A Real C4 problem (LT1)-before I replace the Opti...

[socalman]

First, many of you have tried to help me diagnose my car and I thank all of you that have tried. This is my first stab at trying to fix a computerized/fuel injected car and I'm far from a mechanic. For the past 2 months (off/on) I've been using your help along with the FSM. (92 Auto w/ 52k miles).

The syptom started as an irratic idle running high/low sitting at a stoplight after running only 2 blocks, then when I went to go, the car bogs. I can get up to 30-40 mph, but the car shakes and chugs while getting there.

Sitting still, start up at cold, the car idles irradically but not enough to move the tach needle. After 15 minutes still sitting, the engine revs up and down from 600 to 900 3 or 4 times. I can get full rev sitting still, sounds smooth. Under load, bogs whether after warmed up or taking off immediatly from a cold start up.

No SES light, No codes.

My first question. Would the opti just take a crap, 2 blocks from your house with no prior warning (ran perfect until then)? I believe I'm down to Opti or ECM.

2nd question- can I use a spark tester by plugging it into a spark plug wire and then attaching the other end to the spark plug while still in the block?

3rd question- FSM and some of you have suggested many times about tracing ground wires. Almost all the ground wires, including from the ECM run to one bolt, bolted into the back of the block under the driver side head- impossible to see or get to. But, figuring that everything else works on the car, if there were a ground issue at the final connection, I'd be having problems with other things?

The FSM refers to using the Tech 1, which is tough to find, for many of the testing procedures. Most sensors and the coil module, all refer back to getting a reading on the Tech 1, so I just started replacing parts. I figured it was 18 years old so I'll know that part is now new (kept the old parts for back up now that I know they're still good).

Here's what I've tested or replaced

1.) Spark- new coil, coil module, wires and plugs (what a bitch!)
2.) Fuel filter, Bosch III injectors (pump tested 41psi, 39psi under load)
3.) O2 sensors replaced
4.) Manifold vacuum, hoses etc.- all under specs
5.) PCV valve & hose replaced
6.) MAP sensor replaced (no MAF on 92)
7.) Air Filter replaced
8.) I have the temp sensor and IAT sensor to replace, but haven't yet.
9.) Tested EGR- ok
10.) Tested Cats- zero back pressure (ok)

Thanks for any help/direction you can give.

[Frizlefrak]

One last thing before tugging that opti out of there....have you tested/replaced EGR valve?

[PLRX]

One last thing before tugging that opti out of there....have you tested/replaced EGR valve?

http://i275.photobucket.com/albums/jj290/plrx/Funny/ApplauseMikePLRX-1.gif

[socalman]

One last thing before tugging that opti out of there....have you tested/replaced EGR valve? Forgot that one, yes I tested the EGR- all good. Also tested for plugged cats- Zero back pressure. I basically tested everything I could without the Tech 1 using the FSM.

Any thoughts on using the spark tester the way I described or will I damage something? (is it only for testing coils?)

[socalman]

http://i275.photobucket.com/albums/jj290/plrx/Funny/ApplauseMikePLRX-1.gif

:rofl:

Car repairs are no laughing matter. There's to be no fun in this thread :lolsmile:

[Taurus]

Forgot that one, yes I tested the EGR- all good. Also tested for plugged cats- Zero back pressure. I basically tested everything I could without the Tech 1 using the FSM.

Any thoughts on using the spark tester the way I described or will I damage something? (is it only for testing coils?)

How about the ignition module? Same thing happened to me and that's what it was.

[Frizlefrak]

A spark tester is really only going to tell you if you have spark or not....not the strength of the spark. Are you thinking completely dead cylinder? But your infrared thermometer readings were all relatively close, correct?

[Frizlefrak]

:rofl:

Car repairs are no laughing matter. There's to be no fun in this thread :lolsmile:

BAN THEM!!! :lolsmile: :iagree: :lolsmile:

[socalman]

How about the ignition module? Same thing happened to me and that's what it was. I'm putting on my dunce cap- Ignition module...same as Coil Module (or Driver as referred to in FSM)? I did replace the coil and driver.

A spark tester is really only going to tell you if you have spark or not....not the strength of the spark. Are you thinking completely dead cylinder? But your infrared thermometer readings were all relatively close, correct?

They were sporatic at best. I would get from 200 to 360 depending on how I was holding and aiming it. Cylinder 1 pretty conisitant at low 200's while 3/5 would be 360-80 and Cyl 7 come in at 280-320.

[PLRX]

How about the ignition module? Same thing happened to me and that's what it was.

thats what I wanted to write earlier but, couldn't come up with the f name. :cheers:

That is 85% of the reason people start an opti thread and is not the opti.

[socalman]

I have the Opti, WP, new hoses, thermostat and bypass sitting in the garage. Put in the new Injectors last night and was hoping...but it was :confused5:

If my Opti is still good, I'd like to not pull it, so just trying to figure out if there's any other way to test things.

[Frizlefrak]

If memory serves me correctly (which is a crapshoot these days) you couldn't find anyone that could test the module, correct? So it has been replaced?

[socalman]

If memory serves me correctly (which is a crapshoot these days) you couldn't find anyone that could test the module, correct? So it has been replaced? Dogs have better memories than you think. Yep, replaced, nobody could test. I've sure got a collection of backup parts though :lolsmile:

[PLRX]

Dogs have better memories than you think. Yep, replaced, nobody could test. I've sure got a collection of backup parts though :lolsmile:

did a little mod to the animation

http://i275.photobucket.com/albums/jj290/plrx/Funny/ApplauseMikePLRX-1.gif

[Frizlefrak]

We're running out of possibilities. It's getting down to PCM or Opti. You know I hate replacing parts and spending money unless it's a must, but if you already have the parts bought, may as well change them. I don't know of any way to test a PCM either, other than eliminate everything else from the equation. I have seen them fail and never send out a distress call either.

Roll up you sleeves....gonna be a long weekend. ;)

[five-oh]

Auto Zone advertises it tests icm but they cant test ours.

Hmmmm... the local Autozone tested my icm off of the '93 last year. Tested faulty, replaced it and it worked.

[Frizlefrak]

Hmmmm... the local Autozone tested my icm off of the '93 last year. Tested faulty, replaced it and it worked.

Could be the roasted possum and the quart of 'shine had something to do with that. :rofl:

[five-oh]

Could be the roasted possum and the quart of 'shine had something to do with that. :rofl:

'Possum- probably not. Moonshine, however, makes EVERYTHING better.:lolsmile:

[Frizlefrak]

'Possum- probably not. Moonshine, however, makes EVERYTHING better.:lolsmile:

:iagree: Hell, I woulda just handed you a new Opti for free, just in case the module didn't fix it. :lol:

[socalman]

We're running out of possibilities. It's getting down to PCM or Opti. You know I hate replacing parts and spending money unless it's a must, but if you already have the parts bought, may as well change them. I don't know of any way to test a PCM either, other than eliminate everything else from the equation. I have seen them fail and never send out a distress call either.

Roll up you sleeves....gonna be a long weekend. ;)

I guess so. Not this weekend, it's shot. Not next either- heading to Lost Wages.

Hmmmm... the local Autozone tested my icm off of the '93 last year. Tested faulty, replaced it and it worked.

Can't remember what it was, but the icm for 92 only fits the 92 Vette and 93 F body- somethin like that. I went back to the same store and 4 others, looked in thier books. No pigtails and no listing in their books for that particular part so they had no way to test it.

[drmrman]

If it is the opti, It will not ALWAYS give you a warning that its about to crap out. I put a new AC delco unit in my car. drove it 800 miles (round trip to and from carlisle PA) and the next time I started the car. It started fine... Died while (warming up, idling)... And never came back to life. No sputtering, no rough idle, NO notice at all... The car just shut down and never started again until I replaced the opti again...

Im not saying that this is def. your issue, just reinforcing that it MAY NOT give you a warning when its about to die. :D

[socalman]

If it is the opti, It will not ALWAYS give you a warning that its about to crap out. I put a new AC delco unit in my car. drove it 800 miles (round trip to and from carlisle PA) and the next time I started the car. It started fine... Died while (warming up, idling)... And never came back to life. No sputtering, no rough idle, NO notice at all... The car just shut down and never started again until I replaced the opti again...

Im not saying that this is def. your issue, just reinforcing that it MAY NOT give you a warning when its about to die. :D I wondering if it can run consistantly crappy without dying. I have no problem starting or revving, but have a rough idle and bogs under load (driving).

[Frizlefrak]

Common symptom of a weak spark.

[drmrman]

I wondering if it can run consistantly crappy without dying. I have no problem starting or revving, but have a rough idle and bogs under load (driving).

I can not tell you from experience... But think of your opti as a distributor cap (in terms of functions) it would make sense that it may cause a rough idle and problems under load. Much like a failing spark system in a traditional cap/rotor style system. Once again Im not saying this is DEF the issue... But more just food for thought...

[RedLS1GTO]

They were sporatic at best. I would get from 200 to 360 depending on how I was holding and aiming it. Cylinder 1 pretty conisitant at low 200's while 3/5 would be 360-80 and Cyl 7 come in at 280-320.

The easiest way I have found to see a dead cylinder is to get a crayon or an oil pastel (yes I am an art nerd as well) and touch it to the exhaust manifold on each cylinder. It will be very VERY obvious if one of them is dead.

...that's also why I have green dots on 7 of them. :D

Common symptom of a weak spark.

:iagree:

Which leads to a few other possibilities. I agree that the most likely culprits have already been mentioned but I have also seen a weak/shorted battery produce some of those same symptoms. I am nowhere near a stock ignition but that is exactly how my track car acted when the Optima took a dump.

[PLRX]

Its hard to guess from behind a monitor but, like Friz said signs of weak spark.

The 92's opti is not vented and likely there is rust in there. Dan, I would replace the Opti any way. It has been there for 19+ years. They sell vented ones for 92 you just have to add the vacuum lines.

[drmrman]

Its hard to guess from behind a monitor but, like Friz said signs of weak spark.

The 92's opti is not vented and likely there is rust in there. Dan, I would replace the Opti any way. It has been there for 19+ years. They sell vented ones for 92 you just have to add the vacuum lines.

:iagree:
I put a vented opti on my 93 after the 1st replacement opti went... SO FAR no issues at all! :D

[WW7]

Have you had this car hooked up to a scanner yet. I didn't see any posts saying you have. Scanners can show you alot of whats going on with your engine and the readings you get can sometimes point you to the problem..WW

[socalman]

The easiest way I have found to see a dead cylinder is to get a crayon or an oil pastel (yes I am an art nerd as well) and touch it to the exhaust manifold on each cylinder. It will be very VERY obvious if one of them is dead.

...that's also why I have green dots on 7 of them. :D



:iagree:

Which leads to a few other possibilities. I agree that the most likely culprits have already been mentioned but I have also seen a weak/shorted battery produce some of those same symptoms. I am nowhere near a stock ignition but that is exactly how my track car acted when the Optima took a dump.

I used an infrared thermometer on the exhaust manifold. Got readings from 200 to 450 depending on which way I shot it. The center cylinders, since they are the closest shot, were in the 360ish range, while cylinders 1 and 8 were in the 200ish ranges, but it's harder to get a clear shot with the infrared.

I did shoot them all with the engine cold one day and got all of them to read the same.

Anyone know what temp range I should be getting to know that I'm at least firing on all 8 cyls?

[socalman]

Have you had this car hooked up to a scanner yet. I didn't see any posts saying you have. Scanners can show you alot of whats going on with your engine and the readings you get can sometimes point you to the problem..WW

The only scanner that will do any good is a Vetronix Tech 1 since it's OBD1 system- which the last one made was 98'. Hard to find them with the Mass Storage Cartridge and be sure they have all the last updates. Ebay may have 1 or 2 at a time but most people selling them don't know how to check the software versions or are missing the MSC-which makes it worthless.

[WW7]

I have both the Auto xray 6000 and Datamaster that read OBD 1 . What I was thinking is you can drive around with these hooked up and get a "real time" reading. This would show you things like what your timing is doing, if the maf sensor is working correctly,what your IAC is doing,plus many more readings, these are all things that could be causing your problem.. These scanners really let you see whats going on while your driving and can also record it for looking at later....WW

[socalman]

I have both the Auto xray 6000 and Datamaster that read OBD 1 . What I was thinking is you can drive around with these hooked up and get a "real time" reading. This would show you things like what your timing is doing, if the maf sensor is working correctly,what your IAC is doing, these are all things that could be causing your problem.. These scanners really let you see what going on while your driving...WW

I'll have to look into those. I was led to believe they don't have all the software components to do all the testing as shown in the FSM.

[RedLS1GTO]

I used an infrared thermometer on the exhaust manifold. Got readings from 200 to 450 depending on which way I shot it. The center cylinders, since they are the closest shot, were in the 360ish range, while cylinders 1 and 8 were in the 200ish ranges, but it's harder to get a clear shot with the infrared.

I did shoot them all with the engine cold one day and got all of them to read the same.

Anyone know what temp range I should be getting to know that I'm at least firing on all 8 cyls?

The difficulty getting readings is why I suggested going old school and using a crayon. Touch the crayon to the manifold. It if it firing, it melts very quickly. If it is not firing it is very very easy to tell.

[WW7]

I'll have to look into those. I was led to believe they don't have all the software components to do all the testing as shown in the FSM.

I have helped 2 of my friends fix there cars using my scanners. One we discovered his TPS wasn't working correctly by checking the readings with the key on, motor off, while he stepped on the gas peddle we noticed his tps reading didn't go up smoothly like it should have and it ended up the tps was bad...The second one we saw on the scanner while driving that his 02 sensor reading wasn't moving around like it should have been, so we replaced the 02 sensor and that fixed his problem..Scanners are amazing instruments if you know how to read them properly..I would highly recommend finding someone that has a scanner and knows how to use it, and putting them to work....WW

[socalman]

The difficulty getting readings is why I suggested going old school and using a crayon. Touch the crayon to the manifold. It if it firing, it melts very quickly. If it is not firing it is very very easy to tell. Moving forward a step, if it's not firing-what's the issue?

[socalman]

I have helped 2 of my friends fix there cars using my scanners. One we discovered his TPS wasn't working correctly by checking the readings with the key on, motor off, while he stepped on the gas peddle we noticed his tps reading didn't go up smoothly like it should have and it ended up the tps was bad...The second one we saw on the scanner while driving that his 02 sensor reading wasn't moving around like it should have been, so we replaced the 02 sensor and that fixed his problem..Scanners are amazing instruments if you know how to read them properly..I would highly recommend finding someone that has a scanner and knows how to use it, and putting them to work....WW Would the Auto Xray 6000 test all the sensors? Got a line on buying a used one.

Would the digital temperatures show on your dash if the TPS was bad? or can it just be irratic enough for the PCM to wig out, but still show correct temps on the dash? I broke it off months ago and glued it back on. Didn't have any issues for months though- could that be the culprit?