Klondike

Just buttoned up everything from another Opti surgery. It had random misfires P300 code but nothing else showed. I'm thinking I may not have really needed another Opti now because it runs just as bad as before if I can get it to run at all. I've hooked up the old Opti to the harness and put another wire in the coil to test it and it throws a 1 inch spark when I spin the Opti shaft. I have a spare Ignition module and coil and I hooked them up and got the same results. PLENTY of fire but it misses like crazy when it is all hooked up to drive. The injectors are all working because it is pig rich when it runs, if I can get it started at all. Checked the temp sensor and plug and they test OK too. The only thing left I can think of is a bad coil wire between the new installed Opti and the coil. Of course it is jammed down that little hole behind the water pump housing and I can't get a grip on it to get it pulled out of the new Opti. Anybody got any tricks? I'd like to get it out without destroying it if I can to test it first. I'd like to know if that is my problem or if I have something else going on.

antfarmer2

why did you change the opti? Is there fuel in the oil or in the vacumme line to the fpr?

did all your plug wires click twice

wait till dark and crank it and look for sparks

PatternDayTrader

An EGR valve that is stuck open will do pretty much exactly what your describing.

SJW

It's time to stop throwing parts at this problem, and get it isolated. If it's running pig rich, you're probably barking up the wrong tree by tinkering with the ignition system, but to get some idea of what it's doing, a quick spark check at one or more of the plug wires should tell you a lot about that.

What are you seeing that indicates it's running pig rich? If it is, it's more likely that you're dealing with leaking injector(s), excessive fuel rail pressure, or a faulty sensor such as O2S, MAP, MAF, ECT, IAT, etc.

FWIW, a stuck-open EGR valve presents a massive vacuum leak, and would drive the AFR way lean, rather than pig rich.

What year is the car? OBD1 or OBD2?

Get the car hooked up to a good scanner and/or scope, and see what is revealed. If you don't have the tools and expertise to troubleshoot this on your own, take it to a talented and trustworthy diagnostician for assistance, and you'll be many dollars ahead. You've already sunk wasted cash and hours into solving this problem. Now would be a good time to stop the bleeding.

Good luck with it.

Live well,

SJW

Klondike

LT4 doesn't have an EGR, it's done on this engine with cam overlap.
No fuel in the vacuum line but did have it in the oil. Checked the Coolant temp sensor & harness and all the plug wires checked good and clicked on both ends. Not firing on all of them sometimes.Random misfires on scanner. Barely starts and today I couldn't get it to run at all. 2 different coils and 2 different Ignition Control Modules all check good with another good Opti plugged in and spun for spark test. The only thing left in the High Voltage path is that coil wire and it's trapped down behind the water pump now. I think I could snap another one down in there, but I need to get that one out first without destroying it to confirm whether or not it's bad.

antfarmer2

have you pressure tested the fuel and see how long it holds might be a leaky injector. the random misfires could they be from flooding?

Lloyd Smale

ecu? Ive seen them go bad without even throwing a code. Have it hooked up and checked.

Klondike

Made a loop tool from .065 wire and was able to get the coil wire out from the opti and it looked and tested just fine.
Abandon the damn ignition and go after the fuel now.
Did a pressure test a while ago and when I turned the ignition to run, it went right to 50 lb. BUTas soon as the pump went off, it dropped like a rock. Now I'm thinking the pressure regulator is off it's seat. I know it's not a leaky injector cause ALL the plugs were stinking wet and the scanner showed ALL the cylinders misfiring while it was still running. One injector wouldn't hose down the whole engine and I doubt it would empty a tank of gas in 100 miles like it did. I'm thinking applying full pressure to all the injectors overwhelmed them all. They're Bosch III 28lb. so I'm sure they will flow plenty if pushed. So Its off with the regulator next to have a look at that.

'96 LT4

antfarmer2

you did check the oil for fuel don't want a grenade


or hydrolock

kimmer

To get the wire out next time use a plug wire pliers

Klondike

Changed the Oil when I did the Opti. Car hasn't run 15 min. since then and a max of about 3/4 of a mile in the neighborhood. Wouldn't run right, so back into the garage.
I'm getting so sick of this damn thing breaking down over and over again, I'm almost ready to drain the oil and refill it with gas and run the coil wire down the dipstick hole!

Cliff Harris

Sounds like a problem with the FPR. I don't know how else you could get a lot of fuel in ALL the cylinders otherwise. I guess the ECM could have a problem though...

TorchTarga94

I tend to agree with Cliff. Interested to see what you find out! Also might not be a bad idea to send the injectors out to get tested.

Klondike

Picked up a new FP Reg today. I'll get it on tomorrow I guess. Injectors couldn't have ALL gone bad at once. Has to be something common to all of them like over pressure or wide open signal from computer. They are Bosch III's and have been in there a while and working great. At least I know they will be able to out flow any of my present needs.

1993C4LT1

I hope the new FPR fixes your problem.

kimmer

The C4 is a strange beast.

1993C4LT1

Amen. Possibly the top fact I have heard today.

mtwoolford

Based on my own experience, you sir, have a leaking fuel injector; one of my original multi tec injectors leaked, a drip...drip...drip kinda thing, even with engine off, and in one week of not being driven, it completely filled my crankcase with gas...replaced the multi tecs with new bosch III; probably the only easy job on one of these cars...

or you have a ruptured diaphragm in the fuel pressure regulator.

I re read your earlier post, even one leaking injector can cause it, and I suppose Bosch III's can leak also.

1993C4LT1

Only thing I don't like about the Bosch iii's are that it would be hard to visually inspect them for leaks.

Klondike

That would be a good idea except it filled the oil while I was DRIVING it! Sudden drop in power and multiple cyl misfires. Would barely run! Went through a whole tank of gas in about 100 miles. Had to drive it, no choice, I was out in the middle of nowhere with no cell service. It's had the Bosch III's in it for a while with fresh filter & no problems.
THINK I FOUND MY PROBLEM BY ACCIDENT YESTERDAY!
While checking wiring harness for the temp sensor ground I found it is shared with the MAP sensor. Started checking the connection and noticed that the sensor MOVED when I touched it! Went to take it off to check its condition and the screws were loose. Pulled it off and the little gasket that plugs into the top of the manifold was all ripped apart. No way was that thing making a vacuum tight seal between the MAP and the Manifold. Big Ol' vacuum leak there! A low or NO vacuum reading on that thing would tell the injectors to pour on the fuel! Have to wait to try the dealer for that little thing tomorrow as the other part stores don't have one in stock. Don't know why the scanner doesn't have a fault code for that! Would have saved a TON of time trying to track down a misfire that was actually due to flooding.