Persistent detonation problems

kenny150r

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Hello,

I bought my GT in 2011. Ever since I bought it, ive had detonation problems. Even when it was completely stock, it had to have 91 octane or it would detonate.

Then, I did a PI swap with new heads and cams, plugs, intake, etc. Still detonates, even after a dyno tune. I cleaned all the carbon off the piston tops as well. Also, I replaced the injectors with new Ford replacements.

The thing is, it doesn't detonate at all until it warms up all the way. While it's warming up, it feels so great and drives with a lot of power. But all the power goes away and detonation/pinging happens once it's at normal temperature for about 5 min or so.

I've changed plugs to the tr6's, no luck.
Removing 4-5 degrees of timing reduces the pinging slightly, but the power loss is significant.

Should I buy a cooler thermostat? I have the stock 192 degree thermo in now. How about the MAF? Should I clean that? Idk what it could be. All that is left really is the MAF, EGR stuff, plug wires, and possibly a thermostat.

I think there is something wrong, especially since I only produced 250 rwhp with stage 2 cams and new heads on the dyno.

What should I do?
 

96blak54

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Unplug the maf then go drive it. Report back findings
 

Nuttinbutcrumbs

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Was the motor not warm when it was on the dyno? I'm no modular expert but I think 250 hp sounds about right, stock you were only making around 200 at the wheels. Scan for codes. I'm pretty sure it's not a maf problem. If it was the maf I think it'd run bad cold or warm. My money is on the ect sensor. Did they tuner tell you what your a/f ratio was? If it was detonating it seems like they would have notice when the were doing wot pulls. But no it's not you're maf, when the maf is bad the idle will be shtty.
Scan for codes and call the tuner. If you're having to adjust timing something is a miss. The tuner should have set the timing for optimal performance with out detonating. Was it detonating before the tune? Are you sure the tuner did any tuning?
 

kenny150r

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The tuner definitely did some tuning, baseline pull was around 225 whp, they got it up to 250. The engine was also warm when it was on the dyno as I drove it 10 miles to the tuner. I haven't had the chance to try unplugging the MAF, but yes the car did ping before I took it in to the tuner. I don't know how they didn't notice any pinging... I took it in to the tuning shop during the winter and it was very cold, the detonation is milder when it gets colder. My car throws no codes at all as well. I know my car was lean when I brought it in to the tuner but it was much richer once I left.
 

96blak54

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Unplug maf, drive, report back

I can make a reply to this post 5pages long, but youre gonna have to try my suggestion to narrow down your problem. Eliminating the maf puts car in limp mode. If you ping and rattle after unplugging, your problem lies elsewhere.

Are you sure it is detonation?

Any tuner with heart wouldnt let you leave with a crap detonation tune.
 

Nuttinbutcrumbs

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Unplug maf, drive, report back

I can make a reply to this post 5pages long, but youre gonna have to try my suggestion to narrow down your problem. Eliminating the maf puts car in limp mode. If you ping and rattle after unplugging, your problem lies elsewhere.

Are you sure it is detonation?

Any tuner with heart wouldnt let you leave with a crap detonation tune.
I was kinda wondering the same about the "pinging".. I'm thinking and I could be wrong as I am now and then, but it seems like they wouldn't have set the timing so high to where the motor was detonating. Don't they usually set as much timing as the motor can take but not more than?
Also, if this guy is adjusting the timing at the distributor won't the ecu tune override the retard/advance anyway?

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Nuttinbutcrumbs

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The tuner definitely did some tuning, baseline pull was around 225 whp, they got it up to 250. The engine was also warm when it was on the dyno as I drove it 10 miles to the tuner. I haven't had the chance to try unplugging the MAF, but yes the car did ping before I took it in to the tuner. I don't know how they didn't notice any pinging... I took it in to the tuning shop during the winter and it was very cold, the detonation is milder when it gets colder. My car throws no codes at all as well. I know my car was lean when I brought it in to the tuner but it was much richer once I left.
Is it "pinging" at any rpm or just when you go wide open?
Is it a misfire?

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96blak54

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Timing is a pre-ignition problem. Detonation happens when the piston reaches TDC and squeezes fuel. Tiny liquid pockets detonate creating that pinging sound you hear. Its creating combustion before the crank angle reaches the point of desend. That reversion combustion causes the piston to shake, rods to clank on the crank....so on.

There are only a few reasons a modular will ping/detonation and its limited in scenario possibility. Since the OP has modifications, probability is higher and most likely a fuel supply issue. Another possible scenario is pistons installed backwards, but OP stated it did the same in stock form.
 

kenny150r

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Unplugged the MAF and no luck. Car drives the same with detonation still when warm. Also, it detonates at any rpm, under moderate throttle, and only under load. When I go to WOT the pinging actually almost goes away. I'll try and contact my tuner again today and see if something else is up.
 

Nuttinbutcrumbs

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Timing is a pre-ignition problem. Detonation happens when the piston reaches TDC and squeezes fuel. Tiny liquid pockets detonate creating that pinging sound you hear. Its creating combustion before the crank angle reaches the point of desend. That reversion combustion causes the piston to shake, rods to clank on the crank....so on.

There are only a few reasons a modular will ping/detonation and its limited in scenario possibility. Since the OP has modifications, probability is higher and most likely a fuel supply issue. Another possible scenario is pistons installed backwards, but OP stated it did the same in stock form.

I know but I thought too much advance can cause cylinder pressures to rise too rapidly and the end result being detonating. So you don't think the stock fuel components are adequate to support 250 rwhp? I'm not seeing that at all. Or are you thinking he has a bad injector etc? He said he had the same problem when went in and his base pull was 225. I'm not sure about the modular's but w the 302 and its crap 90 lph intake pump and 19# injectors you can run around with 225 rwhp all day long.
OP: How's your egr? I'm still kinda thinking it's the ect
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kenny150r

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I know but I thought too much advance can cause cylinder pressures to rise too rapidly and the end result being detonating. So you don't think the stock fuel components are adequate to support 250 rwhp? I'm not seeing that at all. Or are you thinking he has a bad injector etc? He said he had the same problem when went in and his base pull was 225. I'm not sure about the modular's but w the 302 and its crap 90 lph intake pump and 19# injectors you can run around with 225 rwhp all day long.
OP: How's your egr? I'm still kinda thinking it's the ect
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I have never messed with the EGR/emissions stuff before... how would I check if it is working correctly? It would throw a code if it wasnt working, right? Also, I've passed smog inspection with the car as it sits, if that makes a difference.

Also, the shortblock is the same. I'm 99.99% sure its detonation because changing the timing does change the severity of the pinging, but only slightly. 5 degrees of timing change should make a big difference, no? All the injectors are brand new, and the problem existed before I changed those as well.

Thank you guys so much for all the help!
 

Nuttinbutcrumbs

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I have never messed with the EGR/emissions stuff before... how would I check if it is working correctly? It would throw a code if it wasnt working, right? Also, I've passed smog inspection with the car as it sits, if that makes a difference.

Also, the shortblock is the same. I'm 99.99% sure its detonation because changing the timing does change the severity of the pinging, but only slightly. 5 degrees of timing change should make a big difference, no? All the injectors are brand new, and the problem existed before I changed those as well.

Thank you guys so much for all the help!
If you've passed emissions then you can pretty much rule out the ect. And more than likely the egr as well but you can test it like this.
Get a length of clean vacuum line and run it to the EGR vac connection (unhook the existing plastic line). With the engine running, suck on the end of the line. The idle should get rough / stall. When you notice it getting rough / stalling, stop sucking. If the idle recovers (almost immediately), your EGR is functioning properly and isn't "sticking" open / closed. If you notice no change in idle, it won't recover once it gets rough, or it doesn't recover within a few seconds, then your EGR needs to be cleaned / replaced.


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96blak54

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Good idea!

other possible scenario
Low fuel pressure!
Could be caused by a weak fuel pump or the fuel presure regulator has weak vacuum or possibly stuck open.
 

Nuttinbutcrumbs

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Good idea!

other possible scenario
Low fuel pressure!
Could be caused by a weak fuel pump or the fuel presure regulator has weak vacuum or possibly stuck open.
To test the fuel pressure regulator after it's been running pull the vac line off of the top and see if you can feel any fuel on that line. If so then it's bad.
Did you ever hear back from the tuner? I'm out of ideas really... It seems like if you're fuel system was bad or inadequate they would've known. I'm also kinda thinking that if the pump and or fpr was bad you'd have starting issues and or it'd die on you. I'm 91% sure that your fuel pump isn't the issue. If it was in good working order I'm pretty sure it'd be able to keep up w the power you're making and if it was "crapping out" it would've "crapped out" by now and you're car wouldn't start. Let's say by the off chance that the stock pump wasn't adequate enough the tuner would've known b/c the a/f ratio would've been junk and more than likely they would've tried to sell you a "boost a pump" or a different in-tank pump.

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