Rough Idle(o2???) Paging Speartech!!!!!!!HELP

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Sep 25, 2004 | 11:59 AM

Remington H.

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From: Friendswood,Texas

Rough Idle(o2???) Paging Speartech!!!!!!!HELP****UPDATED***

I have just finished and gotten running my truck. Its a 91 fullsize blazer and I swapped in a 6.0/4l80e and it runs beautifully on initial startup, but after it warms up and goes into closed loop the rpms just drop to where it almost dies and stays that way. We did have to wire the plugs for the o2s because they were different plugs than what is on the harness so I am thinking that something is not right for going into closed loop because it runs so bad after it warms up and stays that way. If I shut it down and start it back up, it runs good until it warms up and goes back to normal. Is there anything I can check myself, I dont have autotap or anything like that so please help me out, I am in the dark on this one.

Thanks,
Remington

Last edited by Remington H.; Oct 3, 2004 at 01:34 PM. Reason: updated

Sep 25, 2004 | 12:55 PM

crainholio

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Not sure if Speartech can diagnose your car over the Internet, especially given lack of PCM data. Figure that you're asking him to put aside a paying customer's project when you ask for this, and manage your expectations accordingly.

Do you have a working Check Engine light or ALDL connector on your conversion?

Sep 25, 2004 | 07:18 PM

jeromio

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From: Durham, NC

I have the exact same problem on my car. I thought about paying the extra $$$ to get the PCM retuned, but so far I have just been running in open loop - O2 sensors unplugged.

I had 2 sets. First set got fouled, installed the 2nd set, they got fouled. I gave up - certainly wasn't ready to experiment on another $$$ set of O2s. Via Atap I could see that the O2 readings were crap - they'd waiver all over the place even after warmup.

I'm sure the motor is running suboptimally in open loop mode, but it's fine for now.

Sep 25, 2004 | 08:20 PM

Lostpatrolman

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From: Largo, Fl.

hmm... I thought o2s were supposed to jump around. Here is a graph from hptuners. Notice the o2 signals. I think once they slow down their rate is when they get lazy and need to be replaced.

Sep 25, 2004 | 09:57 PM

Remington H.

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From: Friendswood,Texas

yeah I figured that it was a shot in the dark, but I am in a rush right now and it has caught me a little off guard. Yeah I unplugged the o2s also and took it for a drive, it was definitely running better that trip out and I will see in the morning if everything goes smoothly again.

Thanks,
Remington

Sep 27, 2004 | 09:25 AM

Speartech

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Here's some of the things to check, based on what I have seen come in here over the years.

1) Bad O2 sensors.

2) Exhaust system air leak (even a small one) allowing outside air to get to the O2 sensors.

3) Left and right O2 harness wires swapped.

If all else fails, get a scan tool on it somehow so that you can see what's happening.

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Oct 3, 2004 | 01:32 PM

Remington H.

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From: Friendswood,Texas

Ok, over this weekend I have tried my best to figure this thing out and I am at my wits end. 1. I checked the wiring, and rechecked it, still ran like crap 2. So then I installed another set of o2 sensors, still ran like crap. If I leave all 4 plugged in, it runs like crap, just front 2 plugged in runs like crap, just back 2 plugged in runs good. So I am guessing there is something definitely wrong with the front o2 sensors. I took it down to have it inspected without any of the o2s plugged in and while it was on the sniffer, it didnt pass the low speed barely but did for the high speed. Can I get a set of o2 simulators for the front and leave the back sensors alone so the motor will run good and let me pass emissions???? I really want to because this has got me confused because all the wiring is good, and the o2 sensors I put on after first set were brand new. Any Ideas??????