Rough start when warm?
Thread Starter
Instructor
Joined: Jan 2005
Posts: 218
Likes: 0
From: Hernando FL
Rough start when warm?
I know this question could be a million things..but i figured you guys could help me with some starting points. My 86 vette starts right up on a cold morning start. but after i drive for a while..then restart..it takes about five seconds or more of turning the key to catch..and its rough for about six seconds of idle? This problem was present before i did my valve guide seals..and now its bugging me..as the car runs perfect other than this. Its got 80,000 on her..the plugs look good, they are only 6 months old. I replaced fuel pump, fuel filter. And another starnge thing that happened is it it stalled twice in a week..while using the a/c..on a real hot day..upon driving in a parking lot at a real slow speed...never did that before. I also just changed a relay that the code spit out a couple of weeks ago..but didnt help start.. thanks for any comments!
Le Mans Master
Joined: May 2005
Posts: 5,214
Likes: 65
From: Queensland, AUSTRALIA
clean the throttle body, check and adjust the TPS, check the PCV valve, and check and clean out the IAC valve and make sure it is set correctly, the procedure for this will be in any decent service manual. Pull the top cap off the ditributor and check that the carbon contact under the coil is not badly worn down, although i doubt it will be that. Check for any vacuum leaks on the throttle body,plenum and intake manifold. Also check the fitting where the line goes into the brake booster for any vacuum leaks. If these leaks are very small, heating up causes expansion and could be opening up a minor vacuum leak. Check all that and see how you go, post back and tell what you find.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Hard starting only while hot, sounds like flooding.
Originally Posted by blackthumbz
I also just changed a relay that the code spit out a couple of weeks ago..but didnt help start.. thanks for any comments!
RACE ON!!!
Melting Slicks
Joined: May 2003
Posts: 3,490
Likes: 68
From: Hewitt NJ
Originally Posted by rick lambert
You may want to check your injectors for leak down as well-flooding.
Sounds like one of your injectors is leaking, which is not uncommon on a car with 80k miles.
Pro
Joined: May 2005
Posts: 510
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From: crofton maryland
hey your 1986 with 80K sounds just like my 1986 with 85K!! she did it tonight after taking a nice sunday night cruise, stopped for a burger and she took a few seconds more to start then when cold, when cold starts right up. so is leaking injectors real bad or the little bit longer starts the worse??
Le Mans Master
Joined: Dec 2004
Posts: 5,789
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From: Myrtle Beach SC
St. Jude Donor '05-'06
Originally Posted by ed petrucci
hey your 1986 with 80K sounds just like my 1986 with 85K!! she did it tonight after taking a nice sunday night cruise, stopped for a burger and she took a few seconds more to start then when cold, when cold starts right up. so is leaking injectors real bad or the little bit longer starts the worse??
To check for leakdown attach a fuel pressure gauge turn the key on and off and watch for the pressure to drop.It should hold pretty steady for10-15min with mabey a slow drop.The symptoms you describe indicates flooding that evaporates if it sits long enough.
In the future write down any codes so when something bad happens you can tell us more than "I had a code last week" it would be helpfull.
Your stalling may be related to a low idle and excess gasoline from the FPR leaking when the AC kicks in.Fix one thing at a time sometimes it will solve other problems.
Last edited by Redeasysport; Aug 20, 2005 at 11:40 PM.
Team Owner
Joined: Dec 2000
Posts: 90,675
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From: SE NY
Cruise-In II Veteran
If you find that fuel pressure is not holding and an injector is leaking pull the set, including the cold start injector, and send them to Rich at Cruzinperformance (link on my site) for a cleanig. Give him a call first to see how his work load is just now.
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Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
I am also experiencing a hard warm start in my 85. Starts right up when cold, I barely have to move the key, but after she's been running and up to temperature, good luck. I have to crank the engine and then feed it a little gas for it kick over. I was thinking of starting out by cleaning the throttle body and IAC valve first, then work my way over to the ignition system. Anyone else have this problem and what was the solution?
Race Director
Joined: Jun 2005
Posts: 17,640
Likes: 1
From: Lenoir City TN
St. Jude Donor '08-'09-'10-'11
Probably your injectors as to mine does the same thing, I tried this: step on the gas about 3/4 and then try to start engine mine starts right up, I believe the computer goes to "flood" state, this winter I am sending my injectors to Rich along with the cold start injector. Just my thoughts.
Bob
Bob
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
I'll have to try that this weekend when I use the car. I plan on a complete rebuild next year, so I'll replace the injectors then.
I still want to clean out the IAC valve. Anyone care to share their method?
I still want to clean out the IAC valve. Anyone care to share their method?
Race Director
Joined: Jun 2005
Posts: 17,640
Likes: 1
From: Lenoir City TN
St. Jude Donor '08-'09-'10-'11
My IAC valve was also acting up, I took it out of the throttle body and the pintle was stuck, the IAC has a stepping motor in it, so be careful. Rock the pintle from side to side as you pull outward. It should eventually come out, then clean the spring, pintle, and shaft I used a very soft wire wheel to clean the carbon off. Put it back together and my 86 called for I think ~1-1/8" fom base to tip of pintle, install back in car and you should be good to go. Also check in the hole for buildup of carbon. Just my thoughts, hope I did not miss anything some one will chime in if I did.
Bob
Bob
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
The 1 1/8 measurement is correct for the 85 as well (its the same for all the L98's I think).
I am going to test for the leaky injector and if that turns out not be the problem, I'll go and clean out the IAC and throttle body.
I am going to test for the leaky injector and if that turns out not be the problem, I'll go and clean out the IAC and throttle body.
Pro
Joined: May 2005
Posts: 510
Likes: 0
From: crofton maryland
is there a possablitiy it the fuel pump relay causing the longer starts when vette is warm? when i first got my vette the first thing i did was remove the T/B and clean it, remove the IAC and clean it, then took my GM manual and adjusted like it said, and i still get the long starts when warm.
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
OK, all this talk about leaking injectors....say it turns out to be the problem, what's the solution? Replace the injectors? Clean them? I'm curious because I think that's my problem now.
Racer
Joined: Jun 2001
Posts: 376
Likes: 10
From: Chicago IL
I have an 85 with the same hard start problem when warm. Before you purchase new injectors, just try to make sure that is really your problem. Check the plugs for fuel or, the definitive test, but a real pita, is to pull the runners and plenum - disconnect the fuel rail hold down bolts, lift the injectors out of the manifold with the fuel feed and return lines connected, pressurize the system and look for leaks. I did have one or two leaky injectors so I replaced with the pink tops from 5o. New injectors are fine, car runs smoother, but hard start when warm remains. I've determined my problem is when the coolant temp is just warm enough not to activate the cold start injector, like 100 to 140 degrees.
Le Mans Master
Joined: Aug 2005
Posts: 5,002
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From: No Opti Here Tn
St. Jude Donor '06
I had the same problem but my injectors were not just leaking eventually 3 did not work at all
This seems to be a problem with injectors I replaced all of mine
Only replacing some of the injectors seemed to me like replacing some spark plugs Did not make sense and how long till the others went out
Hope this helps
This seems to be a problem with injectors I replaced all of mine
Only replacing some of the injectors seemed to me like replacing some spark plugs Did not make sense and how long till the others went out
Hope this helps
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
Well I did the pedal to the floor test and the car started right up (after it was warm and up to temperature). I'm sorry to the people walking behind me for the smoke. So I guess this means a leaking injector? Is there a way to test the injectors without pulling them out?
Racer
Joined: Jun 2001
Posts: 376
Likes: 10
From: Chicago IL
when mine were leaking, you could see the that a couple of the plugs were wet with fuel - so you can pull the plugs and check. you can also check for resistance across each injector - something like 14-16 ohms each. however, i am not sure if resistance out of range means the injector is leaking.
Melting Slicks
Joined: Feb 2005
Posts: 2,057
Likes: 5
From: Bay Shore, NY
I figured pulling the plugs would be a good way to see which ones are leaking. But once I find the leaking injector, whats the next course of action? Does it have to be replaced or can it be serviced still installed in the engine?