What would cause this? While cruising at 65mph my BLM's are locked at 110 and the interagator is switching from 130 to 120. My O2s are switching lean to rich(300 to 800). Engine temp. is around 160. When I start going up a steep grade and I get no more than 5 pounds of boost, I can hear some light detonation. If I give the car anymore boost than that(10 to 15 pounds), it will act like it back fires. This all started after I installed a fmic, thdp and champion iron heads. I don't drive the car that much because of this weird problem. Maybe I have multiple problems showing up at the same time? If anyone has any ideas, let me know. The ignition system only has about a thousand miles on it(AC Delco coil pack and module w/ MSD wires, AC plugs cr43ts at .035).
Detonation
- Thread starter tmsbuic
- Start date
- Joined
- Aug 1, 2003
have you tried another set of wires or plugs ?
i had a brand new set of msd wires (bought in sept) that ran fine till boost , with ac r43ts at .32 they broke up at around 15-20psi , bucking bad and have the DS files of it , otherwise they were fine , put the old wires back and all was well to 28psi .
checked the MSDs they all ohmed good so I reinstalled and problem was back so i knew it was the wires .
those msds went back and were replaced by seller and so far so good with the new set
if you rule out wires check that the plugs are tight , if theyve been detonating might be good to pull them and inspect and then replace them just incase one was cracked on install
i had a brand new set of msd wires (bought in sept) that ran fine till boost , with ac r43ts at .32 they broke up at around 15-20psi , bucking bad and have the DS files of it , otherwise they were fine , put the old wires back and all was well to 28psi .
checked the MSDs they all ohmed good so I reinstalled and problem was back so i knew it was the wires .
those msds went back and were replaced by seller and so far so good with the new set
if you rule out wires check that the plugs are tight , if theyve been detonating might be good to pull them and inspect and then replace them just incase one was cracked on install
DMan
buh bye
- Joined
- May 25, 2001
Well I probably jumped the gun with the wires 
but the obvious thing that happened is you removed significant air restriction by changing out the heads, ic and downpipe simultaneously. Your car is breathing a lot deeper.
Its highly possible if not a fact that your fueling and/or timing is way out of whack for your new combo and you are too lean/too advanced. Do you have an EGT gauge? Do you have any data from before and after?
You don't mention making any changes to the fueling; mechanical, chip-wise or otherwise. Did you?
but the obvious thing that happened is you removed significant air restriction by changing out the heads, ic and downpipe simultaneously. Your car is breathing a lot deeper.Its highly possible if not a fact that your fueling and/or timing is way out of whack for your new combo and you are too lean/too advanced. Do you have an EGT gauge? Do you have any data from before and after?
You don't mention making any changes to the fueling; mechanical, chip-wise or otherwise. Did you?
I got with eric on the mods and he said he might have to put some more wot fueling in the chip if it shows lean on the top end. This problem is happening under very light throttle with very little boost. The egr control has been taken out with the chip. My alky shows to be working when I hit the test button and watching my o2's. Now this starts happening around 5 lbs of boost. So is the blm's showing it is running super lean?
110 isnt a locked number. 90 is. Its still in adjustable range and the computer has it under control, so I wouldnt sweat it. People get too anal about hitting the perfect 128. So you did a head swap...did you see carbon on the pistons? Did you leave the carbon there? Are you getting knock retard? If so, how much? Whats your fuel pressure? The O2's moving around is normal as long as you arent WOT. I would look into that EGR issue like they said. You're getting more air into the motor, but have retained the same timing curve most likely.
What gas are you running? Arco or BP? That gas is like liquid dynamite. Really prone to Detonation. Chevron, 76, Mobil gas- I can run 89 octane with alky, 27/25 timing, 23 lbs of boost. Arco (same as BP), I can only run 20 lbs with 91 octane with alky, and have to pull 2 degrees of timing. people say its no different than other gas. That is total BS. Every person I know who uses this gas ends up with major pinging issues. These numbers of mine are not just an opinion but real data. When I tell people about my numbers with my scan tool and tuning stuff, they are much more convinced that there is something to this cheap gas theory.
What gas are you running? Arco or BP? That gas is like liquid dynamite. Really prone to Detonation. Chevron, 76, Mobil gas- I can run 89 octane with alky, 27/25 timing, 23 lbs of boost. Arco (same as BP), I can only run 20 lbs with 91 octane with alky, and have to pull 2 degrees of timing. people say its no different than other gas. That is total BS. Every person I know who uses this gas ends up with major pinging issues. These numbers of mine are not just an opinion but real data. When I tell people about my numbers with my scan tool and tuning stuff, they are much more convinced that there is something to this cheap gas theory.
I'm running Chevron 93 gas. The engine only has about 8,000 miles on it. When I had the heads off, there was not any carbon build up at all. Everything ran fine until I put those parts on. I was able to adjust on the translator to get my BLM's back up around 132. I only was running 20 lbs of boost before I did those parts and everything worked great. Now, I can't even get above 5 lbs before I can actually hear detonation. The detonation I'm hearing isn't extremly harsh, but enough that I'm not going to push it up anymore. After I adjusted the translator, I drove it for a while so everything would have enough time to re-learn everything. O2's,blms,int,maf,iac,temp., etc. all seem to stay withen normal limits, but it will still do it at not more than 5 or 6 psi of boost. My fuel pressure is set at 43psi and I double checked it with another gauge to make sure. The fuel pump is a new 340, but it was doing it with the 307 pump also. Fuel filter is new also. I'm going to get another chip from Eric made to be safe. If I do take it up between 10 to 15 lbs of boost, it will backfire pretty bad, so I won't do that anymore until I know whats going on. It will probably end up being something simple that I have overlooked(I Hope). Once I get the other chip in, maybe it will run better. Only time will tell.
Is the crank sensor tight and not flopping around or positioned wrong? Did the cam sensor get pulled out? Is every injector plug on the correct injector? Have you double checked all the plug wires for not only the correct firing order, but to look for damage and arcing? Have you pulled the plugs out and looked at them? Are you getting any KR? You should get some fuel line or a stethoscope and listen to each injector and make sure they are all ticking with the same frequency. Any loose hoses from the turbo/IC to the up-pipe? All the manifold bolts torqued down?
I'll get my stethoscope from work tomorow to listen to the injectors. I have put my old plug wires on with no difference. I pulled the cam sensor and inspected it and re-set it. Same with the crank sensor. Ofcourse, that doesn't mean there still couldn't be a problem electrically wrong either one of those. I have seen some crazy things dealing with crank sensors before on other gm vehicles. Engine seems to idle fine, but an injector might not be flowing like it should under load. I'll look at the plugs for any signs of detonation and maybe I can atleast track down a certain cylinder for injector/ignition problem. My problem is I don't want to throw parts at something, I want to track down exactly what it is. It would be nice to have an EGT to test with, but I don't at this time, so I have to go about this in another way. Anyways, I'll post if I find something.
Well I listened to all the injectors and they all sound the same. I put all knew vacuum lines on recently after this problem began with no difference. I have one of those coil pack/module testers and it shows everything there is working. Plugs have been replaced after problem started with no difference so I can rule those out. Maybe my old set of plug wires is bad also. While driving it some today to get a good feel of what it is doing, I noticed that it doesn't matter if the engine is cold or hot when the problem shows up( the coil and module are knew ac delco units under 1000 miles, it doesn't seem those could be the problem when it does it cold also). It feels like something is breaking down(ignition etc.) as soon as boost goes above 5 psi and above. Go any higher and it will backfire. Can a crank sensor do this under load even though it idles fine and drives fine without boost? The next thing I'm going to check is tape a fuel gauge to the windshield and see what is happening under boost then so I can rule out fuel pressure. I guess I'm really down to either a plug wire problem, fuel pressure under load and/or injector flow under load. What has me puzzled is everything worked great until these knew mods were installed. Its like something went bad while sitting on the table waiting to be put back on.
Have you slowly opened the throttle and watched the TPS voltage to make sure you have no flat spots or problems with the voltage curve? Have you swapped in a different MAF? If you have a translator, is it good? What does your AF (MAF reading) curve look like under WOT?
Pretty dumb question, but did every ground wire make its way back onto the back of the passenger side head? If they are, maybe they could be having problems conducting properly from surface corrosion or something. Just a little oxidation on the mating surface of the connector can kill conductivity in a big way. or its just simply not tight.
Is the chip installed right? try pulling the ECM connector off and check for damaged pins or any other ECM related issues. Reseat the chip.
I think your problem is a wiring issue somewhere, or a chip problem.
Check everywhere for wires that are not grounding right, or are shorting out because of some burnt or worn off insulation that is touching metal somewhere.
Pretty dumb question, but did every ground wire make its way back onto the back of the passenger side head? If they are, maybe they could be having problems conducting properly from surface corrosion or something. Just a little oxidation on the mating surface of the connector can kill conductivity in a big way. or its just simply not tight.
Is the chip installed right? try pulling the ECM connector off and check for damaged pins or any other ECM related issues. Reseat the chip.
I think your problem is a wiring issue somewhere, or a chip problem.
Check everywhere for wires that are not grounding right, or are shorting out because of some burnt or worn off insulation that is touching metal somewhere.
My TPS looks fine and I have one of those TEC-TPS hooked up on it also. My MAF looks good for the little bit I can start to boost up on. Can't even get to WOT. I have the Ground Stretcher kit on, but I will double check the connections on it to make sure all connections are good and tight. I just know it has to be something simple like that to just start happening.
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