Jdjr123

Ok here's a complete rundown on what happened before it started running rich and misfiring. It was running excellent as usual very smooth, great gas milage and very resposive and quick. Also the vette has 214k on it, but ran like new. One day while driving with no warning, started misfiring really bad, like it was running on 4 cylinders. Barely made it home. Max speed was like 35mph. After getting home I remember a similar misfiring one day when I was cleaning and replacing fuses in the fusebox inside the car. The connections of the fuses were corroded and dirty. After I cleaned the fuses and fusebox put them back in the car ran smooth again as usual. That was that one day before this next time it misfired. So this time when I got home I figured I would clean the fuses again since it had the same symptoms. I thought maybe the injector fuses were blown or not making a good connection. Sure enough after I clean them all cylinders were firing again. But another problem began. Now it was running rich to where it would barely idle. And the gas milage and smell of raw fuel was unbearable. Like I said before the misfiring and driving at 35mph max it was all good. What could have happened so suddenly?

DATeem

My 89 just got back from the shop after running fine then stalling at a stop light. Prior to that it would run a little rough on and off. A couple of days later it started and ran ok as far as the shop. Turned out it was a faulty temp sensor. It eould get warm an flood the engine with fuel as the sensor read "cold". They diagnosed it through codes. Good luck with getting it figured out.

Benny42

If the injectors are originals, replace them. Multecs are junk with today's fuel (E10) and are likely failing. There are several preferred sources of good replacements. You'll be glad you did.

Jdjr123

billschroeder5842

Well, you can do it if you want, if you have the time and the money.

The forum members are here to help keeping your car on the road. As you just joined, you will quickly find for every problem, someone else has had the same problem, figured it out and is willing to share solutions.

As mentioned above, your coolant sensor is giving false readings to your engine making a hot engine think it is cold and dumping extra fuel creating a rich condition. You will soon (most likley) throw a fault code as your O2 sensor will detect this condition. Popping your fuses in and out just reset the computer to base readings and your problem came back once there was a change (driving) in the data.

You can pay to have it diagnosed, charged for the sensor swap and have the part marked up considerably after you drop your car ( having someone drop your off and pick you up) at the shop for a full day that you waited 3 days for an appointment. Couple hundred dollars easy.

Or, you can swap the coolant sensor yourself in about 10 minutes for about $15. Plus, you did it yourself with your "forum" team behind you.

Your call.

Jdjr123

That's good advice. I'm just not sure that it is just the coolant sensor. Here's some other symptoms .
Hard to start. Won't start unless accelerator is to the floor. And when it does start from sitting overnight it misses and is running rich blowing black exhaust right off the bat. And continues this way even after it warms up. Could it be fuel pump pressure regulator also? All happened at the same time?

Wayne88

You have to roll up your sleeves and fix these cars yourself, when you can--otherwise you'll go broke bringing it to a shop every time something goes wrong.

kenmohr

If you have a bad fuel odor check your FPR.

whalepirot

Suggest you listen and heed the knowledge bank here and solve this sooner, not later. Rich exhaust WILL ruin the cat(s) and cost way more than all that has been suggested.

Jdjr123

Yep that's why I'm not driving it

Bwbob

could be a bad MAF. did you get any codes? all you need is a paper clip and it will get you in the right direction

duowing

When it comes to old EFI especially based off the older Bosch L-Jet the coolant temp sensor and the O2 sensors can become the biggest pains. They can go bad without necessarily throwing a code and end up causing overly rich or lean conditions. I had an old 280ZX that ran ok when cold and horrible when warm. Above 65mph the thing ran perfectly because it was now running in open loop and ignoring the sensors. If you've never replaced the coolant temp sensor I would recommend replacing it as it's a relatively cheap and easy part to replace and after all these years they are almost guaranteed to be bad or on the way out.

K87ZZ4

I dealt with a rich condition in my 87 for a long time (although the symptoms weren't nearly as bad as you describe). I tried checking LOTS of things myself (see my post: https://www.corvetteforum.com/forums...ning-rich.html) and ended up taking it to a shop to have it diagnosed (which turned out to be ridiculously expensive), BUT they leveraged their skill and experience to solve a tricky problem.

I learned a lot along the way with the help of good people on this forum. It's always ideal to diagnose the problem, but sometimes it's worth it to throw an inexpensive part at the problem, especially if it's easy to replace (and, as Bill pointed out, if it would take less time than getting your car to the shop).

Good luck and let us know how it goes!

aklim

Good point. Pull the Fuel Pressure Regulator hose and see if there is any gas coming through. If there is, your regulator is FUBAR.

If there isn't, I would check fuel pressure. With the Key in run and not cranked, it should shoot up to some 40 psi and hold even with the key off. Lets start with that simple thing before we go any further. OP also needs to get a scanner from Ebay that will read live data.

Jdjr123

Cheking FPR on the next repair. I am almost certain that is my problem. Thanks all. for the help.

Jdjr123

Well finally got around to checking my running rich problem. As was said by one of you members, it was a faulty FPR. As soon as I looked in the plenum there was all kinds of raw fuel dripping out. So as was pointed out by you guys, as one of the symptoms of a faulty FPR that is what it was. My Vette is running normal again. Thanks all.

Jdjr123

Ok here we go again. It ran normal for one day. Now it's missing again feels like it still is running rich but not as much. Could the excessive raw fuel I cleaned out have affected something else due to the bad FPR. Changed the plugs thinking they were fouled out from running rich. What now?

billschroeder5842

Your FPR could have jacked up an injector. Try a little fuel additive and see if that helps clear it out as some crap from the FPR could have worked its way down stream now that it is fully pressurized.

Jdjr123

Ok will try that. Also it backfires a lot when you let off the gas.

aklim

Did you determine what the Injectors are? While you were there, you should have changed it out since they are either Multecs or cruddy Bosch which needs to be cleaned. Also there are no laws saying that you can only only have a single issue.

Additives are good for adding money to the company selling them. Cheap enough you can buy it, expect little and get little to nothing and not get pissed and do it again.

Call Jon at FIC and get injectors that are reman and clean up the TB while you are there. Take off the IAC, IAC housing and top plate, clean passages and reassemble with fresh gaskets.