This has happened all last summer, and now again this god damn summer. I dont know what to make of it...at all.

When its extremely blistering hot out, after a while of driving the car suddenly switches to dogshit mode, even being fully tuned. Car will drive fine for about a half hour, and then all of the sudden when you blip the throttle, the car will go lean.... 21+ on the afr, and then suddenly shoot back down into the normal AFR range, this will go on for 5 minutes and then it starts getting really bad, normal driving AFR will go down into the 11's, and the car will sputter badly when you hit the gas until it gets back into an acceptable AFR where it can move and then it picks up as normal.

Happened tonight, driving home from chic fila for dinner, finally when i got home and pulled in the driveway, car was running like utter crap, i could smell the fuel in the exhaust, AFR was reading in the high 10's low 11's, and when i blipped the throttle it would just sputter and show a lean afr, then richen up, and then lean out again.

Let the car sit for 10 minutes, litterally, came out side with the laptop, started it up, CAR RAN FINE. Plugged the laptop in, all sensors were reading normally, so i took it for a spin, car ran fine, even with 200 ECT and 188 IAT (supercharged, **** gets crazy in there), pulled like a beast. So i drive it around up and down the highway for about 15 minutes, and then it starts doing it again, i check the numbers, all sensors reading normally, nothing out of the ordinary there other then this sputter. ECT and IAT exactly the same, nothing has changed, other then this phantom symptom I keep getting when the car gets hot.


I dont know what to make of it, I can think of two things off of the top of my head that would **** up under extreme heat, 1) the distributor, which has a brand new ICM and coil pack that is less then a year old and 2) the injectors overheating? (dont think this is really possible) bosch 420cc yellow top injectors, type2 style. Anyone have any thoughts?

Here's a vid of me hitting the pedal, mind you im going about 30-40% throttle and the car does absolutely nothing and then all of the sudden revs up.

http://www.youtube.com/watch?v=gjFr_3eLl1w

 

is your fuel pressure fluctuating?

 

i havent been able to check it because the gauge is under the hood but when i have looked it seemed to be fine

 

Only thing im really leaning towards right now is the distributor being overheated badly due to the lack of airflow under the hood. I dont have a vented hood, and I have a full size radiator, with an AC condenser in the front of it.

 

is there a dyno near you to try and replicate the situation?

 

lol you want me to pay for dyno time to replicate something i can replicate by driving up and down the street? ill put a dizzy and a fuel pump in it and see what happens, the Map sensor and IAT sensor are being converted to GM stuff in 2 months anyway, guess ill just have to rough it.

 

I can assume you have edited the IAT tables in ECTune? If you poke through the user calibrations you can see a lot of adjustment going on here in the idle/low load section. With the excessive heat produced by the S/C this becomes more pronounced. Battery offset tables are another place to focus your attention.

There has been discussion with using the GM sensors an I believe the scaling is considerably different. With the wide temperature range the S/C produces it may amplify your problems.

 

What was the ambient temp and humidity for your tune. I have to carry two maps. The humidity has just as much of an affect as big changes in temp.

 

Distributor overheating because of a hot ICM, not from underhood temps. Sounds like the car is leaning out due to detonation from lack of active heat exchange. How is the intercooler / aftercooler for the supercharger?

I'd do as suggested, head to the dyno to see if you can replicate the scenario and recheck the tables. Again, to me, it sounds like ignition issues that are causing the spark to not be as effective, and you're leaning out.. Not in the tune itself.. Once the ICM cools down after a few minutes, car runs normal, as the module is back to normal. Time for upgraded ignition and better heat exchange. This is more why its recommended, and NOT for "making more POWAR!" reasons.

 

I took alot of time to edit the IAT compensation tables to gradually pull fuel as the IAT gets hot, but beyond what I have it set to, it pulls full all the time, because the IAT reads the intake manifold temp, so I read consistently between 150-200 IATs no matter what the ambient temp is. Im not convinced its in the IAT compensation table because after I restarted the car, the ECT was 200 and the IAT was still 180, and the car drove fine. When derek tuned the car we were doing pulls down the highway @ 27 degrees of timing with the IAT at around 202 degrees. The ambient temp changes seem to just make the car run incredibly rich since it cannot pull fuel based on that alone, thats why Im going to move the IAT sensor into the intake tube when I pull the motor. So on WOT on a day like today, im more like 11.7:1 afr where as with a 70 degree ambient temp, im 12.5:1 AFR.

As far as the distributor overheating, thats what I was thinking, when I put the new ICM in I did make sure to use some very high grade heatsink material that I normally use for computers when bolting the two pieces together and to the side of the distributor. I see what your saying, the external coil system would prevent the heat build up problem. I guess thats something im going to have to look into now.

 

was the car tuned in open or closed mode?

 

Open, it always runs in open, it doesnt have o2 sensors, only a wideband for reference and tuning. closed loop in obd1 to me, is kind of useless. anywho, i ran it today let it get hot, did the same thing, checked the fuel pressure, when you hit the throttle its jumping to 50psi or so like normal, so im leaning towards its not being the fuel pump at all....

sorry the camera is so shitty, but you can kinda hear it puttering when i hit the throttle, then it suddenly recovers and revs up to where it should be

http://youtu.be/OeCl8SvOzaM

 

So shodan you mentioned an external coil setup, you have anything particular in mind i should be looking at? Or do you think I should maybe look to a new distributor?

 

Best bang for the buck from what I've read on hear is a summit cdi box, crane or mallory coil, msd cap and wires. I know there's a few guys running it. I have part numbers from whiterice in my pms if youd like me ti forward it to you. I know theshodan has recomended it a few times to ppl.

 

Pretty much, especially if you can't shell out for the M&W10 stuff. Even the MSD 8207 External coils do quite well in addition to the Summit CDI/Mallory ignition box.

 

Are you convinced the external coil setup is absolutely necessary, or if i was able to cut the under the hood temps down by at least 100 degrees, this problem might go away? A coil setup really was not in my budget for the next 2 months, i really dont want this to hamper getting this engine in for august and dyno tuned before burnout weekend in september.

 

You ambient temps under the hood have nothing to do with ICM issues or distributor issues; they're already made to get hot like that. the additional heat overall is what's affecting the ICM's ability to work.

I'm not there to diagnose the problem like a technician, so I'm only going by what you're able to tell us. Its one of those things you have to add in for now and possibly later.

You want it fixed, its more than likely not going to be a "free" repair..

Good luck.

 

Well the primary issue im having here is that this only occurs on blistering hot days, otherwise the car is completely normal. I think if the ICM was having an issue with heat dissipation it would occur whether the ambient was in the 70s, 80s, or 90s, but this only seems to occur on 90+ days where its just difficult for the parts under the hood to get cool. I realize I have alot of negative factors here affecting this, trying to run the AC in that extreme heat, with heat coming off the condenser, then going through a full size rad, then my PLM header which is cheap thin stainless steel pumping ridciulous amounts of heat into the bay, and then an intake manifold that you could roast burgers on during track days.

Its not really something that screams at anyone particular thing, the only thing i am certain of is that it is outside of the realm of the ECU's ability to throw a code for it. Which leaves to to something like the coil or the ICM, or the fuel pump.

The simplicity of the OBD1 system is both a curse and a blessing at the same time, not much in the way of parts to diagnose as a problem, but not really smart enough to give you any real feedback as well, or really help itself in a situation where it has a problem.

 

What are you tuning with

 

ectune

 

THis is not different than a transformer on a HoT day outside over 90 degrees, that's subject to a lot of blackouts. Even with lower temperatures, there's less likely of transformer overload, but it can still overload. The coil is just getting way to hot.

Even on track days that can be a problem.. I"m just saying that as you look at the tuning maps, check the "low tech" approach as well.

 

Point taken sir, point taken. Alright im going to have to think this through and see what I can wing with my budget here.

 

When, i tuned the car, It ran flawless the entire weekend, even beating on it constantly with IATS well over 180-190, the car was fine. I tuned and tweaked both the IAT's and ECT comp tables for everything.. Problem is, i tuned the car when it was 40-60degrees out. I did my best to calculate the tables, but Rob is smart enough to make the adjustments that would be needed at this point in time. The car WOT is tuned perfectly..it could use some minor tweaking of the ign maps on the dyno because i didn't get a chance to perform a full track session as 3 runs isn't enough for me to really do what i wanted.. But the plugs look outstanding and the car pulls really...really hard on and off the meth. With that said, I'm thinking its a issue with something else, but i dont know...At this point in time because the motor is almost about to come out, i wouldn't even worry about it.

Anything tuning wise was fooled with, tipin/out, comp tables, battery offsets..i'm very **** about my tuning..very..nothing was left untouched if it needed to be modified.

 

Once I move the IAT sensor to the intake tube, ill be able to adjust those compensation tables to where they actually make a difference for ambient temp changes. As far as fueling, its doing exactly what it did last year, the ambient air is less dense, so im running richer then what we tuned for on WOT, and theres nothing I can do about it, because the IAT compensation tables are at max because they are reading the blower temp which is consistent regardless of the density of the air outside.

 

Went out and got a new distributor, cardone reman, still seems to have the OEM hitachi ICM in there, new bearings, no play like my last one had, and had a new coil on it which said it was tested. Car seems to be fine, running smooth now although I appear to be getting a slight miss every few minutes, gonna check the plugs tomorrow. I drove it around for a while after getting food and it ran fine but the weather has been cooling off rapidly with this front moving through so It might not have been under the stress that it was under yesterday.

Xenocron 255 pump will be in tomorrow, gonna swap that as well and hope for the best, If i continue to have problems them im gonna order the external coil setup. Header wrap is definitely gonna be a must regardless now. Gonna order 50 feet of the DEI titanium lava wrap.