Racer001

iTrader: (15)

This is on my 89 formula with an OBD2/LS1 pcm swap.

My AFR gauge in my car has been reading rich the last few times I drove it. I never saw anything wrong with the car though.

Tonight I checked my oil and its thinned out and smells of gas.

-Fuel pressure while driving is fine, as per my gauge in my car. like 38-42 as always.
-Injectors all ohm at 12-13 hot
-No leaks from Pressure regulator with car on or off

What next? Check for injector leakdown? Can a bad coolant temp sensor cause this? can bad O2 sensors cause this?

LS1TA_956

iTrader: (1)

I had this problem mine was a damn oxygen sensor it would also stumble when wot or when taking off

Paul Bell

iTrader: (9)

Sounds like an injector is stuck open. It's washing fuel down past the piston rings and ending up in the oil pan. Not a very good lubricant! Also, this can ruin the piston rings/cylinder wall under that injector. This happened to me.

The only running you should do with this engine is just to find the injector.

The injector might be bad OR the wire to the PCM might be grounded. They get power from the INJ fuses and the ground is controlled by the PCM. Check for codes.

After finding and fixing the problem, an oil & filter change is due and pull that spark plug and spray some oil directly into the cylinder.

Racer001

iTrader: (15)

if I were to pressurized the fuel rail and clamp the feed and return lines shut, theoretically shouldnt the fuel pressure gauge maintain pressure? If not....bad injector?

Racer001

iTrader: (15)

ok so I pressurized the system and clamped the feed and return line for about an hour with no change in pressure.

Paul Bell

iTrader: (9)

hmmmm I never heard of testing the injectors like that. While pressurized, was the key in the "on" position?

I think you should do an oil change and test the injectors with the engine running. Do you have access to noid lights?

Racer001

iTrader: (15)

I did 30 minutes with the key off and 30 minutes with the key on.

I can buy a noid light and test the injectors.

Racer001

iTrader: (15)

running out of time and resources, I brought it to a trusted shop. They said my map sensor wasn't reading properly and needed to be replaced first. Updates to follow monday.

(I always figured a map sensor would make the car run much worse than mine was. We shall see)

lippies

How is it running??

Racer001

iTrader: (15)

all sensors read fine. plugs look fine. fuel pressure is fine with no leakdown. Mechanic says NO fuel in oil, so I must be losing my mind or something.

I'm figuring possible injector spray pattern problems, or a slight header leak I kind of hear, causing a rich condition

Racer001

iTrader: (15)

OK so everything scans fine. No exhaust leaks to be found while I was under the car. Pulled the cap and rotor to check them




Look fine to me. The problem is definitely still there. Development though: When cold if I get on the gas too much it backfires through the intake. Once it warms up, it has this rich/stumble problem. I'm going to ohm the injectors cold tomorrow and see what they read. Its definitely running rich though...you can smell it at idle.

Changed the oil today too adn nope, no gas in the oil. Muhbad.

Racer001

iTrader: (15)

While idling I got these temps measured about 1" away from the header flange at the head

#1 160-175*F
#2 170ish*
#3 220-250*F
#4 230-240*F
#5 270ish*F
#6 270ish*F
#7 230-250*F
#8 230ish*F

Racer001

iTrader: (15)

this is with a TPIS Miniram, if that makes a difference. I also am using GM Multec 30lb injectors that were factory on the LT4 cars.

Racer001

iTrader: (15)

when cold, all injectors ohm 12.0-12.3 with the exception of #7 that was 11.8

I swapped plug wires with 1/3 and 2/4 and cylinder 1 and 2 are still reading cold.

#1 150-180*F
#2 130-140*F
#3 200-230*F
#4 230-240*F
#5 230*F
#6 250*F
#7 220*F
#8 230*F

I guess next I swap injectors around.

Racer001

iTrader: (15)

Swapped 1/3 and 2/4 injectors with no difference in temperature

Racer001

iTrader: (15)

ok so I checked a bunch more stuff up until late october. Didnt want to just throw parts at the car. Got sick of it and put it in time out for 6 months. Just replaced the o2 sensors and it seems to be running normal again