I have a 1989 iroc-z with a 350 tpi and an auto trans. I have been having a low idle problem. The car idles at around 600 rpm which sounds low to me for an auto trans car. The car starts to miss out and stumble at idle and when in gear when the car starts to heat up,around 100 degrees.(runs great when cold) One day when I was going to work the car was trying to die out on me when I was going down the road at about 50 mph in OD. I would give it more gas and the car and kept on slowing down.(no throttle response) I let of the gas completely and tried it again and it would not accelerate. (tried this a couple of times) Finally when I came to a stop sign and slowed down completely and took off again, the throttle was responding just fine. Also my cooling fan does not kick on till 250 degrees at idle and cools down to 230 degrees.(going down the road it cools down to around 190 degrees) I have replaced the MAF, coolant temp sensor and sender for the gauge, cooling fan switch, air temp sensor, EGR valve and the switch that screws on to it, and the IAC motor on throttle body. All of these parts are acdelco except the MAF which is a remanufactured piece. The engine is basically stock except it has a SLP cam, crane double rollor chain, K&N filters and edelbrock headers and edelbrock cat back exhaust. If anybody has had a similar problem, let me know how to fix this problem. If anybody needs anymore info, let me know thanks very much

[This message has been edited by jermdm (edited November 07, 2001).]

 

This idle speed is correct for your car. I'm guessing you have either a stock chip or an aftermarket chip, neither of which are optimal for your engine since you have a bigger cam and headers. What you need is a custom-burned chip, preferably one you burn yourself or from someone local that can burn the chip multiple times (using data from a scan tool/program) to tune it up. The dead throttle response sounds like another problem altogether, but you'd need to look at the data from the computer to see what's actually going on to properly diagnose the problem.

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Greg Westphal
'87 IROC 355TPI/A4

 

Thanks for the info. I will be looking into getting a custom prom made. I do have a factory prom and computer # 1227165 which this might not be enough for the mods I have done to the car, maybe I will look into getting an aftermarket chip to see if that helps. If anybody knows what causes my fan to turn on at 250 degrees and kick off at 230 degrees will be greatly appreciated, the other fan only kicks on only when I turn on the AC. The fan, I think should kick on at about 225 or 230 degress and kick off at about 195 degrees. If anybody has any ideas about my dead throttle respose problem, please reply to this message. Thanks everybody

 

J,

What are the cam specs? Especially the duration and LSA...

What is the intake vacuum at idle?

That should give you a good indication of the need for a different PROM. MAF engines are a lot more tolerant to changes than S-D engines, so while a PROM would be a good idea, it might not be the biggest problem you have now.

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Later,
Vader
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If you want to beat the World, it might reach up and pull you down...
Adobe Acrobat Reader

 

I had the same problem with my engine trying to die when I accelerated. It turned out to be a faulty fuel pump. See what kind of fuel pressure you have.

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86 iroc, tpi,compucam,headers,cat-back,stageII chip, adj. fuel pressure, air foil, filters

 

Thanks to everybody who is replying to this message. The slp cam specs are: .480 intake & .487 exhaust, and duration is 258 intake and 264 exhaust, and duration @.50 is 206 intake and 212 exhaust.(I still have the factory cam)I will also check vacuum and let you know.---------- To the second response, I have thought about a fuel problem causing my dead throttle response because I recently put on an adj. fuel regulator, which I think was bad to begin with,(thought I seen a small tear in the diaphram) so I am going to put the factory one back on, so I will let you know if that fixes it.------ Anybody have any ideas about my cooling problem at idle. Can read about it in my previous posts-----Thanks to all

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1989 iroc-z 350 TPI, auto trans, leather int. t-tops, edelbrock headers and cat back system, SLP cam, crane double roller chain, 4 wheel disc, and aftermarket hood. Iroc-z's forever, Ford Mustangs NEVER

 

The chip is programmed to turn the fan on at ~226 degrees F and off at 221, so your dash gauge is a little off. The only way to change these settings is to burn your own chips (or by whoever burns a chip for you).

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Greg Westphal
'87 IROC 355TPI/A4

 

Does the engine light come on when the car doesn't accelerate? If so.. that may be a faulty MAF relay. Something my car had a problem with, sometimes it would be fine, other times it would have no ***** at all, kinda like someone had their hand in front of the Throttle-body blocking the air. There are 2 exactly the same relays on the drivers side firewall in the engine compartment. Swap the wires on them, and see if it fixes the problem the next time it happens. The other relay is for your fuel pump.

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1988 Pontiac Trans Am GTA L98 5.7L, Black on Black with 114,000kms.

Best ET 14.559 @ 95.25MPH
Custom 3" Stainless Exhaust Y-Pipe back (High flow Cat and Flowmaster Mufler)

 

Thanks for all the info. My service engine soon light did not come on when my car hesitated and it has not come on at all for whatever problems I am having.(bulb works) I am thinking my problem is with my cam shaft, since it is a bigger cam than stock, which I do still have the factory cam. Does anybody think I should put the factory cam back in? ------To the other response, I dont think my temp gauge is reading bad. I have two gauges and they read exactly the same(maybe the cam has something to do with my fans not kicking on when thay are suppose to, since it is aftermarket and it might be confusing the computer) Does anybody know how much it would cost to have a custom chip burned?(ballpark figure) I am slowly sorting out these problems, so to everybody that has replied, thanks very much. Anybody have anymore ideas?

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1989 iroc-z 350 TPI, auto trans, leather int. t-tops, edelbrock headers and cat back system, SLP cam, crane double roller chain, 4 wheel disc, and aftermarket hood. Iroc-z's forever, Ford Mustangs NEVER