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Changed plugs, fuel filter and alt pulley, now idle/fuel pressure is 'hunting"

ChicagoMike

TCG Elite Member
Mar 4, 2004
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Ok, took the car out of storage and it seemed to idle fine. Note that the tank of gas is 6 months old, but I am working on getting using it up and staying out of boost. only 1/2 tank left to burn. Hermann tune on the 22nd.

1. Changed fuel filter.

2. Changed alternator pulley from 3.5 to 3.7 per Hermann's advice because of 6lb lower (pa perf 130amp alt)

3. Had TR6 plugs gapped at .035 - per Lyle and others, I was told to switch to BR7EF @ .028. Did compression test inbetween plug swap and numbers were all consistent so no problems there.


The TR6's were white! Lean - Pauls high performance tune, I knew this, I only boosted once or twice lean last year and have stayed out of boost since

Hans THINKS it might be in the tune. When driving the car is seems to respond normal, but the fuel pressure gauge is spiking and dipping while cruising by +5/-5 PSI.

And finally: at IDLE, the fuel pressure gauge is bouncing +5/-5 PSI and you can see the tach "hunting" several hundred RPM's up and down and you can hear pops out of the exhaust when the fuel pressure spikes +5.


Any comments/ideas to what is happening? Think it's in the tune, and if not should I plan to bring some extra parts to the Hermann tune? I can stay the whole weekend if I have to!!!
 

Flyn

Go ahead. I'll catch up.
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Mar 1, 2004
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Tune, bad gas, or both. Fill the tank to dilute the bad gas and drive that thing until the tank is used up. Then refill with fresh gas. Check your plugs after driving it to see how they look. If you have an A/F meter, keep an eye on it. To be safe, stay out of boost.

DO NOT COME TO DAN'S ON FRIDAY! I will be getting my car tuned that day. :D
 

ChicagoMike

TCG Elite Member
Mar 4, 2004
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No AF meter. I know it's running lean so I am staying out of boost and driving it like a grandma (pretty much how I've driven the car for the past 2 years - what a SIN - hopefully after Hermann I can drive it like I stole it and start getting those speeding and loud exhaust tickets!)

I thought it was weird because it was ok for 70 miles until we changed the above. If there's an issue at the event I guess we can always pull the plugs and recheck the gaps.

Flyn high again said:
Tune, bad gas, or both. Fill the tank to dilute the bad gas and drive that thing until the tank is used up. Then refill with fresh gas. Check your plugs after driving it to see how they look. If you have an A/F meter, keep an eye on it. To be safe, stay out of boost.
 

ChicagoMike

TCG Elite Member
Mar 4, 2004
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03 VENOM said:
Mike,what was your A/F the last time you had it on the dyno?

I assume it got leaner after this because I had the blower re-ported from stage 1 to stage 3.5.

PHPDyno.jpg
 

ChicagoMike

TCG Elite Member
Mar 4, 2004
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great idea, will check that

Wiked03 said:
I had a somewhat similar problem after changinf my fuel filter last week. When I restarted the car the fuel pressure (which usually sits at 28~30 at idle) was dropping to 18 and jumping to 35, then dropping back down. Finally found that the fuel filter was not clicked all the way in on one side. Just an idea. :dunno:
 

ChicagoMike

TCG Elite Member
Mar 4, 2004
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Just spoke to Hans. He's 100% that the fuel filter is plugged in all the way. Only 9500 miles on the car now but never changed the fuel filter. Hans said the fuel filter was clogged.

So we're thinking:

Tune related because more fuel, fuel pulse has changed?

OR

FPRS getting ready to crap out? It was bounced off the rev limiter in the past. Do they just go bad or do they have symptoms before complete failure?
 

dun4791

gypsy is a whore!
Mar 2, 2004
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What ain't no country I ever heard of
Mike,

you are running a colder plug and a smaller gap now, I dont know how PHP tunes(Im pretty sure he doesnt just WOT tune),so Im guessing that your idle quality wont be perfect with the old tune.

Dont trust the gauge, you have an Autometer right?

Get some fresh gas in there, stay outa boost, put some miles on it and refill with full tank of gas, see you in a couple weeks...........
 
ChicagoMike said:
FPRS getting ready to crap out? It was bounced off the rev limiter in the past. Do they just go bad or do they have symptoms before complete failure?


They just start carrying guns and knives one day, and using drugs without ever giving you any indication they are on the path to destruction.....

Get a spare and throw it in the glovebox if you are worried.........
 
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