well looks like i'm another person posting here for an engine performance problem..
actually i'm not quite sure if it's an idle or a misfire on my car.

got a 1987 Trans Am with a 305 TPI

here's the story: it just started last monday
on a cold start the car cranks but won't stay idle at all.
I've literally have to rev up the engine to keep the car from dying.
other things i've noticed is that i was getting what smelled like a "lean" exhaust smell from the exhaust..
like as if i wasn't putting enough fuel in the combustion chamber
or perhaps the smell ment i was putting in too much fuel?
When the car is warmed up, In drive the car will not want to idle and it is around 500 rpms and would almost die if i stay at idle to long...but if i put it into netural
the car will idle and it's around 800 rpms...

last week i was trying to get a 02 signal reading at school
but couldn't get a thing off the school's labscope directly from the o2 sensor, however from a scan tool i was able to see a signal from the ecm and the display showed a lean signal....the o2 was replaced about 6 months ago and was "stressed" tested that night at school to see if it was operating correctly, and yes it was responding to the enrichment of our propane bottle, so the 02 does see what goes on in the exhaust chamber...but still i think the car wasn't in fuel control.

after a couple of hour with the 3 days i've been working on my car
i've performed other test ...
although i haven't performed it properly, i shall however do it again tommarow hopefully and recheck it with the specs.
<but before i did these tests, i literally had to run the car for about 15 minutes to at least stay somewhat idle, because even when the car was warmed up the engine was still hesitating>

first thing i did was i used our shop scan tool to see if my car had any stored codes...no codes were found...and the of couse the check engine light wasn't lit....

the next thing i've done was a complete ignition system
funtion check out....looking at our scope in a raster patter i've noticed all cylinders had spark, a few of them were weak..and also i realized that i haven't done a tune up in like 3 years since i rebuilt the heads...so i'm planning on replacing the cap, rotor, wires, plugs, fuel filter... etc.

the next thing i did was i did was a fuel pressure test with the koeo <key on engine off> the pressure rose up to 47 now i'm not sure if that's within specs with the engine not running....

other test methods i'm planning to do is

do a fuel injector balance check on each injector
do a fuel volumn test
check the tps signal
recheck the o2 signal
check the idle air control motor counts and if not do a idle air control relearn....

i really don't know what else to do other then the basics
like check all vacuum lines, and hoses for vacuum leaks...


i'm wondering if the cat. converter have to do anything with this engine performance problem? even though it's orginal and i am gonna replace it
you think it's possible?

or could it possibly be the idle air control motor isn't funtionally properly?

any ideas or suggestions would be appreciated
thanks!

 

wow i'm suprised even though people read what i said, no one did responded...oh well...i guess i'm on my own...
anywayz
today i did more research on my car..
this is what i've done and redone today
-i've already did a full tune up on my car which includes: plugs, wires, cap, rotor, fuel filter, but the pcv is fine...so i didn't replace it, and the air filter is good too..

-i've done a fuel pressure test with the koeo <key on engine off>
the specs. say 40.5-47psi....my readings were 47psi...good
-i've done a fuel volumn test...
the specs. says 1pt for 30 seconds...my collection was 1pt! good

i did an injector balance test today and even though i spent like an hour looking in my mitchell on demand book for the specs
i couldn't find it anywhere!.... if anyone knows what page it's on in the 87 Mitchell tune up/electrical book please let me know! i'm sure it's under the section of computer command control...
this is the results of the injector balance test.
cylinder #1 dropped to 25psi
cylinder #3 dropped to 26psi
cylinder #5 dropped to 22psi
cylinder #7 dropped to 22psi

cylinder #2 dropped to 20psi
cylinder #4 dropped to 21psi
cylinder #6 dropped to 22psi
cylinder #8 dropped to 22psi

i wish i knew what the specs were, because now i'm looking at injector 1 and 3 thinking those are not giving enough fuel into the cylinders...if that is the case it may contribue to the lean condition of my car..


while hooking up the scan tool and doing a road test.
i was looking at my O2 sensor, my injector pulse time, my
EGR % flow, my block long intergrator, my coolant temp., my rpms,
and my idle air control counts...
while in idle i read the o2 sensor and it's reading lean!! i mean we're looking at .3 volts and lower! and it wasn't able to fluctuate over .5 volts!!
while nailing the gas, i noticed the 02 instantly rose knowing that i was dumping fuel into the engine, and it was noticing coming out of the exhaust! it went as high as .82 volts and also i saw the block learn intergrator was going over 140! knowing that it's trying to dump fuel into the intake!...plus my injector pulse width rose from 1.2 to anywhere 4 to 6.1 knowing that it's trying to keep the injector timing open longer when accelerating..

after i did a quick acceleration i got off the gas and instantly the car was reading 0.0 02!!! i was like damn how lean can this be?!then the block learn intergrator was like at 152! it's trying to dump fuel to richen the mixture..
off the scan tool i have 2 displays along with other ones...one shows rich and another shows lean, at a cruise it was staying in lean and looking at the 02 signal it was like reading .1-.2 volts...and i'm like man where is this problem coming from...
i've pretty much checked all the vacuum lines and only had to replace 1 line which went to the manifold...

at this point i've come up with a couple conclusion what could be causing my lean misfire...

1) an injector may not be spraying enough fuel in the cylinder.
2) an injector pulse width is not being retrieved at the injector to operate properly...which i wasn't able to do, because i don't have the noid light to do test each terminal...
3) the ecm isn't sending enough pulses to control all the injectors at certain loads...
or i have a major intake leak but haven't found it ....

i've literally sprayed carb cleaner all over the intake around the base, the air cleaner and pretty much everywhere! and haven't found anything that would cause the rpms to rise..
however it does rise when i spray the cleaner into the air cleaner housing and the o2 signal rose, and the RPMs rose as well!
which it looks like i don't have a vacuum leak after all!!

Tommarow i'm gonna go end up doing some more research
if anything i'm gonna end up buying a noid light and see if the injectors electrical connectors are working properly...

anybody out there with ideas or suggestions, please let me know!

 

RC,

Your fuel pressure looks adequate with the engine off. Have you taken a pressure reading with the engine running, vacuum connected to the FPR? You should see 37 PSIG, ±3 PSIG. Monitoring the fuel pressure while the engine is loaded is also a good diagnostic. The 1 pint of flow in 30 seconds should be adequate, but tesing under actual load can be revealing.

Test the TPS voltage at the idle position. A low TPS can contribute to a lean condition. Make sure you are as close to 0.54VDC as practical.

The O² sensor readings are confusing, too. You should be seeing a lot greater range of variation in the sensor voltage, but since the sensor responds to the propane bottle, it would appear that you actually have a lean condition and good O² sensor.

Your fuel pressure drop tests of the injectors indicates flow problems with at least a couple of injectors. I've been down that road before, and after eliminating all other possibilities, had the injectors cleaned and flow tested/matched. I was not surprised to learn that one injecctor was off standard flow by 38%, and others were off by 15% or more. I had discovered the sourcec of the lean condition and rough idle/low RPM operation.

Don't be surprised if, after exhausting all other possibilities, you have injector flow problems. The fuel rail pressure drop method is a crude way of testing flow balance, and the only accurate way is with a test stand and burette. However, since your crude method has indicated such a great degree of imbalance, I would suspect you will find the more refined methods give you similar results. Additionally, the injector flow may or may not indicate problems with the spray patterns from the injectors, which can affect fuel atomization and effective mixture in the chambers.

If you are curious, check out Cruzin' Performance for injector cleaning and analysis.

 

thanks vader for the input

well this is what i know from the TPS , it's right now reading at idle or with the koeo....reading at .62 volts... this is so because i made an adjustment to it a couple of years ago for performance enhancement....and from the specs it's reads from .54 to .62...

If i have to return it back to .54 volts...i'll do it...

as for the vacuum for the pressure regulator..
i haven't checked that but i will..
in order to check that...do you have to run the engine at idle to get a reading or at a certain rpm ?
also for the fuel flow under load, i'll do that as well..
however i wonder if it's better to do that test under a cold start or a engine that is warmed up...
if anything i'll do both..and compare the results..

you advice is greatly appreciated here..
i'll will continue to do these other tests as well tommarow.

 

RC,

Your YPS voltage should be O.K. at 0.62V. The acceptable range is 0.47-0.61, and I was concerned that you were too low, not high. A low voltage would tend to lean the mixture. That's why you increased it in the first place, to enrich the part throttle mixture a bit.

Get the fuel presure reading at idle with the FPR vacuum connected. It won't matter a lot whether the engine is at full operating temperature. The idea is to assure that the FPR is maintaining adequate pressure with the vacuum connected. As long as there is at least 17" Hg at the FPR, the result should be close enough. You're shooting for 37 PSIG.

As for your original post, I doubt that the cat converter is a problem. If it were burned out, there would be no restriction, and no performance problem. If it were plugged, you would not have any power above idle. A steadily decreasing vacuum should also be a symptom of a plugged cat.

What kind of analyzer are you using? If you have access to an old Sun 920 or 1120, they have a gas analyzer built in. A quick sniff of the exhaust would tell you how rich or lean you are running.

Again, depending on the 'scope you are using, you can test the injector pulse widths (down to the microsecond) with that. Remember that the trigger will have to be set on the negative slope, since the ground is the lead that is switched by the ECM. If you have a digital storage scope set it up on single trigger (or raster) and freeze the display after getting a few waveforms in the pattern.

As a side note, if you end up removing the injectors for cleaning and flow matching, label them for cylinder position before you ship them off. I'll bet a Coke (or your favorite ale) that #2 is streaming and not spraying a mist.

 

thanks again vader,

well the analyzer we have is a 4 gas one, a portable OTC
but i don't access to that right now because all the important dianostic tools are locked up in my bosses office, even though i was able to use the OTC scan tool and the OTC vision 2 scope..
i don't like the OTC vision 2 scope because it's not real time
display like a snap on advantage....it's almost like a 2 second delay on display.
We had an old sun analyzer but my boss got rid of it...
and that was a big ol heavy machine.

and another thing i forgot to mention was that i have a 180 t'stat
i doubt it would cause any problem with the engine.
i mean it would cause the car to stay in open loop for a longer time to get the car warming up to but also it's suppose to keep the car running cooler, even though it recirculates the coolant
much quicker then a 195 stat... i doubt that would cause a probleml as well..
thanks again vader

 

well here's an update on my car right now..

as for what vader suggested i do..

i did fuel volumn test under load at idle....
sure enough i got 1 pt at 30 seconds...so i'm more then convinced that the fuel pump ain't the problem

i also did the vacuum test my reading to the FPR, read 17 on our vacuum tool it's a snap on tool and it read in inches of mercury... <in red lettering> in black lettering it's read at 43 CM Hg....

so i'm assuming these numbers are good and by looking at the gauge it wasn't fluctuating alot and when i goosed the throttle
the Vacuum dropped to almost 7 to 8 cm HG...which shows that vacuum does drop...

another thing i did was that, i checked for resistance in each injector...on my dvom i put the ohms reading to 200 ohms...
so i'm hoping i put it at the correct scale...this is my readings what i got...
injector 1: 16.9 to 17.0 ohms <it was fluctating>
injector 3: 17.1 ohms
injector 5: 17.1 ohms
injector 7: 17.1 ohms
injector 2: 17.3 ohms
injector 4: 17.2 ohms
injector 6: 17.2 ohms
injector 8: 17.2 ohms

if i only could compare these readings to specs i would know whether or not my injectors are out of specs and need replacement....

another test i did was, checking each pulse width at each injector with our shop dso and all of them had around the same
reading in pulse width it varied at idle from 2.58 to 2.68....
and on display all readings were about the same...

now the only conclusion i can possibly think of is that
the injectors of cylinder 1 and 3 aren't throwing enough fuel into the cylinder and it's not completely atomizing the air/fuel mixture. Also since the o2 is on the driver side, it can probably easily show that the 02 is indeed picking up the lean signal from that bank!

now if indeed that is the case i wonder if it's better to purchase new injectors or rather have them clean them and have them blueprinted...
i read that one site you put on your post vader and it seems
it's less expensive by doing that instead of buying fuel injectors
i one time had to replace an injector on my car before and it wasn't cheap it was nearly 110.00 for one from GM!
it pretty much all comes down to a budget deal hehe....

the only thing i hate to do is literally have to take out the plenum
and then have to take out the fuel rail....
well i know i could do some mods while doing so, and plus it wouldn't hurt to clean out the egr since it's right there....

 

So, Do I owe you a Coke? (or ale?)