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Discussion Starter #1
My truck is misfiring like crazy after warming up and I have this code. The o2 sensor is only a year old. Should I go ahead and replace the sensor and is there only 1? I have only located 1 and it is under the truck. Or is there another cause making the o2 read it as being rich?
 

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Discussion Starter #3
I have changed spark plug wires and the ignition coil with no results. It still misfires at idle right after started and then drives fine for the most part, after about 15 minutes of driving it starts stumbling really bad and doesn't want to run and hesitates when given throttle followed by it lurching forward. Everything is good when WOt.
 

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What year truck, throttle body or carb? If throttle body might want to check voltage on tps sensor. Mine was showing low voltage kinda had same symptoms. May also want to check timing.
 

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Mine is also 91 TBI. I just put a new engine in mine. Had same problems. Found out distributor bolt was a bit loose and timing changed a bit.
 

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When you checked voltage on tps sensor you had .5 volts with key on not started and 4.5-5 volts when you open throttle wide open. You want to open throttle gradually to make sure their is no spike in voltage reading.
 

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Discussion Starter #10
When you checked voltage on tps sensor you had .5 volts with key on not started and 4.5-5 volts when you open throttle wide open. You want to open throttle gradually to make sure their is no spike in voltage reading.
Yeah thats exactly how it read. I have a map sensor and ignition module shipping to me right now to try.
 

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Discussion Starter #11
Ignition module made no difference, Map sensor arrives tomorrow. I guess next in line is EGR or 02 sensor? So far I have changed:

Wires, ignition module, ignition coil, and checked the TPS. Spark plugs are only a year old and I'll change them as well if issues continue.
 

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I'm having same issue in my 87.
new O2, CTS, TPS, MAP, EGR sol, rebuilt TB. I'm at my wits end.
I'm now convinced the cat is clogged, punched hole in check port - ran even worse!
 

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Discussion Starter #13
I'm having same issue in my 87.
new O2, CTS, TPS, MAP, EGR sol, rebuilt TB. I'm at my wits end.
I'm now convinced the cat is clogged, punched hole in check port - ran even worse!
Please let me know if you figure it out, I'll keep this thread up to date until I find the issue. I'm lost as well.
 

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Man I been dorking with this thing and posting here for ideas for upwards of 2 months with <strike>little to</strike> no progress.
hell I even bought another beater to relieve the stress of having a crappy running s10 and my replacement car ate its transmission last weekend, so I'm convinced the universe is plotting against me.
One factor that puzzles me is that when at idle if I quickly rev the engine, like snap rev; the idle comeback is less and less until it chokes and dies, every other vehicle that you do that on will either steady ramp up rev or respond per rev and keep steady idle.
Today I'm reseating the TB gasket, checking fuel pressure, replacing cap and rotor (again), checking ground straps, checking/setting timing, then I suppose I'll just eat the 10MPG to reno and back for a replacement tranny for my toyota.
 

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Clogged cat can be determined easily with a vacuum guage in the brake booster line and 2500 rpms.
 

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yea well I'm a cheap bastard. was looking at a fuel pressure gauge at orileys when I saw it was $52 I said "I'd rather save $30 and get a new fuel pump.
same thing with the cat, I'm going to Reno for a transmission for my tercel and I'd rather just buy a new cat at the summit racing for $45 and have some oakland hipster weld it in.

Runs a little better now, well as bad as it did when it started running like shit, reseated the TB and put tacky on both sides, new cap and rotor, reset to 10°BTDC and fixed a bad connection at the starter.
**** it, if donner pass eats it its available on I-80 for free, I'll leave the title in the glove box.
I'm so done with this piece of shit.
 

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Hmm I wonder if yours is like mine Dross93; at low RPM's, low speed acts like shit, power to brake booster and idle downturn when brakes applied - get on the freeway and it screams; just did overall average of 60MPH up and over donner pass, there is a sweet spot in the acceleration, I'll say ~2800 - 3200 RPMS in 3rd gear, but when it kicks into overdrive it struggles a little bit, coasting in OD is a jerky thing, best done in 3rd, keeps the RPM's higher in the 2000's.
I'm going to adjust the TPS again and think more about the cat on this cold day in reno.
 

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Well unless I move to nevada (cali resident now) I need to keep the cat on.
 

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Discussion Starter #20
Since USPS lost my new map sensor, I went to the junkyard and grabbed a couple to try and the first one I threw on made it run great! I swear I can hear a slight misfire at idle, but I drove it for 30 minutes with no issues. I bet the misfire is just fouled plugs from running rich. I will update later on in the week if the issue reoccurs.
 
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