Explain this one.
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Joined: Jun 2012
Posts: 89
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From: Zimmerman MN
My car does the EXACT same thing. I don't think my chip or ecm has been altered in any way, so I kind of doubt the problem is in the software. I was leaning toward bad O2 sensors on mine, mainly because it smells very rich when idling with warm engine.
Starts hard after warmed up, have to give it a little gas to get it to fire, revs high for a few seconds then drops to normal.
Starts hard after warmed up, have to give it a little gas to get it to fire, revs high for a few seconds then drops to normal.
Le Mans Master
Joined: Sep 2006
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From: Phoenix AZ
2021 C4 of the Year - Modified Finalist
Ok, my 86 did this when I bought it. the ECM went bad, and I changed the ecm, using the same chip. Nothing changed.
I bought an 87 chip and stuck it in thinking I was going to get a different spark table, and the car starts, idles 150 RPM high, then drops down to 600 RPM right away, no high revving. I was amazed, I put my stock chip in, and yup, it does that.
So, I am running an ARAP chip, and it is great.
Unfortunately, you can't do that on an 85. It has a different computer.
But it is in the chip
I bought an 87 chip and stuck it in thinking I was going to get a different spark table, and the car starts, idles 150 RPM high, then drops down to 600 RPM right away, no high revving. I was amazed, I put my stock chip in, and yup, it does that.
So, I am running an ARAP chip, and it is great.
Unfortunately, you can't do that on an 85. It has a different computer.
But it is in the chip
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Le Mans Master
Joined: May 2004
Posts: 5,866
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From: Hellinois
Finalist 2020 C4 of the Year - Modified
That is the only place it can be, I've changed everything else. I guess I can live with it or see if I can contact the guy who did the chip. Today I disconnected the cold start injector and it does the same thing so it's not there and that was the last place I have to look. He is no longer on this forum so I don't have a clue as to how to contact him. I think I am going to just wait & maybe have the car dynoed and have a chip made just for my combination instead of a mail-order tune.
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Joined: Jun 2012
Posts: 89
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From: Zimmerman MN
Well, it might be a little early to say for sure, but I think I fixed mine with 2 new oxygen sensors. I replaced both upstream O2 sensors and my car has not done the "hard start/high rev" thing since. I haven't driven it much since replacing the sensors, but I did drive it enough to say that I'm pretty sure it fixed the issue. A good hot day and a few heat soaks will tell for sure.
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From: Overland Park Kansas
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Joined: Jun 2012
Posts: 89
Likes: 3
From: Zimmerman MN
Yes, O2 data is ignored in open loop, but the O2 sensors are what sets the block learn multiplier (BLM). The last stored BLM values are what the ecm uses durring a cold start to determine where to start the fuel mixture at on a cold start (open loop).
I drove my car around a lot today, in heavy traffic and made a few short stops. Every time I restarted the car, it started and idled perfectly. I'm quite convinced that the new O2 sensors fixed my problem.
Even though my car is an LT1 and Midnight85's is an L98, the O2 sensors still affect BLM the same way.
I drove my car around a lot today, in heavy traffic and made a few short stops. Every time I restarted the car, it started and idled perfectly. I'm quite convinced that the new O2 sensors fixed my problem.
Even though my car is an LT1 and Midnight85's is an L98, the O2 sensors still affect BLM the same way.
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Joined: Jun 2012
Posts: 89
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From: Zimmerman MN
Oh, also wanted to say that I have been fighting this problem for a while now and I had already replaced the TPS, IAC and throttle body gaskets. I also cleaned the throttle body. None of those things made any difference at all.
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Le Mans Master
Joined: May 2004
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From: Hellinois
Finalist 2020 C4 of the Year - Modified
I did have a bad O2 so I replaced it but for a separate issue, the car was not going into closed loop. It is now and the idle thing is still present. GREGGPENN & coupeguy have called it I believe, it is in the chip. This is going to cost me another chip since the individual who burnt the chip is refusing to correspond with me making his "Warranty" complete b.s. Naturally I find out about this clown once I have already paid him for my chip.
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Joined: Nov 2003
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From: Overland Park Kansas
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I did have a bad O2 so I replaced it but for a separate issue, the car was not going into closed loop. It is now and the idle thing is still present. GREGGPENN & coupeguy have called it I believe, it is in the chip. This is going to cost me another chip since the individual who burnt the chip is refusing to correspond with me making his "Warranty" complete b.s. Naturally I find out about this clown once I have already paid him for my chip.
for the name of said 
