Does heat contribute to fuel cut/hesitation?

[ChopstickHero]

Scenario: Driving from LA to Las Vegas yday. About 120F weather.... with the A/C on, going slightly uphill. Everything going fine until a huge accident pretty much made traffic come to a slow crawl. I was dumb and forgot to turn off the A/C. When traffic started to flow again, I accelerated and pretty much hit fuel cut, hesitation, car started bucking, CEL came on. I pulled over immediately (like 2 secs after i felt it). Popped the hood, didn't see any loose connectors/hoses. Vacuum read -20 (normal). Coolant level was fine and clean, not boiling. No smoke. Luckily I always car some tools, so I reset the ECU by disconnecting the battery.

So the question is: Does too much heat contribute to fuel cut? That's the only explanation I have. Modifications in my signature. I have the Unichip and it has pretty much run 99% flawless for almost 2 years. Would the extreme heat have altered the timing to the point where it pulled too much and i experienced the bucking?

 

[terbow]

yes. if its too hot (if the iat sensor senses it), the car will pull alot of timing. im not sure on the bucking though but fuel cut is a safety feature so i wouldnt discount them as being related.

 

[ChopstickHero]

yes. if its too hot (if the iat sensor senses it), the car will pull alot of timing. im not sure on the bucking though but fuel cut is a safety feature so i wouldnt discount them as being related.

It was almost 120F AIR temperature. I have no clue what the ROAD temperature was in the slow moving traffic, probably even more. Hmm..... i guess there's no real solution other than to be more careful, turn off the A/C and make sure you're moving to get some air flow.

I need a ScanGauge tool .... i was curious to see what CEL it was, but didn't want to drive with it on.

 

[terbow]

yea coolant temp is the big one. if its too hot itll pull timing.

 

[JCell]

boo, that explains why my car runs weird when it's HOT, but when it's cool, under 70, like a champ all day long

 

[hoindawall]

It was almost 120F AIR temperature. I have no clue what the ROAD temperature was in the slow moving traffic, probably even more. Hmm..... i guess there's no real solution other than to be more careful, turn off the A/C and make sure you're moving to get some air flow.

I need a ScanGauge tool .... i was curious to see what CEL it was, but didn't want to drive with it on.

i've noticed that its better to leave the a/c on while sitting in traffic. water temps stay about 10-15 degrees C cooler than with the a/c off. i think it has to do with the fact the fans stay on all the time while running a/c

 

[orng1]

Damn 120 run through the desert, I know everyone was moving til you got to that accident. Probably the car was used to the airflow then all of a sudden the hot air just made it bog, I have been aving that recently at lower RPM.

 

[fr0st]

i made a research/test a while ago on my previous car.. i installed a short ram ( N/A motor) and got a digital thermometer on the filter itself.. just to know what exactly is going on at certain temperatures... coze the car was less powerful above 80 degrees.. but from 70 and even 60-65 the car ran like a champ. and when it got to 10 degrees and below.. ran like crap again..

to give you an idea, for some odd reason it's not as linear as i thought.. from 70 and below the cone filter temperature was very close to the outside temp.. but from 75-80 and up , it would multiply.. at 80, the under hood temp was over a 100.. now imagine in a 120 F outside temperature.

my test lead me to tyhe conclusion that the turning point of under hood temp was 75 degrees. from below it stays rather cool.. from above, it raises in a expotential way.

 

[ChopstickHero]

i made a research/test a while ago on my previous car.. i installed a short ram ( N/A motor) and got a digital thermometer on the filter itself.. just to know what exactly is going on at certain temperatures... coze the car was less powerful above 80 degrees.. but from 70 and even 60-65 the car ran like a champ. and when it got to 10 degrees and below.. ran like crap again..

to give you an idea, for some odd reason it's not as linear as i thought.. from 70 and below the cone filter temperature was very close to the outside temp.. but from 75-80 and up , it would multiply.. at 80, the under hood temp was over a 100.. now imagine in a 120 F outside temperature.

my test lead me to tyhe conclusion that the turning point of under hood temp was 75 degrees. from below it stays rather cool.. from above, it raises in a expotential way.

interesting results. I know my car runs like crap in very very hot weather. I think even in those conditions, an upgraded radiator would only make a minor difference. it's just way too hot. actually, i did see quite a number of cars pulled over with their hood's popped open.

 

[fr0st]

interesting results. I know my car runs like crap in very very hot weather. I think even in those conditions, an upgraded radiator would only make a minor difference. it's just way too hot. actually, i did see quite a number of cars pulled over with their hood's popped open.

the key word here is air density. if air is denser when it's colder, hence better performance then hot, it's because more can go in at a time.

when your turbo is pushing in 10 psi of air @ 100 F, the amount of air pushed is less than if the air was at 70 F .. it takes less place when it,s denser and will fill up the cylinder with more oxygen @ 70 F then at 100 F.. this is something the EFI cannot compensate enough.. if you have less air.. it HAS to give less fuel.. thats one of the reason of the IAT sensor.. that and the fact that the MAF sees the flow of air.. but since air flow at 100F is not the same amount as 70 F ( less dense vs. more dense) the IAT is used to help the measurement.. it's called temperature compensation... the majority of flow meters in the industrial world have that option.. i say option because not all will it ai as not all measure things flowing with such a temperature range.. some meause stuff at constant temperature so they just enter the temp setting in the menu....

but im way off track here..sorry.. too much work lol


it,s like in dead cold winter.. a car will take ALOT more gas.. it's inevitable. just for idling at 700 RPM and the piston goes down to fill up the cylinder it sucks a certain amount of air at -30 F.. now THAt is deanse air with alot more oxygen then at 100 F.. what does the EFI do? compensate.. add more fuel

and since it can add more fuel to more oxygen.. the car pulls alot better..

Fr0st

 

[fr0st]

interesting results. I know my car runs like crap in very very hot weather. I think even in those conditions, an upgraded radiator would only make a minor difference. it's just way too hot. actually, i did see quite a number of cars pulled over with their hood's popped open.

up grading the rad would not help.. as a rad is used to cool down the engine.. it's a heat dissipator.. even if you put an enormous rad thats 3 inch thick, it will only dissipate an X amount of heat and cool the engine until the the thermostat closes.. the engine wants to hold a 180 degrees temp.. and that converts to joules..as in energy.. the amount of heat build up will be almost if not the same with a bigger radiator.. the problem is not the rad..or it's size.. you cannot cool off more than the egine wants to anyway.. the problem is where it's placed.. if ya could have vents on the hood that run deep like on a ford GT to let the heat OUT of the hood instead of having the heat blow on the engine. getting the heat out of the hood is the solution.. but, sadly, it,s not an easy thing to do with all the plumbing under the hood.

 

[Brian MP5T]

If you want the engine to run colder, the T-Stat must be made to open sooner.

 

[fr0st]

If you want the engine to run colder, the T-Stat must be made to open sooner.

yeah but thats not gonna help performance.. it might even get in the way..

 

[FF Racer]

I've got a similar question. Lets say I relocate the MAF but I keep the IAT sensor on the CAI... would this cause/lead to fuel cut?

 

[fr0st]

I've got a similar question. Lets say I relocate the MAF but I keep the IAT sensor on the CAI... would this cause/lead to fuel cut?

hard to say... alot of things can cause fuel cut.. never experienced it myself though.

one thing is for sure, relocating the MAF to read hot(er) air than the IAT reads will surely give off non precise reading to whats really happening..

but for some reason, the car reacts better with a relocated MAF..and thats why im doing mine this week.

 

[Brian MP5T]

I've got a similar question. Lets say I relocate the MAF but I keep the IAT sensor on the CAI... would this cause/lead to fuel cut?

No, Worked fine for me for 4 Years.

 

[FF Racer]

I've having trouble with a relocated MAF. I always hit fuel cut at 10psi with high rpms. I was wondering if the IAT on the CAI would cause this. I'm also wondering if it could be with a tuning problem with my Unichip...

But with the MAF in it's correct location, I dont have any cut at all.

 

[ChopstickHero]

UPDATE

I'm having the same issue! BUT, this time I was cruising last NIGHT when the ambient temps were in the 70F range. So it couldn't have been a heat issue. It was the same situation though, where on the highway i was slowing down to almost a stop because of traffic. When the traffic cleared up a bit, I started to accelerate and started noticing the bogging. It's like the RPMs were jumping all over the place. No CEL this time. I wish it would pop a CEL so at least I can see what is going on.

I pulled my spark plugs today, they look fine, only 1 year old.

Could it be EGR related?!?! wouldn't the EGR causing stalling at idle and low speeds, but not bogging under acceleration?

Really hard to reproduce the problem and I doubt bringing it to a shop will help since I can't reproduce the problem.

Any hints? this is really bugging me.

 

[mspHtown]

UPDATE

I'm having the same issue! BUT, this time I was cruising last NIGHT when the ambient temps were in the 70F range. So it couldn't have been a heat issue. It was the same situation though, where on the highway i was slowing down to almost a stop because of traffic. When the traffic cleared up a bit, I started to accelerate and started noticing the bogging. It's like the RPMs were jumping all over the place. No CEL this time. I wish it would pop a CEL so at least I can see what is going on.

I pulled my spark plugs today, they look fine, only 1 year old.

Could it be EGR related?!?! wouldn't the EGR causing stalling at idle and low speeds, but not bogging under acceleration?

Really hard to reproduce the problem and I doubt bringing it to a shop will help since I can't reproduce the problem.

Any hints? this is really bugging me.

get the car scanned. there could always be a code pending which wont trip the cel.

 

[ChopstickHero]

get the car scanned. there could always be a code pending which wont trip the cel.

UPDATE

So I drove to my friend's place and it felt like it was hesitating/bogging/fuel cut, luckily i got there in time and parked. Afterwards, the car wouldn't even rev correctly in neutral. I sit there revving it and all it does is bounce all over the place. I took a vid on my cell phone camera when the RPMs were all over the place. it's kind of interesting to see the revs bounce like that. I'll try and post that up tonight.

I figured if it had to be something, it may be my Unichip EMS. I pulled it and the boost controller out of my car (about 20 mins) and now my car runs fine. HMMMMMM.... how could it have gone out just like that? I gotta email Unichip and talk to them about my issue. I'm going to run the car for the next week or so and see if this solves my problem.

Before, I was thinking it could be the timing belt, but then if it was, i don't think i would be able to drive it like it runs now.

Anybody else with the Unichip that has had this problem? I looked over most of the wires on the harness and none of them are melted/stripped/burnt.