No one in the Tech section replied to this question. I'm hoping for a reply in this section....
As the title says my fuel trims are reading passenger side -100 and driver's side I believe is +30. The pass.fuel trim doesn't change.
We think this is pointing to a bad PCM on my 1997 C5. It has a '98 program in it also.
The PCM went into a lock mode when the tuner tried to overwrite the tune with a previous tune.
The tuner can't get the tune over 370rwhp with new performance heads and a ported LS6 intake. The rest of my mods are in my signature. Before the head and ported intake..t was at 376 RWHP with the same dyno and tuner.
Is this a PCM going South?
So what are the thoughts from the CF members?
Thanks,
SLPRC5
How are the cars street manners?
Does it buck/surge, or have a rough idle?
Are the O2 sensors in good shape, and are you sure all of the injectors are in good shape?
How many miles on the car?
Sorry, I hate answering questions with more questions, but I think this info will help diagnose the situation.
How are the cars street manners?
Does it buck/surge, or have a rough idle?
Are the O2 sensors in good shape, and are you sure all of the injectors are in good shape?
How many miles on the car?
Sorry, I hate answering questions with more questions, but I think this info will help diagnose the situation.
Thanks
Mike
Good questions.
1. The car is going thru a tune after Patriot 243 heads milled to 62cc chambers were installed.
Prior to that the car being a A4 didn't have any bucking and idled good at 800 RPM with a 224/224 cam.
2. The O2 sensors are about 2 years old and no codes thrown on them.
3. The injectors are a year old and are 30#
4. The car has 66K on it..but all the bolt ons are new. i.e. cam, heads, oil pum, timing chain, knock semsors, belt tensioners an T-stat.
The PCM had to be re-flashed last week because it shut down after the tuner tried to over-write the tune. The dealer got it back up and re-flased...it runs fine. When the tuner went to dyno tune it, it only made 370rwhp...and the AFR was all over the place. He started checking the tables and that is when he founf the #2 fuel bank was -100 and would not change. So after talking to HP and the dealer tech the conlussion is that the PCM is going bad.
I hope this is enough infor for you to come up with some input.
Thanks,
SLPRC5
It is probably just a scanner issue. The 97-98's have some issues.
Load up the default scanner and try it again.
Thank you ....I'll pass this on to the tuner
My tuner says there is a engine ping also.
The AFR is at 13. I believe he said the timing is 22 and 25 .
He said if he toke it down to 16 to get rid of the ping...my RWHP would be below 300.
HPtuners is being used and the fuel trim issue is not the real problem the problem is that the car came up with a pretty bad ping a week or so ago and the only thing that was noticed/ changed in the time frame was that reading on the scanner which may not be accurate due to the 97/8 issue with hptuner.
We just need to see what has caused the detonation as it is audible ranging from 2-4* of retard being pulled. I know that we will find it but in the mean time All ideas are welcome. The air fuel is 12.8:1 and is now detonating at 20* timing when it used to handle 23*. You can bring it down to 11.5 and the knock goes away but so does the power, and there is no need to run a h/c car at 11.5 or anyless than 22* timing!
i didnt think the VCM could have fuel trims that hi/low.
Isnt the fuel trim limit +/- 25% max?
must be a scanner issue like someone else said.
I hear that HP has issues with tuning the '97&'98..my tuner said the new edition has settled the issuses.
The engine also has a ping...looking at changing the plugs and the air tempeture sensor in the air bridge.. my sensor is relocated to the back of the Blackwing.
The tuner says hwe isn't worried about the fuel tirm readings.
Remove a couple of the pids out of the table on the scanner, such as the speedo, ect, and tps.
I have had the same problem many times with 97/98 cars...
Any more than 24 bytes and the fuel trims will not read...........
Yup, we see this happen alot where a tuner will use a config for a 99+ LS1 that has 25+ bytes being used but 98's only allow for 24bytes therefore the scanner will allow you to scan but drop a couple of PID's to get to the 24byte mark.
Using the default config and staying under the designated 24bytes mark usually is the fix.
When pulling on the dyno the car at WOT is going open loop. So really the fuel trims shouldnt be affecting power. I think the problem is in the pinging and KR. I would do a quick leakdown and see whats going on. I would also check the PCV system to make sure you arent getting some oil in the intake when you go WOT. Why not just run the car open loop and see how the car runs? If it runs better in open loop you know you have an 02 sensor problem. Hope this helps a little.
At this point..not sure of the fuel trim status. The tuner replaced the PCM hoping this will fix the engine ping it has.
He has tried everything, changed plugs, checked the wire, vacuum leaks, changed the IAT sensor. The only way to get rid of the ping is to set the timing back to 16* from the 22*, but at 16* there is a huge lost of power because the engine is running rich.
As mentioned the new heads were installed, the piston tops were de-carbed. Thinking of running Sea Foam through the engine to see if that will get rid of the ping.
When pulling on the dyno the car at WOT is going open loop. So really the fuel trims shouldnt be affecting power. I think the problem is in the pinging and KR. I would do a quick leakdown and see whats going on. I would also check the PCV system to make sure you arent getting some oil in the intake when you go WOT. Why not just run the car open loop and see how the car runs? If it runs better in open loop you know you have an 02 sensor problem. Hope this helps a little.
The tuner has checked the intake and PCV for oil. The engine has a catch can with a glass sight tube in the line to the TB to see if any oil is going to the TB and there is none noticed.
I believe he has done all the things you have mentioned.
Thanks for you input..
SLPRC5
Seem replacing the PCM with a new one and the replacement of the Optima Red battery (because it wasn't charging fully and holding it) has done the trick..No more engine PING.
Next is the dyno tune to see what RWHP I'm putting down with the Patriot heads and porting the LS6 intake.
Will get back with the dyno sheet as soon as it's done.
Thank everyone for their valuable input.
Seem replacing the PCM with a new one and the replacement of the Optima Red battery (because it wasn't charging fully and holding it) has done the trick..No more engine PING.
Next is the dyno tune to see what RWHP I'm putting down with the Patriot heads and porting the LS6 intake.
Will get back with the dyno sheet as soon as it's done.
Thank everyone for their valuable input.
Did you port your own intake? If so, care to share any ideas, I'm getting ready to attempt this.
Did you port your own intake? If so, care to share any ideas, I'm getting ready to attempt this.
No I had it done. But the person that did it said he matched the runners up to the inlets on the heads..so it sounds like he enlarged the intake runners to the size of the inlets on the heads and smoothed out any imperfections.
Seem replacing the PCM with a new one and the replacement of the Optima Red battery (because it wasn't charging fully and holding it) has done the trick..No more engine PING.
Next is the dyno tune to see what RWHP I'm putting down with the Patriot heads and porting the LS6 intake.
Will get back with the dyno sheet as soon as it's done.
Thank everyone for their valuable input.
I'm disappointed in my RWHP. It dyno'd at 380 RWHP and 362 RWTQ.
So I didn't make the 400 like I expected too.
No I had it done. But the person that did it said he matched the runners up to the inlets on the heads..so it sounds like he enlarged the intake runners to the size of the inlets on the heads and smoothed out any imperfections.
That's pretty much what I had in mind to do. I'd love to get 15-20 rwhp like a lot of others seem to be getting.
Quote:
Originally Posted by SleeperC5
I'm disappointed in my RWHP. It dyno'd at 380 RWHP and 362 RWTQ.
So I didn't make the 400 like I expected too.
That does sound low, even for an A4 car. Did you put the PE back to 12.8 after getting the ping issues taken care of?
Corvette Store
#2 fuel trim is reading -100
