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Need 4.9 Expert by fierofool
Started on: 06-13-2021 06:33 PM
Replies: 63 (1077 views)
Last post by: fierofool on 09-21-2021 08:43 PM
racer37
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Report this Post08-30-2021 08:38 PM Click Here to See the Profile for racer37Click Here to Email racer37Send a Private Message to racer37Edit/Delete MessageReply w/QuoteDirect Link to This Post
I had a bit of time last night and I don't understand why the engine is behaving this way: started engine, computer did its idle adjust thing. When idle settled down I had to advance timing to get it to run smooth. Jumpered A&B (no check engine light) and set timing to about 13°. Pulled jumper and engine immediately died. What am I missing?
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Dennis LaGrua
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Report this Post08-30-2021 10:30 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by racer37:

I had a bit of time last night and I don't understand why the engine is behaving this way: started engine, computer did its idle adjust thing. When idle settled down I had to advance timing to get it to run smooth. Jumpered A&B (no check engine light) and set timing to about 13°. Pulled jumper and engine immediately died. What am I missing?


The jumper places the ECM in open loop mode. When you remove it the ECM goes into closed loop mode and seeks all of the sensor inputs to function but it takes a drive to about 40 mph to reset properly. Start engine and drive it, then see what happens.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
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87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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racer37
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Report this Post08-30-2021 10:43 PM Click Here to See the Profile for racer37Click Here to Email racer37Send a Private Message to racer37Edit/Delete MessageReply w/QuoteDirect Link to This Post
I can do that.

I do need to ask where do I start? Set timing with jumper 1st or set timing by ear (without jumper)?

If you could write up a step by step procedure that would be a tremendous help. I have never been able to find that in all of the research that I have done. Apparently GOOGLE does NOT know everything
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imacflier
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Report this Post08-31-2021 02:01 PM Click Here to See the Profile for imacflierClick Here to Email imacflierSend a Private Message to imacflierEdit/Delete MessageReply w/QuoteDirect Link to This Post
Welcome to the addiction: "Own a Fiero, learn to be a mechanic!"

You should check out the How-to section.

To read codes (means using a jumper) go here: https://www.fiero.nl/forum/Forum9/HTML/000040.html

Good luck!


Larry
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87convert
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Report this Post08-31-2021 02:53 PM Click Here to See the Profile for 87convertSend a Private Message to 87convertEdit/Delete MessageReply w/QuoteDirect Link to This Post
Just a point of information. Both my 92 and 93 factory service manuals recommend 10 degree base timing. This is what I run in both of my 4.9 cars. In the automatic car any more timing induces significant spark knock under load; The manual transmission seems more forgiving tolerating 12 degrees without knock. Both have RockCrawl chips in the ECM which adds timing advance throughout the engines operating range when in closed loop.

Rolland

[This message has been edited by 87convert (edited 08-31-2021).]

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fierofool
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Report this Post09-16-2021 12:41 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Racer37 has allowed me to move the Formula to someone who is familiar with Fieros and some of the engine transplants. This was to get a fresh view of the situation from an outsider. He is not a member of PFF and has asked me to be an intermediary to post questions from him. He isn't registered here and doesn't desire to. At the present time, only he and I know the location of the 4.9 Formula. He will read any comments and suggestions posted here.

This is what he sent me for posting. I will just give him the username of Troubleshooter.

Heading: 4.9 runs smoothly with A-B jumpered, rough without

I'm working on a Fiero with a 4.9 Cadillac engine. It runs smooth when
the A and B terminals on the ALDL connector are jumpered, and very rough
without the jumper. I found a thread on Pennock's that describes the
same problem:
https://www.fiero.nl/forum/...060811-2-068938.html
But his solution, a new ignition coil, does not fix the problem on this car.
Another symptom I have observed is that, without the jumper, cylinder
one fires regularly on the timing light. But I tried it on cylinder 8,
and it fires very irregularly.
I would like replies from people who have experienced this problem and
found a fix. Please do not reply with lessons on timing or firing order.
I assure you that these are correct in this case.

[This message has been edited by fierofool (edited 09-16-2021).]

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Raydar
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Report this Post09-17-2021 06:25 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
Watching. I thought this was no longer an issue.
Did the chip/memcal help? To be honest, other than VATS and some trouble codes being turned off, and a bump in the idle speed, it really shouldn't make much of a difference.
("It didn't." is an acceptable response.)

Please let me know if I can do anything.
Since "Troubleshooter" is on it, I'll be quiet, and won't offer any suggestions that may derail his thought process.
But I have a set of manuals, and some other resources, available. Please don't hesitate to ask.

[This message has been edited by Raydar (edited 09-17-2021).]

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lou_dias
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Report this Post09-17-2021 08:08 PM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

Racer37 has allowed me to move the Formula to someone who is familiar with Fieros and some of the engine transplants. This was to get a fresh view of the situation from an outsider. He is not a member of PFF and has asked me to be an intermediary to post questions from him. He isn't registered here and doesn't desire to. At the present time, only he and I know the location of the 4.9 Formula. He will read any comments and suggestions posted here.

This is what he sent me for posting. I will just give him the username of Troubleshooter.

Heading: 4.9 runs smoothly with A-B jumpered, rough without

That's a timing issue as with A-B jumped the computer isn't adding any timing advance.

 
quote
I'm working on a Fiero with a 4.9 Cadillac engine. It runs smooth when
the A and B terminals on the ALDL connector are jumpered, and very rough
without the jumper. I found a thread on Pennock's that describes the
same problem:
https://www.fiero.nl/forum/...060811-2-068938.html
But his solution, a new ignition coil, does not fix the problem on this car.
Another symptom I have observed is that, without the jumper, cylinder
one fires regularly on the timing light. But I tried it on cylinder 8,
and it fires very irregularly.
I would like replies from people who have experienced this problem and
found a fix. Please do not reply with lessons on timing or firing order.
I assure you that these are correct in this case.


So the other possibilities are a bad spark plug or plug-wire on # 8 and you should probably check the others as well...
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fierofool
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Report this Post09-17-2021 09:23 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
He had told me he replaced the spark plug wire with one he had from another car and it made no difference. That was why he replaced the ignition coil.
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Raydar
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Report this Post09-18-2021 10:11 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

He had told me he replaced the spark plug wire with one he had from another car and it made no difference. That was why he replaced the ignition coil.


It seems to be something operating "right on the ragged edge", that is stressed by the timing advance being added.
All that are left (ignition-wise) are the distributor cap (the #8 terminal, specifically - I would look for carbon tracks) and the spark plug. Pretty much everything else is "common" to the entire system.

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fierofool
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Report this Post09-18-2021 11:34 AM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
Steve, he said the chip didnt help, either.
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olejoedad
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Report this Post09-18-2021 11:46 AM Click Here to See the Profile for olejoedadClick Here to Email olejoedadSend a Private Message to olejoedadEdit/Delete MessageReply w/QuoteDirect Link to This Post
It there a possibility that the engine has jumped time?
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Raydar
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Report this Post09-18-2021 11:56 AM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

Steve, he said the chip didnt help, either.


I didn't expect major changes. It was mostly small stuff. Should run without the external VATS module under the console, though.
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Dennis LaGrua
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Report this Post09-18-2021 05:24 PM Click Here to See the Profile for Dennis LaGruaClick Here to Email Dennis LaGruaSend a Private Message to Dennis LaGruaEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by olejoedad:

It there a possibility that the engine has jumped time?


That was one of my guesses as well but I also thought that a rocker arm retainer bolt might have stripped out of the aluminum support and changed the valve timing on two valves. That is often a problem on the HT v8 engines.

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

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fierofool
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Report this Post09-18-2021 05:35 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
The timing was verified by Racer37 and a couple of others several times. It was rechecked after I delivered it to Troubleshooter. The timing is correct.
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fierofool
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Report this Post09-18-2021 05:43 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think this has to be an electrical issue. The jumper wire won't fix a pulled rocker stud. It won't fix a bad distributor cap terminal or remove carbon tracking. Other than taking the sensors out of the picture, what circuits going to the ECM change with and without AB jumpered?

If one sensor at a time were unplugged, might that reveal the problem area? It's like one of the sensors is giving some incorrect info to the ECM.
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lou_dias
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Report this Post09-19-2021 10:28 AM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasEdit/Delete MessageReply w/QuoteDirect Link to This Post
...still no mention of changing the plugs... /sigh
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Report this Post09-19-2021 01:24 PM Click Here to See the Profile for pmbrunelleClick Here to Email pmbrunelleSend a Private Message to pmbrunelleEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by fierofool:

The timing was verified by Racer37 and a couple of others several times. It was rechecked after I delivered it to Troubleshooter. The timing is correct.


Is the 4.9 like the Fiero 2.8 where a slipped harmonic balancer causes incorrect timing readings?
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fierofool
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Report this Post09-19-2021 01:55 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I think a slipped balancer could be common on most cars. Aren't most outer rings mounted on a rubber cushion? The scanner was showing 25* last setting I was told about. I think Troubleshooter only used the timing light to check for firing on each wire. I'll send him a message about the plugs. But if a wire or plug is bad, the ALDL jumper wouldn't cure that problem. It would still run rough.
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fierofool
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Report this Post09-19-2021 08:07 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
This week's update. September 19

I used an oscilloscope to check some things. I checked with the
engine running with A-B jumpered, and then pulled the jumper out to see
if there was any difference. Here's what I checked.
Distributor Reference (pin D8 on the PCM). This is a crank position
signal, and should be a regular square wave with 8 pulses for every
crank rotation. This signal is supplied to the PCM by the distributor.
It looked OK for both cases, considering that the frequency wasn't
steady as the engine sputtered with the jumper out.

Electronic Spark Timing (pin C8 on the PCM). This is supposed to be like
the crank signal, but advanced or retarded as required by the engine.
This signal is supplied to the distributor by the PCM. This also looked
normal. Of course, I couldn't tell if it was advanced or retarded.

Cam Position Sensor (pin C5 on the PCM). According to the manual, this
is supposed to be one pulse for each time the intake valve for cylinder
one is about to open. This signal is supplied to the PCM by the
distributor. This also looked normal, but there's no way I could tell if
it was in the right place.
The belt was thrown when I pulled the jumper in this test, so that's all
I did for now.

There is another line, Bypass (C7 on the PCM), controls whether the ICM
uses the EST signal or the signal directly from the pickup coil to
trigger the spark coil. I need to measure that line with the jumper in
and out to see if that is the mechanism for using fixed park with A-B
jumpered. If so, that would mean that the PCM is doing nothing at all
with A-B jumpered, as far as ignition goes.

But the belt was thrown when I pulled the jumper in the Cam Position
test, so that's all I did for now.
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fierofool
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Report this Post09-20-2021 01:06 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
I got an email this morning from Troubleshooter. Anybody in the Northern half of Georgia have a Dual-Trace oscilloscope that I could borrow for a while?

From Troubleshooter:

If I had a dual trace oscilloscope, I could compare traces, to see if the EST signal is advanced or retarded compared to the crank signal, and I could compare the cam signal to the crank signal, to see if there is one pulse for every 16 crank pulses. But I don't have one, and they are expensive.
I wonder if any of your members has a dual trace oscilloscope.
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racer37
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Report this Post09-20-2021 10:04 PM Click Here to See the Profile for racer37Click Here to Email racer37Send a Private Message to racer37Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by imacflier:

Welcome to the addiction: "Own a Fiero, learn to be a mechanic!"

You should check out the How-to section.

To read codes (means using a jumper) go here: https://www.fiero.nl/forum/Forum9/HTML/000040.html

Good luck!


Larry


Having been a Fiero owner for over 20 years I knew that. This case is a cadillac ecm and doesn't work that way since it is designed to use the hvac display to show codes

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racer37
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Report this Post09-20-2021 10:38 PM Click Here to See the Profile for racer37Click Here to Email racer37Send a Private Message to racer37Edit/Delete MessageReply w/QuoteDirect Link to This Post
Another clue: Charlie has some videos that I sent him showing how the car runs with and without the jumper. You can adjust the rough running out of it by retarding(?) the distributor. Turn the distributor counterclockwise about 20-25° and it runs smoother.

I will agree that it is something in the timing circuit, or rather something in the wiring for the timing circuit. I say wiring since this behavior doesn't change when the ecm is changed. There should be another ecm in the car to verify.

Also need to say that everything in the ignition system except the plug wires are new. The plug wires passed testing with a DVM. Spark plugs are new gapped at .060. New cap, rotor button, ICM, cam sensor,

Static timing has been checked, rechecked, re rechecked, and re re re reverified. Timing chain is good. Compression is good, 15# difference between highest & lowest.

There is a red paint marker line on the balancer to verify it has not slipped.
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Report this Post09-21-2021 08:43 PM Click Here to See the Profile for fierofoolClick Here to visit fierofool's HomePageClick Here to Email fierofoolSend a Private Message to fierofoolEdit/Delete MessageReply w/QuoteDirect Link to This Post
September 21 update from Troubleshooter:

Today I found that the Bypass signal is always high, which means that the spark is always controlled by the EST siignal, regardless of whether A-B is jumpered or not. So the PCM must send the crank signal directly to the EST output when the jumper is in place, and controls it when the jumper is out. So the timing must be thrown way off when the jumper is out. The only thing that I can think of that would cause that is the cam signal must be way off.

BTW, if the Bypass line is disconnected, the engine really does run directly off the pickup coil, and the ICM shorts the EST line to ground. It actually runs quite smoothly this way, but at a fixed advance. The Bypass line must be a kind of limp home thing in case the PCM spark control completely fails. The Bypass line must be at 5 volts in order for the ICM to use the EST signal.

Also, I figured out why it is throwing the belt. Compared to a picture from Pennock's, the tensioner is in the wrong place. I'd have to make a new home-made bracket to fix it, and get a new belt, because the existing one would then be too long.

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