3.4 V6 advice

[stimey]

Noobie here, I have been hanging out reading and learning. So here is what I have 1986 GMC S15 with a 95 model 3.4 camaro V6. This has the TBI off of the 2.8 that was originaly in the S15. This truck has set around for a bit until I purchased it. This thing really runs good, lots of HP, the problem I am having is it idles rough, sounds like it is loading up to rich. No black smoke just a rough idle after it warms up and idles down. It doesnt idle as low as I think it should either. Can you guys maybe point out the pros and cons about this set up, and what I might do about the rough idle? I know I need to do the tune up and cleaning etc. but any additional info would be greatly appreciated. Any info on the ECM might be interesting as well, my main focus in to make it run smooth and get good fuel mileage. This motor has 65,000 mile on it.

[60dgrzbelow0]

Fill in the blanks on whether you have the NA(TBI?) intake setup from the 2.8L original engine...or whether the 3.4L in the truck is ECM controlled, as in the original F-Body... The more info and symptoms you can describe...the higher the quality of the answers you'll get ...and the sooner the problems get sorted out.

[stimey]

First thanks for taking time to reply, please keep in mind I am very new at this V6 stuff , and computer controlled. I talked to the guy that done the work and he told me that the intake and Tbi was the original that was on the truck. The only thing he done was pulled the motor out of the camaro and dropped it in the truck, bolted the intake manifold and the TBI on it. I know I said ECM, and I truly dont have a clue if that is the correct terminology for the the computer. I have a general understanding what the TPC, EGR, O2 sensor etc are and how they work in conjuction with the computer. I know the guy bolted the motor in and hooked wires back up. He used everything that was original with the 86 GMC S15. So all the electrical is the same. When I start the truck it high idles until it warms up and then it idles down, this thing doesnt vibrate all over, its just not as smooth as it should be. It idles as though it had a mild cam. Please direct me to any thing that i am leaving out that might help you to answer me. Also what is NA(TBI?)

[60dgrzbelow0]

Please forgive me the use of the TLAs (Three Letter Acronyms) I have the same problem with understanding some of the arcane TLAs the other, more capable and experienced members of our forum frequently use in describing many aspects of Tuning, Supercharging and Turbocharging.

NA/TBI stands for: Naturally Aspirated(/or) Throttle Body Injection. NA vehicles function with just Carburetors. TBI engines have kind of a funky carburetor...with an injector delivering fuel close to the front of the intake...or Throttle Body...where a mechanical Butterfly air intake control is located.

Your very best source for help for any S-10 (15) issues here...is a lead member called 'betterthanyou'... Seek his advice in all matters relating to your problems. If anybody knows what to do... He is the Man to Know It.

[stimey]

Thanks I understand mormally aspirated, lol just didnt think about it long enough. I will read and figure out how to get the question to betterthanyou. I think the motor is gumed up in areas and just needs some cleaning maybe replace a TPC or o2 sensor. A tune up would help a bunch also, probably need to do that first. Done alot of motor work and such when i was in my early 20s, that was a long time ago. Cars was much different then.

[60dgrzbelow0]

Thanks. I understand normally aspirated, lol just didn't think about it long enough. I will read and figure out how to get the question to betterthanyou. I think the motor is gummed up in areas and just needs some cleaning maybe replace a TPC or o2 sensor. A tune up would help a bunch also, probably need to do that first. Done a lot of motor work and such when I was in my early 20s. That was a long time ago. Cars were much different then.

I understand. While you are becoming better acquainted with the site... Take a few minutes and explore using the "Advanced Search" feature located at the top of the Main Page Marquis (Search) by framing your questions with the right Key Search Words... I'm betting that you can dig up some older posts that will have many of the answers you are after completely covered... but nested inside the other tens of thousands of posts that are warehoused here.

[bszopi]

If it idles fine when warm, then its not the O2 sensor.

From the 60V6 Family Tree:

• Introduction of TBI (Throttle Body Injection) on S-10's only, which consisted of a 2 bore throttle body perched atop the engine much like a carburetor. One injector above each bore delivered fuel. Each bore measured 1-3/8"
• OBD I computer system introduced with TBI models
• Mechanical fuel pump is replaced with an electronic in tank pump
• Engines use a fully electronic ignition
• All engines now used large valve heads
• Engines on S-10's used a combination vee belt and serpentine setup. Water pump was still standard direction
• F-bodies now used a full serpentine belt system with reverse rotation water pump.
• Horsepower 125 (TBI only)
• Torque 150 (TBI only)
• Compression Ratio 8.9:1

I would guess its something on the TBI unit that just needs to be adjusted.

[neo71665]

I would check the Idle Air Control (IAC) valve.

[stimey]

You all have no idea how much I appreciate your replies, I have so much fun learning about new projects, and i seem to go way over board when I start one of these things. It idles rough when it is warm also. I plan on start going through all of this and check wire connections, ohm out the plug wires etc. Its about 17 degrees here today so dont know how much I am going to get done tonight. This little V6 is so much fun, back when I was 20, V6 wasnt even talked about. We done a lot with the straight six, a buddy of mine had one fast 55 chevy with a straight 6 in it. Thanks again and I will keep reading.

[ezrollin]

I had to go through a "learning process" too when I got my 87 s-blazer.Get a factory shop manual off ebay for $ 25-35,it will give detailed info on the fuel and electronics,sensors etc,it's worth every cent.Are you aware you can access trouble codes from you computer that may indicate your problem.I can tell you how to access and interpet the codes if you need it.

[geoffinbc]

Even though the enine is warm it can still be the O2 Sensor. The big problem with S-Trucks is the O2 sensor does not stay hot enough at idle to keep the ECM in closed loop. A heated sensor will solve the problem.

I replied to the original poster in a PM. But I would first verify that the correct injectors were installed during the swap. The truck needs 4.3L injectors to run right. I would then verify Throttle Position Sensor voltage and then if all else checks out I would replace the stock O2 sensor with a heated one. I noticed a huge improvement in idle quality and off idle performance when I replaced my O2 sensor with a heated one.

[stimey]

EZROLLIN mentioned accessing codes, and how to do that, I have read a little about that. One thing is my check engine light is not working, I assume burned out. I was going to replace some instrument lights until I needed to figure out a way to do that with out tearing the dash completly out. I could go to the local auto parts and have them read the codes for me as well. If there is another way I am all for it. Betterthenyou you mentioned 4.3 injectors, I am near certain the injectors are the same as what was on the original motor. I am pretty certain that was a 2.8. I have read through the process of changing the injectors, not a big deal, what is a good source for 4.3 injectors? I should put new O rings and such in at the same time? Of course I will get carb cleaner and clean everything down, I feel the O2 sensor should change to the warm air one anyway. From what I am reading about staying in a close loop it makes sense. I am pretty certain that I read another swap that talked about the 2.8 injectors would run rich, and should be changed for this reason. When a person changes these items they should undo the negative battery cable and doing so also resets the computer? Guys sure appreciate your time her answering these elementary questions, but to me this is really cool stuff. Correct me if I am wrong, I have a OBD-1 system? I have a buddy that runs a Garage and really is into the technical side of all this, he is just so busy I hate ask him to do anything. He will do it but I have to leave my truck for a week, after a week I deffinatly get a good answer, but then I have to pay him, LOL Its a good thing I don't have money or I wouldn't learn anything. Thanks again, I hope I can get a little better weather her shortly, it was sure hard working on anything last night. I did start degreasing a cleaning a bit. If I run down to the salvage to get the heated O2 with the 4 wire connector that I need, what car would I look for to pull from? I will buy a new O2 sensor, but i will need the plug off the car correct?

[neo71665]

Pulling codes

http://www.s10planet.com/forum/showthread.php?t=17707

[stimey]

Thanks neo71665 that makes it easier, I definitely will go get a code reader, I got a 89 trooper I am waiting for the head to be rebuilt. So when that gets put back together the reader will be used there as well. I have learned a lot in about 4 days, found out if I do more reading then talking, I usually answer my own questions, just not my character though the wife always says to shut up listen. I seen here that I can buy the 02 sensor with the wires and plug already on, just got to pick up the right one.

[geoffinbc]

I would never trust a junkyard sensor always buy a new one.

Here is a writeup on the procedure. http://members.shaw.ca/betterthanyou...gen_sensor.htm

You can try and use injectors from a 4.3L S-10 in a junkyard but there are no guarantees they will still work or have a good spray pattern. Reman ones from a parts store and usually pretty good and will come with O-Rings.