1986 Surging issues
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
1986 Surging issues
Hi my name is Jared. I just traded my boat for a 1986 Corvette. I'm pretty excited to own a Corvette. Already I am noticing that the guy before me didn't give this car any love at all. I have a lot of work to do but am excited about the challenge. I have an issue that I'm trying to resolve as soon as possible in order to get it smogged and the title transferred. When I start her she runs pretty smooth but then after a bit she surges like she want to go. Doesn't matter if she is in gear or in neutral. I also noticed that the guy put a switch to turn the fan on obviously because a sensor went bad. I am going to get started on tracking down a few issues this weekend. Any help would be much appreciated.
Thanks
Jared
Thanks
Jared
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
On a side note I noticed that the owner before me had bosch sparksplugs, which to my understanding you should only run A/C Delcos. He is also running diesel oil for the zinc. But won't the zinc burn out the catalytic converter. I was thinking just the called out 5-30 and possible go with a syn blend. My dash lights for speedometer also do not illuminate at night. I know lot of problems, but it is a corvette and I am confident with a little love and help that I can bring her back.
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Instead of Diesel you can use a half pint of STP to add the zinc.
Some of the "high mileage" oils also have the zinc additive as well.
That being said, I'd go after the fuel system first.
Fresh fuel, filter, and most importantly pressure.
You can find the press tap on the right bank of the fuel rail.
Others will chime in with the pressure specs here soon.
Some of the "high mileage" oils also have the zinc additive as well.
That being said, I'd go after the fuel system first.
Fresh fuel, filter, and most importantly pressure.
You can find the press tap on the right bank of the fuel rail.
Others will chime in with the pressure specs here soon.
Advanced
Joined: Jun 2013
Posts: 51
Likes: 2
Instead of Diesel you can use a half pint of STP to add the zinc.
Some of the "high mileage" oils also have the zinc additive as well.
That being said, I'd go after the fuel system first.
Fresh fuel, filter, and most importantly pressure.
You can find the press tap on the right bank of the fuel rail.
Others will chime in with the pressure specs here soon.
Some of the "high mileage" oils also have the zinc additive as well.
That being said, I'd go after the fuel system first.
Fresh fuel, filter, and most importantly pressure.
You can find the press tap on the right bank of the fuel rail.
Others will chime in with the pressure specs here soon.
Thanks
Fast Freddie
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
This guy that I got the car from said that the older engines needed zinc. I have asked a few others their thoughts and don't think it is worth the chance of destroying the cat converter. A few mechanics agree and suggest putting regular oil. I have been happy using a syn blend in my work van
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
I just got a new MAF. I am gonna change the spark plugs back to ac delco as well. I don't know why bosch plugs were installed. Everyone keeps telling me bosch plugs are for foreign cars
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Le Mans Master
Joined: Aug 2007
Posts: 8,735
Likes: 412
From: WV
On the passenger side fuel rail there is a small cap on a valve, this is called the schrader valve, you need to hook up a gauge to check your fuel pressure..The fuel pressure should be around 40-42 psi with the key on.. When you start the engine the pressure will probably drop to around 38-40 psi if everything is ok...If your motor doesn't start surging until the coolant temperture gets to around 130 degrees it may be a bad or dirty sensor causing the problem..This temperture is where the car goes into closed loop and starts using all the sensors for feedback to the ecm..Usually, if you have a vacuuam leak that's causing surging it does it all the time, not just in closed loop....You may want to replace the 02 sensor , this sensor gets dirty with age and may cause surging if not working properly...As far as spark plugs go, just use the regular AC Delco plugs, nothing fancy needed to make it run right....WW
Last edited by WW7; Aug 25, 2013 at 07:24 AM.
Team Owner
Joined: Sep 2003
Posts: 20,172
Likes: 672
From: Freedom is never more than one generation away from extinction.
St. Jude '03 thru '24
Bottom line L98's from 1986 and earlier have flat tappet cams and require zinc (zddp) for cam lobe lubrication.
Later L98's have roller lifter cams, thereby removing the need for zinc.
Lots of mfgrs have different products that are quite expensive.
A google research proved to me that half a bottle of STP works ust as well.
Been running Mobil1 for tens years without an issue.
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
I think I have those in my car, come to think of it...
They might be NGK Iridium...
Race Director
Joined: Apr 2002
Posts: 10,036
Likes: 346
From: Anaheim CA
Just for reference, the part on the left is the cold start injector thermo switch.
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
alright I have been super busy, however I was able to get the MAF sensor off and replaced with a new one. It is still surging and idling sporadically. I am going to try the O2 sensor, Coolant Temp Sensor, changing the sparkplugs and flushing and changing the oil back to the factory recommended 5W-30 syn blend. Anything else anyone can recommend to start with. I want to start by getting this bad boy smogged then decide what I'm gonna go after next.
Thanks!
Doc (Jared)
Thanks!
Doc (Jared)
Team Owner
Joined: Jul 2004
Posts: 28,356
Likes: 3,253
From: Hartford WI
alright I have been super busy, however I was able to get the MAF sensor off and replaced with a new one. It is still surging and idling sporadically. I am going to try the O2 sensor, Coolant Temp Sensor, changing the sparkplugs and flushing and changing the oil back to the factory recommended 5W-30 syn blend. Anything else anyone can recommend to start with. I want to start by getting this bad boy smogged then decide what I'm gonna go after next.
Thanks!
Doc (Jared)
Thanks!
Doc (Jared)
I would take the throttle body off and the IAC housing (6 or 7 torx bolts) under the TB off and clean them all out with brake cleaner. Get new gaskets for the entire TB. After all, you don't reuse condoms so don't reuse gaskets. Run the gas down as low as you can and get fresh 93 octane in it. I can't imagine that the gas is good seeing as how the previous owner took such poor care of the car.
Thread Starter
Heel & Toe
Joined: Aug 2013
Posts: 17
Likes: 0
From: San Diego California
I changed out the MAF (brand BOSCH) from Oreilleys Auto Parts. I have heard good and of course the bad. I was told by a mechanic that that and the thermostat sensor were throwing codes. I am finding better luck talking to all you guys here on the forum than going to a mechanic and opening my wallet every time in a luck of the draw. In regards to the MAF. It is the same brand that came out. Figured it wouldn't and couldn't hurt to be sure that it is new. I have a manual (haynes) that I got with the car. I do need to get a scanner. I have one that will read my ford van (work truck) but see that the vette takes a special one or just different than what I have.
Doc
Doc
Team Owner
Joined: Jul 2004
Posts: 28,356
Likes: 3,253
From: Hartford WI
I changed out the MAF (brand BOSCH) from Oreilleys Auto Parts. I have heard good and of course the bad. I was told by a mechanic that that and the thermostat sensor were throwing codes. I am finding better luck talking to all you guys here on the forum than going to a mechanic and opening my wallet every time in a luck of the draw. In regards to the MAF. It is the same brand that came out. Figured it wouldn't and couldn't hurt to be sure that it is new. I have a manual (haynes) that I got with the car. I do need to get a scanner. I have one that will read my ford van (work truck) but see that the vette takes a special one or just different than what I have.
Doc
Doc
Haynes is useful for making packing material or just starting a fire.
Vette takes an OBDI, I believe.
Pro
Joined: Sep 2012
Posts: 732
Likes: 72
From: the confused state CT
I would start with a tune up first, Spark plugs, spark plug wires, distributor cap and rotor,
air filter, fuel filter, o2 sensor, pcv valve, clean the throttle plates and iac, set the timing and check the fuel pressure. Also, fresh gas. This way you know you have the basics in place. Almost anyone of those will cause your surge. If you just start replacing sensors and the basics are not good you'll be chasing your tail.
Gary
air filter, fuel filter, o2 sensor, pcv valve, clean the throttle plates and iac, set the timing and check the fuel pressure. Also, fresh gas. This way you know you have the basics in place. Almost anyone of those will cause your surge. If you just start replacing sensors and the basics are not good you'll be chasing your tail.
Gary
Drifting
Joined: May 2011
Posts: 1,521
Likes: 53
I would take the throttle body off and the IAC housing (6 or 7 torx bolts) under the TB off and clean them all out with brake cleaner. Get new gaskets for the entire TB. After all, you don't reuse condoms so don't reuse gaskets. Run the gas down as low as you can and get fresh 93 octane in it. I can't imagine that the gas is good seeing as how the previous owner took such poor care of the car.
if I was a betting man I'd put my money on dirty nasty TB and IAC. Btw pay the $80-$90 for anAC Delco one. I bought a cheapie b4 and it only lasted 1 year