ok first post in the v6 section but got a felling it wont be the last lol i am no stranger to the 2.8 i have had a ton of s10 with the 2.8 its really a good motor if you can get threw the 130,00-135,00o mile mark i have found the like to throw a rod or spin a bearing but it you can get passed that magic time they will run forever.....well in a deal that a friend and i cooked up i got rid of a truck and in return picked up two 87 fir birds one 5.0 and one 2.8...but the 2.8 is giving me crap and i am stumped....when you start it it runs fine and smooth within a few seconds it runs up to around 1200-1500 rpms and gets a "check engine" light drops back down to around 750-850rpm and runs like she is a lawn mower....or like you removed half the plugs and removed the engine mounts also run her up to 3000 and up she has some vibration but not so bad and it goes away and she runs like a champ......now for what i have done it it so far...new ICM, cap, rotor,wires,plugs(the ones that were removed were new but loaded with gas) maf,and ecm,fuel filter,oil and tranny change, air filter and set timing to 10* and the snap-on scanner says 16* so not sure what to think there...maybe new dampener and its off about 6*

 

idve said timing initially??? bad coil?? vacuum leak after maf????
check codes...

 

yep did all that...code came back as maf that why i replaced it.....did nothing but make my wallet lighter

 

almost sounds like it goes deeper.. as the ecu screwing up not all cylenders fireing... id start with checking coil/plug spark maybe even injectors.. fuel soaked plugs.. running very rich im still thinking bad coil..

 

yeah def not burning right bad coil check that and earths......

 

i'll give that a try in a few days i have the v-8 in the shop now getting ready to start on the headers then my jeep goes in after that then i'll get the 6 in and see what happens

 

Do you have access to a multimeter?
If so, unplug BOTH ends of the injector harness, so as to aviod backfeeding into the ECM and frying it. Using the DMM, probe (on the front connector) the first and third, and the second and fourth terminals, to test each bank of injectors, on the 200 ohm scale. If the DMM reads over 4 ohms, you have a bad injector or two, and you need to do some further checks. Each injector should test at 12 ohms or thereabouts, with no more than 20% variation between the highest and lowest injectors.

I say this because you have gone through the ignition and control systems, but you haven't gone through the fuel system yet, and you are still having probs. It sounds to me like you have a fuel problem, probably not enough fuel getting to where it needs to go.

Oh, and throw an ign coil at it, just for kicks. Sounds like you might have a weak spark as well.

 

The best part of doing our own repairs is fixing something by narrowing it down to a few possibilities. Sometimes, codes don't always appear, for a problem.
You said that you are getting the MAF code, and that you changed it out. Did you replace the MAP relay?

Also, check your fuel pressure, by connecting the gauge at the rear of the intake, to the right of the fuel intake line. You might have a bad fuel pressure regulator. It is a simple fix. You will require a #10 Torx bit for the retaining screws.


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I meant MAF relay, not MAP relay. Sorry for that.

 

ok its been i while but finally got around to the car he we go...replaced..Air temp sensor maf sensor and relay six new injectors and regulator tps coolant temp sensor ecm iac valve harmonic balancer,fuel filter.....car still has vibration at idle to 2500 rpm the cleans up idle is everywhere going to start with vac. lines next the i'm done with it i am fed up with dealing with it
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oh yeah new plugs cap rotor and coil

 

Odviously, the vibration occuring only in the idle - 2500RPM range is giving you a pinpointed range. At this range, fuel volume and spark is at its lowest. As the RPM's go up, so does fuel usage and output from the alternator.
If you had a bad bearing or something that was out of balance, then it would be a problem throughout the entire RPM range (I have to logically assume).
Whether you have good plugs or premium plugs, the spark will get greater with the increased vaccum and current created by the increased RPM's. So that is a "cheap" good sign of you ignition performing at the higher ranges.
There is more besides the ignition coil that doesn't last as long, that I would be concerned or questioning.
1.) The distributor's pick-up coil
2.) The ignition module
3.) When you set the timing, you are suppose to unplug the EST bypass
wire, did you remember to reconnect it?

Ruling out the ignition all together, how is your individual cylinder compressions? Any exhaust odors?
The third idea, which is a strong one, would be the timing chain. You didn't mention that on the replacement list. Is there any possibilities that this engine has an aftermarket camshaft?

 

i did replace the ignition module it was the first thing i replaced when i got the car thought the low rmp went out or was going out..i have the ford ranger injectors in it from the 2.9

it doesn't have a performance cam in it......this car couldn't get out of its own way until it passes the 2500rpm range then it runs like a 2.8 but from idle to then its a 5hp lawn mower that shakes more than a harley

yeah got the timing set perfect at 10* and made sure i pluged it back in and ps the new maf and maf relay didn't do anything and the CEL is still on and throwing the same 34 code?

 

I had simmilar problems when I had problems with my throttle position sensor (no power below 2,100rpm, idle too high). If you've replaced the sensor already, check the wiring going down the front of the block. Mine had actually broken the plastic shield, rubbed through the insulation and was grounding on the block.

 

yeah it was replaced an wiring is good set it at .54 on my DMM
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oh and compression is good and no exhuast smells that rule anything to be wrong just normal

 

Did you check over all of the other wiring?

 

yes and used cleaner on all pigtails

 

A fuel injection system can be tricky. If a sensor or reading is going bad or below limits, then the ECM will compensate by making the adjustments. It isn't rare for a code to come up and have it not be the root of the problem, but just the part/sensor that is most effected (compensating the most) due to the change in the system. Remember, you have the engine and the computer working together, yet both independent.
You are at the point were you have replaced a lot of the odvious issues, but still having the problem exist.
I have an Auto x-Ray scanner, which is really good. It provides "real time" operating data which comes in handy when evaluating the ranges coming from the sensors. I don't know if your Snap-On scanner provides that, but you'll know what the computer is getting for information.
You sound pretty knowledgable with what you are doing. It is also not uncommon for even the best of us mechanics to look at something two or three times, and still not see the odvious problem or mistake right in front of us; especially when we are frustrated. It isn't impossible to buy a sensor that is deffective as well.
Make sure you are replacing your sensors with the correct corresponding OEM numbers. It may be the same year/engine/model, but part number variations do exist. Check your Ohm value on the distributor pick-up coil to make sure it is good. Replace your timing chain. Lastly, I am going to say that you might want to clean/replace your EGR valve/solenoids.
I can definately say you have captured our attention with your car's problem, and we all want to know the problem when it is found.
On my car, I had replaced the O2 sensor, shortly after I bought the vehicle. When I was removing the sensor, it came out with about 10" of wire still attached. The wire was burnt/cut from a previous owner and was never discovered as a problem. It didn't even show up as a trouble code on the scanner!

 

i will keep everyone informed on what going on with it,my other bird wasn't used for over four years and i had less problems than i have had with this one...vac lines are going to be my project today also the alt. cause bought on for my bird but never put on so going to throw it the the wolf and watch her eat another part for nothing lol...oh well vac lines are a no go still the same crap, and just out of a thought of hope from other post that i searched unplugged the egr valve to see what would happen can ran pretty good for a second or two then right back to vibrations and pooh plug it back in same thing good for a second back to crap so that might narrow it down for me alittle but really doubt it...i realy think this car hates me maybe cause i have spent so much time on mine that it feels like the bastard son or something but at this point it is

 

well i'm just going to take the loss and sell this thing i dunno but i do know i have gas in my oil which is never good so im just done with this car all together

 

oh and also noticed it is poppng through the throttle body when i rev it then goose the throttle

 

gas in oil.. leaky injectors. sounds like fuel washing the cylenders. must be running very rich

 

the car runs the same with maf unpluged or plugged in...all injection is brand new.i even unplugged the cold start injector thinking maybe it was running or leaking but samething car is a turd no need to polish it up spent to much time and money with it ...i have more in injectors and new parts on that car than its worth to sell or pull the motor and replace with my old 305 so just going to sell the thing and hope i can get 750.00 or so out of it and i would still be at a loss on the money end