TransAmMike

hey guys. i have a most confusing problem.

its like this: i have a 91 firebird 3.1 v6 automatic. it starts up okay but idles rough. i can rev it up but it doesnt sound right (this is only in park). when i shift into drive, it idles rougher. if i give it gas, most of the time it will stall the second i hit the gas, unless i keep the gas down n try my hardest to get the gears up (it struggles). if it comes down to like 2nd or 1st tho it'll stall.

ive had this problem before when i was making a trip down to NJ. it struggled half the way n i couldnt get it over 75MPH. it was towed to a guy down there who said it was only firing on 3 injectors. he said he didnt really do anything except messed around with the wires going to the injectors n suddenly it started firing on all 6 again. he couldnt recreate the problem tho.

recently the problem happened again. i had a fuel pump and fuel filter replaced n that didnt really fix anything. supposedly it was running again but when i went to pick it up it was doing the same thing. this mechanic said something about the ground wires going to the injectors were going positive. i was really confused, n my friend said thats not possible.

has this happened to anyone before? i would really appreciate any help. thanks

Dale

iTrader: (12)

no trouble codes in the ecm?

I would suspect TPS, O2, or some bad wiring.

TransAmMike

the last mechanic it was at said there were some trouble codes, the only one i remember was the EGR valve tho, which i already knew about cuz it was burnt out the first time the car broke down. but having a burnt out EGR valve didnt stop the car from running for the month it was driveable after that trip to NJ.

also, i already replaced the spark plugs. i suspect it might be bad wiring but im no good with electrical stuff like wiring.

TransAmMike

and it has a brand new ECM.

Naft

if 3 of your injectors werent firing, then the guy wiggled some wires and they started firing, i'd say its definitly electrical.

2_point8_boy

Here's a whole list of things to check:

Clogged Converter
Running RICH due to bad MAF/MAP, IAT, or CTS

The converter will give you revving problems and limit your top end RPM because of the restricted exhaust flow and if bad enugh, could cause stalling.

The gas pedal thing makes it sound like it might also be running SUPER rich, the 3 sensors that I mentioned will cause that and the kicker is that you'll never know if the vehicle never goes into closed loop. The car does have at least a 185* t-stat, right?

A quick way to check for closed loop operation is to let the car idle until the radiator fans kick on, then install a jumper between pins A and B on the ALDL. If the MIL(Check Engine/Service engine soon light) blinks fast, it's still in open loop and there's a good chance that it never gets into closed loop. If it's blinking slow (~1 on/off cycle per second)then it's closed loop and there's another problem that needs attending.

My money says that the car is running RICH because of a bad sensor, causing it to never go closed loop, and the RICH condition detroyed the catalyst, which is giving you your revving problems.

Hope you find something useful in there.

Jeff

TransAmMike

Running rich is when theres too much fuel in the air/fuel ratio, right? If so, i think its the opposite. My friend says I'm getting plenty of spark and theres not enough fuel being burned.

The catalytic converter was clogged at one point, but most of the crap inside was pulled out and i was driving the car for a while with it like that.

I'm unsure about the sensors, but I think one of the mechanics would have suggested replacing those if that was it, right?

Andddd also I dont know wut the A and B pins or the ALDL are.

I might just replace the senors anyway tho, so I have something to do in school.

I'm thinking Naft is right. If so, what should I do? Can I get new wires just for the injectors or do I have to get a new wire harness or something?

aronside

Try and clean the distributor-axle! It gets rusty sometimes. (Best way is to chnge it but be observant on its exact position)The small signal wont be enogh för the pickupcoil and the amplifier in the distributor! Check the O2 sensor! If the cable comes near the exhaust system you can get a short to the ground an the idle will be very rough. The ECM will compansate and so on and the car will go much to rich!

TransAmMike

thats something i havent heard yet. ill try that. thanks

mvftw

iTrader: (1)

Pull the plugs...they will tell you whats going on...

V6sucker

If the EGR is sticking opem, it is gonna run like a dog.
Be hard to start, not want to rev, be on the edge of stalling all the time.

85berlinetta2.8

try a wrecker for a new injector harness

AM91Camaro_RS

if you want just the injector harness, i have a spare one lying around somewhere...

aronside, what signal are you referring to as going throught the distributor shaft? also, o2 sensors produces low volatage as a signal...it is not high enough voltage to arc to a ground unless you are saying "check for burnt insulation on the wire".

aronside

Hi
Well no signal is going through the axle but there is a magnet on the axle andthe small shift in the magneticfield will be detected by the pickup (The resistance between the two terminals should be 500-1000 ohm.)! At least I think it works like that! if the magnet and axle is rusty the **** wont work and it it will misfire! About the O2 sensor yes I know that the signal should be 0.35- 0.55 vdc under normal circumstances. But the wire that goes from the sensor can be burnt as you say and will interminent be grounded case of vibrations and so on and that realy will make troble for the ECM!
Aronside

TransAmMike

allright well got a lot of work done today. took off the throttle body and upper plenum of the manifold, pulled the injectors. took a circuit tester to the injector wires... only one of them has electricity going thru it.

should i replace the wiring harness? or can i replace just those wires without too much of a hassle? i have a feeling this is gonna be a lot of tedious work

also now that i have all this stuff off, i wanna get like performance/high-flow replacement parts. where can i get like a performance intake manifold for a v6?

2_point8_boy

Nope, currently I don't think there is anyone that has them ready for sale, but some people are working on replacment units.

Now, you know that the injectors are on a batch fire system, meaning that 3 of them are wired into the same circuit in parallel and the other 3 are wired on a different circuit in parallel, right?

If you have power to 1 of them, the the other 3 on that side should have power too, plus the fact that the car ran up to the point that you took it apart. That tells me that more than one injector has power to it because it would be kind of hard to run a V6 on a single hole. Something just doesn't add up. I would go back through everything on last time before you go hacking up wiring. Check fuses and fusable links before you cut anything. Check your powers and grounds all the way back to the source and the computer to make sure that nothing further down the line is bad.

I would hate to see you go through the effort of replacing an injector harness just to find that you have a bad connection somewhere else.

TransAmMike

Yea thats wut i mean, i figure i have a shorted out wire somewhere, n my friend checked the fuses with the circuit tester.. maybe he forgot to tell me something.

If it is a short in the wire, tho, how would i find it? i followed the wires that go thru the black hose all t he way to the firewall, but at that point it was difficult to see anything at all, especially since daylight was fading fast.

Also, now that i have the upper plenum off i realize how dirty and caked up it is in there.. is there some type of cleaning solution meant for cleaning out intakes?

a little off topic and probably a silly question, but would a 2 valve throttle body fit where my single valve throttle body is supposed to go? im really looking for some high-flow alternatives here to increase horsepower while im down in there.

**edit** when i tested the injectors, i touched the circuit tester to each of the 2 little prongs in the injectors. on the one injector that did make the tester light up, only one of the prongs could make it light up. is that normal?

AM91Camaro_RS

you could (you have to be EXTREMELY CAREFUL) pull the fuel rail out and hit the starter while someone watches the injectors to see if they're firing. make sure the fuel does not spray on something that is hot or anything like that but just watching them for spray is an easy way to test the whole system to see if they're working.

Another throttle body alone isn't really going to do much for you. clean the intake out...you can use brake cleaner to get some of it out. cleaning it will probably be about your best bet. a bigger throttle body (which isn't even available anywhere as a bolt on) alone won't really cut it...the manifold itself is very restrictive. look into the arising options for that and see what you like.

TransAmMike

K I'll try that, ill figure out some way to prevent gas getting on stuff, maybe cover everything with a towel or something.

What are my alternatives to the intake? I dont suppose they make TPI or TBI setups for a v6? doubt it

**edit** is there a way of boring out the plenums? lol

AM91Camaro_RS

the design of the stock plenum is pretty bad. my original plan was the rework a stock one to make it flow a lot better but I cut it open and saw the inside of it and said "no way". so, I built one from scratch. It can be found here. The Trueleo intake is another option. If you haven't already, you can sort through the 6 page thread/discussion about it with the subject line R&D on Trueleo intake (or something like that).

as for the tpi or tbi setups...our setup is basically the same as the tpi setup. slightly different but the main difference is the name...v8 is tpi, v6 is mpfi. tbi, you wouldn't want, anyways. edelbrock does make a setup to run a 4-barrel carb on these motors, the is a good option for letting the motor breath if you don't mind ditching the computer.

TransAmMike

hmm.. well i wanna keep my car street legal and able to pass inspection so i guess i would have to keep the computer.

i was actually looking thru that topic late last night. it looks great, but i cant really afford to fork out 600 bucks for it.

the one in that link tho i might consider due to its affordability. would my stock throttle body fit onto it or do i have to get the $300 TB too?

AM91Camaro_RS

stock throttle body will fit our manifold but it is then the restrictive point. the manifold alone should help but in conjunction with a bigger TB, you will see better results.

TransAmMike

Okay time for an update on the situation. Spent another afternoon working on the firebird yesterday... I realized that the reason why only one injector was lighting up is cuz a new one lights up after after start. So im not really sure if any of them r faulty since i didnt get a chance to test them all.

I cleaned out the manifold with this stuff called Sea Foam, which eliminates carbon build-up and what not. After i sprayed all that stuff in there, i put everything back together and started it up. So much crap came out the exhaust it was pretty funny.

I was able to take it around the block but it ran like crap due to the lack of gaskets.

Today i'm gonna pick up some RTV sealant, depressurize the fuel system, and clean out the injectors. Then ill see where im at.

TransAmMike

Wooooow... well i think i found the REAL problem. Apparently when i checked over the fuses a month ago i glanced over them a little too quickly, cuz one of the injector fuses was blown when i happened to look today.

I'm still changing the injectors tho. And on that note, i'm trying to depressurize the fuel system as directed in my Hayne's manual. Only thing is, i cant find the fuel pump fuse. Its not under the steering wheel, and according to the book its supposed to be on the right side of the dash.

Thing is ive pulled just about every piece of the dash off and cannot find the fuel pump fuse. And ive also found a couple devices that i dont even know wut they are (not the ECU). Heres a pic of the passenger side with the panels off:

Highwind

Have you noticed when the car stumbles, does the fan activate? I noticed this on my Mother's 3.1. The car will be fine at first, then start to stumble, then the fan activates (even from a cold start). It finally flashed a code 14, but I recently changed the CTS with no problems until recently.

When the car stumbles and dies...I can only start it again by cranking and holding the gas pedal as if the fuel pump isn't automatically priming and holding the gas till the RPM is at normal idle. After a minute it will hold it's own without dying. Seems like there's a lot happening I dont know where to start, but also sounds somewhat similar to yours though. I'll check out the fuses but it seems like random problem.

Is your car constantly running rough or just intermittently?