles fishing is pretty cool.

I don't doubt that you have at least one marginal connection that is changing resistance with temperature. It could be in a promary power connection, ground, or even a cable or fusible link. Those links run up to the firewall right from the starter and past the headers. It might not be related to the "4K rev limiter" problem, but may well have a bearing on the hot no-start.

3.8TransAM

At this point in time i believe the heat soak starter condition is simply the original 10 yr old starter :-) oh well, plan on getting a high torque version anyhow for some insurance.


the car will start and run for ohhh roughly 3-5 min now and shut down. Appears to be losing both spark and fuel.. Whatever is causing it is consistenly getting worse as time goes by.
Going to start it up today and check the pickup coil directly after it stalls out(checked ok prior but condition was intermittent) and hopefully see if thats it or not.

Pinned the ecm grds and while i did find a few questionable ones, after i cleaned and lubed the grds on the drvr head the all checked ok at the ecm and the prob still is the same

Will keep updated as problems/fixes are found.. I dont care what it is anymore, long as it wil be fixed lol'
thanks for the help
Jeremy

3.8TransAM

It apparently has fixed itself ?

Had p/up coil and module leads unplugged and the cap pulled(obvioulsy) came in and downloaded wiring diagrams as i mailed vader lol..

Went back out and reassembled it to try running with the timing connector unhooked and guesss what? It ran and stayed running! I let it run for 30-45 min and closed the hood and heat soaked the hell out of it and then i drove it for 30-45 min and it was gone....... like a whole new car now...

I let it run when i got back home and played with all connectors and wiring and the car never missed a beat.. i unplugged them one at a time and restarted the car and nothing showed up... Played with the wiring yet some more and i cant find it and it will not duplicate itself....

As of right now current theories are:

Dialectric grease from module get into p/up coil leads and temp short it out?(hot grease migration) not visible when unplugged obvioulsy..

loose pin or connector? i removed all connectors and pulled wires from one end and watched pin on the other, i also checked for continuity as well..

confused hate when this stuff happens cause what do u do next time if it happens again

thanks for the help and later
Jeremy