[Slick_Sammy]

Guys, got a problem here that I can't figure out. I have an 89 4.3L blazer with 163,000 miles. For about 6 months now, when cold, she'll stumble bad off idle. The power slowly comes back to me. It doesn't do it every time, but often. ONce warm, it runs good. Also it idles not very well when cold (rpm goes up and down sometimes).

I've replaced (for whatever reason):
plugs or wires
distributor rotor
distributor module
PCV valve
Fuel filter

I'd appreciate any advice, I just can't figure out what is causing this. I know it's got a lot of miles so I just live with the situation but it's getting worse. No 1 plug keeps fouling (oil buildup) so I'm going to replace the valve seals soon. Thanks!

 

[nunze51]

is that carburated or injected?

 

[Derrick824]

Last time I had a problem similiar to that it was my timing.

 

[XCELLRTR]

IF ITS THROTTLE BODY INJECTED SPRAY SOME CARB CLEANER, WD-40 OR SOMETHING AROUND THE BASE OF THE THROTTLE BODY TO CHECK IF GASKET IS LEAKING WHICH THEY ARE PRONE TO THEY LEAK MORE WHEN COLD AND GET BETTER AS ENGINE WARMS AND EXPANDS MANIFOLD AND TB AND SOMEWHAT SEALS LEAK ITS WIRTH A SHOT OTHER THAN THAT IT COULD BE A TP SENSOR OR IDLE AIR CONTROL VALVE

 

[Slick_Sammy]

Could it be throwing codes without the SES light being on? Or would it throw codes if a sensor was bad?

 

[SY2932]

Pull the codes and you will know is going on. All you have to do is use a paper clip to jumper the ground and diagnostic pins on the Assembly Line Data Link (ALDL). This is located under the dash near the fuse panel. Pin "A" is the one in the upper right hand corner and pin "B" is the one immediately to the left of pin "A". Attach the jumper and turn the ignition to "ON" but, do not start the truck. The "Service Engine Soon" light will flash a "code 12" by flashing the "Service Enigine Soon" light once followed by a brief pause and then flashing it twice quickly. It will flash a code 12 three times then any codes that are stored in the Electronic Control Module (ECM) will be displayed. Each code stored in the ECM will be displayed three times. All you have to do it count the flashes to determine what code is stored. A "code reader" like a garage uses is easier to use but, why pay for something that you can do yourself for free?

Anywho, based on your problem, I'm guessing that you may have a oxygen sensor (O2) problem. If it is the culprit, it will manifest itself by making your truck run rough until it gets good and hot. If you are still following this post, pull the codes and post what you get and I will tell ya what the code means. Or you can pick up a Haynes repair manual and decode it yourself. HTH

Mike

 

[Slick_Sammy]

Thanks for the help, but...

I tried pulling the codes and only got the code 12 to flash repeatedly, so I guess all the sensors are reporting ok.

Could it really be the timing? As bad as it stumbles sometimes, I would think that if that was caused by the timing, then it would be more obvious at other times. Once warmed up it runs good, but doesn't always idle well. I just don't know.

 

[rsharpe]

Have you checked you cat?

 

[SY2932]

Ok, no codes stored in the ECM huh? Then you may want to cofirm that your timing is set correctly. Make sure that you disconnected the ESC (Electronic Spark Control) first. Look at the VECI (Vehicle Emission Control Information) sticker under your hood and it will give you the low down on what to do. There should be a tan wire with a black stripe that you will have to disconnect prior to adjusting the timing. It will probably be under the carpet on the passenger's side. It will be a single wire with a connector on it. After it has checked, it is reconnected. This is important to do because if you don't your timing will be WAY off.

Another thing you might want to consider checking is your EGR (Exhaust Gas Recirculation ) valve. Check it when the engine is cold so that you don't burn yourself. You should be able to press the diaphragm up and down inside the housing. Unless of course, you have a sealed valve and in that case you can't check it. HTH

Mike