85 EURO Auto full throttle surge

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12 Jan 2011 15:45 #2833 by pcar928fan
85 EURO Auto full throttle surge was created by pcar928fan
Guys this is a progressive thing... Car was running great till a couple of days ago and it has had a surge at full throttle that is slowly getting worse.

Any thoughts?

James
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12 Jan 2011 16:03 #2835 by 928mac
Replied by 928mac on topic 85 EURO Auto full throttle surge
James this is a common problem on a lot of brands that happens when the fuel filter gets dirty.
Under load, like climbing a hill or WOT the engine will surge because it is starving for fuel. (If this is your problem)
Change it first as it is a cheap way to check if your fuel pressure is dropping under load due to a plugged filter. That is where I would start anyway, but I would have felt the symptom and would know if that was it.

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12 Jan 2011 16:25 #2836 by pcar928fan
Replied by pcar928fan on topic 85 EURO Auto full throttle surge
Brad,

I just looked on the parts list of stuff that was sent to Dr. Bob in CA when he was working on the car for me right after he picked it up and that was all belts and hoses on the front of the engine.

SO, not sure we did anything to the back and I suspect it is WAY PAST due for a fuel filter!

James
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12 Jan 2011 17:06 #2837 by 928mac
Replied by 928mac on topic 85 EURO Auto full throttle surge

Brad,

I just looked on the parts list of stuff that was sent to Dr. Bob in CA when he was working on the car for me right after he picked it up and that was all belts and hoses on the front of the engine.

SO, not sure we did anything to the back and I suspect it is WAY PAST due for a fuel filter!


If it feels like it's a running out of fuel type of surge,
Then that is where I would start.
It could be anything, but a lean fuel surge is like running out of gas type of feeling.
Hope its a easy fix.

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12 Jan 2011 17:51 #2838 by pcar928fan
Replied by pcar928fan on topic 85 EURO Auto full throttle surge
I was thinking MAF failure...and hoping it is not that... also possible air leak in the intake system under full throttle. There are a zillion things it could be, but best to start with simple stuff like fuel filter!

James
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12 Jan 2011 21:49 #2839 by 928mac
Replied by 928mac on topic 85 EURO Auto full throttle surge

I was thinking MAF failure...and hoping it is not that... also possible air leak in the intake system under full throttle. There are a zillion things it could be, but best to start with simple stuff like fuel filter!


I would, but remember I am not familiar with this brand car and it still fools those that are.

As a mechanic it helps to diagnose a problem when you know what it isn't.

If it is not the filter and it still looses power under load then maybe a few pulls with a sharktunner will point the direction so that you don't go replacing expensive electrical parts. Let me know what you find.

Brad

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13 Jan 2011 08:31 #2842 by Kiln_Red
Replied by Kiln_Red on topic 85 EURO Auto full throttle surge
I think I interpret the word "surge" in a completely different way than you guys. What does that term mean to you guys? James, are the symptoms only felt at WOT?

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13 Jan 2011 16:46 #2852 by pcar928fan
Replied by pcar928fan on topic 85 EURO Auto full throttle surge
The symptom and what "surge" means to me is that the car is accelerating but the rate of that accel is not smooth. So the car is surging or the accel is strong and then not as strong and then strong and not as strong...

It does not seem to be happening at 100% throttle with kick down switch engaged but more like at 85% to 95% throttle and mostly felt between say 3k rpm and 5k rpm or so... I need to do some more driving and testing to get the effect really narrowed down.

It felt fine in 3rd gear accelerating past 120 mph today... :D

James
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84 Ruby Red / Black AO84
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13 Jan 2011 16:48 #2854 by 928mac
Replied by 928mac on topic 85 EURO Auto full throttle surge

The symptom and what "surge" means to me is that the car is accelerating but the rate of that accel is not smooth. So the car is surging or the accel is strong and then not as strong and then strong and not as strong...

It does not seem to be happening at 100% throttle with kick down switch engaged but more like at 85% to 95% throttle and mostly felt between say 3k rpm and 5k rpm or so... I need to do some more driving and testing to get the effect really narrowed down.

It felt fine in 3rd gear accelerating past 120 mph today... :D


Hmmm maybe I was wrong.

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14 Jan 2011 13:20 #2869 by Kiln_Red
Replied by Kiln_Red on topic 85 EURO Auto full throttle surge
So are the symptoms very minor and/or inconsistent. Are we talking about an intermittent running condition here? It sounds like it's running very well to me. :D

If it's only a slight hesitation every now and again, then I would think simple. Did you say that you just recently did an ignition tune-up?

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14 Jan 2011 15:59 #2870 by pcar928fan
Replied by pcar928fan on topic 85 EURO Auto full throttle surge
The hesitation seems to be getting worse and more prominent.

Just had plugs and plug wires replaced and everything checked out and right after all that work was done it was running VERY, VERY WELL, but has trailed off and then started the surging as more miles have been put on... Weather is bad the next few days so it won't get out to be checked till next week.

It is NOT an intermittent problem and other than that 3/4ths to 95% throttle surge it is running quite well, but still seems a bit slow off the bottom and at the very top, but it is not surging at those places in the rev/power band. Only that 75% to 95% throttle position and in the 3k to 5.5k rev range...

James
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88 Dark Blue / Linen-Black
92 Polar Silver / Dark Blue 92EURO
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15 Jan 2011 09:06 #2875 by Kiln_Red
Replied by Kiln_Red on topic 85 EURO Auto full throttle surge
As specific and constant as this sounds, it kind of has me thinking MAF too. Do the resistance check on it outlined in the WSM. Should only take a few minutes.

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