Heat + A/C = Car runs like crap

[webshot]

I am having a issue when I drive my car on long trips in the heat. It is a 88 GT bone stock and it is my daily driver. Lately we have been having a heat wave and I have been experiencing strange happenings with the car. 1st problem is when I drive for a small time and I turn it off. The car wont start. Acts like the battery is drained. If I wait for a few minutes, then it starts right up. Second issue is if I drive it non stop (for example the 70 miles I drive everyday in it), the car develops a very rough idol and I have to goose the pedals to keep it running when at a stop light. And when I do this I get small back fires thru the top of the engine and hesitation. Car runs slightly hotter than usual and the problem is worse when the AC is on (the problems start sooner) So far the things I have done, is adjust the timing (12 degrees currently runnin 91 gas), changed egr, changed plugs and wires. Gonna change oil and drain radiator today. Trouble codes when engine is off is 11, when on is 44 and 94. Which I was told earlier wont hurt the car to drive like this.

Any other things I can look at? Got a sneaking feeling the car will leave me stranded very soon.

Thanks

 

[BK_CAULEY]

the not starting after being ran for a while could be the starter. it could be locking because of the excessive engine heat. and as far as it running like crap after being ran a long time....dont really know. i know our car measure engine temps and adjusts air/fuel to compensate but im not sure what to check for. have you checked the thermostat? i live in south GA and during the summer months i remove my thermostat and it stays fairly cool. if i leave it in it gets hot no matter how its driven. sorry i wasnt much of a help but thats the only things i can tell you.

 

[webshot]

thanks I will check the t-stat, every little piece of info helps me at this point...

Also I read somewhere taking out the t-stat is not a very good idea. Is this not true?

 

[Daggar]

The backfiring to me, is an indication of an incomplete spark issue. Keep a muti-meter in the car with you to rule a charging issue.

Another thought is that the coil might be heating up and having fits (an indication that it may be going bad).

Also... look at your plug wires, cap, and rotor, for condition.


None of these things would explain the hard start when the engine is hot though. The only single item(s) that come to mind that would account for all the symptoms you've listed would be a fault in the charging system somewhere.

 

[webshot]

thanks, just to add, ran codes again and when engine is on, I am getting code 12 and 21.

Daggar, what am I checking for with the multi meter? When the car is hot, check for AMPs through the battery terminals? I'll change the cap and rotor too, forgot to do that when I changed wires.

 

[HISSIN50]

When it won't crank, does it act like the battery is drained with respect to the starter motor, or in general? Does just the starter act up or do your lights and other accessories not work also?

Your IAC isnt doing too hot from the sound of it. I'd remove and clean it. Also ohm out your ECT to see what the issue is with it. It could be playing into your issues here. If it ohms out ok at several temps, double check the signal voltage going to the computer so you know the wiring is ok.

Good luck.

 

[webshot]

lights seem to be fine, just in respect to the starter.

Could you give me some tips on checking the ECT? Also what are the correct numbers to look for when checking voltage to the computer.

Thanks for the tips thus far.

 

[HISSIN50]

Go to the first post of Jrichker's idle surging sticky. He lists the ECT resistance and voltages a ways down the opening post.

For resistance checks, disconnect the electrical connector and put your meter leads across the ECT's terminals.
For a voltage check, ground the black meter lead and then check the signal voltage with the red lead.

 

[Daggar]

thanks, just to add, ran codes again and when engine is on, I am getting code 12 and 21.

Daggar, what am I checking for with the multi meter? When the car is hot, check for AMPs through the battery terminals? I'll change the cap and rotor too, forgot to do that when I changed wires.

Shut the car down and check for voltage at teh battery when it's in the "wierd" condition that you're talking about. If voltage is low then you at least know that you're having some sort of charging issue whether it be a constant one or one that just shows it's head when hot.

Items that might cause a charging issue only when hot are things like poor wire connections or corroded wiring etc.

 

[webshot]

Update

I changed the coil, clean battery, cap and rotor, flushed radiator and changed oil. I drove the car after coil change and it seemed to have alleviated the hard start when warm issue (I think real test will be tomorrow). I check all wires I could see and they looked good.

Real test will be tomorrow when I drive to work in triple digit heat. *crosses fingers*

(I was also told by a local mechanic dude that a bad or failing coil will cause these issues. Is this true?)

Oh and removed the t-stat just to test things out that way.

 

[Daggar]

(I was also told by a local mechanic dude that a bad or failing coil will cause these issues. Is this true?)

Hmmmm... I think that may have been mentioned within this thread before.

 

[ninety15.0]

Another thing you need to look at is your neg bat terminal ground cable. Make sure you are making a good connection. I actually run two ground cables from the neg battery terminal and that really helped my hot start issue. Another thing you can look into is swapping out the stock starter to a SN-95 starter. They use a PMGR starter which are much more efficient (read: less heat) PMGR is permanent magnet gear-reduction and unlike the stock EMF positive engagement starters they use no coil windings. Therefore you get awesome hot start and high compression start performance and the unit is much smaller than the stocker. You should look into picking one of these up. I never worry about starting my 10:1 motor in the triple digits!