Corvette Forum : DigitalCorvettes.com Corvette Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
30 Posts
Discussion Starter #1
Hi, I have a 1987 Vette. It is running very rich, blows black smoke rich, and when it begins to warm up it starts to run rough and acts like its loading up. When you give it some Rpm's it gets a miss and when returned to idle it dies. Now after letting it sit and coming back to mess with it, it smells of raw gas and is hard to crank, when it eventually does it sputters badly and dies. Almost like a car that has flooded. I replaced the coil, cap and rotor with a kit from DUI. It also has a new egr valve and IAC, and temp sensors aside from the MAT, along with new injectors. The throttle body and intake have all been taken apart and cleaned and had new gaskets installed. The TPS and fuel pressure checks out good and there is no fuel in the vacuum line to the fuel regulator. It is now giving code 45, witch suggests the next thing on the list to check is the o2 sensor. The only things that aren't new is the MAF, MAT, ECM, o2 sensor and TPS, plugs are new-ish, I've cleaned them, but they probably have been through the ringer now.... Thats all I can think of off hand. Any suggestions on what could be going on? Thanks.
 

·
Super Moderator
Joined
·
8,453 Posts
Id adjust the TPS and IAC as a quick check, as its easily done and costs nothing, your running rich is obviously something related to a defective control sensor or defective part,
code 45 is a rich exhaust, you already know your running rich, fuel enters the cylinders from the injectors or a defective fuel pressure regulator, and the maf is the major control on fuel flow rates, test heat sensor.
Id start by verifying the injectors are not leaking, they may be new, but that does not mean they are functioning correctly,
Id test and if required replace the MAF and the relays behind the battery on the engine compartment firewall ,and the oxygen sensors as they are most likely trash at this point, you also did not mention the fuel pressure, if you turn on the key but not start the engine, the fuel pump should pressurize the fuel rail, to about 40 psi, it should remain pressurized for at least 6=7 minutes before slowly losing pressure, if it loses pressure the fuel is leaking at the injectors or fuel pressure regulator or the fuel pump, if its the fuel pump, it would not cause your issue, if you block off the fuel pressure return line and it still loses pressure you know its the injectors

http://garage.grumpysperformance.com/index.php?threads/i-want-some-suggestions-on-potential-problem-sources-1987-corvette.15596/#post-93275
 

·
Registered
Joined
·
30 Posts
Discussion Starter #3
Id adjust the TPS and IAC as a quick check, as its easily done and costs nothing, your running rich is obviously something related to a defective control sensor or defective part,
code 45 is a rich exhaust, you already know your running rich, fuel enters the cylinders from the injectors or a defective fuel pressure regulator, and the maf is the major control on fuel flow rates, test heat sensor.
Id start by verifying the injectors are not leaking, they may be new, but that does not mean they are functioning correctly,
Id test and if required replace the MAF and the relays behind the battery on the engine compartment firewall ,and the oxygen sensors as they are most likely trash at this point, you also did not mention the fuel pressure, if you turn on the key but not start the engine, the fuel pump should pressurize the fuel rail, to about 40 psi, it should remain pressurized for at least 6=7 minutes before slowly losing pressure, if it loses pressure the fuel is leaking at the injectors or fuel pressure regulator or the fuel pump, if its the fuel pump, it would not cause your issue, if you block off the fuel pressure return line and it still loses pressure you know its the injectors

http://garage.grumpysperformance.com/index.php?threads/i-want-some-suggestions-on-potential-problem-sources-1987-corvette.15596/#post-93275
I rechecked the fuel pressure and it did not drop off. I rechecked the TPS also, it has previously been adjusted to the correct spec. Pulled the o2 sensor out, and as expected it was trashed, picked up a new Bosch unit. I will do the reset on the IAC next. Also got the relays out from behind the battery, are they suppose to be the same part number? I saw a thread on a Camaro forum that said they are suppose to be different. Thankyou for the links, they are alot of help.
 

·
Super Moderator
Joined
·
8,453 Posts
Glad I could help,
I built that whole web site to help the guys with less experience wade through the all too typical, delays, B.S. most repair shops provide,
and allow guys to learn, how to think logically, isolate and test,
and in the process learn how to do their own correct diagnoses and repair work without having to spend 50 plus years gaining personal experience the hard way.:thumbsup:

I got really tired of being lied to, stalled, and having crappy machine work passed off as "NORMAL" and having guys try to B.S. you so the billing could be pushed higher as I slowly gained experience and knowledge.
 

·
Registered
Joined
·
30 Posts
Discussion Starter #5
Glad I could help,
I built that whole web site to help the guys with less experience wade through the all too typical, delays, B.S. most repair shops provide,
and allow guys to learn, how to think logically, isolate and test,
and in the process learn how to do their own correct diagnoses and repair work without having to spend 50 plus years gaining personal experience the hard way.:thumbsup:

I got really tired of being lied to, stalled, and having crappy machine work passed off as "NORMAL" and having guys try to B.S. you so the billing could be pushed higher as I slowly gained experience and knowledge.
Man, you ain't lying. Alot of shops just are not worth a damn, not to mention dealers these days. And the parts you get to... if they are not some overpriced, cheap china replacement... It's a chinese counterfeit in a brand name box. Just makes everything harder and take longer. Well, I got back to messing with the car. Went ahead and got a new Delphi MAF, MAF relay and burn off relay. Checked all the voltage to them and it checks out good. Also got new spark plugs. Cranked it up and it started doing the same thing, blowing black smoke, sounding like it's got a big cam in it and missing. So this lead me to look at the computer. I checked to see if it has ground and it does. I pulled it out and it has the service number # 1227165. I've read about these specifically being prone to failure, so it's suspected that this may be the problem. Now, do I send this thing off and have it gone through or go ahead and get a new one? Also, are there any grounds that go to the back of the cylinder heads? Thanks again for the help.
 

·
Registered
Joined
·
927 Posts
The 85 had a seperate cold start inj,after that it was built into the ecm to richen the mix,there's a water temp sender in the right side head,check the connection there.Just a no cost thought.
Somewhere on grumpys site theres a procrdure the ecm goes thru on start up.
Theres ground wires bolted to the motor on the drivers side by the disy/oil presure switch.
I gota split for wowk,so im short on time.
 
1 - 7 of 7 Posts
Top