Hey there everyone!

I've been having a bit of an issue with my Corvette and i'm hoping ya'll could help me out. I have a 1987 C4 Corvette 350ci with recently 90k miles

Yesterday I was driving around the city, about 35 miles in total till I came home. The temperature was normal as always. Fluctuates from 230 down to 200. Fans kick on at 227 like normal. I stopped at Taco Bell to grab some dinner. When I restarted the car it felt fine until I threw it into reverse, It died on me. I restarted the car, threw it into reverse and it worked just fine. I drove home without an issue. Later I started my car just to check fluids. The car had a rough idle, like it was going to die on me. I shut it off and decided to figure it out in the morning. The next morning (today) I started up the car and headed to school. The entire way there the car would bog down and almost stall out on me. I checked the injectors two weeks ago and this morning for their "tick and vibration" Only 5 out of the 8 were ticking both times. A buddy of mine thought it could be the spark plugs or the cap and rotor not giving enough spark to the rear fuel injectors (the ones that are not firing; 1 on driver side, 2 on passanger side, both closest to the distributor/firewall.) The injectors that do fire have a strong tick. I let it sit for an hour and just now rechecked my car. It started up just fine, idled, I threw it into reverse and then started to bog, badly. It was a bog i've never felt before. I threw it back into park and it would bog to lower RPM and then the engine would rev up higher to get back to normal idle. Then bog again, rev up. Bog again, rev up. Until I shut it off. I then restarted it and it went away.

This just started happening today so i'm not really sure what it could be. Electrical? Fuel? Spark?

It's almost like it's starving for fuel pressure but I'm not really sure. There is no fuel pump whine of any kind but I have not trialed that posibility out.

Any ideas on this will be much help, it's quite frustrating! I'm supposed to be going on a trip this weekend and I need my car. Thanks in advance!

 

Does your car still have the original injectors? Ohm check them when the engine is cold and again when its hot. They should be reading about 14 or 15. If you have any reading 6 or under, that may be your problem. The original injectors were not made to handle ethanol. It breaks down the seal and they short. If it is the injectors, do yourself a favor and replace them all at the same time.

If you don't have an ohmmeter, the one you can get for free with coupon (or for a couple of dollars without a coupon) at Harbor Freight will work fine for this test.

 

They are original injectors so I should have guessed they would be the major culprit. I'll test them and replace them. Should I look into a new fuel rail as well? I found a few bundles on ebay that sell a brand new fuel rail with new 24lb injectors (8).

Thanks for the response! I really appreciate it.

 

You replace the O-rings in the fuelrail, but not the rail itself. Call Jon at www.fuelinjectorconnection.com and see what he can provide for you. A 24 lb injector may require reprogramming.

 

Thanks for the response! I'll give a call probably tomorrow. And sorry I didn't mean 24lb, I meant 22lb. Would it be worth it to replace the rail at all or just a waste of money? I opened shopkey5 that we have provided from my technical institute and it said there is a lot of things to replace since it hit 90k miles. Fuel injectors was one of them and it said to inspect the rail. If ya'll don't think I'd need it then I won't bother.
Again, thanks!


EDIT: On my way to work I noticed that it's driving like it usually does now. The temp is 201 and it's a steady idle. No bog. Maybe a slight one but nothing like earlier. So basically the issue goes away after it's warmed up? Could that still be injectors? I know the computer shuts off injectors when it feels it has sufficient fuel, right?

 

i threw 24lb bosch 3s in my 85 and it loves them. im pretty sure 24lb is stock

 

Before you spend money on injectors, do the ohm check -- hot and cold.

 

For a 85

 

Have you done the obvious and pulled the codes to see if anything showing?

http://www.corvettephotographs.com/c4vettes/codes.htm

 

I'll do the ohm test. I checked codes and it's throwing one for the knock sensor. It's unhooked because the pigtail snapped off. Other than that no code

 

A good start would be to repair the current fault. It may be retarding timing? The connector is the same as some coolant temp sensors, so it my be at your local auto parts store.

 

Is the coolant temp sensor on the driver side block? Because that one isn't hooked up either yet I'm still getting a temperature reading.

 

if im correct the sensor under the TB is for the computer to know what your temp is. and the one on the passenger side i think is the straight line to the dash. correct me if im wrong.

 

Well if that we're true than how would I be getting a temperature reading? Also, I'm not entirely sure how to do an oHm test on the injectors. I have a Cen Tech 96652 clamp meter.

 

Could you be confusing the secondary fan switch for the cts for the dash gauge?

 

Because that is a fan switch in '86+ engines , the temp gauge sender unit is in the pass side head
Owners of the one year only 85 cars ,think all later engines are like theirs and confuse people

Google works

 

The Coolant Temp Sensor (CTS ) for the ECM is under the TB

 

I checked the injectors with a noid light set and an oHm meter. All injectors checked out just fine. I had a buddy of mine come down with a few tools and we went to town on the Vette. We checked just about everything on this thing. Checked codes, ran vacuum lines, coolant pressure tested it, followed leaks, figured out why theirs oil in my radiator and reserve tank. So on so forth. The MAP sensor threw codes, the MAF sensor threw codes, and the Knock sensor threw codes. The knock sensor is now hooked up but I need a new pigtail. I will be purchasing a new MAP sensor and seeing what happens. The MAF will be avoided at all costs. That sensor I was referring to that was located on the driver side of the block, is for the external fan switch. The smaller fan in front of the radiator. Someone had ripped the entire pigtail off and stuffed the rest of the wire into the harness. The run down is new MAP sensor, PCV, upper and lower plenum gasket, two radiator fan control switch pigtails (one for fan and one for knock sensor), fuel filter, new dip stick, sea foam, belt, power steering pulley. So it's not as bad as I thought it would be. I'm going to also get the tranny flushed just for giggles since i'm sure it's never been done. He said that since the injectors are getting power and the car isn't misfiring or pinging in any way, they are probably working, just not very well.

 

'87s don't have a MAP sensor. Maybe you're talking about the MAT (Manifold Air Temperature) sensor, mounted on the bottom of the plenum.

You might want to replace the MAF relays. It's fairly common for them to go bad. They are relatively cheap, so it's usually easier to just replace them rather than try to troubleshoot them.

The ECM tests the knock sensor when the engine first starts, so that will throw a code if it is disconnected.

A note on fuel injectors: All 8 injectors are connected together and they all fire at the same time. If one is bad it will affect all of them. There are two injector fuses, one for the left bank and one for the right bank.

 

I would avoid (if your car is an automatic) hooking your trans up to one of those flushing machines. Its best to drop the pan and replace the filter and then top off the trans. There should be a magnet in the transmission pan that traps metal filings. Flushing will loosen these particles up and run them through your tranny. BTW, did you check the injectors when the engine was hot and cold? Did they look like the original Multec injectors (metal)?

With respect to the trans, see a couple pics I took when I dropped the pan on my 1990 at:
http://forums.corvetteforum.com/c4-t...post1580117027