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Pushrod 3.4 detonation problem by Doug Chase
Started on: 04-27-2006 11:40 PM
Replies: 15
Last post by: tjm4fun on 04-30-2006 01:25 AM
Doug Chase
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Report this Post04-27-2006 11:40 PM Click Here to See the Profile for Doug ChaseSend a Private Message to Doug ChaseDirect Link to This Post

I put a pushrod 3.4 (Camaro motor) into an '86 SE automatic as a replacement for the knocking 2.8. This motor is said to have about 35k miles on it and I believe it. It looked very clean inside, and after a couple hundred miles the oil is still so clean you can hardly read the dipstick.

Unfortunately, it pings. It pings in some part throttle situations, it pings at WOT. I used up all the old gas in the tank and filled it up with new fuel. I filled it with 87 octane because I'm sure it should run fine on that. Still pings. Other than this, it runs great. If I back the base timing off 10 degrees it runs fine with no detonation.

Here's what I know:

- The timing table in the ECM is unmodified from the stock Fiero PROM.
- I have verified that the base timing is set correctly.
- I have TDC'd it manually to verify that the mark on the balancer (which I cut) is correct.
- Injectors are brand new 19lb/hr Accel injectors.
- Fuel pressure is stock and is correct.
- The O2 sensor is switching normally and the BLMs are pretty close to 128 (123 - 131) using the stock fuel table so I'm pretty sure it's not running lean.
- I disabled EGR (in the PROM) and it still pings so EGR isn't the problem (shouldn't have been the problem at WOT anyway, but maybe at part throttle).
- Spark plugs are new and are the stock heat range (AC R42TS). They look good - nice even tan.
- I ran about 3 quarts of water through the intake in an attempt to decarbonize it. The steam coming out of the tailpipes was nice and clean - no icky nasty soot.

Quite honestly, I'm stumped.

Anybody have any ideas? Have any of you 3.4 swap people encountered this problem? Does your 3.4 run fine on 87 octane with stock timing?

Thanks for any help you can offer.

------------------
Doug Chase
Chase Race
Custom: cages, exhausts, fabrication
Duvall, WA
425-269-5636

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Lilchief
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Report this Post04-27-2006 11:51 PM Click Here to See the Profile for LilchiefSend a Private Message to LilchiefDirect Link to This Post

I have no detonation problems with my modified 3.4 but I run 91+ octane , 180 stat , 6" rods , no egr with 9.7 cr. Try higher octane or colder stat. Just an idea

------------------
85 GT 3.4
Auto 3.08
14.9 @ 90 1.9 60"

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Oreif
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Report this Post04-28-2006 12:15 AM Click Here to See the Profile for OreifClick Here to visit Oreif's HomePageClick Here to Email OreifSend a Private Message to OreifDirect Link to This Post

Here are a few things I can think of:
Are you using the stock ignition system? Aftermarket ones can be sensitive to wire routing.
If stock, How does the pick-up coil look? How new is the ignition module and what brand?
I had an ignition module that actually added 4*, So once it was set to 10* and you swapped out the module, It was now 6* (???)
I decided not to use Auto Zone modules after that.
What condition is the distributor in? A loose shaft or a damage hall-effect ring can mess up timing as well.

On the 3.4L EFI I built we used an adjustable fuel pressure regulator, We had to increase the FP for the 19# injectors.
If everything is tuned right it should run fine on 87.

On the timing mark, How sure are you it is accurate? Did you mic the TDC or go by "feel"?
It could be off. Does the balancer have the timing marks for the right side timing scale or are you using the 3.4L damper?
If it has the right side scale timing mark, Your new timing mark should be 4.600" to the left of it. You should be able to advance the timing to 12* with no problems. Since it's at 10* and having problems but slightly retarding it runs fine, I would look into the timing first.

I used AC Delco Rapid-Fire plugs on both 3.4L engines I built. I doubt this would have any effect on your pinging.


Lastly,

Have you tried retarding the ignition and then power-timing it with a vacuum gauge? Then see where the timing is with a light.
With a power-timing you should be around 12*/13* on a 60* V-6 pushrod engine. If it's below 10*, then I would think your timing mark is slightly off.

Oh, Just thought of something else, How hot is the engine running? Or does it ping even when the engine is cool?

------------------

Happiness isn't around the corner...
Happiness IS the corner.

ZZ4 Powered !!

[This message has been edited by Oreif (edited 04-28-2006).]

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3800superfast
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Report this Post04-28-2006 01:42 AM Click Here to See the Profile for 3800superfastSend a Private Message to 3800superfastDirect Link to This Post

Doug, Anyway to post your winaldl logs ?

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Doug Chase
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Report this Post04-28-2006 02:25 AM Click Here to See the Profile for Doug ChaseSend a Private Message to Doug ChaseDirect Link to This Post

 
quote
Originally posted by Oreif:

Here are a few things I can think of:
Are you using the stock ignition system?


Yes

 
quote

If stock, How does the pick-up coil look?


It looks like a 20 year old pick up coil that's in decent shape for its age. I've seen much worse that are still working fine but I haven't tested this one.

 
quote

How new is the ignition module and what brand?


The same. GM.

 
quote

I had an ignition module that actually added 4*, So once it was set to 10* and you swapped out the module, It was now 6* (???)


Now that's very interesting. I have a handful of GM modules around. I'll try one.

 
quote

What condition is the distributor in? A loose shaft or a damage hall-effect ring can mess up timing as well.


Good. No excessive side play or end play in the shaft. Good wear pattern on the gear. Little rust on the top end. Cap looks good.

 
quote

On the 3.4L EFI I built we used an adjustable fuel pressure regulator, We had to increase the FP for the 19# injectors.


I've heard that being done, but I decided to do it in software. The ECM indicates that everything is fine, but maybe I should find a wideband.

 
quote

If everything is tuned right it should run fine on 87.


Thanks. It's good to have that verified.

 
quote

On the timing mark, How sure are you it is accurate?


Very.

 
quote

Did you mic the TDC or go by "feel"?


I am using the balancer from the 3.4. When I was swapping parts from the 2.8, I lined up both balancers and cut a mark in the 3.4 balancer based on the mark on the 2.8 balancer. After I got it running and discovered the detonation problem, it occurred to me that the 2.8 balancer could have moved on the rubber ring. At this point I manually verified that TDC was correct to 0 degrees on the timing tab (I'm using the Fiero front cover). Here's how: Position # 1 piston a small and carefully measured amount down the bore a few degrees before, and a few degrees after TDC. Mark the balancer at these two points. TDC lies exactly halfway between them. Do this a couple times and you can get extremely close. Do it with a dial indicator and the head off and you can do it perfect. Unfortunately I didn't have that luxury. I can go into detail on my method of doing it in the car if anyone is interested, but it takes up too much space to type right now and it's not relevant.

 
quote

If it has the right side scale timing mark, Your new timing mark should be 4.600" to the left of it.


Good info. For clarification, if I'm looking at the pulley side of the balancer and wrap a (theoretically perfect) tape measure around the balancer counterclockwise with 0 at the existing timing mark, then the Fiero mark belongs at 4.600"? I'll check.

 
quote

Since it's at 10* and having problems but slightly retarding it runs fine, I would look into the timing first.


I agree.

 
quote

Have you tried retarding the ignition and then power-timing it with a vacuum gauge? Then see where the timing is with a light.
With a power-timing you should be around 12*/13* on a 60* V-6 pushrod engine.


No. My experience with non-EFI cars is limited so I've never done this. Care to explain how?

 
quote
Oh, Just thought of something else, How hot is the engine running? Or does it ping even when the engine is cool?


Right around 200 degrees with the new thermostat. It pings with the original thermostat which doesn't let it get over about 170 degrees. The only time I was able to get on it without pinging was once at night. The car was cold from sitting for a couple days, ambient air was 45 - 50F, and the car hadn't warmed up much. If coolant is 200F and MAT is below about 75F degrees it pings a little, mainly at WOT. When coolant is 200F and MAT is around 100F (ambient air is about 70F at this point) it pings at part throttle, too.

Lilchief, it sounds like you have a fun motor!
------------------
Doug Chase
Chase Race
Custom: cages, exhausts, fabrication
Duvall, WA
425-269-5636

[edit: spelling, grammar, clarification, the usual...]

[This message has been edited by Doug Chase (edited 04-28-2006).]

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Doug Chase
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Report this Post04-28-2006 02:42 AM Click Here to See the Profile for Doug ChaseSend a Private Message to Doug ChaseDirect Link to This Post

 
quote
Originally posted by 3800superfast:

Doug, Anyway to post your winaldl logs ?


All I've done so far is to save the BLM tables to calculate new values for the Base VE RPM vs MAP table.

I haven't used WinALDL's datalogging functionality. I'll try that tomorrow and post some logs. It would be ideal if the engine had a knock sensor but we'll have to live without.

------------------
Doug Chase
Chase Race
Custom: cages, exhausts, fabrication
Duvall, WA
425-269-5636

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Fierobsessed
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Report this Post04-28-2006 06:27 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedDirect Link to This Post

Mine pings too, doesn't matter what I use for fuel. I know for a fact that it's a fuel problem and I am trying to find a good way of dealing with it. The timing could be off I suppose, but the power feels erratic. Symptoms are as follows: On cold Start ups, the engine cannot hold a steady idle for the first 2-3 minutes, surges heavily, once the engine hits closed loop the idle settles down. When letting out the clutch the engine suddenly looses power, and with more throttle, springs to life. Lot's of bucking issues at low RPM's, especially in first gear. When driving, transition from off throttle to light throttle has an on/off type responce, as you press the pedal power dissapears, then hits a surge suddenly. Once at operating temperature my engine pings heavily, especially on the highway in fifth. God forbid I enable my EGR, the throttle responce becomes very erratic at low throttles.

These are the problems I have been having ever since I put the 3.4 in. I don't know what to do exactly, but I think the computer just doesn't like having an extra .6L of engine, without being reprogrammed. I've been debaiting increasing fuel pressure (once I have some datalogs to show me that I need it) I need to figure it out, because 91 octane is getting costly for an engine that shouldn't need it.

Thaughts?

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Joseph Upson
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Report this Post04-28-2006 06:52 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post

Fierobsessed your engine troubles sound ignition module related, and in regards to what someone else mentioned earlier about the Autozone ignition module they definately differ across brands and it manifests in idle and driveability. I destroyed my first 3.4L due to a ground strap being left disconnected after install that resulted in immediate and sustained detonation just off throttle. I didn't discover it until I lowered the cradle to make changes to the turbo(twin setup) system which as a result of the detonation never reached a detectable level of boost since I could not hold acceleration for more than a second without detonation. 3 out of six pistons were chipped on the outer perimeter exposing parts of the top piston rings. The damage wasn't evident until a few hundred miles later when it started to burn oil as one broken ring cut into the cylinder bore.

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Fierobsessed
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Report this Post04-29-2006 06:26 AM Click Here to See the Profile for FierobsessedClick Here to Email FierobsessedSend a Private Message to FierobsessedDirect Link to This Post

hmmm... Interesting. I'll bite. Give it a shot tomarrow. I need a backup anyway.

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tjm4fun
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Report this Post04-29-2006 06:50 AM Click Here to See the Profile for tjm4funClick Here to Email tjm4funSend a Private Message to tjm4funDirect Link to This Post

I would second a log of aldl. it shows the advance the ecm is pushing at various rpms. that is also a tunable feature with custom chips. would be curious to see that plot vs rpm. that would give you something to hunt down, what is the correct total advance for the 3.4? it may be less than the 2.8, which would explain the retard of base timing clearing the problem.

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Joseph Upson
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Report this Post04-29-2006 07:08 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post

Base timing in the F-body 2.8 was 6 degrees as opposed to 10 for the Fiero so it is very likely to be the same for the 3.4, the F-body engines were MAF operated along with the MAP also up to and including the 3.4 I believe.

[This message has been edited by Joseph Upson (edited 04-29-2006).]

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lou_dias
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Report this Post04-29-2006 07:35 AM Click Here to See the Profile for lou_diasClick Here to Email lou_diasSend a Private Message to lou_diasDirect Link to This Post

Fierobessed, I had symptons like that with a bad fuel pump.

Doug,
Maybe your spark plugs are all off by 1 on the distributor. That's what is sounds like to me.

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Joseph Upson
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Report this Post04-29-2006 08:54 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post

You need to look at MAP and TPS values, your base timing can be right on but if you apply 30% throttle and the signal from the TPS or MAP sensor which ever is first in line for signal input at the ECM is sending a signal for 50% the timing will be advanced accordingly too early and that could very well be the reason everything is perfect when you check but detonation is still occuring. I accidently got got my TPS sensor wet in my camaro and it ran about as smooth as a wild bull ride bucking and kicking, sometimes a code is not set for a problem like this especially if it is appearing as a smooth transitional signal that is out of sync by too much or to little at a given point.

And a bad fuel pump nearly got me killed or severely injured because it was intermittent and read what appeared to be normal when checked, it was under acceleration that it misbehaved, and one day nearly left me stranded broad side in on coming traffic when I tried to pull off of a side road to get into the median for merging. It will run lean and cause detonation problems to.

[This message has been edited by Joseph Upson (edited 04-29-2006).]

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Oreif
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Report this Post04-29-2006 09:01 AM Click Here to See the Profile for OreifClick Here to visit Oreif's HomePageClick Here to Email OreifSend a Private Message to OreifDirect Link to This Post

 
quote
Originally posted by Joseph Upson:

Base timing in the F-body 2.8 was 6 degrees as opposed to 10 for the Fiero so it is very likely to be the same for the 3.4, the F-body engines were MAF operated along with the MAP also up to and including the 3.4 I believe.



All the 60* V-6 pushrod engines have a 12* ignition timing for the mechanical base. This is based on the 60* of the cylinders.
The Fiero 2.8L is at 10* to aid in emission control.
A 1983 Firebird with the 2.8L has a factory spec of 12* for timing (I just looked it up in the service manual.)
The 1993-1995 Firebird/Camaro has a base timing of 11* +/- 1* (It is programmed in because the engine is DIS and will vary based on the program.)

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Joseph Upson
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Report this Post04-29-2006 09:37 AM Click Here to See the Profile for Joseph UpsonClick Here to Email Joseph UpsonSend a Private Message to Joseph UpsonDirect Link to This Post

I'm referring to the setting recommeded on the GM applied sticker underneath the hood of my 1985 MPFI 2.8 firebird when setting the timing with a timing light, which is different than what's on the sticker found beneath the decklid of the Fiero of the same year.

I discovered the 93-95 timing setting flexibility yesterday while looking over TGP code planned for my next engine swap which will require an external reluctor wheel, since I can program the chip I don't necessarily have to have an adjustable crank trigger sensor as long as it's close, I can fine tune it by changing the base timing in the chip.

[This message has been edited by Joseph Upson (edited 04-29-2006).]

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tjm4fun
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Report this Post04-30-2006 01:25 AM Click Here to See the Profile for tjm4funClick Here to Email tjm4funSend a Private Message to tjm4funDirect Link to This Post

base timing is fine, but the ecm throws in advance too. what you really need to find, is the TOTAL advance in the motor at various rpms. most controlled timing now will run the advnce up, hold it and start to decrease it at wot to reduce pinging.
According to my aldl logs, I saw from 6 to 47 degrees advance thrown in (the 47 was during deceleration into a hard turn, still think that's off the wall, or there is a bug in the code). I would log it stting there, and floor the acclerator slowly up to wot, then take a look at what the timing does. turn on the tack output of aldl, and note the rpms where you hear pings, so you have something to look for to correlate if the timing is being over advanced for some reason.
map sensor I believe affects the timing, along with rpm, so could be something there too.

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