Timing issue??
Thread Starter
Intermediate
Joined: Aug 2015
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Timing issue??
1990 Coupe, l98, automatic, 72k miles.
Just had a minor tune up done on the vehicle - it still had the original plugs, wires, and dist. cap. After the tune up the car was running great, drove it roughly 110 miles back home with the A/C turned on. No misses or stuttering on the interstate. When I got back into town I noticed a very prominent miss when the car was stopped and A/C off, almost like it wanted to stall out but didn't - just a surge, and only happens when the car is stopped - I'm a little stumped?? All OEM parts were installed - AC Delco plugs, wires, dist. cap and rotor - did NOT replace ignition coil and was told my plugs were actually in pretty good condition being 25yrs old but the wires of course were terrible as was the old dist cap (hole had burned thru to the rotor. Has anyone had this issue? No SES light on, runs great with no misses or hesitation while 'driving' just while idling in Drive, Neutral, or reverse. It was not doing this when I drove it out of the garage, started doing it after the drive home off of the interstate.
Just had a minor tune up done on the vehicle - it still had the original plugs, wires, and dist. cap. After the tune up the car was running great, drove it roughly 110 miles back home with the A/C turned on. No misses or stuttering on the interstate. When I got back into town I noticed a very prominent miss when the car was stopped and A/C off, almost like it wanted to stall out but didn't - just a surge, and only happens when the car is stopped - I'm a little stumped?? All OEM parts were installed - AC Delco plugs, wires, dist. cap and rotor - did NOT replace ignition coil and was told my plugs were actually in pretty good condition being 25yrs old but the wires of course were terrible as was the old dist cap (hole had burned thru to the rotor. Has anyone had this issue? No SES light on, runs great with no misses or hesitation while 'driving' just while idling in Drive, Neutral, or reverse. It was not doing this when I drove it out of the garage, started doing it after the drive home off of the interstate.
Le Mans Master
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From: near the thumb in the mitten
If you had at a shop take it back. If not review what you did. Plug wires fully seated on both ends and not too close to manifold, vacuum leak(s), Throttle body carboned up?
Team Owner
Joined: Aug 2004
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From: Park City Utah
I would look for plug wires routed too close to the exhaust that are melted/shorting. Easy to find in the dark, hood open engine running....you'll see a "light show".
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I did have it done at a shop, however, it was family - and I was charged next to nothing, so I don't want to complain or even say there is a new issue - I think the 110 mile drive home has jiggled a plug wire or two loose, that's the only thing I can think of - and it does seem he routed things not exactly the way they were in the beginning. I twisted one of the plug wires (driver side back plug) and it wasn't stalling out but still had a bit of a 'miss'
Thread Starter
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Alright, went thru all of the wires, no shorts, everything is routed correctly... and this is what it's doing after the tune up - getting progressively worse - now it is constantly stalling unless one foot on gas one foot on brake - could it be a fuel filter clogging up? There was supposed to be a video attached, if it didn't upload, here is the link:
Team Owner
Joined: Aug 2004
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From: Park City Utah
Seems like it's running fine until you put it in gear.
it could be fuel pressure -that is an easy enough test.
Could you also rig a spark tester and observe spark as it's stalling? Coil wire would give you a better view.
it could be fuel pressure -that is an easy enough test.
Could you also rig a spark tester and observe spark as it's stalling? Coil wire would give you a better view.
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Thread Starter
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In response, it's actually not running fine while the car is in idle, surging up and down UNLESS a/c compressor is 'on'... still misses and surges but won't die (will die if A/C is off). It took 4 starts just to get it back into the garage earlier. I'm wondering if this is the fuel regulator or fuel filter still - but just so coincidental right after new plugs and wires. I cannot find any vac leaks at all. The HVAC line has been plugged, cruise still works perfect, but, that whole system needs to be refurbished - speaking of the climate control, and it was that way before the tune up, i'm just stumped.
Team Owner
Joined: Jul 2004
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From: Hartford WI
Have you started diagnostics yet? What is the fuel pressure? Pull the FPR hose off and see if you smell gas. Get your hoe off and see what you can get for pressure. Should be around 45psi give or take? Hose back, do a WOT run, what is the pressure? Should drop off some and hit a steady number. After shutdown, does it hold pressure? That will determine the shape of your pump. You might even have to take the pump out and find out if the sock is full of crap.
Do you have a scanner? Engine off and key in run and depress the gas pedal slowly. Does the voltage go up smoothly? In 1990, the TPS start point is where the voltage is when the key is turned on so monitor it only. No setting. Should be around 0.5 to 0.7, IIRC. When the engine is idling with everything off, what is the IAC count?
Do you have a scanner? Engine off and key in run and depress the gas pedal slowly. Does the voltage go up smoothly? In 1990, the TPS start point is where the voltage is when the key is turned on so monitor it only. No setting. Should be around 0.5 to 0.7, IIRC. When the engine is idling with everything off, what is the IAC count?
Thread Starter
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Have you started diagnostics yet? What is the fuel pressure? Pull the FPR hose off and see if you smell gas. Get your hoe off and see what you can get for pressure. Should be around 45psi give or take? Hose back, do a WOT run, what is the pressure? Should drop off some and hit a steady number. After shutdown, does it hold pressure? That will determine the shape of your pump. You might even have to take the pump out and find out if the sock is full of crap.
Do you have a scanner? Engine off and key in run and depress the gas pedal slowly. Does the voltage go up smoothly? In 1990, the TPS start point is where the voltage is when the key is turned on so monitor it only. No setting. Should be around 0.5 to 0.7, IIRC. When the engine is idling with everything off, what is the IAC count?
Do you have a scanner? Engine off and key in run and depress the gas pedal slowly. Does the voltage go up smoothly? In 1990, the TPS start point is where the voltage is when the key is turned on so monitor it only. No setting. Should be around 0.5 to 0.7, IIRC. When the engine is idling with everything off, what is the IAC count?
Team Owner
Joined: Jul 2004
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From: Hartford WI
I do thank you for the input, but, have a feeling this will be a take it to the shop thing - I do have a scanner but only the basic one that blinks the SES for codes - no codes stored. I do not have the garage space, tools, etc to truly figure this out, I just don't get why it was driveable other than a small miss due to 25yr old plug wires, minor tune up w/ wires, plugs, dist cap and rotor now I can't even get it out of the garage
I suggest you get a scanner not a code reader. that way, we can help you better instead of throwing parts and money at it. Even if you have to have them do it, if you know what you are asking for, you can't be so easily bent over.
Team Owner
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From: Hartford WI
Thread Starter
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You do NOT have a scanner. You have overpaid for a paperclip which is what I would use to get codes only. http://www.corvettebuyers.com/c4vettes/codes.htm
I suggest you get a scanner not a code reader. that way, we can help you better instead of throwing parts and money at it. Even if you have to have them do it, if you know what you are asking for, you can't be so easily bent over.
I suggest you get a scanner not a code reader. that way, we can help you better instead of throwing parts and money at it. Even if you have to have them do it, if you know what you are asking for, you can't be so easily bent over.
Team Owner
Joined: Jul 2004
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From: Hartford WI
Understood - now I see why they wanted the 100.00 to 'scan' it. i'm used to OBDII readers that give a bit more info- so yes, wasted money when I should have just taken it to the shop to see what was going on - even if it's foreign language to me I could give better input. Just frustrated right now to have it sitting in the garage w/ a disconnected battery and thinking tow it or try to figure it out on my own.
Like I said, even if I miracled it to your shop, how can you trust that they would diagnose it honestly? For all you know, the plug wires were wrongly placed. Did you watch and document everything that was done or did you leave it there and pick it up when done? I find the latter gives me bad results usually.
Usually, unless I know the mechanic personally, I have it diagnosed, tell the service advisor what needs to be done and the time required, he does the formality of an estimate and the tech I select does the work.
Last edited by aklim; Oct 30, 2015 at 10:09 PM.
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St. Jude Donor '16-'17-'18,'19
Sorry if I sent him off in the wrong direction.
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From: Park City Utah
OTC Monitor 2000
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A lot less than a few hundred will get you a fantastic scan tool. I have this one. It does data stream, runs diagnostic tests on systems, snap shots...and tons more. Thing is awesome.
OTC Monitor 2000
OTC Monitor 2000