Detonation Dilemma

[Umby]

I have my car out today and I'm driving it pretty hard since I wanted to hear my new pro dumps in action ... BUT... all I hear is my car starting to detonate every time I put a load on it. Lately the temp has been creeping up at idle so I am sure I have some timing issues, but is there anything else I need to check???

 

[Michael Yount]

Increased detonation is likely with increased operating temps. Likely the higher temperatures are what's contributing to the detonation. Focus on solving the temp problem and the detonation will probably take care of itself. Why is it running warmer than before?

 

[HISSIN50]

Continuing Michael's thought: .......And with detonation comes increased temps - it is a snowball effect.

Since you noted that it runs hotter at idle, how is your fan set up?

Dialing back some timing might be wise. Good luck.

 

[Michael Yount]

...it's the heating up at idle that got my attention JT. It won't be detonating at idle. But if it's overheating there -- seemed more likely to me that the higher temps are what's contributing to the detonation potential -- rather than it being the other way around.

 

[jrichker]

What are your mods? How much spark advance are you running? What octane gas? Have you changed gas stations reciently? What was the last mod you did? Have you dumped the codes?

 

[Umby]

Haven't dumped the codes yet...

Driving temp is actually quite low... I'm using the stock guage, but I'd put it somwhere around 175-180... since I have a 180* stat, that would be about right.... but sitting still the car starts to get warm... I'd say 215-225 at idle but I've seen it get all the way up to the "A" in "normal" during heavy traffic.

The heating up makes no sense to me though because less than 3 months ago I went throught the WHOLE cooling system and put in a new heater core, 180* stat, high miler hoses, and a 2 row aluminum radiator... the shroud is in good shape and I'm running the standard clutch fan... but the blade and clutch are in good shape... the air deflector is missing since the prior owned lowered the car a good bit.

I usually run 87 in the car and it normally does fine since my motor is still in stock trim. If I ever got what I considered to be a "bad tank" the car might ping a little over about 4800 RPM if I was really hitting it, even at normal temps... today was the first time it really made some noise.

 

[HISSIN50]

Umby, couple things jump out at me and Herr Yount. The hot idle issue Michael was talking about is worrysome. As you know, you really cant interpolate the stock gauge. But With your new parts, sans the fan stuff, you are running cool at speed - just like you would figure.
But the old fan and clutch are letting you heat up while stationary, it seems to me. Swapping an elec fan in, or renewing those components might be a good idea.

Many folks like the SSP clutches. Some feel that the parts store HD units are too tight (this is what I run and not an issue for me - I live where it is hot).

Good luck.

 

[Umby]

Yeah, I'm thinking of trying a new fan clutch... the only thing stopping me is that the old one seems to be in good shape (holds tight and no viscous fluid leaking)...

I'd like tp upgrade to an elec, but first I'll have to upgrade my alt which will involve sorting out the rats nest of misc wire that appear under my hood...

But even still... the fact that it was still pinging even when it was cool is what really has me shaking my head...

 

[Michael Yount]

Your MIA air deflector is designed to aid cooling at speed -- but since you're not having a problem there, the new radiator is probably taking care of that for you.

As richker says - dump the codes and see if they provide a clue as to what's going on. I suspect the increased operating temps are directly related to the onset of detonation.

 

[5.0tbirdguy]

Make sure the hot air isn't being recirculated at idle from the missing air deflector.

My car is a tbird but the same principles apply. I had a bad idle overheating problem. Ran cool on the highway. New 2 row Summit radiator with NEW stock clutch fan made airflow WORSE than stock 1 row radiator. Anytime the a/c was on I couldn't idle and not overheat.

Solution- MarkVIII fan and dcc controller. The fan never hits high speed.

Never overheated at idle anymore but warmed up on the interstate. The clutch fan pulled enough air at high rpm to nullify the missing air deflector. I had to buy a new lower valance panel from Ford. Now with u/d pullies temps are stable.

Airflow is very important.

 

[Umby]

Solution- MarkVIII fan and dcc controller. The fan never hits high speed.

An electric fan would be nice, but again, I have to do an alt upgrade first...

I drove the car A LOT today and its still detonating when under load, even when cool... I guess at this point I'll try pulling some timing out or running a highter octane and see what happens...

I'll also pull the codes...

 

[iapexl8r]

interesting

have had similar problems with a 347 (10.5 comp ratio w/aluminum heads) changed o2 sensors (not faulted) and seemed to cut pre ignition (clattering pinning ect) by 50 % but problem still exists. When it first started I took it to the dyno to re burn my chip and it wouldnt do it(detonate). next I will change the air charge temp sensor in the manifold. please keep me posted Chris

 

[Michael Yount]

Chris - have you pulled codes?

 

[Umby]

I'll def keep ya posteed, Chris. I'm gonna try to pull my codes tonite and see if it gives me anything...

 

[iapexl8r]

well yes and no

Here in lies the problem, the car has a custom chip. when I go to pull codes it only gives me some code about a computer failure. (It definatly is the chip that causes this code because my other EEC IV car has the same chip and gives the same exact code.) Now to remove the chip I disconect the battery ground lead(read erase maint memory) the car doesnt run too good with the chip removed so I dont drive it, just let it reach operating temp. then it just gives the usual code for egr. Chris

 

[iapexl8r]

bury me under hey thats prety damn cool realy liked the one about the puppet on the string.. chris rock on