89 Formula 350 TPI - Car runs fantastic until it gets hot and goes into closed loop, then misses and runs rough. When it gets hot it gets real hot, real fast. Only mods are SLP intake runners and ported, matched plenum.

New parts include, 19 lb injectors, fuel pump, fuel filter, plugs, wires, rotor, cap, ign module, Ign coil, dist and all sensor pigtails, IAC, TPS, O2, thermostat 180 degree, vacuum hoses replaced, EGR valve, IAT, and many other parts I'm sure I've forgot. Timing is set correctly. Bought the car 2 years ago and it's never ran right.

Car throws no codes. It's to the point now that it's so depressing it's comical. Ahhhh, but those first five minutes, before it heats up are magical.

If you have a shred of decency...please help.

Thank you

 

that would tend to be o2 sensor or so it sounds like to me

As the car heats up and gets ready to go into closed, it doesnt use the o2 sensor. Once it hits closed loop it uses the o2 sensor.

But you say you have a new sensor so that seems odd. I'd check the wiring to the o2 sensor and such to see if its all good as the ecm may not being reading it.

Also are there any vacuum leaks that could have a influence on this?

I dont think its MAF related as open loop uses MAF just the same as closed.


Do you have a laptop and scanner cable to connect to the ALDL port to see whats goin on as it goes to closed loop?


Also, is this happening on every startup including hot/warm starts? Like first start of the day is the coldest. Does it run great till it hits closed loop and warms up alittle? if so, shut it off and wait a minute, then restart it again and see how it runs for the few seconds before it goes into closed loop again. Does it run poorly this time as well?

 

Thanks for the reply. I have checked the O2 sensor wiring and initially found it to be cracked so I spliced in a new section. Using the proper gauge and terminations.

I do have a laptop but no cable. I would imagine this requires special software? Where would I get something like this?

The car has never ran well enough to be a daily driver in the two years I had it. It began with a fuel probelme... I've never really taken it anywhere...it's been a nightmare. But on the few times I have taken it to the gas station, it has the same problem upon restart. Once it cools down it's fine.
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And, I can't imagine that it has a vacuum leak. I have replaced every related hose.

 

Interesting

For cable/tuning stuff go to moates.net and check out his ALDL cable and there is Tunerpro RT software. You could look into getting a chip burner (tunerpro RT comes with it for free), the chip adapter, and that cable to start tuning your own chips and such which is great for the long run. These cars benefit from some tuning

But basically tunerpro RT and that cable or some other hand held scanner is necessary to truely know whats goin on in the engine.

But the problem sounds like something timing/o2 sensor related. I'm not sure what all is governed by closed loop. I'm not sure if timing control from the EST/ESC stuff comes into play with closed loop.

I run my car open loop and i notice my timing doesnt change so i dont think timing is controlled differently in closed loop as in open loop.

Atleast with tunerpro you can watch o2 voltage, MAF signals, engine spark timing, etc all at same time and see whats changing as the problem occurs. Could help figure out the problem

 

It looks like the cable is $80 and the software is a $30.00 donation. Does this seem correct? I guess I could see what changes and try to figure it out from there. You say you run your car in open loop. This would eliminate my problem. How is this accomplished? I would imagine a change in the ECM correct?

 

there is one value you change in the chip. In tunerpro you just set closed loop enable temperature to like 300 degrees instead of 104 or whatever it is stock. It will never get to closed loop works good. I tune with wideband o2 sensor and airfuel gauge and have a good running car but my closed loop worked before i just had a lean start issue i couldnt figure out but i think i know what the problem was, just never bothered to try my solution

yes, cable is 80 and 30 dollar donation for the tunerpro RT but it may come with the cable. I know i recieved a copy with my burn1 programmer that moates has for 80-85 bucks and i got another copy that i think i got with the cable.

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