gta ta

I need some help. I have been fighting this for 6 months and noboby seems to be able to help not even GM mechanics...

My 86 TA 5L has a high idle. 900+ unless it is hot like 220 then it will idle down. I also get a code 44 when I stop after driveing 55.

new GM IAC motor
all new intake gaskets
new GM O2 sensor
new GM EGR sensor and solinod
new MAT
no vacumm leaks
fuel pressure 35
manifold vacuum 22

SO today I decided to work on it again. I set the minuim idle at 450 then adjusted the TPS to .54. Unhooked battery to clear code 44. I then started it and it idled perfectly at 650. Ran just like it was suppose to. AFter about 15 miles stoped for gas. Started it back up and SES light came on with code 44 and there goes the idle back up to 900 and stays. I then shut it off hooked up my laptop and fired up WINALDL and went for a drive. I have logged what happens in WINaldl. WHen at idle and in closed loop the O2 reading drop to .1 and stay there. After a few minutes it drops out of closed loop and flashes code 44. This only happens after stopping after driveing 55. I think the O2 sensor is cooing off and drops it out of closed loop.

The high idle is being caused by the ECM and the IAC notor. How can I lower it? Do I need a new prom since this is an 86? My 87 GTA doesn't idle up like this.

I really could use any advice anyone can give me!!!!

Morley

Was the origional PROM ever replaced? If not you need to do that, there was a service bulliten on them (not a recall). If the PROM was changed then try getting another O2 sensor, the reading you are getting is way off and if you still have the stock exhaust manifolds on there then there is no way that O2 sensor is cooling off too fast, not in the time it takes to pump gas (unless you live in North Dakota or Montana)

mrr23

is the FP 35 with the vacuum line off? if so, then your FP is on the way out. and causing the lean code 44

gta ta

Thanks for the reply.

The O2 is one month old. Replaced a good one throwing parts at the problem. I didn't know there was a prom problem till reading past post tonight. If its not cooling off, then it has to be lean. The computer must be leaning the injectors. Can the air pump lean it out? But if it is the prom, I have just been chaseing my tail.

gta ta

FP 35 was with the vacuum line on. Didn't know I was suppose to take it off. WHat should my FP be?

Benny

Mine is about 36 with the vacuum line on and about 42 with it off.

gta ta

I did notice that when I shut the car off the pressure dropped to 0. It should hold it for what 20 minutes? I have to crank the engine for 20 seconds before it will start. I figured it was wet soak. I don't think leaky injectors would cause lean condition?

Morley

If the AIR pump doesn't switch to convert or dump, then yes it would cause the O2 to read way lean because it is pumping air into the manifolds ahead of the o2 sensor. Checking this is a simple matter. After the engine is warmed up good go to the rubber hose that connects to the AIR tubes on the manifold (driver side for this), slightly pinch the rubber hose and see if you can feel a pulsating in the hose. If it is pulsating get 2 small pieces of wood and put them on either side of the hose and clamp them down with vicegrips (or suitable clamp) so that the hose is pinched off, check the O2 readings now. If the O2 readings go up towards "normal" then your PEDEs valve is shot or not being commanded to switch to convert/dump.

gta ta

If I disconnect the two electrical connectors on the air pump won't that disable it? But a problem with the air pump won't cause a high idle right. Could this be telling the ECM that it is leaner then it is and the ECM is adding more fuel.

Morley

That could very well be your high idle. Disconnecting the PEDES valve won't cure the problem if the valve is stuck.

Morley

double post

gta ta

I don't know if this will load right on the forum but here is my winaldl data file just after SES comes on...

Time >PROMID >IAC >Coolant Temp >SPEED >EGR >RPM >TPS >INT >O2 >MAT >OLDPA3 >BLM >rich / lean counter >MAF >BPW
0.3 8291 24 101 0 0 975 0.2 158 0.177 2 158 4 4 5.38 3758096384
1.8 8291 24 101.8 0 0 975 0.2 161 0.199 2 158 4 4 5.36 3221225472
3.3 8291 24 101.8 0 0 950 0.2 163 0.221 2 158 4 4 5.48 536870912
4.8 8291 26 101.8 0 0 975 0.2 128 0.212 2 158 4 4 5.49 2147483648
6.3 8291 26 101.8 0 0 1050 0.2 128 0.15 2 158 4 4 5.45 2684354560
7.9 8291 26 101.8 0 0 1050 0.2 134 0.137 2 158 4 4 5.52 3221225472
9.4 8291 26 101.8 0 0 1050 0.2 138 0.146 2 158 4 4 5.39 2684354560
10.9 8291 25 101.8 0 0 1050 0.2 141 0.141 2 128 4 4 7.3 536870912
12.4 8291 45 101.8 0 0 1225 0.2 132 0.137 2 128 5 5 8.52 3758096384
13.9 8291 59 101.8 0 0 1425 0.2 132 0.186 2 128 6 6 6.76 3221225472
15.4 8291 32 101.8 0 0 1100 0.2 132 0.146 2 158 6 6 5.52 536870912
16.9 8291 25 102.5 0 0 1050 0.2 135 0.146 2 158 6 6 5.52 3221225472
18.4 8291 25 102.5 0 0 1075 0.2 139 0.141 2 158 6 6 5.48 2684354560
20 8291 24 102.5 0 0 1025 0.2 142 0.146 2 158 6 6 5.43 2147483648
21.5 8291 24 102.5 0 0 1025 0.2 146 0.141 2 158 6 6 5.49 2147483648
23 8291 24 102.5 0 0 1075 2.6 151 0.15 2 128 6 6 8.49 1610612736
24.5 8291 32 103.3 0 0 1350 2.6 142 0.115 2 128 6 6 12.86 3758096384
26 8291 37 103.3 0 0 1350 0.7 133 0.115 2 158 6 6 5.53 2684354560
27.5 8291 24 103.3 0 0 1050 0.2 134 0.124 2 158 6 6 5.5 2147483648
29 8291 23 103.3 0 0 1025 0.7 138 0.133 2 158 6 6 5.49 536870912
30.6 8291 23 104 0 0 1050 0.7 141 0.133 2 158 6 6 5.49 0
32.1 8291 23 104 0 0 1050 0.7 142 0.141 2 158 6 6 5.46 2684354560
33.6 8291 22 104 0 0 1025 0.7 145 0.15 2 158 6 6 5.49 2147483648
35.1 8291 22 104 0 0 1000 0.7 148 0.159 2 158 6 6 5.49 2684354560
36.6 8291 22 104 0 0 1000 0.7 151 0.172 2 158 6 6 5.46 1073741824

gta ta

I didn't think it would turn out but as you can see my O2 reading never raised over .2 for over 30 seconds at idle after curseing 55 and stopping. The O2 has to be fine replaced it twice and have the same results...

My engine vacuum is 22. I have never seen one so high. I thought it was suppose to be 18.

mrr23

mine is 21" with the zz4 cam