[fastford3388]

So i've got an 89 mustang GT that hates the cool weather..

I get a misfire, almost even a pre-detonation condition ONLY when my car is not warmed up yet. I've got a 180 t stat in it and as soon as it opens up the car runs fine... No codes... I've got no smog pump, no EGR and i've bypassed the coolant that runs into the TB spacer.

I was putting 87 in it cuz it normally works fine with it. I decided to put 93 in and it ran better until it dropped below 45 degrees outside.

Any clues?

[1slo5.0]

What the hell is "pre-detonation"? It either experiences detonation or it doesn't...

What do you mean no EGR? You took your EGR off or you changed intakes and no longer have an intake that has an exhaust gas passage? I guess if you still have the EGR spacer on your car that you took the coolant lines off of then you need to hook them back up because you just introduced a ton of heat into your intake. The coolant lines are there too cool, not heat. Removing the EGR valve from the spacer doesn't remove the heat from the spacer. I'd put the EGR valve back on if it was me. Removing it does nothing for performance. As for the misfire, does the car run rough when driving or just when it is idling? How long have you owned the car and have you ever changed the oxygen sensors?

[grnstang]

what is your timing set at? Mine runs a little rough when i first start it up if the weather is cold

[fastford3388]

I guess the word I was looking for is Pre-Ignition. The process of igniting the fuel/air mixture before top dead center.

The EGR is completely removed, everything from the egr system was gone before I owned the car. I'd put it on if i could. I bypassed the coolant that was running to the TB spacer because when I installed the 70mm spacer on my gt-40 intake coolant leaked. also, seems stupid to run hot coolant near the intake if the egr is removed...

As far as I know, the timing is set to base. 10 degrees i think it is?

and could O2 sensors do that even if i don't have an O2 sensor code?

I've owned the car 2 years and I think i've replaced every sensor except the O2 sensors...

[1slo5.0]

Originally Posted by fastford3388 I guess the word I was looking for is Pre-Ignition. The process of igniting the fuel/air mixture before top dead center. The EGR is completely removed, everything from the egr system was gone before I owned the car. I'd put it on if i could. I bypassed the coolant that was running to the TB spacer because when I installed the 70mm spacer on my gt-40 intake coolant leaked. also, seems stupid to run hot coolant near the intake if the egr is removed... As far as I know, the timing is set to base. 10 degrees i think it is? and could O2 sensors do that even if i don't have an O2 sensor code? I've owned the car 2 years and I think i've replaced every sensor except the O2 sensors...

So are you hearing pinging under load (detonation) or is the car dieseling (pre-ignition) when you shut it off? Igniting the a/f mixture before TDC is not preignition. Your timing from the factory is set to ignite the mixture 10 degrees before top dead center.

As far as the EGR goes, the EGR itself does not bring the heat into the intake. The intake brings the heat into the intake. There are exhaust passages in the heads (unless they are blocked off) that direct exhaust gas into the intake thru a passage up to the EGR spacer and then on to the EGR valve. If the EGR spacer is still on the car you need the coolant lines hooked up or you have just successfully more than tripled your air intake temperature. The coolant lines are there to cool the EGR spacer, not to heat the intake. Why is that so hard for people to understand? If the intake has no exhaust gas passage on it then you don't have to worry about it. But your GT40 intake has an exhaust gas passage so if you are running an EGR spacer, you need the coolant lines hooked up unless you prefer to heat your incoming air.

Timing - Don't think or assume, check it.

Oxygen sensors - Yes they can be bad and not throw a code. This goes for all sensors. If you have a voltmeter you can test them. Google "oxygen sensor test".

[fastford3388]

I've got a gt-40 manifold off of an 01 mercury mountaineer. is this going to make a difference in the operation of my egr? I know some years of the explorer intakes were internal egr, while others were not.

I will test my 02 sensors because i just replaced my head gaskets. I read that burning coolant (which is what I was doing) is terrible for the 02 sensors. this is most likely the problem.

[1slo5.0]

Originally Posted by fastford3388 I've got a gt-40 manifold off of an 01 mercury mountaineer. is this going to make a difference in the operation of my egr? I know some years of the explorer intakes were internal egr, while others were not. I will test my 02 sensors because i just replaced my head gaskets. I read that burning coolant (which is what I was doing) is terrible for the 02 sensors. this is most likely the problem.

Then you don't have a GT40 intake, you have an Explorer/Mountaineer intake. Big difference with the major difference in your case being the lack of EGR spacer on the Explorers and the lack of the same EGR system as a Mustang.

[fastford3388]

so am i correct in saying that my egr system is unusable with my intake setup? and should i still hook up my coolant lines to my egr spacer?