jim91gta

1991 Firebird GTA. (daily Driver)
5.7
SLP 1 3/4 hedders
MSD 6AL
MSD Coil
No Cats(removed after problems started)
Holly AFPR

My Symptoms

Starts fine
WOT car hauls butt
Exhaust smells of gas
Idle is fine on cold morning start
As car heats up it shakes(The hotter it gets the more violent it shakes)
IDle goes from ~700 - 400 in park
In Drive the car wants to stall but does not.

The Car has 102,000 miles on it and I was going to replace all sensors etc. to keep her running smooth anyway. I love my car, but my car hates me.LOL

Any help would be greatly apperciated as I drive the car everyday and need to fix it before my wife finds out!

I Replaced the following parts with AC-Delco (yes there is a difference)

PCV Valve
TPS
CTS(Under throttle body)
IAC Valve
Knock Sensor
EGR Valve
EGR Solenoid
IAT Sensor
MAP Sensor
Ignition Module


The following were replaced with Non AC-Delco

Spark Plugs(Accell U-Groove shorty's)
Cap & Rotor(Accell Tan)
Wires = same but test good(Taylor 8mm 600-1000ohms)
O2 Sensor(Unheated Bosch)(old was heated Bosch)
Fuel Pressure Regulator(Holly Adjustable)

Vacuum Hoses replaced

PCV Valve to lower intake
Passenger Valve cover to Throttle Body
Map Sensor to Plenum
Fuel Pressure Regulator to Plenum
Plenum to heater controls
Throttle Body to evap canister

Vacuum hoses yet to be replaced

Environment controls to Cruise control
Environment controls to the unknown black sphere by cruise control
EGR Valve to EGR solenoid
EGR Solenoid to Throttle Body

Things yet unchanged/Untested

Evap Canister Purge valve
Evap Canister Solenoid
Evap Canister Charcoal Filter
Fuel Injectors(Fat Ugly Grey ones)

AM I Forgetting something???

How Do I test

EVAP Canister Purge Valve?

EVAP Canister Solenoid?

Fuel Injectors?

I just started reading Helms manual but it always references GM test tools.

I will be ordering cables from Craig @ Moates.net(who, just from his email responses, seems like a great guy)

Hopefully I will be datalogging by next week. Maybe start programming after that.

3.8TransAM

Replace 02 with delco afs-20 or the afs-74 heated version only.

the bosch single wire sensors have known grounding issues with them, causing less than optimum readings even on known good cars.

Injectors...............

Never mentioned this once.

If factory they should al ohm in the 16-17 ohm range. If they are all over the place or u have one or two at 3 or 10 ohm then electrically they are on the way out. Somthing worth checking, wont guarantee there is something mechanical wrong with them, but should show u there current state electrically.

Pick up coils can be good for intermittent misses. They break down internally on the wires and the inuslation degrades. Lot of the time they just die on you, seen a decent number cause misfire and random issues also.

Did u set the IAC(min air rate) per the tech article on this site?

If the min is too low u could be hitting the stall saver in the prom and it will get stupid on u real quick also.

later
Jeremy

jim91gta

I will price out heated O2 on gmparts direct, maybe get that.( it was saturday and I wasn't thinking straight)

I'm going to check the Injectors today

The IAC I set per Helms...start car for 5 seconds, turn off then start car. Will read article and re-adjust.

Thank you

vernw

iTrader: (2)

Good plan, Jeremy is leading you in the right direction.

Even if your unheated Bosch sensor does not have the grounding problem, there is an excellent chance with your SLP headers that the O2 sensor is cooling off and going off-line on you. It is a very common problem with headers, they pretty much require you to use a heated O2 sensor.

Good Luck!

jim91gta

I had a heated o2 in car before changing to no-heated.

I had it going into autometer afr gauge. It was sweeping but prior to my changing to single wire it just showed 1 green light.

The purple signal wire was crimped into a connector that went to both the ECM and afr guage.

I will put signal wire to afr guage and see what I get. I have no idea why I didn't plug it in yet. call it a brain fart.

I'm still going to change to AC-delco. they are worth the money.

jim91gta

I was waiting at traffic light and the car went from slight shake to violent shake. I looked at temp guage and it had just hit 195*

When I replaced CTS that is located in manifold under Throttle body I noticed it was better. will the other 2 sensors in heads cause this? I think the driver side is for temp guage and pass side is for 2nd fan. I was going to replace them last because I thought they wouldn't cause this issue.

jim91gta

IDLE description update

I drove home late today to avoide rush hour traffic.

When I stopped for traffic light Idle would go between 550 & 450 sometimes spending a couple of seconds at 500. The car still shakes and has slight hessitation with initial acceleration.

My last change was PCV Valve this morning.(stopped by gm parts counter on way to work)

I will check for codes then check Injectors.

jim91gta

3.8TransAM
vernw

I think It's the Injectors

#1 - 5.7 Ohms
#2 - 9.5 Ohms
#3 - 17.4 Ohms
#4 - 17.4 Ohms
#5 - 17.5 Ohms
#6 - 12.6 Ohms
#7 - 17.5 Ohms
#8 - 17.5 Ohms

Now the question is which injectors should I buy?

Actually 2 questions

1) which Injectors will be direct replacement
2) which injectors are better but need prom change?




P.S. when doing a search I saw 91GTA had the same problem/resolution.

joker37

Don't know if you still care, but to test the EVAP:

As per the GM Service Manual:

Apply a short lenght of hose to the lower tube of the purge valve, and attempt to blow through it. Little or no air should pass into the canister. (A small amount of air will pass if the canister has a constant purge hole).

With hand vacuum pump, apply vacuum (15"Hg or 51 kPA) to the control vacuum tube (upper tube). The diaphragm should hold vacuum for at least 20 seconds. If not, the canister must be replaced. If the diaphragm holds vacuum, again try to blow through the hose connected to the lower tube while vacuum is still being applied. An increased flow of air should be observed. If not, the canister must be replaced.

For the Tank Pressure Control Valve:

Same thing as above. Apply vacuum to the upper valve, should hold, if not bad. If it does, try to blow through it. If you can't, its bad.

Simple eh? OH, by the way.. if it's bad.. its like having a really quiet vacuum leak, and makes your car idle like crap when in drive. You can always just plug up the vacuum hose leading from the throttle body to the top valve and see if you get a better idle. I looked up a new set made by AC Delco, and it came to about $60 bucks for both parts. Might want to try this before you do the injectors. They are easy to change if you really need to do them, just the parts cost a bit more.

jim91gta

joker37

Will test. better to know than its good than to think it's good!

jim91gta

The evap purge vale held pressure so that's good

I broke top vac connector on evap purge solenoid so guess i'll buy a new one. On the list to buy anyway.LOL AC-Delco of course

I'm looking at the SVO 24# injectors. started reading and looks like they will fit just need to lower Fuel pressure.(until I learn to burn Prom)

Are the 24#SVO's the best choice or would Accell 24# be better?

3.8TransAM

Accel 24# are garbage.

I run the SVO as they are by far the best bang for the buck whenit comes to new winjectors(short of the take outs)

The 24# will force your block learn low, to like 108-112 in some instances. Adjusting the fuel pressure is only a crutch and really doesnt work as well as some people think it does.

Best bet would be run the 24# and grab the free prom tuning stuff and run an injectors constant of 23.8 with them

later
Jeremy

Jekyll & Hyde

+1

I haven't had a problem with accel parts, but I will agree that 'the best for your buck' is with the SVO injectors.

vernw

iTrader: (2)

From the looks of those injector readings, I'd quit wasting my time and money on other stuff. The #1 and #2 readings are definitely way out of range and need to be replaced. If I were you, and seeing how it's a stock 350 motor, I'd probably get either 22 or 24 pound injectors, and if I got the 24's I'd have some one fix my prom for me to support the higher rating (until I could do it myself).

I would not just adjust the fuel pressure, especially since you're talking about lowering it. The injectors need the minimum pressure to have the right spray pattern. The ECM MIGHT be able to make up for it, but I would always wonder if it really was doing as good as it could.

And the SVO are better 24# injectors in my opinion than the Accel versions. Some folks do fine with them, others have problems almost immediately. I wouldn't chance it if it were me. I've also got some good used Holley 24# injectors for sale in the classifieds, but they're a lot more expensive than the SVO injectors ($470 new, $275 used). SVO is probably your best bang for the buck right now, lots of folks have had great luck with them. I'd look on eBay for them to get the best price and be sure to get new SVOs as opposed to used ones.

Just my two cents.....


- Vern

91Z28-350

Your injectors are screwed up. Get a new set.

http://www.fiveomotorsport.com/Injector_SetsTPI.asp

Pink top Bosch injectors if you don't want to or can't tweak your tune.

jim91gta

Thanks Guys! I Just ordered cable to do datalogging and next week going to buy Prom Burning tools. (moates.net)

I will do alot of reading in between and try to burn chip myself(with lots of questions and help from Prom board)

Better to do it right the first time.

jim91gta

Just got my ALDL cable from Craig moates. I still have bad injectors in car and started logging. My BLM = 118 INT = 128 @ start up and BLM=108 INT=123 while running. This was done from a cold start and running in my driveway the whole time. Mostly Idling some revs to 2700 but numbers stayed consistant. Would this prove bad injectors? Injectors open and dripping fuel into cylinders?

What else should prove bad injectors?

I will be doing more reading/searching just alot of info to soak up.

91Z28-350

No. It doesn't prove bad injectors, just that you're rich. And you can be rich from a billion causes.

The resistance test proves bad injectors. An injector balance test proves bad injectors. Your injectors are bad from your resistance testing. Replace them.

jim91gta

Injectors are being replaced no question about that. I Just started datalogging and am putting together baseline so I can see effects of new injectors. Just trying to compare what should be to what is.