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| Andrew | New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
 
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Now that the high rpm oil pressure problem has been corrected, the car has developed a hard start issue, which it never had in the past.
Anytime I disconnect the battery, it takes a while for the car to figure out how to idle. So, in the beginning, I thought this was this issue and it would go away. The car is idling, almost like normal, and the car is still hard to start, especially when warm. Once running, no problems at all. When cool, the car starts easier. When warm, I have to crank the motor way too much. It smells really rich until it starts running. When cranking, I hear that nice "woofing" sound as if timing is off. Installing the oil pan, I had to remove the O2 censor, crank the motor backwards to check for clearances, and disconnect the battery for a few day. Everything else that was done would have no effect on how the car is running or starting. I checked the O2 censor and connections, all looks good there. GRRRR, this car is moving to my bad list!! |
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Posted on: 2012/3/5 21:01
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2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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Also, no codes....
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Posted on: 2012/3/5 21:13
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2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| 1Fast04Vert | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
 
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Any chance your fuel pressure regulator is leaking? The 02 wouldn't have anything to do with hard starting (open loop).
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Posted on: 2012/3/5 22:42
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2004 Vert. 475hp. Built by Vengeance Racing |
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| Woodstock | Re: New Problem - Hard Starting LT4 | ||
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Senior Guru
 
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Check fuel pressure. A friend with an 88 had similar symptoms and asked me to replace the injectors. We checked resistance and for leakage, but the injectors were fine.
Replacing the fuel pump solved the issue. |
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Posted on: 2012/3/5 23:00
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91 convertible |
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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FP is good; regulator seems good (I didn't see any gas in the vacuum line). Once the car is cold, it fires within 1/2 a second. When hot, near impossible to start. Let it sit about 15 minutes, hard to start, but I have to pump the gas pedal. When it starts, I can smell raw fuel…
ICM?? Once I get it started, it runs great. |
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Posted on: 2012/3/6 0:24
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2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| 1Fast04Vert | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
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Thought you weren't supposed to pump the gas on an LT series engine.?. Try turning the key to start, count to 5, and then crank the engine - gives time for the pump to build pressure to the injectors.
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Posted on: 2012/3/6 0:37
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2004 Vert. 475hp. Built by Vengeance Racing |
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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I tried that and it did not start. I have an on board FP gage and it is a steady 40 PSI. The only way I could get it to fire is push the gas.
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Posted on: 2012/3/6 0:43
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| bogus | Re: New Problem - Hard Starting LT4 | ||
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Grand Imperial Pooh-Bah
 
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IAC or TPS.
It makes me think the IAC is sticking when hot. There is a reset procedure, but I can't remember it off hand... damn it. |
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Posted on: 2012/3/6 1:01
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| Matatk | Re: New Problem - Hard Starting LT4 | ||
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Webmaster
 
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I had similar problems with my 89 when the FPR was bad. Have you visually inspected it?
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Posted on: 2012/3/6 1:04
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2002 EBM convertible, Magnusson supercharger, cam, headers, etc. 1989 Corvette...RIP |
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| bogus | Re: New Problem - Hard Starting LT4 | ||
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Grand Imperial Pooh-Bah
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The thing is, if the FPR fails on an LT1/LT4, it does suck.
I had one fail and it filled up 2 cylinders and the crankcase with premium unleaded. And yes, there would be fuel in the vacuum lines, and I believe he said they were dry. |
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Posted on: 2012/3/6 1:06
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| josephf31 | Re: New Problem - Hard Starting LT4 | ||
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Senior Guru
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Quote:
I wouldn't rule out the fuel pump just yet. I chased a hard warm start for months, eventually the car just flat out died when hot, ran like a champ when cold. Turned out the fuel pump got hot and took a dump..also turns out it's a known issue on a C4... |
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Posted on: 2012/3/6 1:33
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2002 Magnetic Red C5 6 spd LS1 convertible |
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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How do I test the IAC, TPS, or fuel pump?
I pulled the IAC and it was very dirty. The plunger moved, but was tight. If I push the gas, just off idle and try to start, it starts right up. This leads me to believe TPS? |
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Posted on: 2012/3/6 2:22
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| bogus | Re: New Problem - Hard Starting LT4 | ||
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Grand Imperial Pooh-Bah
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that symptom tells me IAC more than TPS.
The IAC is exposed to more crap than the TPS. If it was that dirty and stiff, I would replace. |
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Posted on: 2012/3/6 3:07
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The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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| 1Fast04Vert | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
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Quote:
Everything here says you need to replace the IAC. You can clean it, but they are cheap. |
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Posted on: 2012/3/6 3:19
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2004 Vert. 475hp. Built by Vengeance Racing |
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| josephf31 | Re: New Problem - Hard Starting LT4 | ||
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Senior Guru
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Quote:
The Factory Service Manual has detailed procedures on all that...although my fuel pump passed the test since I could not simulate the temperature conditions in the tank on a hot summer day... |
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Posted on: 2012/3/6 3:19
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2002 Magnetic Red C5 6 spd LS1 convertible |
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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How about this one? Is this a fair price?
http://www.ebay.com/itm/FAST-307015-I ... sh=item3a70d1fb75&vxp=mtr |
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Posted on: 2012/3/6 14:13
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| tjpreul | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
 
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Quote:
Be sure it is the correct connection. I see that one has two screws to hold it on. Some screw into the tb themselves. |
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Posted on: 2012/3/6 15:08
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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Quote:
How is your build going? Will it be ready to go for the summer? |
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Posted on: 2012/3/6 15:19
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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| BillH | Re: New Problem - Hard Starting LT4 | ||
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The Stig Moderator
 
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Quote:
I wonder if Fast is the same guys who make the C5 stuff? IF it's a quality part, the price is good. Summit lists one made by Standard Motor (good quality) for $105. |
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Posted on: 2012/3/6 15:24
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Every man dies but not every man lives. |
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| 1Fast04Vert | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
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I was just reading my FSM (1995). To rest the IAC give partial throttle and start/run engine for 5 seconds, turnoff the engine, wait 10 seconds and then restart. The TPS is not likely the problem, but if so it needs a tech 1 to reset it properly according to the FSM.
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Posted on: 2012/3/6 15:26
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_________________
2004 Vert. 475hp. Built by Vengeance Racing |
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| tjpreul | Re: New Problem - Hard Starting LT4 | ||
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Elite Guru
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Quote:
I just have to tune it. Waiting on good weather. The idle is set, and I have done a few run cycles. My tune sessions have only been 10min due to my laptop battery. The new one should be in today. |
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Posted on: 2012/3/6 16:08
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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I took the car out and wanted to let you know what I found out.
Car starts just like normal when cold. As it warms up, it gets harder and harder to start. I could get it started each time. The warmer it got, the more I had to push the gas to get it going. When warm, I had to hold 1/8 throttle. When hot, about 1/4 to 1/3, while slightly pumping the gas. When it started, it would jump to 2200 rpm and hold for about 10 seconds, then idle down to normal. After that, ran as normal. It's got to be some type of idle control. I purchased the IAC, so hope that is what is going on. |
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Posted on: 2012/3/7 2:51
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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Transfer
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| bogus | Re: New Problem - Hard Starting LT4 | ||
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Grand Imperial Pooh-Bah
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sounds like a bad IAC... replace, retest, report.
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Posted on: 2012/3/7 3:01
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_________________
The single biggest problem with communication is the illusion that it has taken place. - George Bernard Shaw Education is the best tool to overcome irrational fear. - me |
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Transfer
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| Andrew | Re: New Problem - Hard Starting LT4 | ||
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2013 Memorial Day Car Show Winner!
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After spending some time testing, I noticed the digital coolant gage was reading 193 and would not increase, while the analogue gage showed 215. Right after turning the car off, the analogue would remain constant and within 10 seconds, the digital gage dropped below 100. Then, the hard start returned. After some investigation, the PCM uses the same sensor as the dig gage. So, it thought the car was cold, when it was actually hot, causing it to dump waaay to much fuel down the motor. Well, I'm embarrassed to say it was disconnected! I had the exact same issue as Gas Junkie did and after taking things apart so much, the sensor connections were completely shot, but the sensor is still good. I was able to connect it back and the car started immediately every time. To test, I disconnected and it began the hard start again (woofing sound and all). Connected it back and started immediately every time again.
WOW, I didn't realize something this small could cause so many problems! Anyway, I'm going to get a new sender and connector. Thanks to everyone for all of the help!! |
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Posted on: 2012/3/18 23:48
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_________________
2003 Atomic Orange Z06 Sold - 1996 Competition Yellow LT4 - DRM 383, NX N2O, Line Lock, LT Headers, 3" stainless exhaust, Power Effects, and many more mods SOLD 1996 Competition Yellow LT4 SOLD 1979 4 Speed with 383 |
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