Mechanics

CHEVY IDLES REALLY BAD AND KILLS PLEASE HELP

1999 Chevrolet Blazer

Engine Performance problem
1999 Chevy Blazer 4 cyl Four Wheel Drive Automatic 197000 miles

I recently posted about this and had a reply about the P1351 code. I was given a diagram that is hard for me to understand. So please dont send it again. But here is an update.

I replaced the crankshaft sensor. I used an ohmmeter and checked all the wiring and nothing is wrong that I can find and I am stumped. I dont know what the problem is.

It starts. But it idles really bad and then it kills. If I press the gas pedal too hard it will kill. If I press the gas pedal lightly, the engine slowly catches up with me and revs up. Sometimes at idle, it will act like its going to die, but then revs up by itself. If I put it into drive or reverse it kills.

The RPMs do not work.

I replaced the starter, plugs, plug wires, distributor cap, rotor, ignition module, camshaft sensor, crankshaft sensor, MAP sensor, fuel filter. Checked and cleaned the air idle control valve and sensor, checked the throttle control sensor, cleaned the egr valve and pcv, patched up all the vacuum leaks I can find, oil change, radiator flush, checked and cleaned the MAF sensor. Checked the fuel pump and fuel pressure and it is good. I also checked and double checked to see if the timing was correct and it is correct by the book.

I scanned it with a scanner too.

Here are the codes:

P1351 Ignition Coil Control Circuit High Voltage
P0140 Downstream heated o2 sensor circuit high voltage(bank1, sensor2)
P0108 Manifold Absolute Pressure sensor circuit high input. (I keep getting the code, but I already put 2 new MAP sensors in it with in the last week, and I still get the code)

I know that the O2 sensors are bad, but I should still be able to drive it. Some mechanic told me the other day that my catalytic converter could be the problem. He told me to take out the O2 sensor after the engine before the cat, and if it was the problem I would be able to drive it. But still I have a problem. I did tap on the converter with a rubber hammer and I heard rattling.

Please Help. I hope this is enough info. I have a 1999 Chevy Blazer 4.3l 4wd V6 Enhanced Distributor Ignition.
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Jkhamistos
April 1, 2009.



Check the convertor, either remove and inspect it or have a CAT backpressure test performed.

If clogged bad enough, removing the O2 sensor will not help, and depending where it is located and where the hole points can actually cause more damage (burn wiring harness, cause a fire).
A MAP sensor failure will cause the engine to run rich and ruin the convertor.
The downstream O2 sensor error is most likely caused by the convertor.

Mmprince4000
Apr 2, 2009.
I will more throughly check the converter today.

But why do I keep getting the MAP sensor code when I already replaced it with a brand new working sensor? Just to make sure I brought one back just in case it may of been defective and got another one and put that on, and still the code comes up.

What do I have to replace with the P1351 code? The diagram doesnt make any since, but I understand what Im supposed to be checking. There is no rubbed through or broken wires and im getting power to all the sensors. And all the sensors are new.

What causes my RPMs not to work?

Im also thinking the PCM is at fault and needs to be replaced. Because some idiot last month said that my cpu was the problem for my no start and he took mine off and put a used one on. And still no start. It turned out it wasnt the cpu. It was that the guy took my distributor out and didnt know how to time it. So I bought the book and followed the directions and got it to start and I replaced a couple of sensors too.

Tiny
Jkhamistos
Apr 2, 2009.
The MAP error is most likely related to the CAT since the MAP uses vacuum to send signals to PCM. Assuming the CAT is clogged it would create a vaccum problem (out of the normal range) and would set the MAP code.

I think if you do indeed have a clogged CAT, both the coil error and the MAP error may be fixed, since you are getting excessive backpressure in the cylinders, but check the CAT and let me know the results.

Mmprince4000
Apr 3, 2009.